Assessment of general and specific combining abilities in doubled haploid lines of rapeseed (Brassica napus L.)

Industrial Crops & Products 141 (2019) 111754

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Assessment of general and specific combining abilities in doubled haploid lines of rapeseed (Brassica napus L.)

T

Pegah M. Dezfoulia, Mohammad Sedghia, Mehran E. Shariatpanahib, , Mohsen Niazianb, Bahram Alizadehc ⁎

a

Department of Agronomy and Plant Breeding, University of Mohaghegh Ardabili | UMA, Ardabil, Iran Department of Tissue and Cell Culture, Agricultural Biotechnology Research Institute of Iran (ABRII), Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran c Department of Oilseeds Research, Seed and Plant Improvement Institute (SPII), Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran b

ARTICLE INFO

ABSTRACT

Keywords: Diallel cross Doubled haploid General and specific combining abilities Isolated microspore culture Rapeseed

The high content of oil and protein make rapeseed as good plant material for different industries. Isolated microspore culture method has become a common biotech tool for speeding up breeding programs of rapeseed. In the present study, the general and specific combining ability of microspore-derived doubled haploid (DH) lines of rapeseed was assessed using diallel cross analysis. The six superior DH lines, including DH21, DH10, DH13, DH1, DH8, and DH11 were entered to Griffing’s model II-method 4 of diallel mating cross, based on their estimated general combining ability (GCA) in the top-cross analysis. The results of diallel cross analysis showed significant mean squares for both GCA and specific combining ability (SCA) effects in investigated DH lines. The highest positive GCA for seed yield was corresponded to DH13. The highest positive SCA for seed yield was produced by the DH13 × DH10 cross. The GCA ranking of the studied DHs for seed yield was DH13 > DH21 > DH8 > DH1 > DH10 > DH11. The SCA ranking for seed yield was DH13 × DH10 > DH21 × DH1 > DH1 × DH8 > DH10 × DH11 > DH1 × DH11 > DH10 × DH8 > DH13 × DH1 > DH21 × DH11 > DH1 × DH10 > DH21 × DH8 > DH8 × DH11 > DH21 × DH10 > DH13 × DH21 > DH13 × DH11 > DH13 × DH8. The analysis of phenotypic and genotypic variances showed higher SCA variance than GCA variance for seed yield and other studied traits, which implies presence of non-additive gene actions and heterosis in controlling these traits. The highest estimated narrow-sense heritability was related to the days to flowering trait ( h2s = 58%). The obtained results of the present study are applicable to produce desired F1hybrids, which can be more stable and vigorous than those hybrids produced by conventional selfing programs.

1. Introduction Rapeseed (Brassica napus L.) is the second important oil seed crop, after soybean (Glycine max L.), with many useful applications in food and energy fields (Friedt et al., 2018). Apart from nutritional aspect (both human and animal consumptions), rapeseed is also considered as an industrial crop with many industrial uses including production of biogas and other different by-products (Delgado et al., 2018; Fridrihsone et al., 2018; Ofori and Becker, 2008). Rapeseed is partially self-pollinated and partially cross-pollinated crop. Although rapeseed is predominantly a self-pollinating plant species, cross-pollination can further increase yield and quality (Zou et al.,

2017), therefore, hybrid production and using heterosis (hybrid vigor) can be considered as one of the most important breeding methods in this crop. Heterosis refers to the superiority of a hybrid to its homozygous parents from phenotypic and physiological aspects, including growth rate, reproductive success, resistance to biotic and abiotic stresses, and yield (Lippman and Zamir, 2007). Indeed, the hybrid vigor is a quantitative phenotype altered through environment (Lippman and Zamir, 2007). F1 hybrid progenies are usually more powerful than their inbred parents. The hybrid vigor is an attracting issue for plant breeders and commercial producers. Conventionally, hybrid plants are the results of crossing two inbred parental lines. Clearly the production of inbred parents is the first prerequisite for reaching F1 hybrids. The

Abbreviations: ANOVA, Analysis of variance; DH, Doubled haploid; GCA, General combining ability; IMC, Isolated microspore culture; SCA, Specific combining ability ⁎ Corresponding author at: Mahdasht Road, P. O. Box 31535-1897, Karaj, Iran. E-mail address: [email protected] (M. E. Shariatpanahi). https://doi.org/10.1016/j.indcrop.2019.111754 Received 22 May 2019; Received in revised form 31 August 2019; Accepted 2 September 2019 0926-6690/ © 2019 Elsevier B.V. All rights reserved.

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second prerequisite to produce F1 hybrids is control pollination of desired inbred lines and prevent the self-pollination of the maternal parent. The fastest shortcut to create homozygous lines is the haploidy system. In the haploid induction method, 100% homozygosity is achievable whereas it is hard to reach in conventional methods (Germanà, 2006). Currently, the “speed breeding” method was reported by which the fully-enclosed controlled-environment growth chambers can be used to accelerate the developmental rate of plants and shorten their generation time (Watson et al., 2018). It is a conventional method in which environmental factors, such as supplemental lighting in a glasshouse, are used to shorten the generation time of plants and produce homozygous lines in a faster manner. This method can be more effective in self-pollinated plants, but in cross-pollinated plants we usually face an, inbreeding depression problem. In addition, the complete homozygosity (100%) is not achievable by this method. The haploidy system and production of doubled haploids have been well developed and improved in B. napus, especially through isolated microspore culture (IMC) system (Ahmadi et al., 2014a, b; Ahmadi and Shariatpanahi, 2015). In addition to F1-hybrid breeding program, doubled haploids have the other useful applications in rapeseed breeding programs. The DH populations of rapeseed have been used to develop high-density consensus maps with many breeding purposes (Raman et al., 2013). The prediction of parental combinations and nature of their combining ability is very critical in F1-hybrid breeding programs of rapeseed (Werner et al., 2018). Therefore, the selection of the superior combinational homozygous DH lines, and knowledge about the nature of gene actions involved, can increase the success of hybrids production with desired characteristics. The general and specific combining ability effects (GCA and SCA) are important indicators to identify superior parental inbred lines and use the heterosis in breeding programs of rapeseed (Ishaq et al., 2017a; Rameeh, 2016). There are two main mating designs that allow breeders to assess the both GCA and SCA of their homozygous parental lines. Methods including line × tester, and diallel cross have been used to calculate the both GCA and SCA indicators in rapeseed for different breeding purposes (Rameeh, 2016; Ishaq et al., 2017a, b; Tian et al., 2017; Channa et al., 2018; Oghan et al., 2018). The North Carolina design has also been used to assess the heterosis and general combining ability of inbred lines of rapeseed (Koscielny et al., 2018). In diallel cross analysis, all inbred lines will be crossed in all possible combinations, therefore diallel mating design has been reported as the most appropriate method to assess the potential of inbred lines (Aslam et al., 2015). There are some reports in which diallel cross analysis has been used on DH lines of rapeseed to evaluate in vitro characteristics, such as microspore embryogenic ability (Zhang and Takahata, 2001), and callus induction and shoot regeneration in anther culture experiments (Etedali et al., 2011; El-Hennawy et al., 2016). However, yet there is no report on application of diallel cross to assess the GCA and SCA of DH lines of rapeseed for important agronomical traits. The F1-hybrid production is a creative strategy for higher seed yield production in rapeseed. The hybrid system consists of two steps including the production of parental inbred lines, and cross pollination of the superior inbred lines. Assessing the general and specific combining abilities is a critical step for establishment of a powerful F1-hybrid system. Using conventional mating breeding programs such as diallel cross, subsequent to a biotechnology-based breeding program, like haploid induction, can complete the whole F1-hybrid breeding schedule. The aim of the present study was to assess the both GCA and SCA of DH lines of rapeseed, developed by isolated microspore culture system, to find the superior homozygous DH parental lines for being used in F1–hybrid breeding program and increase the seed yield of rapeseed.

2. Material and methods 2.1. Plant materials and doubled haploid procedure The rapeseed genotypes Hyola 420 and F1 hybrid of RGS003 × ARC5 cross, two genotypes with high level of heterosis and better field performance, provided by the Seed and Plant Improvement Institute (SPII) of Iran were used as plant materials for isolated microspore culture trials and production of DH lines. Seeds of donor plant genotypes were cultivated in the greenhouse of Agricultural Biotechnology Research Institute of Iran (ABRII) (25 °C with 60% relative humidity under 16/8 [light/dark] photoperiod). The regular irrigation was conducted with five days interval until emergence of flower buds. The flower buds were selected with a length of 2.5–3.5 mm, which are the best buds for microspore culture of rapeseed. The microspore developmental stage was determined by staining with DAPI (4′6-diamidino-2-phenylindole) and under the fluorescence microscopy. The microspore isolation and embryogenesis induction steps were conducted according to our previous optimized procedure (Ahmadi et al., 2014a, b; Ahmadi and Shariatpanahi, 2015). The regenerated haploid seedlings, at 5–7 leaves stage, were treated with colchicine (Fletcher et al., 1998; Gil-Humanes and Barro, 2009) for chromosome doubling and production of DH parental lines. The ploidy level of DH lines was determined by flow cytometry analysis. 2.2. Elimination of unfavorable DH lines The top-cross analysis was conducted to reduce the number of DH lines produced (50 DH lines). All doubled haploid lines were crossed in a greenhouse condition with a common tester (Hyola 420) for assessing their general combining ability. The Hyola 420, a commercial F1 hybrid genotype with highest degree of combining ability and heterozygosity among all available genotypes in SPII, was used as paternal tester parent and 50 DH lines were used as maternal parents. The harvested F1 offspring were evaluated in a field experiment trail. Only 28 DH lines out of the 50 available lines produced the top-cross progeny. The general combining ability of DH lines was assessed for morphological and yield characteristics, such as plant height, number of pods per main stem, number of pods per branch, number of pods per plant, number of branches, main stem length, number of seeds per pod, the height of the first pod from the ground, stem diameter, pod length, 1000-seed weight, single plant yield and oil content percentage. The six superior DH lines, with higher GCA for aforementioned characteristics, were chosen to assess their general and specific combining ability through diallel cross analysis. 2.3. Diallel cross procedure The gathered seeds of top-cross selected superior DH lines were cultivated in plastic pots (10 cm in diameter and 15 cm in height) and grown in greenhouse condition. The half-diallel mating design was used and six parental DH lines, DH21, DH10, DH13, DH1, DH8, and DH11, were crossed in all possible combinations. The DH1 and DH21 lines were obtained from IMC of Hyola 420 genotype and the rest of them came from IMC of F1 hybrid of RGS003 × ARC5 cross. The diallel cross was conducted using Griffing’s model II -method 4 of diallel analysis (Griffing, 1956). Because the used parents were fully inbred (DH), therefore reciprocal crosses and selfed parents were omitted from analyses (Möhring et al., 2011) and therefore, Griffing’s model II – method 4 was used. The 15 F1 hybrids were cultivated in the greenhouse (with aforementioned condition) in form of randomized complete block design (RCBD) with three replications. The standard maintenance practices were done for growing plants and

2

3

0.049 0.162a 0.021 12.87% 0.006 0.132a 0.024 13.66% 48.5 992.4a 24.295 12.82% 22.31 1986.25a 11.592 12.34% 236.167 2841.086a 43.756 5.35% 0.176 0.282a 0.091 9.64% 5.81 204.471a 54.63 10.75% a

Significant at 1% probability level.

0.473 1.79a 0.157 8.82% 2 14 28 Replication Treatment error C.V

0.056 1.219a 0.099 6.70%

Seed yield Seed weight of sub pod Seed weight of main pod Days to physiological maturity Days to end of flowering Degree of freedom Source of variation

2 14 28

Sub pod length

Main pod length

Height of first pod from the ground

1000-seed weight

Days to flowering

0.009 0.065a 0.004 7.53% 74.667 1244.346a 51.385 13.07 5.738 48.652a 4.482 12.31% 1.167 28.954a 3.679 10.34% 1.238 5.189a 1.084 22.66% 259.738 2920.27a 449.251 18.55% 187.714 1833.1a 330.689 25.77% 51.452 265.94a 30.811 12.71%

Number of branches Pod per plant

Replication Treatment error C.V

The results of ANOVA showed significant differences among investigated F1-hybrids for all studied traits at 1% probability level (Table 1). The results of means comparison analysis using Duncan’s multiple range test showed that the highest mean of plant height was related to the DH8 × DH21 hybrid, however there was no significant difference between this hybrid and DH11 × DH21 hybrid at 5% probability level (Table 2). The highest means of pod in the main branch and main stem length were also obtained from DH8 × DH21 hybrid (Table 2). For pod number in branches, pod per plant, and seed yield traits, the highest means were obtained from DH10 × DH13 hybrid (Table 2). The DH10 × DH21 cross showed highest means for number of branches and 1000-seed weight traits (Table 2). Although the highest mean values of NB and TSW traits were observed in a same hybrid, however no high positive correlation has been reported for them (Lu et al., 2011; Zhang and Zhou, 2006). These results imply variability of these traits and their relationship among different genotypes and experimental conditions. The highest means of number of seed per main pod, number of seed per sub pod, main pod length, sub pod length, seed weight of main pod, and seed weight of sub pod were observed from DH1 × DH21 hybrid (Table 2). Based on the results of means comparison analysis using Duncan multiple test at 5% probability level, the highest means of stem diameter, days to flowering, and days to end of flowering traits were obtained from DH11 × DH8 cross (Table 2). The highest means of height of first pod from the ground and days to physiological maturity traits were corresponded to the DH11 × DH21 and DH11 × DH10 hybrids, respectively (Table 2).

Pod number in branches

3.1. The means comparison analysis of morphological, phenological, and yield component traits in diallel’s F1-hybrids

Pod in the main branch

3. Results

Plant height

Where μ is the population’s average, g(i) is the GCA effect for (i) parent, g(j) is the GCA effect for (j) parent, s(i,j) is the SCA effect for (I and j) parents, b(k) is the block (repeat) effect, and e(i,j,k) is the trial error (Burow and Coors, 1994). Because the parental lines were completely homozygous DH, therefore, in estimation of additive and dominance effect’s variances, the inbreeding coefficient F was one (F = 1).

Degree of freedom

(1)

Source of variation

X(i,j,k)= μ + g(i) + g(j) + s(i,j) + b(k) + e(i,j,k)

Table 1 The analysis of variance of randomized complete block design for morphological, phenological, and yield component traits of doubled haploid lines of rapeseed.

The analysis of variance (ANOVA) was conducted using SAS® software (SAS Institute Inc., Cary, NC). The Duncan’s multiple range means comparison analysis test at 5% was conducted using SAS® software (SAS Institute Inc., Cary, NC). The general and specific combining ability effects (GCA and SCA) were estimated following Griffing’s model II using DIALLEL (Version 1.1) software (Burow and Coors, 1994). The used model in the DIALL software was:

Number of seed per main pod

Number of seed per sub pod

2.4. Data analysis

26 1225.17a 104.821 8.44%

Main stem length

Stem diameter

the morphological, phenological, and yield characteristics including plant height (PH), pod in the main branch (PMB), pod in the sub branch (PSB), pod per plant (PP), number of branches (NB), number of seeds per main pod (NSMP), number of seeds per sub pod (NSSP), main stem length (MSL), stem diameter (SD), main pod length (MPL), sub pod length (SPL), the height of the first pod from the ground (HFPG), 1000seed weight (TSW), days to flowering (DF), days to end flowering (DEF), days to physiological maturity (DPM), seed weight of main pod (SWMP), seed weight of sub pod (SWSP), and seed yield (SY) were recorded at the maturity stage.

0.88 5.119a 0.897 21.24%

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4

0.93b 0.73ef 0.83cd 0.72ef 0.71ef 0.96b 0.63fg 0.71ef 0.74de 0.57g 0.87bc 0.83cd 0.73def 0.96b 1.10a DEF 115.00g 117.00fg 133.00e 163.00cd 159.33d 122.00f 115.00g 133.33e 135.00e 138.33e 159.66d 166.00c 166.66c 184.00b 193.33a

58.66c 57.66c 50.00cd 49.33cd 42.00de 47.33cd 55.00cd 104.66a 77.33b 72.33b 51.00cd 42.33de 34.00e 34.66e 30.33e

DF

85.00g 96.00f 115.00e 141.33d 146.00cd 79.00g 85.00g 112.00e 110.66e 121.33e 152.66bcd 145.33cd 157.00bc 159.66ab 169.66a

DH21 × DH13 DH1×DH13 DH10 × DH13 DH8×DH13 DH11×DH13 DH1 × DH21 DH10 × DH21 DH8 × DH21 DH11 × DH21 DH8×DH1 DH11×DH1 DH10×DH1 DH8×DH10 DH11 × DH10 DH11 × DH8

F1-hybrids

DH21 × DH13 DH1×DH13 DH10 × DH13 DH8×DH13 DH11×DH13 DH1 × DH21 DH10 × DH21 DH8 × DH21 DH11 × DH21 DH8×DH1 DH11×DH1 DH10×DH1 DH8×DH10 DH11 × DH10 DH11 × DH8

86.33bcd 56.67defg 117.70a 82.00bcd 71.33cdef 47.67efg 79.33bcde 93.33abc 107.30ab 82.33bcd 43.67fg 42.16fg 71.33cdef 45.00fg 37.33g

PSB

145.00f 152.00ef 169.00d 189.00b 186.33b 150.00ef 155.00e 173.66cd 178.00c 173.00cd 195.00ab 187.33b 187.66b 199.00a 193.33ab

DPM

5.30a 5.30a 5.13ab 4.26c 4.23c 5.66a 4.33c 5.13ab 4.70bc 5.30a 4.60bc 4.12c 4.30c 4.23c 3.30d

MPL (cm)

121.00bcde 111.00cdef 169.66a 122.66bcde 119.00bcdef 85.66efg 122.00bcde 149.00abc 156.33ab 133.00abcd 88.66efg 83.64fg 105.33def 81.66fg 57.66g

PP

1.37bc 1.24bc 1.31b 1.01cde 1.02cde 1.67a 1.10bcd 1.16bc 1.10bcd 1.16bcd 1.09bcd 1.11bcd 1.01cde 0.79e 0.90de

SWMP

5.33ab 5.00bc 5.40ab 3.96ef 4.03def 5.60a 4.40de 5.00bc 4.60cd 5.10abc 3.60f 3.66f 4.10def 3.76f 3.03g

SPL (cm)

5.33bcd 3.66de 6.00ab 5.00bcd 5.00bcd 3.33de 7.33a 3.33de 6.33ab 4.00cde 3.00e 4.33cd 5.66abc 4.00cde 4.00cde

NB

1.34b 1.16bcd 1.31bc 1.04def 0.79f 1.74a 1.04def 1.17bcd 1.10bcde 1.01def 1.02def 1.06cdef 1.06cdef 1.02def 0.85ef

SWSP

69.00bcde 68.33bcde 72.66abc 64.33cde 81.00ab 63.00cde 56.00e 59.00de 84.66a 68.00bcde 74.66abc 59.33de 58.66de 73.00abc 70.00bcd

HFPG (cm)

16.66e 23.00ab 20.00bcd 16.00e 15.66e 24.33a 15.00e 20.33bcd 17.00de 21.33ab 17.66cde 17.00de 17.00de 17.00de 14.33e

NSMP

Means followed by the same letters within columns are not significantly different at the 5% level. PH: Plant height; PMB: Pod in the main branch; PSB: Pod in the sub branch; PP: Pod per plant; NB: Number of branches; NSMP: Number of seeds per main pod; NSSP: Number of seeds per sub pod. MSL: Main stem length; SD: Stem diameter; MPL: Main pod length; SPL: Sub pod length; HFPG: The height of the first pod from the ground; TSW: 1000- seed weight. DF: Days to flowering; DEF: Day to end flowering; DPM: Days to physiological maturity; SWMP: Seed weight of main pod; SWSP: Seed weight of sub pod; SY: Seed yield.

SD (cm)

MSL (cm)

52.00abc 54.33ab 52.00abc 40.66defg 47.66abcde 38.00efg 42.66cdefg 55.66a 49.00abcd 50.66abcd 45.00bcdef 43.12cde 34.00g 36.66fg 20.33h

122.12bcd 125.00bc 122.33bcd 114.00cde 119.66bcd 110.00cde 111.33cde 160.00a 157.33a 137.66b 122.00bcd 120.33cd 88.33f 104.66def 98.00ef

DH21 × DH13 DH1 × DH13 DH10 × DH13 DH8 × DH13 DH11 × DH13 DH1 × DH21 DH10 × DH21 DH8 × DH21 DH11 × DH21 DH8 × DH1 DH11 × DH1 DH10× DH1 DH8 × DH10 DH11 × DH10 DH11 × DH8

F1-hybrids

PMB

PH

F1-hybrids

5.36bc 5.53b 7.36a 4.53bcde 3.63de 5.76b 3.16e 5.13bcd 4.10bcde 5.03bcd 3.20e 3.76de 3.73cde 2.96e 2.90e

SY

3.20abcde 2.66e 3.16abcde 3.43abc 3.10bcde 3.46ab 3.70a 3.16abcde 3.23abcd 2.66e 3.30abcd 2.80de 2.80de 2.90cde 2.90cde

TSW (g)

15.66cd 21.33ab 21.66ab 13.66de 14.00de 24.33a 14.66cde 18.00bc 16.33cd 20.00ab 13.66de 17.33cd 15.66cd 13.33de 11.66e

NSSP

Table 2 The means comparisons analysis for investigated morphological, phenological, and yield component traits in F1-hybrids of diallel cross of doubled haploid lines of rapeseed using Duncan’s multiple range test at 5% probability level. P. M. Dezfouli, et al.

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5

0.04 0.36a 0.42a 0.02 0.003 0.48a 0.34a 0.02

SWMP

45.26 9269.23a 5780.66a 22.79

DPM

20.82 10006.38a 3881.15a 10.86 220.42 10913.08a 2793.43a 41.75

DEF DF

2 5 9 28 Rep GCA SCA Error

0.16 2.52a 2.03a 0.08

Degree of freedom Traits

TSW

175.20 2595.70a 2755.26a 307.96 48.02 556.62a 668.13a 28.85 24.26 5802.83a 3122.4a 97.45

PH: Plant height; PMB: Pod in the main branch; PSB: Pod in the sub branch; PP: Pod per plant; NB: Number of branches; NSMP: Number of seeds per main pod; NSSP: Number of seeds per sub pod; MSL: Main stem length; SD: Stem diameter; MPL: Main pod length; SPL: Sub pod length; HFPG: The height of the first pod from the ground; TSW: 1000- seed weight; DF: Days to flowering; DEF: Day to end flowering; DPM: Days to physiological maturity; SWMP: Seed weight of main pod; SWSP: Seed weight of sub pod; SY: Seed yield. a significant at 1% of probability level.

SY

5.42 1660.22a 842.97a 50.75 0.05 4.95a 5.87a 0.09 0.008 0.18a 0.19a 0.003 84.35 2510.38a 1215.33a 47.97 6.20 107.20a 100.74a 4.03 1.08 81.68a 103.46a 3.42 1.15 10.35a 8.31a 1.01 242.42 4767.52a 5629.66a 418.39

MSL NSSP NSMP NB PP PSB PMB

2 5 9 28

Increasing the seed yield remains as an important objective in breeding programs of rapeseed (Luo et al., 2018). The seed yield is a highly complex quantitative trait controlled by several genes and mainly influenced by the environment (Luo et al., 2017; Niazian et al., 2017). Using the simple yield component traits, such as plant height, branching, flowering time and pod number, which have correlation with seed yield, breeders can succeed in breeding of seed yield (Luo et al., 2017). The analysis of yield components through ANOVA can provide the knowledge about the genetic variability and formulate an efficient breeding program (Niazian et al., 2017). The high significant

Rep GCA SCA Error

4. Discussion

PH

The dominance variance for all evaluated traits, except for days to flowering trait, was more than additive variance (Table 6). Also, the variance of SCA effect was more than GCA for all investigated characteristics (Table 6). The highest estimated broad sense heritability indexes were related to DEF and DPM traits (Table 6) and the lowest estimated one was related to PSB trait (Table 6). The highest estimated narrow-sense heritability was related to the days to flowering trait ( h2s = 58%).

Degree of freedom

3.3. Analysis of phenotypic and genotypic variances and heritability of studied traits

Traits

Table 3 Analysis of variance of diallel cross mating design for investigated morphological, phenological, and yield component traits in doubled haploid lines of rapeseed.

SD

MPL

SWSP

SPL

The ANOVA of diallel cross revealed the significant mean squares for both GCA and SCA indicators in all investigated traits at 1% probability level (Table 3). The highest positive and negative GCA values for pH were related to DH21 and DH10 doubled haploids, respectively (Table 4). The highest positive GCA values for PMB, PSB, PP, NSMP, and SY were observed from DH13 line (Table 4). For NB, NSSP, MSL, MPL, SPL, TSW, SWMP, and SWSP characteristics, the highest positive GCA values were obtained from DH21 (Table 4). The highest positive and significant GCA values for SD, HFPG, DF, DEF, and DPM traits were estimated from DH11 line (Table 4). At all, the highest positive GCA values for all investigated morphological, phenological, and yield component traits were corresponded to DH11, DH13, and DH21 (Table 4), whereas the highest negative estimated GCA values were observed from DH1 and DH10 lines (Table 4). The highest positive and negative GCA values of seed yield trait were related to DH13 and DH10, respectively (Table 4). In the next step, the SCA of the studied traits was calculated for F1hybrids obtained from diallel cross of six DH lines of rapeseed. The highest positive and negative SCA values for PH, PMB, and HFPG traits were obtained by DH1 × DH8 and DH8 × DH11 crosses, respectively (Table 5). The DH13 × DH10 cross showed the highest positive and significant SCA values for PSB, PP, NSSP, MPL, SPL, and SWMP traits (Table 5). The highest positive and significant SCA values for SD, DEF, and SWSP traits were obtained from cross of DH21 × DH1 (Table 5). For NB trait the highest positive and negative estimated SCA values were obtained from DH21 × DH10 and DH21 × DH8 crosses, respectively (Table 5).The highest positive and negative estimated SCA values for NSMP trait were obtained from DH10 × DH11 and DH13 × DH8 crosses, respectively (Table 5). For 1000-seed weight trait, the highest positive and negative SCA were observed by DH1 × DH11 and DH13 × DH21 crosses, respectively (Table 5). The highest positive SCA values for days to flowering and days to physiological maturity traits were obtained from DH1 × DH11 cross, whereas the highest negative SCA values for these traits were obtained from DH8 × DH11 cross (Table 5). The DH21 × DH1 showed the highest positive SCA values for days to end of flowering and seed weight of sub- pod traits (Table 5). For seed yield trait, the highest positive SCA value was estimated from DH13 × DH10 cross and the highest negative SCA was obtained from DH13 × DH11 (Table 5).

0.44 6.12a 5.46a 0.14

HFPG

3.2. Analysis of general and specific combining abilities of DH lines

0.82 10.47a 7.76a 0.83

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10.66 25.08 −17.83 −34.83 8.00 8.91 2.60 4.03

DH 13 DH 21 DH 1 DH 10 DH 8 DH 11 SE (gi) SE(gi-gj)

8.88 6.55 −3.94 −9.61 −0.61 −1.27 1.41 2.19

PMB

12.83 12.83 −24.75 −4.00 9.25 −6.16 4.62 7.16

PSB

21.72 19.38 −28.69 −13.61 8.63 −7.44 5.39 8.35

PP 0.47 0.63 −1.86 0.39 0.14 0.22 0.26 0.41

NB 2.27 2.27 −0.05 −4.38 0.61 −1.22 0.48 0.75

NSMP 3.08 3.75 −0.16 −3.66 −0.25 −2.75 0.82 0.82

NSSP 0.72 22.05 −6.61 −20.27 8.97 −4.86 1.82 2.82

MSL (cm) 0.04 0.06 −0.15 −0.14 0.02 0.16 0.01 0.02

SD (cm) 0.57 0.80 −0.26 −0.98 0.09 −0.21 0.08 0.12

MPL (cm) 0.69 0.98 −0.42 −0.82 0.05 −0.48 0.10 0.15

SPL (cm) 8.64 2.72 −11.69 −15.11 −0.19 15.64 1.87 2.91

HFPG (cm) 0.25 0.55 −0.61 −0.50 0.10 0.21 0.07 0.12

TSW (gr) 1.64 −26.27 −31.94 −15.02 31.14 40.47 1.70 2.64

DF 2.27 −14.47 −35.30 −19.88 29.11 38.27 0.87 1.34

DEF 6.50 −3.41 −36.33 −26.16 25.33 34.08 1.25 1.95

DPM 0.15 0.29 −0.04 −0.28 −0.00 −0.11 0.03 0.05

SWMP (gr) 0.10 0.29 −0.07 −0.19 −0.02 −0.10 0.03 0.05

SWSP (gr)

1.40 0.68 −0.32 −0.89 0.13 −1.00 0.24 0.37

SY (gr)

6

Parent 1

−21.28 18.96 33.30 −17.86 −13.11 −10.45 7.88 13.71 10.13 34.30 17.71 11.23 1.96 17.38 −32.11 4.41 6.98 5.69

PH (cm)

−11.53 8.63 11.96 −8.36 −0.70 −5.36 4.96 8.96 2.96 14.46 9.46 6.42 3.46 6.80 −18.53 2.40 3.79 3.10

PMB

−38.53 2.71 42.96 −5.95 −1.20 −6.28 4.63 5.38 34.80 31.96 8.71 0.44 0.21 −10.70 −31.61 7.84 12.40 10.13

PSB −50.06 11.35 54.93 −14.31 −1.90 −11.65 9.60 14.35 37.76 46.43 18.18 11.43 3.68 −3.90 −50.15 9.14 14.46 11.81

PP −1.73 0.76 0.85 0.10 0.01 0.26 2.01 −3 1.7 1.18 3 1.4 5 0.3 0.21 5 0.8 −0 0.9 −5 0.6 0.45 0.71 0.58

NB −1.36 3.46 4.80 − 4.20 − 2.70 4.30 − 0.70 − 0.36 − 1.86 3.46 1.63 1.21 3.46 5.30 −2.36 0.82 1.30 1.06

NSMP − 1.16 2.41 6.25 − 5.16 −2.33 4.75 − 1.41 −1.50 − 0.66 4.41 0.58 2.01 3.58 3.75 −1.33 0.89 1.42 1.15

NSSP −15.06 12.60 18.60 − 11.31 −4.81 − 19.06 2.26 22.68 9.18 19.01 11.51 8.42 −5.65 8.85 − 24.73 3.09 4.89 3.99

MSL (cm( 0.07 0.08 0.18 −0.09 − 0.24 0.30 − 0.03 − 0.12 − 0.22 −0.05 0.11 0.11 0.11 0.19 0.16 0.02 0.04 0.03

SD (cm) −0.46 0.60 1.15 − 0.78 −0.51 0.74 0.13 − 0.14 − 0.27 1.08 0.69 0.46 0.80 1.04 − 0.96 0.13 0.21 0.17

MPL (cm) −0.54 0.53 1.34 −0.97 −0.36 0.83 0.04 −0.24 − 0.09 1.26 0.31 0.54 0.67 0.88 −0.73 0.17 0.27 0.22

SPL (cm)

−1 6.5 3 7.2 8 14.9 −8.26 −3 7.4 1 7.8 3 4.2 − 7.68 2.15 15.73 6.56 5.21 9.81 8.31 −0 9.6 3.18 5.03 4.11

HFPG (cm)

−0.51 0.12 0 0.5 0.17 −0.28 2 0.6 3 0.7 −0.39 −4 0.4 0.27 0.78 0.36 0.28 0.27 −0.33 0.13 0.20 0.16

TSW (gr)

−1 5.7 5 10.9 13.03 −0 6.8 − 11.46 21.86 10.95 −1 8.2 − 18.88 6.78 28.78 20.32 3 25.5 18.86 −17.30 2.88 4.56 3.73

DF

−8.45 14.38 14.96 − 4.03 −16.86 3 36.1 1 13.7 −5 16.9 −5 24.4 8.88 21.05 20.47 0 21.8 6 29.9 −0 9.7 1.47 2.33 1.90

DEF

−5 21.1 18.76 25.60 − 5.90 −1 17.3 26.68 1 21.5 −1 11.3 −3 15.7 3 20.9 34.18 27.05 3 25.4 1 28.0 −5 29.1 2.13 3.37 2.75

DPM

− 0.14 0.06 0.37 0.20 − 0.09 0.35 0.04 −0.10 − 0.15 0.14 0.18 0.16 0.22 0.11 − 0.05 0.06 0.10 0.08

SWMP (gr)

−0.10 0.08 0.36 −0.09 −0.25 0.47 −0.09 −0.14 −0.12 0.06 0.16 0.12 0.23 0.27 −0.06 0.06 0.09 0.08

SWSP (gr)

−0.88 0.28 2.69 − 1.16 −0.93 1.24 − 0.78 0.16 0.26 1.06 0.36 0.21 0.33 0.70 −0.39 0.41 0.64 0.53

SY (gr)

*,**:significant at the 5 and 1% of probability level, respectively; ns = not significant. PH: Plant height; PMB: Pod in the main branch; PSB: Pod in the sub branch; PP: Pod per plant; NB: Number of branches; NSMP: Number of seeds per main pod; NSSP: Number of seeds per sub pod; MSL: Main stem length; SD: Stem diameter; MPL: Main pod length; SPL: Sub pod length; HFPG: The height of the first pod from the ground; TSW: 1000− seed weight; DF: days to flowering; DEF: Day to end flowering; DPM: Days to physiological maturity; SWMP: Seed weight of main pod; SWSP: Seed weight of sub pod; SY: Seed yield.

DH13× DH21 DH13× DH1 DH13× DH10 DH13× DH8 DH13× DH11 DH21× DH1 DH21× DH10 DH21× DH8 DH21× DH11 DH1× DH8 DH1× DH11 DH1× DH10 DH10× DH8 DH10× DH11 DH8× DH11 SE[s(i,j)] SE[s(i,j)−s(i,k)] SE[s(i,j)−s(k,l)]

Parent 2

Table 5 Estimated specific combining ability values for morphological, phenological, and yield component traits in doubled haploid lines of rapeseed using diallel cross mating design.

PH: Plant height; PMB: Pod in the main branch; PSB: Pod in the sub branch; PP: Pod per plant; NB: Number of branches; NSMP: Number of seeds per main pod; NSSP: Number of seeds per sub pod; MSL: Main stem length; SD: Stem diameter; MPL: Main pod length; SPL: Sub pod length; HFPG: The height of the first pod from the ground; TSW: 1000- seed weight; DF: Days to flowering; DEF: Day to end flowering; DPM: Days to physiological maturity; SWMP: Seed weight of main pod; SWSP: Seed weight of sub pod; SY: Seed yield.

PH (cm)

Genotypes

Table 4 Estimated general combining ability values for morphological, phenological, and yield component traits in doubled haploid lines of rapeseed using diallel cross mating design.

P. M. Dezfouli, et al.

Industrial Crops & Products 141 (2019) 111754

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PH: Plant height; PMB: pod in the main branch; PCB: pod in the sub branch; PP: pod per plant; NB: Number of branches; NSMP: Number of seeds per main pod; NSSP: Number of seeds per sub− pod; MSL: Main stem length; SD: Stem diameter; MPL: Main pod length; SPL: sub pod length; HFPG: The height of the first pod from the ground; TSW: 1000− seed weight; DF: days to flowering; DEF: Day to end flowering; DPM: days to physiological maturity; SWMP: seed weight of main pod; SWSP: seed weight of sub pod; SY: Seed yield.

3.59 0.12 0.76 0.14 −0.06 0.86 0.15 0.14 0.87 2523.51 0.23 1.00 2321.83 0.44 1.00 2312.25 0.58 0.98 0.81 0.10 0.89 451.03 0.30 0.88 2.03 0.05 0.92 1.86 −0.08 0.95 0.06 −0.02 0.94 652.93 0.33 0.92 37.34 0.03 0.89 33.14 −0.11 0.89 3.78 0.09 0.73 2011.79 −0.07 0.79 223.36 −0.08 0.87 1552.51 0.28 0.93

1097.13 −0.02 0.72

2.31 0.13 0.11 1919.29 1290.09 917.22 0.65 264.07 1.77 1.92 0.06 389.12 32.23 33.34 2.43 1737.09 213.09 1008.31

815.76

0.45 2.31 0.83 0.21 −0.009 0.13 0.02 −0.004 0.02 0.11 0.02 0.01 581.42 1919.29 22.79 290.70 1020.87 1290.09 10.86 510.41 1353.27 917.22 41.75 676.61 0.081 0.65 0.08 0.04 136.21 264.07 50.75 68.10 0.11 1.77 0.14 0.05 −0.15 1.92 0.09 −0.08 −0.001 0.06 0.003 −0.0007 215.84 389.12 47.97 108.00 1.07 32.23 4.03 0.52 −3.62 33.34 3.42 −1.80 0.34 2.43 1.01 0.21 −143.69 1737.09 418.39 −71.80 −18.58 213.09 28.85 −9.32 446.73 1008.31 97.45 223.41

Additive variance Dominance variance Error variance General combining ability variance Specific combining ability variance Phenotypic variance Narrow sense heritability Broad sense heritability

−26.59 815.76 307.96 −13.33

SWMP (gr) DPM DEF DF TSW (gr) HFPG (cm) SPL (cm) MPL (cm) SD (cm) MSL (cm) NSSP NSMP NB PP PSB PMB PH (cm) Characters

Table 6 Estimated phenotypic and genotypic variances and heritability of morphological, phenological, and yield component traits in doubled haploid lines of rapeseed using diallel cross mating design.

SWSP (gr)

SY (gr)

P. M. Dezfouli, et al.

mean squares of morphological, phenological, and yield components traits in the present study showed high genetic variability among the studied DH lines. Therefore, the produced heterogenic and homozygous DH population is a rich resource for different breeding strategies and creates new varieties of rapeseed. The F1-hybrid of DH10 × DH13 showed the highest means of seed yield, pod number in branches, and pod per plant characteristics. This hybrid also showed the high means for seed weight of main pod and seed weight of sub pod traits. The pod number per unit area has been reported as an important determining factor in seed yield of rapeseed (Diepenbrock, 2000; Sadat et al., 2010). Therefore, this trait can be considered as a selection criterion for improving seed yield in produced DH maternal lines. Currently, the development of doubled haploid lines and the exploitation of heterosis, for seed and oil yield, is the main focus of the rapeseed breeding programs (McVetty and Duncan, 2015). The androgenesis-based haploid induction is a routine method to produce completely homozygous lines, with full genetic stability, in rapeseed (Szała et al., 2018). The assessment of produced DH lines is important to reach the breeding goals in rapeseed. The multivariate statistical methods have been developed for evaluation of the DH lines of rapeseed in term of quantitative and qualitative traits such as content of fatty acids and seed yield (Kaczmarek et al., 2005; Szała et al., 2018). However, assessing the combining ability and selection of the superior DH lines is necessary to choose best parental lines in F1-hybrid breeding program of rapeseed. The GCA and SCA indicators are important in breeding programs. The GCA refers to the average performance of a line in hybrid combinations and reflects the breeding value of a parent, connected with the additive genetic effects. The SCA refers to the deviation of a certain cross from the average performance of the lines (relative performance of a cross) and connects to the non-additive gene action, contributed by dominance, epistasis, and/or genotype × environment effects (Rukundo et al., 2017). The genetic analysis of crops through mating designs can help evaluation of breeding potential of the parents or identify the best combiners (Ene et al., 2019). In rapeseed, the diallel mating design has been mainly deployed to assess the GCA and SCA of homozygous parental lines created through conventional inbreeding methods (Tian et al., 2017), on the other hand, the combining ability of DH lines are mainly evaluated through line × tester mating design (Adamska et al., 2007). Therefore, assessing the GCA and SCA of DH lines through diallel mating design can provide more comprehensive information about the combining ability of DH lines. For all investigated traits in the present study, both GCA and SCA effects were significant. The highest significant positive GCA effect for seed yield was related to DH13 line, which indicates that this DH line would increase seed yield in its hybrids. According to the SCA effect, F1 hybrid DH13 × DH10 was proved as the best hybrid for seed yield and can be considered in rapeseed breeding programs. The contribution of additive and non-additive gene actions involved in the inheritance of different traits can be determined through the GCA and SCA variances (Channa et al., 2018). The significant estimated GCA and SCA variances in the present study showed the existence of both additive and non-additive nature of gene actions in controlling the morphological, phenological, and yield components characteristics of DH lines of rapeseed. However, according to the results of the analysis of phenotypic and genotypic variances, the SCA variance of all traits were more than GCA variance and the dominance variance was more than additive variance, which indicate the non-additive effects of genes in controlling the studied traits in completely homozygous DH lines of rapeseed. The non-additive gene action in controlling some morphological, phenological, and yield traits of rapeseed, such as primary branches per plant, pods on terminal raceme, pods per plant, seeds per pod, seed yield per plant, days to flowering, days to physiological maturity, 1000-seed weight, oil content, and seed yield, has been reported in previous studies (Channa et al., 2018; Oghan et al., 2018). 7

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The higher SCA indicates the higher heterosis in diallel crosses (Niazian et al., 2013). Heterosis has positive impact on seed yield, therefore, the produced DH lines are valuable to develop the new varieties of rapeseed with higher seed yield. The high estimated narrow-sense heritability for days to flowering trait indicates that direct selection can be useful for breeding DH lines for this trait. Although there has been reported a great interaction between genetic and environment for processes regulating crop development, such as DEF and DPM (Slafer et al., 2015), however, the contribution of genetic part can be much larger than environment. Oghan et al (2018) used Line × Tester mating design to assess the genetic parameters for different characteristics in 100 F1 and F2 hybrids of rapeseed and reported high broad and narrow sense heritability for days to flowering (H2 = 81.31–82.70; h2 = 48.93–62.57), and days to physiological maturity (H2 = 85.83–90.80; h2 = 52.85–83.94). As decisive moment for rapeseed development, the floral initiation can determine the number of leaf primordia in life cycle and the beginning of floral bud differentiation in rapeseed (Luo et al., 2018).

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5. Conclusions At this study, we evaluated the general and specific combining abilities of six superior DH lines of rapeseed, produced through isolated microspore culture system and first screened through top-cross analysis. The highest positive GCA value for seed yield was related to the DH13 line. The GCA ranking of the studied DHs for seed yield was DH13 > DH21 > DH8 > DH1 > DH10 > DH11. The highest positive SCA value for seed yield was obtained from DH13 × DH10 cross. The SCA ranking for seed yield was DH13 × DH10 > DH21 × DH1 > DH1 × DH8 > DH10 × DH11 > DH1 × DH11 > DH10 × DH8 > DH13 × DH1 > DH21 × DH11 > DH1 × DH10 > DH21 × DH8 > DH8 × DH11 > DH21 × DH10 > DH13 × DH21 > DH13 × DH11 > DH13 × DH8. It is obvious that DH13 and DH21 lines are the superior produced doubled haploid lines that their combination with other DHs can lead to F1 hybrids with higher plant seed yield. Regarding to the specific combining ability indicator, the cross of DH13 and DH10 is the best cross for producing F1 hybrid with higher seed yield. The higher estimated dominance variance, in comparison with estimated additive variance, showed the non-additive effects of involved genes in controlling morphological, phenological, and yield component traits in studied DH lines of rapeseed. The GCA and SCA indicators are powerful, however, the integration of genomic selection methods with conventional phenotype-based GCA and SCA indicators can lead to more reliable selection and reduce the required volume of the field experiments (Werner et al., 2018). In addition to conventional diallel analysis, there is possibility to link diallel cross with genotype × environment interaction (GGE) biplot method for finding the best entry and testers (Niazian et al., 2009, 2013), and/ or powerful computational method of artificial neural network (ANN), for more precise interpretation of diallel mating design data (Abdipour et al., 2018). Author contribution P M D performed diallel crosses and data analyses of the experiment, M S supervised the project, M E.S supervised the project and corrected the manuscript, M N wrote the body of manuscript and contributed in statistical analyses, B A supervised the project and contributed in statistical analyses. References Abdipour, M., Ramazani, S.H.R., Younessi‐Hmazekhanlu, M., Niazian, M., 2018. Modeling oil content of sesame (Sesamum indicum L.) using artificial neural network and multiple linear regression approaches. J. Am. Oil Chem. Soc. 95 (3), 283–297. Adamska, E., Szala, L., Cegielska-Taras, T., Kaczmarek, Z., 2007. Multidimensional GCA

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