Effect of Verticillium wilt (Verticillium dahliae Kleb.) and mycorrhiza (Glomus mosseae) on root colonization, growth and nutrient uptake in tomato and eggplant seedlings

Scientia Horticulturae 94 (2002) 145±156

Effect of Verticillium wilt (Verticillium dahliae Kleb.) and mycorrhiza (Glomus mosseae) on root colonization, growth and nutrient uptake in tomato and eggplant seedlings Nikitas Karagiannidisa,1, Fotios Bletsosb,*, Nikolaos Stavropoulosb a

National Agricultural Research Foundation (NAGREF), Soil Science Institute of Thesalloniki, P.O. Box 435, 57001 Thermi-Thessaloniki, Greece b National Agricultural Research Foundation (NAGREF), Agricultural Research Centre of Macedonia and Thrace, P.O. Box 312, 57001 Thermi-Thessaloniki, Greece Accepted 3 July 2001

Abstract The effect of the arbuscular mycorrhizal fungus (AMF) Glomus mosseae and the soil-borne Verticillium dahliae and their interaction on root colonization, plant growth and nutrient uptake were studied in eggplant and tomato seedlings grown in pots. It was found that: (a) root colonization by the AMF as well as spore formation was higher (34.6 and 30.5%, respectively) in the eggplant than in tomato. Also it was twice as high in the mycorrhiza treatment than in the treatment with the double inoculation …mycorrhiza ‡ Verticillium†; (b) the mycorrhiza treatment increased fresh and dry weight and mean plant height in tomato by 96, 114 and 21% compared to controls. The respective values in eggplant were 114, 104 and 30%; (c) infection by Verticillium reduced fresh weight by 28%, dry weight by 35% and plant height by 14% in tomato. The respective reductions in eggplant were 27, 37 and 12%; (d) the treatment combining both V: dahliae ‡ G: mosseae increased fresh weight by 33%, dry weight by 24% and mean plant height by 21% in tomato. The respective increases in eggplant were 32, 10 and 16%. This leads to the conclusion that the bene®cial effect of the AMF supersedes the pathogenic effect of V. dahliae; (e) P and N uptake were higher in mycorrhizal treatments than in controls, although no difference in K, Ca, Mg and B uptake was observed between treatments; (f) mycorrhizal treatments had lower concentrations of micronutrients Zn, Mn, Fe and Cu in shoots and leaves than controls. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Arbuscular mycorrhiza; Verticillium dahliae; Glomus mosseae; Nutrient uptake; Tomato; Eggplant; Biological control * Corresponding author. Tel.: ‡30-31-471544; fax: ‡30-31-471209. E-mail address: [email protected] (F. Bletsos). 1 Fax: ‡30-31-471280.

0304-4238/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 4 2 3 8 ( 0 1 ) 0 0 3 3 6 - 3

146

N. Karagiannidis et al. / Scientia Horticulturae 94 (2002) 145±156

1. Introduction Under natural conditions, nearly 90% of all plant species are estimated to form arbuscular mycorrhizae fungi (AMF) (Mosse et al., 1981; Smith and Read, 1997). The importance of this type of symbiotic fungal infection for plant nutrition and health (Smith and Gianinazzi-Pearson, 1988), makes it a useful biological resource for increasing plant production with minimal agrochemicals inputs. AMF are currently studied as biological control agents against soil-borne diseases (Hooker et al., 1994). Their effects in plant±pathogen interactions range from disease reduction (Rosendahl and Rosendahl, 1990; Smith et al., 1990; Liu, 1995) to a neutral action (Baath and Hayman, 1983, 1984; Reddy et al., 1989). However, in cotton plants, interaction of Verticillium with arbuscular fungus Glomus fasciculatum has been reported to increase disease severity (Davis et al., 1979). These contradictory results may be attributed either to various environmental factors interfering with the evaluation of disease severity or to differences in experimental procedures and designs (Linderman, 1994). The pathogenic fungus Verticillium dahliae, causes yellow-bronze leaf spots, vascular discoloration, yield losses, reduction of growth, fruit quality and plant death in tomato and eggplants (Cirulli et al., 1990; Bletsos et al., 1997a, 1999). Continuous cultivation of sensitive plants in the same ®elds increases soil-borne inoculum of this pathogen (O'Brien, 1983). Chemical control of Verticillium is expensive and dif®cult to apply (Sakata et al., 1989), while the use of chemical growth retardants of Verticillium (Pix and Cycocel) did not produce satisfactory results in cotton (Tjamos et al., 1981). Other control methods, such as several rotation systems (Cirulli et al., 1990), are not practically applicable because land allocated to vegetable production is intensively cultivated. Finally, grafting of eggplant on Solanum torvum is used as an agricultural practice in Japan and Greece (Sakata et al., 1989; Bletsos, 1998). While tomato and eggplant are species sensitive to various fungal diseases (Cordier et al., 1996; Trotta et al., 1996; Bletsos et al., 1997b), the current methods of disease control are not particularly effective or economical. The present experimental work aimed at studying the response of two crop species of the Solanaceae family to the double inoculation of their roots with the pathogenic fungus V. dahliae Kleb., and the symbiotic fungus Glomus mosseae, and at monitoring root colonization, rate of plant height increase and concentrations of macro- and microelements, under greenhouse conditions and Mediterranean climate. 2. Materials and methods Experiments were carried out in an unheated plastic greenhouse on the campus of the Hellenic Agricultural School in 1997 and 1998. They began in early May and lasted for 7 weeks. Plants were grown in pots of 2 kg capacity, ®lled with soil collected from a 0 to 10 cm depth from a ®eld at the Soil Science Institute of Thessaloniki. Soil poor in available P was deliberately chosen and sterilized at 120 8C for 20 min to eliminate any microorganisms that could affect the function of the arbuscular mycorrhiza or the pathogenic fungus. Table 1 shows the physicochemical properties of the soil used. Determination of

N. Karagiannidis et al. / Scientia Horticulturae 94 (2002) 145±156

147

Table 1 Physicochemical characteristics of the soil used in the experiments Mechanical analysis

Sandy loam (SL)

Sand (%) Clay (%) Loam (%) pH (1:1 in H2O) CaCO3 (%) EC (mO/cm) Organic matter (%) Available P (mg kg 1 soil, Olsen) Exchangeable K (mg kg 1 soil, am. ac.) B (mg kg 1 soil) Zn (mg kg 1 soil) Mn (mg kg 1 soil) Fe (mg kg 1 soil) Cu (mg kg 1 soil)

60 15 25 7.60 3.6 0.72 1.80 7.0 330 0.86 1.13 27.8 31.7 1.96

the minerals P, K, B, Zn, Mn, Fe and Cu was based on the methods of Olsen et al. (1954) and Jackson (1960). Mineral nutrients were mixed with the soil at rates corresponding to 200 kg N ha 1 (NH4NO3), 80 kg K ha 1 (K2SO4), 10 kg Mg ha 1 (MgCl2
6H2O) and 90 kg P ha 1 (Ca2(PO4)3OH). Hydroxyapatite, a not readily soluble P form, was used as a phosphorus nutrition source, since it is known that arbuscular mycorrhizal fungi (AMF) have the ability to dissolve insoluble P substrate, subsequently making it accessible to plants (Diederichs, 1991). For the infection of pots with Verticillium, an inoculum of the fungus V. dahliae was grown over 30 days in 1 L glass jars containing 200 g growth substrate consisting of corn meal:perlite:water in a ratio of 1:1:4 (w/w/w) (Bletsos et al., 1997b). The content of each jar was poured in each pot (16 cm diameter, 2 kg capacity) and mixed with its soil. Uniform, 30 day-old plants, of `Early pack' tomato (Lycopersicum esculentum Mill.) and of `Tsakoniki' eggplant (Solanum melongena L.) were inoculated with the AMF G. mosseae. The mycorrhizal inoculum was obtained from the collection of Goettingen University and maintained at the greenhouse of the Soil Science Institute of Thessaloniki as pure cultures on maize host plants. The inoculum consisted of spores, chlamydospores, hyphae and heavily colonized corn roots cut into small pieces, blended with sterile distilled water in order to form a dense liquid paste (25 g corn roots ‡ 100 ml water). The roots of the experimental plants were dipped in this paste immediately before transplanting into the experimental pots (Karagiannidis, 1980). Three plantlets were transplanted in each pot. Plants were regularly irrigated every other day. After 7 weeks, plant height was measured and the aerial plant part was cut at the level of cotyledons and fresh weight recorded. Thereafter aerial parts were washed to remove dust and dried at 72 8C until constant weight was achieved; dry weight was recorded and the material was ®nely ground and stored in plastic bags. Analyses performed using 1 g of dry matter, ashed at 540 8C, dissolved in 6 N HCl and diluted with distilled water: N was determined by the Kjeldahl procedure,

148

N. Karagiannidis et al. / Scientia Horticulturae 94 (2002) 145±156

Fig. 1. Height (cm), fresh and dry shoot weight (g) of tomato and eggplant seedlings 7 weeks after transplantation. Values followed by different letters are significantly different at 5% level (V: Verticillium wilt plants; M: mycorrhizal plants; O: control plants).

N. Karagiannidis et al. / Scientia Horticulturae 94 (2002) 145±156

149

P spectrometrically, K photometrically, Ca and Mg volumetrically with 0.01 EDTA, B by the curcumin method, and Zn, Mn, Fe and Cu by atomic absorption spectrophotometry (Jackson, 1960; Cottenie, 1980). Soil samples were taken from each pot at the end of the experiment and maintained in closed plastic bags at 4 8C until processing, not later than 15 days after being collected. The samples were carefully homogenized and the AMF spores were isolated from 100 g soil by a wet sieving and decanting technique followed by sucrose centrifugation (Gerdemann and Nicolson, 1963; Sieverding, 1991). The isolated spores that appeared healthy were counted using a dissecting microscope (60) from each pot, and ®ne roots (<1 mm diameter) were collected and stained in trypan blue according to the method of Phillips and Hayman (1970). Percentage infection was assessed by the gridline method of Giovannetti and Mosse (1980). A minimum of 100 intercepts were scored for each sample. The experimental design used was that of complete randomized blocks with four treatments (inoculation with Verticillium, with mycorrhizal fungi, with mycorrhizal fungi ‡ Verticillium, and controls) with four replications and three plants per replication. The overall number of plants in the experiment was 384 (192 plants for each species). The results of the 2 years were analyzed jointly after con®rming the homogeneity of their variance using Bartlett's test. Comparison of the means for the recorded characteristics was based on Duncan's multiple range test at 5% level of signi®cance. 3. Results Inoculation with the AMF signi®cantly increased …p < 0:05† net and dry shoot weight in both species, compared to the control plants (Fig. 1, Table 2). This fungus also had a bene®cial effect on plant height in both species (Fig. 1): the ratio M/O (M: mycorrhizal plants, O: control plants) for plant height was 1.2 in tomato and 1.3 in eggplant. Contrary to this, inoculation with Verticillium reduced fresh and dry weight and plant height in both the species, as is apparent from the ratio V/O (V: Verticillium inoculated plants) which for these three characteristics was 0.72, 0.70 and 0.87, respectively, in tomato and 0.73, 0.64 and 0.88, respectively, in eggplant (Table 2). The combination of these two fungi Table 2 The V/O, M/O, M ‡ V=O and M/V ratios of shoot fresh weight (FW), shoot dry weight (DW) and plant height of tomato and eggplant seedlings (V: Verticillium wilt plants; M: mycorrhizal plants; O: control plants)a Tomato FW V/O M/O M ‡ V=O M/V

0.72 1.96 1.33 2.80

Eggplant DW

d b c a

0.70 2.14 1.24 3.26

c b c a

Height

FW

0.87 1.21 1.21 1.40

0.73 2.14 1.32 2.95

c b b a

DW c b c a

0.64 2.04 1.11 3.22

Height c b c a

0.88 1.30 1.16 1.48

c ab b a

a Numbers in the same column followed by the same letter (a, b, c, d) are not significantly different at the 5% level of significance.

150

N. Karagiannidis et al. / Scientia Horticulturae 94 (2002) 145±156

Fig. 2. Macronutrient leaf P, N, K, Ca, Mg content (%) of tomato and eggplant seedlings 7 weeks after transplantation. Values followed by different letters are significantly different at 5% level (V: Verticillium wilt plants; M: mycorrhizal plants; O: control plants).

N. Karagiannidis et al. / Scientia Horticulturae 94 (2002) 145±156

151

(symbiotic and pathogenic) had a positive effect on shoot growth in both the species. Plants in this treatment were weaker compared to the M inoculated plants (though in tomato they had equal height), but much stronger compared to the Verticillium inoculated plants and to the control plants as regards their height and fresh weight (Fig. 1). From Table 2, it can be seen that the ratio M ‡ V=O ranges between 1.2 and 1.3, while the ratio M/V was circa 3.0 for fresh weight, 3.2 for dry weight and about 1.5 for plant height. Examination of the concentrations of the main nutrient elements in the plant tissue of both the species (Fig. 2) reveals that inoculation with the mycorrhizal and the pathogenic fungi and their combination increased P and N concentration in the tissues of both the species, compared with the controls. In eggplant, Verticillium inoculated plants had lower K concentration in comparison with both M inoculated plants and the controls. K concentration in tomato and Ca and Mg concentration in both the species did not differ signi®cantly. The highest V/O, M/O, M ‡ V=O, M/V ratios were found for the nutrient element P and the lowest for Mg in tomato (Table 3). The concentration of the microelements Zn, Mn, Fe and Cu was lower in the M and M ‡ V treatments compared to the V treatment and the controls (Fig. 3). Table 3 shows that the M/O, M ‡ V=O, M/V ratios fall in most cases between 0.6 and 0.7. No differences were observed between treatments regarding uptake of the microelement B (Fig. 3). Root colonization percentage by AMF (Table 4) was generally higher in eggplant than in tomato. Eggplants were 66% colonized in the M treatment and 33% colonized in the M ‡ V treatment. The respective colonization percentages in tomato were 49 and 26%. Similarly the number of spores of the AMF per 100 g soil was higher in eggplant than in tomato (Table 4), being in direct relation to the corresponding root colonization percentages (r ˆ 0:627 in tomato and r ˆ 0:919 in eggplant). Plants of the double inoculation treatment showed no external symptoms and appeared completely healthy, in contrast to plants inoculated only with Verticillium. Table 3 The V/O, M/O, M ‡ V=O and M/V ratios of mineral content in shoots of tomato and eggplant seedlings (V: Verticillium wilt plants; M: mycorrhizal plants; O: control plants)a N (%)

P (%)

K (%)

Ca (%)

Mg (%) B (%)

Zn (ppm)

Mn (ppm)

Cu (ppm)

Fe (ppm)

Tomato V/O M/O M ‡ V=O M/V

1.27 1.36 1.39 1.07

ab a a b

1.08 1.42 1.50 1.31

a a a a

1.05 1.08 1.08 1.03

a a a a

0.96 0.96 1.03 1.00

a a a a

0.97 0.78 0.82 0.81

a b b b

0.79 0.80 0.86 1.01

a a a a

1.05 0.69 0.72 0.66

a b b b

1.09 0.62 0.59 0.57

a b b b

1.06 0.62 0.64 0.58

a b b b

0.96 0.66 0.71 0.69

a b b b

Eggplant V/O M/O M ‡ V=O M/V

1.08 1.05 1.28 0.97

ab ab a b

1.27 1.36 1.64 1.07

ab ab a b

0.89 1.10 1.05 1.24

c ab bc a

1.00 1.10 1.10 1.11

a a a a

0.96 1.08 1.14 1.12

a a a a

1.25 1.39 0.98 1.39

a a a a

1.07 0.59 0.66 0.55

a bc b c

0.88 0.51 0.58 0.58

a b b b

1.01 0.61 0.57 0.60

a b b b

1.15 0.67 0.72 0.58

a b b b

a Numbers in the same column followed by the same letter (a, b, c) are not significantly different at the 5% level of significance.

152

N. Karagiannidis et al. / Scientia Horticulturae 94 (2002) 145±156

Fig. 3. Micronutrient leaf Zn, Mn, Cu, Fe, B content (mg kg 1) of tomato and eggplant seedlings 7 weeks after transplantation. Values followed by different letters are significantly different at 5% level (V: Verticillium wilt plants; M: mycorrhizal plants; O: control plants).

N. Karagiannidis et al. / Scientia Horticulturae 94 (2002) 145±156

153

Table 4 Mycorrhizal colonization (%) in roots and number of spores per 100 g soil of mycorrhizal tomato and eggplant seedlings (V: Verticillium wilt plants; M: mycorrhizal plants; O: control plants)a

O V M M‡V a

Tomato (% infection)

Eggplant (% infection)

Tomato (spores/100 g)

Eggplant (spores/100 g)

0 0 49 ab 26.8 c

0 0 66 a 33 bc

0 0 157.5 b 59.5 d

0 0 205.5 a 99.5 c

Numbers followed by the same letter (a, b, c) are not significantly different at the 5% level of significance.

4. Discussion Interactions of the AMF with pathogenic or non-pathogenic soil fungi have been reported by various authors, e.g. the saprophytic fungi Trichoderma koniigii and Fusarium solani (McAllister et al., 1994), with the phosphate producing fungus Aspergillus fumigantus (Tarafdar and Marschner, 1995), with the pathogenic fungi Phytophthora fragariae (Mark and Cassells, 1996; Norman et al., 1996) and Phytophthora nicotianae (Cordier et al., 1996; Trotta et al., 1996) with the wilt pathogen Fusarium oxysporum and the shoot pathogen Oidium lini (Dugassa et al., 1996), with the conclusion that AMF increases tolerance to the disease. Inoculation of tomato and eggplant seedlings with the AMF G. mosseae signi®cantly increased their height and their fresh and dry weight. The combination of the AM and the pathogenic fungus on the other hand signi®cantly reduced height and fresh and dry shoot weight in eggplant and tomato (except plant height) in comparison to the M plants, but signi®cantly increased plant height and fresh weight in both the species when compared with the controls. Substantially lower values for these three characteristics were recorded for both the species in Verticillium inoculated plants when compared with the controls. The bene®cial effect of the mycorrhiza over the detrimental effect of Verticillium can be explained by the enhanced resistance acquired by plants following the double inoculation treatment, which is almost exclusively attributed to the endomycorrhiza. According to Morandi (1996), this resistance is due to the fact that mycorrhizal fungi cause an accumulation of phenolics, in particular phytoalexins and associated ¯avonoids and iso¯avonoids, in the roots of their host plants. Similar results on the growth of wild strawberries have been reported by Mark and Cassells (1996), where it was observed that the bene®cial effect of the endomycorrhizal fungus Glomus ®stulosum prevailed over the pathogenic deterioration by the fungus P. fragariae. Trotta et al. (1996) working with wild strawberry and tomato plants found that the effect of the endomycorrhiza offset the negative effect of the pathogenic fungi P. fragariae and P. nicotinae, respectively. In tomato, uptake of N was signi®cantly and positively affected by the mycorrhiza treatments (M and M ‡ V), Mg was signi®cantly and negatively affected, while no signi®cant effect was recorded for K and Ca uptake. In the Verticillium treatment, the concentration of the above elements in the shoot remained similar to that of control plants (Ca, Mg, K), but increased signi®cantly for N (Fig. 2). In eggplant, only the concentration of N in the double inoculation treatment …M ‡ V† increased signi®cantly. K concentration

154

N. Karagiannidis et al. / Scientia Horticulturae 94 (2002) 145±156

was signi®cantly reduced only in the Verticillium treatment. Cuenca and AzcoÁn (1994) report an overall improved uptake of all microelements following AM inoculation. Karagiannidis et al. (1995) also reported a non-statistically signi®cant increase of macronutrients uptake by M plants in the grapevine, attributed to their improved growth. Tarafdar and Marschner (1995) report a signi®cant improvement of K and Mg uptake by M plants in wheat, while Raju et al. (1990) only of K. According to Entry et al. (1996), the mycorrhiza did not affect nutrient concentration in maize. In all relevant literature, the improved P uptake by the mycorrhizal plants is emphasized (Nurlaeny et al., 1996). This was also con®rmed by the present experiments, regarding the AM treatments, as in the Verticillium treatment, P concentration were found to be similar to that of controls (Fig. 2). The main contribution of AMF to the host is to reach and translocate phosphate through their extracortical hyphae, which can extend up to 9 cm in the soil (Sylvia, 1998). No signi®cant differences were observed in B concentration between the different treatments in either species (Fig. 3), a result in agreement with Bavaresco and Fogher (1996). As regards uptake of heavy metals, a reduced concentration of the microelements Mn, Zn, Fe and Cu was found in the leaves of AM plants (Fig. 3), a ®nding that coincides with the previous reports for other plant species (Weissenhorn et al., 1995). Contrary to this, Gildon and Tinker (1983) support that the mycorrhiza contributes to the better uptake and, therefore, to the higher accumulation of these microelements in the M plants. According to Manjunath and Habte (1988), under conditions of excess Cu, soil supply Cu is bound in the root system and not transported to the aerial plant part. Although this is a speculation, such a response perhaps holds true for the above-mentioned heavy metals. Root colonization in both the plant species is reduced by nearly 50% following the double inoculation …V ‡ M†, compared to AM inoculation only (Table 4). According to McAllister et al. (1994), pathogenic fungi reduced mycorrhizal formation, when present in the rizosphere before or at the same time as mycorrhizal fungi were established on a root system. The opposite holds true when AMF are already established in the roots prior to their inoculation with pathogenic fungi. In conclusion, the AMF G. mosseae enhances tolerance by eggplant and tomato plants of the disease caused by the pathogenic soil fungus V. dahliae. There is, however, a need to study the performance of more tomato and eggplant cultivars under the combined effect and interaction of V. dahliae with the AMF to account for species speci®city. In cultivars of Linum and winter barley (Dehne, 1987; Dugassa et al., 1996), levels of AMF colonization were not correlated to the bene®cial AM effect against soil-borne fungal pathogens. These examples indicate that the in¯uence of AM symbiosis on plant health depends more on the genotypes of host and pathogen, and less on AMF colonization levels. This should be one of the most important factors to be considered in plant breeding. References Baath, E., Hayman, D.S., 1983. Plant responses to vesicular±arbuscular mycorrhiza. XIV. Interactions with Verticillium wilt on tomato plants. New Phytol. 95, 419±426. Baath, E., Hayman, D.S., 1984. No effect of VA mycorrhiza on red core disease of strawberry. Trans. Br. Mycol. Soc. 82, 534±536.

N. Karagiannidis et al. / Scientia Horticulturae 94 (2002) 145±156

155

Bavaresco, L., Fogher, C., 1996. Lime-induced chlorosis of grapevine as affected by rootstock and root infection with arbuscular mycorrhiza and Pseudomonas fluorescens. Vitis 35 (3), 119±123. Bletsos, F.A., 1998. Increase of eggplant production by grafting on Solanum torvum Sw. In: Proceedings of the Seventh Scientific Congress on Genetics and Plant Breeding, Heraclion Kreta, Greece, October 21±23, 1998, pp. 351±355 (in Greek with English abstract). Bletsos, F.A., Thanassoulopoulos, C.C., Roupakias, D.G., 1997a. Level of resistance to Verticillium dahliae of an interspecific F1 hybrid …Solanum melongena  Solanum torvum†. J. Genet. Breed. 51, 69±73. Bletsos, F.A., Thanassoulopoulos, C.C., Roupakias, D.G., 1997b. The susceptibility of Greek eggplant varieties to Verticillium wilt. Acta Hort. 462, 211±216. Bletsos, F.A., Thanassoulopoulos, C.C., Roupakias, D.G., 1999. Water stress and Verticillium wilt severity on eggplant (Solanum melongena L.). J. Phytopathol. 147, 243±248. Cirulli, M., Ciccarese, F., Amenduni, M., 1990. Progress in the search for Verticillium wilt resistant eggplant. Phytopathol. Medit. 29, 184±190. Cordier, C., Gianinazzi, S., Gianinazzi-Pearson, V., 1996. Colonisation patterns of root tissues by Phytophthora nicotianae var. parasitica related to reduced disease in mycorrhizal tomato. Plant and Soil 185, 223±232. Cottenie, A., 1980. Soil and plant testing as a basis of fertilizers recommendation. FAO Soil Bulletin 38/2, Rome. Cuenca, G., AzcoÁn, R., 1994. Effects of ammonium and nitrate on the growth of vesicular±arbuscular mycorrhizal Erythrina poeppigiana 0.I. Cook seedlings. Biol. Fertil. Soils 18, 249±254. Davis, R.M., Menge, J.A., Erwin, D.C., 1979. Influence of Glomus fasciculatum and soil phosphorus on Verticillium wilt of cotton. Phytopathology 69, 453±456. Dehne, H.W., 1987. Zur Bedeutung der vesikulaÈr±arbuskulaÈren (VA-) Mykorrhiza fuÈr die Pflanzengesundheit. Habil. Univ. Hannover, Germany. Diederichs, C., 1991. Influence of different P sources on the efficiency of several tropical endomycorrhizal fungi in promoting the growth of Zea mays L. Fert. Res. 30, 39±46. Dugassa, G.D., von Alten, H., SchoÈnbeck, F., 1996. Effects of arbuscular mycorrhiza (AM) on health of Linum usitatissimum L., infected by fungal pathogens. Plant and Soil 185, 173±182. Entry, J.A., Reeves, D.W., Mudd, E., Lee, W.J., Guertal, E., Raper, R.L., 1996. Influence of compaction from wheel traffic and tillage on arbuscular mycorrhizae infection and nutrient uptake by Zea mays. Plant and Soil 180, 139±146. Gerdemann, J.W., Nicolson, T.H., 1963. Spores of mycorrhizal endogene species extracted from soil by wet sieving. Trans. Br. Mycol. Soc. 46, 234±235. Gildon, A., Tinker, P.B., 1983. Interactions of vesicular±arbuscular mycorrhizal infection and heavy metals in plants. I. The effects of heavy metals on the development of vesicular±arbuscular mycorrhizae. New Phytol. 95, 247±261. Giovannetti, M., Mosse, B., 1980. An evaluation of techniques for measuring vesicular±arbuscular mycorrhizal infection in roots. New Phytol. 84, 489±500. Hooker, J.E., Jaizme-Vega, M., Atkinson, D., 1994. Biocontrol of plant pathogens using arbuscular mycorrhizal fungi. In: Gianinazzi, S., SchuÈepp, H. (Eds.), Impact of Arbuscular Mycorrhizae on Sustainable Agriculture and Natural Ecosystems. BirkhaÈuser Verlag, Basel, Switzerland, pp. 191±200. Jackson, M.L., 1960. Soil Chemical Analysis. Constable and Ltd., London. Karagiannidis, N., 1980. Untersuchungen uÈber die Effizienz der vesikulaÈr±arbuskulaÈren (VA-) mykorrhiza verschiedener Herkunft bei unterschiedlichen tropischen und subtropischen Pflanzen, Phosphatformen, Boden-pH-Werten und Bodentemperaturen. Dissertation. University of GoÈttingen, Germany. Karagiannidis, N., Nikolaou, N., Mattheou, A., 1995. Wirkung dreier VA-Mykorrhizapilze auf Ertrag und Nhrstoffaufnahme von drei Unterlagen und einer Tafeltraubensorte. Vitis 34, 85±89. Linderman, R.G., 1994. Role of VAM fungi in biocontrol. In: Pfleger, F.L., Linderman, R.G. (Eds.), Mycorrhizae and Plant Health. APS Press, St. Paul, USA, pp. 1±25. Liu, R.J., 1995. Effects of vesicular±arbuscular mycorrhizal fungi on Verticillium wilt of cotton. Mycorrhiza 5, 293±297. Manjunath, A., Habte, M., 1988. Development of vesicular±arbuscular mycorrhizal infection and the uptake of immobile nutrients in Leucaena leucocephala. Plant and Soil 106, 97±103. Mark, G.L., Cassells, A.C., 1996. Genotype-dependence in the interaction between Glomus fistulosum, Phytophthora fragariae and the wild strawberry (Fragaria vesca). Plant and Soil 185, 233±239.

156

N. Karagiannidis et al. / Scientia Horticulturae 94 (2002) 145±156

McAllister, C.B., Garcia-Romera, I., Godeas, A., Ocampo, J.A., 1994. Interactions between Trichoderma koningii, Fusarium solani and Glomus mosseae: effects on plant growth, arbuscular mycorrhizae and the saprophyte inoculants. Soil Biol. Biochem. 26 (10), 1363±1367. Morandi, D., 1996. Occurrence of phytoalexins and phenolic compounds in endomycorrhizal interactions, and their potential role in biological control. Plant and Soil 185, 241±251. Mosse, B., Stribley, D.P., Letacon, F., 1981. Ecology of mycorrhizae and mycorrhizal fungi. Adv. Microbiol. Ecol. 5, 137±210. Norman, J.R., Atkinson, D., Hooker, J.E., 1996. Arbuscular mycorrhizal fungal-induced alteration to root architecture in strawberry and induced resistance to the root pathogen Phytophthora fragariae. Plant and Soil 185, 191±198. Nurlaeny, N., Marschner, H., George, E., 1996. Effects of liming and mycorrhizal colonization on soil phosphate depletion and phosphate uptake by maize (Zea mays L.) and soybean (Glycine max L.) grown in two tropical acid soils. Plant and Soil 181, 275±285. O' Brien, M., 1983. Evaluation of eggplant accessions and cultivars for resistance to Verticillium wilt. Plant. Dis. Reptr. 67, 763±764. Olsen, S.R., Cole, C.V., Watanabe, F.S., Dean, L.A., 1954. Estimation of available phosphorus in soils by extraction with sodium bicarbonate. US Stages Dept. of Agric. Circular 939, 19. Phillips, J.M., Hayman, D.S., 1970. Improved procedures for clearing roots and staining parasitic and vesicular± arbuscular mycorrhizal fungi for rapid assessment of infection. Trans. Br. Mycol. Soc. 55, 158±161. Raju, P.S., Clark, R.B., Ellis, J.R., Maranville, J.W., 1990. Effects of species of VA-mycorrhizal fungi on growth and mineral uptake of sorghum at different temperatures. Plant and Soil 121, 165±170. Reddy, M.V., Rao, J.N., Krishna, K.R., 1989. Influence of vesicular±arbuscular mycorrhizae on Fusarium wilt on pigeonpea. Int. Pig. Newsl. 9, 23. Rosendahl, C.N., Rosendahl, S., 1990. The role of vesicular±arbuscular mycorrhiza in controlling damping-off and growth reduction in cucumber caused by Pythium ultimum. Symbiosis 9, 363±366. Sakata, Y., Nishio, T., Hon'ma, S., 1989. Resistance of Solanum species to Verticillium wilt and bacterial wilt. In: Proceedings of the Seventh Eucarpia Meeting on Genetics and Breeding on Capsicum and Eggplant, pp. 177±181. Sieverding, E., 1991. Vesicular±Arbuscular Mycorrhiza Management in Tropical Agrosystems. GTZ, Eschborn, Germany. Smith, S.E., Gianinazzi-Pearson, V., 1988. Physiological interactions between symbionts in vesicular±arbuscular mycorrhizal plants. Annu. Rev. Plant Physiol. Plant Mol. Biol. 39, 211±244. Smith, S.E., Read, D.J., 1997. Mycorrhizal Symbioses, 2nd Edition. Academic Press, London. Smith, V.L., Wicox, W.F., Harman, G.E., 1990. Potential for biological control of Phytophthora root and crown rots of apple by Trichoderma and Gliocladium spp. Phytopathology 80, 880±885. Sylvia, D.M., 1998. Activity of external hyphae of vesicular±arbuscular mycorrhizal fungi. Soil Biol. Biochem. 20 (1), 39±43. Tarafdar, J.C., Marschner, H., 1995. Dual inoculation with Aspergillus fumigatus and Glomus mosseae enhances biomass production and nutrient uptake in wheat (Triticum aestivum L.) supplied with organic phosphorus as Na-phytate. Plant and Soil 173, 97±102. Tjamos, E.C., Chitzanidis, A., Kornaros, E., 1981. Failure of two growth retardants to suppress Verticillium wilt symptoms and increase yield in cotton field trials in Greece. In: Proceedings of the Third International Verticillium Symposium, Bari, Italy, 1981, p. 60 (Abstract). Trotta, A., Varese, G.C., Gnavi, E., Fusconi, A., Sampo, S., Berta, G., 1996. Interactions between the soilborne root pathogen Phytophthora nicotianae var. parasitica and the arbuscular mycorrhizal fungus Glomus mosseae in tomato plants. Plant and Soil 185, 199±209. Weissenhorn, I., Mench, M., Leyval, C., 1995. Bioavailability of heavy metals and arbuscular mycorrhizae in a sewage-sludge-amended sandy soil. Soil Biol. Biochem. 27 (3), 287±296.