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Response of chilli (Capsicum annuum L.) to the inoculation of an efficient vesicular-arbuscular mycorrhizal fungus
Scientia Horticvlturae, 53 ( 1993 ) 45-52
45
Elsevier Science Publishers B.V., Amsterdam
Response of chilli (Capsicum a n n u u m L. ) to the inoculation of an efficient vesicular-arbuscular mycorrhizal fungus M.N. Sreenivasa, P.U. Krishnaraj, G.A. Gangadhara and H.M. Manjunathaiah Divisions of Agricultural Microbiology and Black Cotton Soil Research, University of Agricultural Sciences, Dharwad-580005, India (Accepted 28 May 1992)
ABSTRACT Sreenivasa, M.N., Krishnaraj, P.U., Gangadhara, G.A. and Manjunathaiah, H.M., 1993. Response of chilli (Capsicum annuum L. ) to the inoculation of an efficient vesicular-arbuscular mycorrhizal fungus. Scientia Hortic., 53: 45-52. The response of 30-day-old transplanted chilli to the inoculation of an efficient vesicular-arbuscular mycorrhizai (VAM) fungus Glomus macrocarpum was studied in comparison with Glomusfascicuiatum at different levels of phosphorus fertilization (0, 25, 50 and 100% of the recommended dose) incorporated in soluble (super phosphate) or insoluble (rock phosphate) forms in unsterile soil. Of these two VAM fungi, G. macrocarpum caused maximum increases in growth, yield and nutrient status of chilli, especially P, Zn, Cu, Mn, and Fe at 50% of the recommended dose added in the soluble form of P. The response of chilli to the inoculation of either VAM fungi in the presence of insoluble P was not encouraging when compared with the soluble form. The results suggest that P-fertilizers in their soluble form could be used more efficiently in the presence of an efficient VAM fungus and thus a net saving of P-fertilizers can be achieved. Keywords: Capsicum annuum L.; Glomus fasciculatum; Glomus macrocarpum; P-levels; P-sources; vesciular-arbuscular mycorrhizal fungus. Abbreviation: RP = rock phosphate; SP = super phosphate; VAM = vesicular-arbuscular mycorrhiza.
INTRODUCTION
The benefit of endotrophic vesicular-arbuscular mycorrhizal (VAM) fungi in the nutrition and development of host plants is well known. VAM fungi have been inoculated to different crop plants in an attempt to study the possibility of saving phosphate fertilizer and improving plants growth and yield Correspondence to: M.N. Sreenivasa, Divisions of Agricultural Microbiology and Black Cotton Soil Research, University of Agricultural Sciences, Dharwad 580005, India.
46
M.N. SREENIVASA ET AL.
(Sreeramulu and Bagyaraj, 1986). Many pot culture trials have proven that plants respond to inoculation with efficient VAM fungi (Jeffries, 1987), but lack of a readily available source of inoculation continues to hinder research on and the utilization of VAM fungi on a large scale. This is because VAM fungi are obligate symbionts (Sreenivasa, 1986 ). The best way to utilize VAM fungi for crop production may be to concentrate on crops like chilli which are normally grown in nursery beds. They could be easily inoculated with an efficient VAM fungus either at the time of seeding, or when transplanted. In an earlier study, we found a local isolate Glomus macrocarpum to be best in order to improve growth and nutrition of chilli (Sreenivasa, 1992 ). The present pot trial was carded out to study the effects of inoculation with the local isolate of G. macrocarpum in comparison with Glomusfasciculatum at different levels of two sources of phosphorus in chilli pepper (preceding a field evaluation). MATERIALS AND METHODS
Earthen pots of 8 I capacity were filled with 5 kg unsterile field soil. The soil used was a P-deficient black clayey soil with pH 7.0 (13 mg P kg -~ NH4F+ HCI extractable). The recommended dose of fertilizer N (150 kg ha- t ) and K (75 kg ha- ~) were given while two sources of phosphorus viz., soluble super phosphate ( S P - 16% P205 ) and insoluble Mussorie rock phosphate (RP= 18% P2Os) were applied at 0, 25, 50 and 100% of the recommended levels i.e. 0, 29.3, 58.5 and I 17 mg of SP and 0, 26, 52 and 104 mg of RP per pot respectively. The experiment was conducted in July-November, 1989. Pots were inoculated with G. macrocarpum or G. fasciculatum at 30 g per pot having an inoculum potential of 0.19 × 104 g-t. The inoculum was placed 2 cm below the soil surface as a thin uniform layer. Three 30-day-old chilli seedlings cultivar 'Byadagi' were transplanted per pot. Suitable control pots without mycorrhizal inoculation were maintained. There were four replication pots in each treatment and standard cultivation measures were followed. The crop was harvested 90 days after transplantation. Shoot dry weight, green chilli fruit weight, percent VAM root colonization, spore counts, number of infective propagules, and shoot P, Zn, Cu, Mn, and Fe concentrations were recorded following the procedures mentioned by Sreenivasa (1992). The data were analysed statistically following three factor completely randomized design with added control. RESULTS
Chilli plants responded well to the inoculation with both VAM fungi, but to a varying extent. VAM colonization and sporulation increased with in-
47
RESPONSE OF CHILLI TO THE INOCULATION OF FUNGUS
creasing P-levels up to 50% of the recommended dose of super phosphate and decreased thereafter (Table l ). Of the two forms used, SP encouraged higher colonization and sporulation, whereas RP gave hardly any effect. G. macro° carpum showed significantly more sporulation compared with G. fasciculaTABLE I Effects of inoculation of different mycorrhizal fungi and different forms and levels of P on percent root colonization, spore count and number of infective propagules in chilli Forms of P
Control
Super phosphate
Level of P (% of the recommended dose)
0
25
50
I00
Rock phosphate
25
50
100
ANOVA VAM fungi (A) P-forms (B) P-levels (C) Interactions A×B AXC BXC ABC Control
VAM fungi
Percent root colonization
GF GM NI GF GM NI GF GM NI GF GM NI GF GM NI GF GM NI GF GM NI
37 ¢ 42 c'd 18a 62 e'f 66 f 26 ~'b 87 g 89 s 31 b,c 53 d'e 58 e'f 35 b'c
38 c'd 44 c'd 18a 42 c'd 48 d 21 a,b 48 d 50 d'e 28 b
Spore count per 50 g soil
219 c 230 c,a 66 a 353 g 405 h 94 b 470 i 497 j l l 0b 232 c'd 243 d 91 b 231 c'd 250 d,~ 75 a,b 236 d 260 ~,f 90 b 280 f 284 f 101 b
No. of infective propagules per g of soil ( X 1000) 27 29 0.02 31 36 0.03 48 65 0.06 42 53 0.04 28 29 0.03 29 31 0.04 33 37 0.06
d.f. 2 l 2
F 570 551 68
** ** **
F 1237 363 98
** ** **
2 4 2 4 l
55 15 84 19 254
** ** ** ** **
74 23 205 37 370
** ** ** ** **
G E G. fasciculatum; GM, G. macrocarpum; NI, not inoculated. Different letters indicate significant differences according to LSD method at P= 0.05. Significance of ANOVA is indicated by**, NS refers to non-significance.
48
M.N. SREENIVASA ET AL.
tum, though there was no significant difference in percentage root colonization between them (Table 1 ). G. macrocarpum produced a higher number of infective propagules per gram of soil compared with G. fasciculatum when SP was used. The maximum was found at 50% of the recommended dose with both the fungi (Table 1 ). Inoculation with G. macrocarpum resulted in a significantly higher shoot dry biomass and fruit yield compared with G. fasciculatum (Table 2). SP TABLE 2 Effects of inoculation with different mycorrhizal fungi and different forms and levels of P on shoot dry biomass, fruit yield and shoot P concentration in chilli. Abbreviations as in Table 1 Forms of P
Control
Super phosphate
Level of P (% recommended dose ) 0
25
50
I00
Rock phosphate
25
50
100
ANOVA VAM fungi (A) P-forms (B) P-levels (C) Interactions A×B A XC BXC ABC Control
d.f. 2 l 2 2 4 2 4 l
VAM fungi
Shoot dry biomass (g per plant )
GF GM
12 b 13 b
40 b'c 44 c
0.04 b 0.05 b
NI GF GM
25 a 97 b
NI
5a 15 b'~ 16 b'c 7 a'b
0.02 a 0.18 h 0.19 h 0.12 d'e
GF
20 c'd
136 i
0.25 j
GM
25 d
157 j
0.22*
NI GF GM
12 b 20 c'd 24 d
69 f 13 ! i 14 °)
0.13 ~'r 0.2~ 0.28 k
NI
15 b'~
96 h
0.18 h
GF GM NI GF GM NI GF GM NI
12 b 14 b 6 "'b 13 b 14 b 9 a'b 13 b 14b 11 b
46 c'd 48 c'd 32 a'b 59 e 65 e'r 46 e'd 67 r* 74 g 54 d
0.08 c 0.09 c 0.04 b 0.12 a'e 0.14 r 0.08 c 0.16 g 0.18 b 0.11 d
F 103.2 195.2 29.4 2.81 6. i 10.8 3. l 5.91
Fruit yield (g per pot )
Shoot P concentration (%)
104 h
38 b'c
F
F
** ** **
507 1064 99
** ** **
256.5 I I 12.0 266.0
** ** **
NS ** ** ** **
222 Il 33 9 138
** ** ** ** **
19.0 9.5 0.6 9.5 513.0
** ** NS ** **
Different letters indicate significant differences according to the LSD method at P = 0.05. Significance at P=0.01 in ANOVA is indicated by *% NS refers to non significance.
RESPONSE OF CHILLI TO THE INOCULATION OF FUNGUS
49
TABLE 3 Effects o f inoculation with different m y c o n alzal fungi a n d different forms a n d levels o f P on concentrations o f Z n , Cu, M n a n d Fe in chilli shoots. A b b r e v i a t i o n s as in Table 1 Forms of P
Level o f P (% recommended dose)
Control
VAM fungi
Zn (ppm)
Cu (ppm)
GF GM
30 d 32 d
15 d 18 e
54 b'c 57 b'c
204 c 258 d
25
NI GF GM
12" 36 e 39 f
4a 18 e 21 f'g
77 a 399 f 436 f
50
NI GF GM
14 a'b 46 h 49 iJ
8 b'c 22 g 28 i
32 a 67 c'd 82 d 3 8 a'b
0
Super phosphate
100
Rock p h o s p h a t e
25
50
100
ANOVA VAM fungi ( A ) P-forms ( B ) P-levels ( C ) Interactions A× B A× C B XC ABC Control
d.f. 2 ! 2 2 4 2 4 l
F 1816 37 167 2.8 !4 0.93 0.41 538
NI
16 b
12 c'd
GF GM
48 h'i 5P
24 g 30 i
NI GF
20 ~ 32 d
14 d 19 e'f
GM NI GF GM
38 e'f 13 a 42 g 46 h
19e'f
NI
15 b
I0 c
GF GM NI
44 g 48 h 17 b
22 g 27 h'i 12 c'd
6 a'b 20 e'f'g
25 h
Mn (ppm)
137 g 159 h 42 b
Fe (ppm)
131 b 679 i 786 j 180 b'c
138 g 161 h
689 i 793J
44 b 64 ~
179 b'c 341 e
80 d
393 e
33 a 95 ~ 104 e'f
466 g 487 r"
38 a'b 97 e I 14 r 42 b
96 a'b
I 18 a'b 588 h 631 h 134 b
*** ** **
F 555 26 103
*** ** **
F 13081 2965 3640
** ** **
F 382335 63828 73876
** ** **
NS ** NS NS **
1.95 4.26 1.50 0.70 338
NS ** NS NS **
536 638 543 162 3567
** ** ** ** **
5697 i 0946 8741 1870 107192
** ** ** ** **
Different letters indicate significant differences according to the LSD m e t h o d at P = 0.05. Significance at P = 0.01 in ANOVA is indicated by **, NS refers to non-significance.
showed its superiority over RP in increasing both these characters. With the increasing levels of SP, an increase in shoot dry weight and fruit yield was achieved, but there was no significant difference between 50 and 100% of the recommended dose of SP added (Table 2 ). Remarkably, when RP was used, a significant VAM effect only occurred at the 0 or 25% dose and not at the higher rates. Shoot P concentration increased significantly with increasing levels of P irrespective ofthe form used° Phosphorus applied in a soluble form
~0
M.N. SREENIVASAET AL.
was significantly better mobilized by G. macrocarpum than by G. fasciculaturn. No significant interaction was observed between forms and levels of P added (Table 2). VAM inoculation always significantly increased the uptake of Zn, Cu, Mn and Fe, and G. macrocarpum was found more effective in this respect than G. fasciculatum (Table 3). These increases in the micronutrient uptake in the inoculated plants were significantly higher upto the 50% P dose beyond which they remained practically constant. The soluble form of P was better found associated with these increases in micro-nutrient uptake than the insoluble form. In respect of Zn and Cu uptake, interactions were found to be nonsignificant (Table 3), except fungal interaction with the levels of P added. DISCUSSION
In this study, we noticed that in general, chilli plants responded better to super phosphate than to rock phosphate. The cm=lparison between super phosphate and rock phosphate is complicated by the much lower availability of the latter form. The recommended dose was based on SP. When plants were inoculated with VAM fungi, percentage root colonization and sporulation were significantly higher compared with these characters produced by native endophytes in the non-inoculated objects (Table 1). Out of the two strains, G. macrocarpum produced a higher number infective units compared with G. fasciculatum (Table 1). The number of infective propagules was lower at the fall dose of P compared with the half dose when SP was used but not when RP was used. The high availability of P may have depressed VAM development (Bagyaraj and Powell, 1085). The mechanism for P inhibition of mycorrhizal formation may be associated with membrane mediated root ex. udation (Ratnayake et al., 1978; Graham et al., 1981 ). Shoot dry. biomass and fruit yield of plants inoculated with G. macrocarpure or G. fasciculatum increased significantly with the increase in the level of P added. However, these two characters did not differ significantly between 50% and 100% of the recommended dose of SP, suggesting that the application of phosphate fertilizer could be reduced through inoculation with efficient strains of mycorrhizal fungi (Table 2). In a field study conducted on red sandy loam soil with 'Jwala' the most popular chilli cultivar grown in that soil, Bagyaraj and Sreeramulu (1982) found increased plant growth and yield upon inoculation with GIomus albidum. However, similar studies conducted on black clayey soil revealed G. fasciculatum to be better for Chilli cultivar 'Byadagi' (Sreeramulu and Bagyaraj, 1986). G. fasciculatum caused higher fruit yield, shoot dry weight, shoot P and Zn content and percent root colonization at 50% of the recommended dose of SP added than at the dose recommended by Sreeramulu and Bagyaraj (1986). However, in our study, G. macrocarpum, a local isolate, performed better than G. fasciculatum, an im-
RESPONSE OF CHILLI TO THE INOCULATION OF FUNGUS
51
ported str~-!~:~lfrom Invermay, New Zealand. The maximum effect was obtained at 50% of the recommended dose of SP. It should be noted that the further increase in P level did not enhance growth or yield in this investigation at least when selected VAM fungi were inoculated. These results clearly indicate ~:hepotential savings in phosphate fertilizers with the use of an effective VAM fungus (Table 2). Haas et al. (1986) observed 41-188°/o increase in weight of bell pepper upon inoculation with G. macrocarpum. Also, in our study an increase in yield of 50% was recorded in VAM inoculated plants over uninoculated plants when SP was used (Table 2 ). VAM fungi increase the growth of many plant species by increasing the uptake and translocation of P, Zn, Cu, Mn etc. (Sreenivasa, 1992; Plenchette et al., 1981 ). In the present investigation increased uptake of P, Zn, Cu, Mn and Fe was also observed in the inoculated plants (Tables 2 and 3 ). Though P uptake increased with the increase in the level of P added, higher values of Zn, Cu, Mn and Fe were noticed at 50% of the recommended dose of SP added than at 100% of the recommended dose (Tables 2 and 3 ). This may be ascribed to higher colonization and sporulation of VAM at the former level of SP than at the latter level (Table l ). The overall impact of this improved development of VAM at 50% ofthe recommended P added, resulted in a better uptake ofmicronutrients which seem to be adequate for good plant growth at this P level, and may have also resulted in better uptake of water and production of higher amount ofgrowth promoting substances by VAM fungi. Chilli is one of the predominant crops of India grown in a large area especially in the Dharwad district. Our study clearly showed that the most effective VAM fungus improving growth and yield of chilli was G. macrocarpum, the local isolate which seems to be better adapted to this environment. It appears profitable to use a soluble form of P at 50% of the recommended dose whenever effective strains of VAM fungi are inoculated in chilli. It suggests that the application of phosphate fertilizers could be reduced through inoculation of such efficient strains of VAM fungi. Field trials are required to confirm this before practical application can be recommended. ACKNOWLEDGEMENTS
The authors wish to thank Dr. Venkatesha Murthy, Sri A.R.S. Bhat and Dr. M.R. Advani, Department of Statistics, University of Agricultural Sciences, Dharwad, for their kind assistance for Statistical analysis.
REFERENCES Bagyaraj, D.J. and Powell, C.L., 1985. Effect of vesicular arbuscular mycorrhizal inoculation and fertilizerapplication on the growth of marigold. N. Z. J. Agric. Res., 28: 169-I 73.
52
M.N. SREENiVASA ET AL.
Bagyaraj, D.J. and Sreeramulu, K.R., 1982. Preinoculation with VA mycorrhiza improves growth and yield of chilli transplanted in the field and saves phosphatic fertilizer. Plant Soil, 69: 375-381. Graham, J.H., Leonard, R.J. and Menge, J.A., 198 I. Membrane mediated decrease in root exudation responsible for phosphorus inhibition of Vesicular arbuscular mycorrhizal formation. Plant Physiol., 58: 548-552. Haas, J.H., Banal, A., Bar Yosef and Krikun, J., 1986. Nutrient availability effects of Vesicular arbuscular mycorrhizal bell pepper (Capsicum annuum) seedlings and transplants. Ann. Appl. Biol., 108: 171-179. Jeffries, P., 1987. Use of mycorrhizae in agriculture. CRC Critical Reviews in Biotechnology, 5:319-359. Plenchette, C., Furlan, V. and Fortin, J.A., 1981. Growth stimulation of apple trees in unsterilized soil under field conditions with VA mycorrhizal inoculation. Can. J. Bot., 59: 20032008. Ratnayake, M., Leonard, R.T. and Menge, J.A., 1978. Root exudation in relation to suppl~/of phosphorus and its possible relevance to mycorrhizal formation. New Phytol., 81: 543-552. Sreenivasa, M.N., 1986. Inoculum production of the vesicular arbuscular mycorrhizal fungus, Giomusfasciculatum. Ph.D. Thesis, University of Agricultural Sciences, Bangalore, 155 pp. Sreenivasa, M.N., 1991. Selection of an efficient Vesicular arbuscular mycorrhizal fungus for chilli (Capsicum annuum L. ). Scientia Hortic., 50: 53-58. Sreeramulu, K.R. and Bagyaraj, D.J., 1986. Field response of chilli to VA mycorrhiza on black clayey soil. Plant Soil, 93: 299-302.
45
Elsevier Science Publishers B.V., Amsterdam
Response of chilli (Capsicum a n n u u m L. ) to the inoculation of an efficient vesicular-arbuscular mycorrhizal fungus M.N. Sreenivasa, P.U. Krishnaraj, G.A. Gangadhara and H.M. Manjunathaiah Divisions of Agricultural Microbiology and Black Cotton Soil Research, University of Agricultural Sciences, Dharwad-580005, India (Accepted 28 May 1992)
ABSTRACT Sreenivasa, M.N., Krishnaraj, P.U., Gangadhara, G.A. and Manjunathaiah, H.M., 1993. Response of chilli (Capsicum annuum L. ) to the inoculation of an efficient vesicular-arbuscular mycorrhizal fungus. Scientia Hortic., 53: 45-52. The response of 30-day-old transplanted chilli to the inoculation of an efficient vesicular-arbuscular mycorrhizai (VAM) fungus Glomus macrocarpum was studied in comparison with Glomusfascicuiatum at different levels of phosphorus fertilization (0, 25, 50 and 100% of the recommended dose) incorporated in soluble (super phosphate) or insoluble (rock phosphate) forms in unsterile soil. Of these two VAM fungi, G. macrocarpum caused maximum increases in growth, yield and nutrient status of chilli, especially P, Zn, Cu, Mn, and Fe at 50% of the recommended dose added in the soluble form of P. The response of chilli to the inoculation of either VAM fungi in the presence of insoluble P was not encouraging when compared with the soluble form. The results suggest that P-fertilizers in their soluble form could be used more efficiently in the presence of an efficient VAM fungus and thus a net saving of P-fertilizers can be achieved. Keywords: Capsicum annuum L.; Glomus fasciculatum; Glomus macrocarpum; P-levels; P-sources; vesciular-arbuscular mycorrhizal fungus. Abbreviation: RP = rock phosphate; SP = super phosphate; VAM = vesicular-arbuscular mycorrhiza.
INTRODUCTION
The benefit of endotrophic vesicular-arbuscular mycorrhizal (VAM) fungi in the nutrition and development of host plants is well known. VAM fungi have been inoculated to different crop plants in an attempt to study the possibility of saving phosphate fertilizer and improving plants growth and yield Correspondence to: M.N. Sreenivasa, Divisions of Agricultural Microbiology and Black Cotton Soil Research, University of Agricultural Sciences, Dharwad 580005, India.
46
M.N. SREENIVASA ET AL.
(Sreeramulu and Bagyaraj, 1986). Many pot culture trials have proven that plants respond to inoculation with efficient VAM fungi (Jeffries, 1987), but lack of a readily available source of inoculation continues to hinder research on and the utilization of VAM fungi on a large scale. This is because VAM fungi are obligate symbionts (Sreenivasa, 1986 ). The best way to utilize VAM fungi for crop production may be to concentrate on crops like chilli which are normally grown in nursery beds. They could be easily inoculated with an efficient VAM fungus either at the time of seeding, or when transplanted. In an earlier study, we found a local isolate Glomus macrocarpum to be best in order to improve growth and nutrition of chilli (Sreenivasa, 1992 ). The present pot trial was carded out to study the effects of inoculation with the local isolate of G. macrocarpum in comparison with Glomusfasciculatum at different levels of two sources of phosphorus in chilli pepper (preceding a field evaluation). MATERIALS AND METHODS
Earthen pots of 8 I capacity were filled with 5 kg unsterile field soil. The soil used was a P-deficient black clayey soil with pH 7.0 (13 mg P kg -~ NH4F+ HCI extractable). The recommended dose of fertilizer N (150 kg ha- t ) and K (75 kg ha- ~) were given while two sources of phosphorus viz., soluble super phosphate ( S P - 16% P205 ) and insoluble Mussorie rock phosphate (RP= 18% P2Os) were applied at 0, 25, 50 and 100% of the recommended levels i.e. 0, 29.3, 58.5 and I 17 mg of SP and 0, 26, 52 and 104 mg of RP per pot respectively. The experiment was conducted in July-November, 1989. Pots were inoculated with G. macrocarpum or G. fasciculatum at 30 g per pot having an inoculum potential of 0.19 × 104 g-t. The inoculum was placed 2 cm below the soil surface as a thin uniform layer. Three 30-day-old chilli seedlings cultivar 'Byadagi' were transplanted per pot. Suitable control pots without mycorrhizal inoculation were maintained. There were four replication pots in each treatment and standard cultivation measures were followed. The crop was harvested 90 days after transplantation. Shoot dry weight, green chilli fruit weight, percent VAM root colonization, spore counts, number of infective propagules, and shoot P, Zn, Cu, Mn, and Fe concentrations were recorded following the procedures mentioned by Sreenivasa (1992). The data were analysed statistically following three factor completely randomized design with added control. RESULTS
Chilli plants responded well to the inoculation with both VAM fungi, but to a varying extent. VAM colonization and sporulation increased with in-
47
RESPONSE OF CHILLI TO THE INOCULATION OF FUNGUS
creasing P-levels up to 50% of the recommended dose of super phosphate and decreased thereafter (Table l ). Of the two forms used, SP encouraged higher colonization and sporulation, whereas RP gave hardly any effect. G. macro° carpum showed significantly more sporulation compared with G. fasciculaTABLE I Effects of inoculation of different mycorrhizal fungi and different forms and levels of P on percent root colonization, spore count and number of infective propagules in chilli Forms of P
Control
Super phosphate
Level of P (% of the recommended dose)
0
25
50
I00
Rock phosphate
25
50
100
ANOVA VAM fungi (A) P-forms (B) P-levels (C) Interactions A×B AXC BXC ABC Control
VAM fungi
Percent root colonization
GF GM NI GF GM NI GF GM NI GF GM NI GF GM NI GF GM NI GF GM NI
37 ¢ 42 c'd 18a 62 e'f 66 f 26 ~'b 87 g 89 s 31 b,c 53 d'e 58 e'f 35 b'c
38 c'd 44 c'd 18a 42 c'd 48 d 21 a,b 48 d 50 d'e 28 b
Spore count per 50 g soil
219 c 230 c,a 66 a 353 g 405 h 94 b 470 i 497 j l l 0b 232 c'd 243 d 91 b 231 c'd 250 d,~ 75 a,b 236 d 260 ~,f 90 b 280 f 284 f 101 b
No. of infective propagules per g of soil ( X 1000) 27 29 0.02 31 36 0.03 48 65 0.06 42 53 0.04 28 29 0.03 29 31 0.04 33 37 0.06
d.f. 2 l 2
F 570 551 68
** ** **
F 1237 363 98
** ** **
2 4 2 4 l
55 15 84 19 254
** ** ** ** **
74 23 205 37 370
** ** ** ** **
G E G. fasciculatum; GM, G. macrocarpum; NI, not inoculated. Different letters indicate significant differences according to LSD method at P= 0.05. Significance of ANOVA is indicated by**, NS refers to non-significance.
48
M.N. SREENIVASA ET AL.
tum, though there was no significant difference in percentage root colonization between them (Table 1 ). G. macrocarpum produced a higher number of infective propagules per gram of soil compared with G. fasciculatum when SP was used. The maximum was found at 50% of the recommended dose with both the fungi (Table 1 ). Inoculation with G. macrocarpum resulted in a significantly higher shoot dry biomass and fruit yield compared with G. fasciculatum (Table 2). SP TABLE 2 Effects of inoculation with different mycorrhizal fungi and different forms and levels of P on shoot dry biomass, fruit yield and shoot P concentration in chilli. Abbreviations as in Table 1 Forms of P
Control
Super phosphate
Level of P (% recommended dose ) 0
25
50
I00
Rock phosphate
25
50
100
ANOVA VAM fungi (A) P-forms (B) P-levels (C) Interactions A×B A XC BXC ABC Control
d.f. 2 l 2 2 4 2 4 l
VAM fungi
Shoot dry biomass (g per plant )
GF GM
12 b 13 b
40 b'c 44 c
0.04 b 0.05 b
NI GF GM
25 a 97 b
NI
5a 15 b'~ 16 b'c 7 a'b
0.02 a 0.18 h 0.19 h 0.12 d'e
GF
20 c'd
136 i
0.25 j
GM
25 d
157 j
0.22*
NI GF GM
12 b 20 c'd 24 d
69 f 13 ! i 14 °)
0.13 ~'r 0.2~ 0.28 k
NI
15 b'~
96 h
0.18 h
GF GM NI GF GM NI GF GM NI
12 b 14 b 6 "'b 13 b 14 b 9 a'b 13 b 14b 11 b
46 c'd 48 c'd 32 a'b 59 e 65 e'r 46 e'd 67 r* 74 g 54 d
0.08 c 0.09 c 0.04 b 0.12 a'e 0.14 r 0.08 c 0.16 g 0.18 b 0.11 d
F 103.2 195.2 29.4 2.81 6. i 10.8 3. l 5.91
Fruit yield (g per pot )
Shoot P concentration (%)
104 h
38 b'c
F
F
** ** **
507 1064 99
** ** **
256.5 I I 12.0 266.0
** ** **
NS ** ** ** **
222 Il 33 9 138
** ** ** ** **
19.0 9.5 0.6 9.5 513.0
** ** NS ** **
Different letters indicate significant differences according to the LSD method at P = 0.05. Significance at P=0.01 in ANOVA is indicated by *% NS refers to non significance.
RESPONSE OF CHILLI TO THE INOCULATION OF FUNGUS
49
TABLE 3 Effects o f inoculation with different m y c o n alzal fungi a n d different forms a n d levels o f P on concentrations o f Z n , Cu, M n a n d Fe in chilli shoots. A b b r e v i a t i o n s as in Table 1 Forms of P
Level o f P (% recommended dose)
Control
VAM fungi
Zn (ppm)
Cu (ppm)
GF GM
30 d 32 d
15 d 18 e
54 b'c 57 b'c
204 c 258 d
25
NI GF GM
12" 36 e 39 f
4a 18 e 21 f'g
77 a 399 f 436 f
50
NI GF GM
14 a'b 46 h 49 iJ
8 b'c 22 g 28 i
32 a 67 c'd 82 d 3 8 a'b
0
Super phosphate
100
Rock p h o s p h a t e
25
50
100
ANOVA VAM fungi ( A ) P-forms ( B ) P-levels ( C ) Interactions A× B A× C B XC ABC Control
d.f. 2 ! 2 2 4 2 4 l
F 1816 37 167 2.8 !4 0.93 0.41 538
NI
16 b
12 c'd
GF GM
48 h'i 5P
24 g 30 i
NI GF
20 ~ 32 d
14 d 19 e'f
GM NI GF GM
38 e'f 13 a 42 g 46 h
19e'f
NI
15 b
I0 c
GF GM NI
44 g 48 h 17 b
22 g 27 h'i 12 c'd
6 a'b 20 e'f'g
25 h
Mn (ppm)
137 g 159 h 42 b
Fe (ppm)
131 b 679 i 786 j 180 b'c
138 g 161 h
689 i 793J
44 b 64 ~
179 b'c 341 e
80 d
393 e
33 a 95 ~ 104 e'f
466 g 487 r"
38 a'b 97 e I 14 r 42 b
96 a'b
I 18 a'b 588 h 631 h 134 b
*** ** **
F 555 26 103
*** ** **
F 13081 2965 3640
** ** **
F 382335 63828 73876
** ** **
NS ** NS NS **
1.95 4.26 1.50 0.70 338
NS ** NS NS **
536 638 543 162 3567
** ** ** ** **
5697 i 0946 8741 1870 107192
** ** ** ** **
Different letters indicate significant differences according to the LSD m e t h o d at P = 0.05. Significance at P = 0.01 in ANOVA is indicated by **, NS refers to non-significance.
showed its superiority over RP in increasing both these characters. With the increasing levels of SP, an increase in shoot dry weight and fruit yield was achieved, but there was no significant difference between 50 and 100% of the recommended dose of SP added (Table 2 ). Remarkably, when RP was used, a significant VAM effect only occurred at the 0 or 25% dose and not at the higher rates. Shoot P concentration increased significantly with increasing levels of P irrespective ofthe form used° Phosphorus applied in a soluble form
~0
M.N. SREENIVASAET AL.
was significantly better mobilized by G. macrocarpum than by G. fasciculaturn. No significant interaction was observed between forms and levels of P added (Table 2). VAM inoculation always significantly increased the uptake of Zn, Cu, Mn and Fe, and G. macrocarpum was found more effective in this respect than G. fasciculatum (Table 3). These increases in the micronutrient uptake in the inoculated plants were significantly higher upto the 50% P dose beyond which they remained practically constant. The soluble form of P was better found associated with these increases in micro-nutrient uptake than the insoluble form. In respect of Zn and Cu uptake, interactions were found to be nonsignificant (Table 3), except fungal interaction with the levels of P added. DISCUSSION
In this study, we noticed that in general, chilli plants responded better to super phosphate than to rock phosphate. The cm=lparison between super phosphate and rock phosphate is complicated by the much lower availability of the latter form. The recommended dose was based on SP. When plants were inoculated with VAM fungi, percentage root colonization and sporulation were significantly higher compared with these characters produced by native endophytes in the non-inoculated objects (Table 1). Out of the two strains, G. macrocarpum produced a higher number infective units compared with G. fasciculatum (Table 1). The number of infective propagules was lower at the fall dose of P compared with the half dose when SP was used but not when RP was used. The high availability of P may have depressed VAM development (Bagyaraj and Powell, 1085). The mechanism for P inhibition of mycorrhizal formation may be associated with membrane mediated root ex. udation (Ratnayake et al., 1978; Graham et al., 1981 ). Shoot dry. biomass and fruit yield of plants inoculated with G. macrocarpure or G. fasciculatum increased significantly with the increase in the level of P added. However, these two characters did not differ significantly between 50% and 100% of the recommended dose of SP, suggesting that the application of phosphate fertilizer could be reduced through inoculation with efficient strains of mycorrhizal fungi (Table 2). In a field study conducted on red sandy loam soil with 'Jwala' the most popular chilli cultivar grown in that soil, Bagyaraj and Sreeramulu (1982) found increased plant growth and yield upon inoculation with GIomus albidum. However, similar studies conducted on black clayey soil revealed G. fasciculatum to be better for Chilli cultivar 'Byadagi' (Sreeramulu and Bagyaraj, 1986). G. fasciculatum caused higher fruit yield, shoot dry weight, shoot P and Zn content and percent root colonization at 50% of the recommended dose of SP added than at the dose recommended by Sreeramulu and Bagyaraj (1986). However, in our study, G. macrocarpum, a local isolate, performed better than G. fasciculatum, an im-
RESPONSE OF CHILLI TO THE INOCULATION OF FUNGUS
51
ported str~-!~:~lfrom Invermay, New Zealand. The maximum effect was obtained at 50% of the recommended dose of SP. It should be noted that the further increase in P level did not enhance growth or yield in this investigation at least when selected VAM fungi were inoculated. These results clearly indicate ~:hepotential savings in phosphate fertilizers with the use of an effective VAM fungus (Table 2). Haas et al. (1986) observed 41-188°/o increase in weight of bell pepper upon inoculation with G. macrocarpum. Also, in our study an increase in yield of 50% was recorded in VAM inoculated plants over uninoculated plants when SP was used (Table 2 ). VAM fungi increase the growth of many plant species by increasing the uptake and translocation of P, Zn, Cu, Mn etc. (Sreenivasa, 1992; Plenchette et al., 1981 ). In the present investigation increased uptake of P, Zn, Cu, Mn and Fe was also observed in the inoculated plants (Tables 2 and 3 ). Though P uptake increased with the increase in the level of P added, higher values of Zn, Cu, Mn and Fe were noticed at 50% of the recommended dose of SP added than at 100% of the recommended dose (Tables 2 and 3 ). This may be ascribed to higher colonization and sporulation of VAM at the former level of SP than at the latter level (Table l ). The overall impact of this improved development of VAM at 50% ofthe recommended P added, resulted in a better uptake ofmicronutrients which seem to be adequate for good plant growth at this P level, and may have also resulted in better uptake of water and production of higher amount ofgrowth promoting substances by VAM fungi. Chilli is one of the predominant crops of India grown in a large area especially in the Dharwad district. Our study clearly showed that the most effective VAM fungus improving growth and yield of chilli was G. macrocarpum, the local isolate which seems to be better adapted to this environment. It appears profitable to use a soluble form of P at 50% of the recommended dose whenever effective strains of VAM fungi are inoculated in chilli. It suggests that the application of phosphate fertilizers could be reduced through inoculation of such efficient strains of VAM fungi. Field trials are required to confirm this before practical application can be recommended. ACKNOWLEDGEMENTS
The authors wish to thank Dr. Venkatesha Murthy, Sri A.R.S. Bhat and Dr. M.R. Advani, Department of Statistics, University of Agricultural Sciences, Dharwad, for their kind assistance for Statistical analysis.
REFERENCES Bagyaraj, D.J. and Powell, C.L., 1985. Effect of vesicular arbuscular mycorrhizal inoculation and fertilizerapplication on the growth of marigold. N. Z. J. Agric. Res., 28: 169-I 73.
52
M.N. SREENiVASA ET AL.
Bagyaraj, D.J. and Sreeramulu, K.R., 1982. Preinoculation with VA mycorrhiza improves growth and yield of chilli transplanted in the field and saves phosphatic fertilizer. Plant Soil, 69: 375-381. Graham, J.H., Leonard, R.J. and Menge, J.A., 198 I. Membrane mediated decrease in root exudation responsible for phosphorus inhibition of Vesicular arbuscular mycorrhizal formation. Plant Physiol., 58: 548-552. Haas, J.H., Banal, A., Bar Yosef and Krikun, J., 1986. Nutrient availability effects of Vesicular arbuscular mycorrhizal bell pepper (Capsicum annuum) seedlings and transplants. Ann. Appl. Biol., 108: 171-179. Jeffries, P., 1987. Use of mycorrhizae in agriculture. CRC Critical Reviews in Biotechnology, 5:319-359. Plenchette, C., Furlan, V. and Fortin, J.A., 1981. Growth stimulation of apple trees in unsterilized soil under field conditions with VA mycorrhizal inoculation. Can. J. Bot., 59: 20032008. Ratnayake, M., Leonard, R.T. and Menge, J.A., 1978. Root exudation in relation to suppl~/of phosphorus and its possible relevance to mycorrhizal formation. New Phytol., 81: 543-552. Sreenivasa, M.N., 1986. Inoculum production of the vesicular arbuscular mycorrhizal fungus, Giomusfasciculatum. Ph.D. Thesis, University of Agricultural Sciences, Bangalore, 155 pp. Sreenivasa, M.N., 1991. Selection of an efficient Vesicular arbuscular mycorrhizal fungus for chilli (Capsicum annuum L. ). Scientia Hortic., 50: 53-58. Sreeramulu, K.R. and Bagyaraj, D.J., 1986. Field response of chilli to VA mycorrhiza on black clayey soil. Plant Soil, 93: 299-302.