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İbrahim ORTAŞ The University of Çukurova, Department of Soil Science, Adana- Turkey Abstract Nutrient deficiency is a common nutritional problem in crop production in Turkey. This problem results in the application of increasing amounts of P, N, Zn and other fertilizers. Mycorrhizal inoculation or indigenous potential of mycorrhizae in soil is a critical factor in crop production under low supply of P and Zn. Under semiarid conditions mycorrhizae contributes to overcoming mineral nutrient deficiencies. Under field conditions mycorrhizal dependence of several plants and effect of indigenous mycorrhiza on plant growth and root infection has been tested with and without methyl bromide application for three years. Between 1997- 1999, under field conditions several plants were treated with and without methyl bromide, mycorrhizal inoculation and phosphorus application. Three years of experiments revealed that under field conditions mycorrhiza spores effectively infected pepper, eggplant and tomato plants. So far results showed that indigenous mycorrhiza successfully infected plant roots resulting in better plant growth. The effect of mycorrhizal inoculation on plant growth is changed by effectiveness of inoculum and time. Compared to non-inoculated control plants, mycorrhizal inoculation increased yield but some years did not. In general horticultural plants such as green peppers and eggplants are more mycorrhizal dependent plants. After three years of field experiments it has been concluded that for field crops, soil and plant management systems, but for horticultural plants mycorrhizal inoculation is more practical and advised to be used. In another experiment under greenhouse condition mycorrhizal dependence was searched in term of Zinc (Zn) and phosphorus (P) requirements. In the study the role of mycorrhizal inoculation on growth of maize, bean, and pepper in two calcareous soils with both Zn and P deficiency were searched. The results revealed that plants are strongly dependent on mycorrhizal infection. Although addition of Zn increased plant growth, but mycorrhizal dependence is much more depend on P nutrition. Introduction Nearly 90% of plant communities are mycorrhizal (Smith and Read, 1997). The majority of plant species are naturally arbucular mycorrhizae (AM). Plants neither benefit from this symbiosis nor the factors responsible for different degrees of mycorrhiza formation and host dependence are well-defined and understood. One of the most dramatic effects of mycorrhizal infection on the host plant is the increase in phosphorus (P) uptake (Koide, 1991, Ortaş et al., 1996) and Zn (Lambert et al., 1979; Kothari et al., 1991; Ortas et al., 2001), mainly due to the capacity of the mycorrhizal fungi to absorb phosphate from soil and transfer it to the host roots (Asimi, et al. 1980). In addition, mycorrhizal infection results in an increase in the uptake of other macro and micronutrient (George et al., 1995). Based on plant ability to grow with or without mycorrhizae at different levels of nutrients, plants can be separated into two major groups: non-mycotrophic and mycotrophic. Mycotrophic plants are also classified according to their degree of dependence on the mycorrhizae from obligatory to facultative. Plants get benefits from mycorrhiza by enhancing nutrient and water uptake and other benefits such as resistance to stress factors. Considering the plant-fungus interaction, it is to be expected that the extent of mycorrhizal colonization of the root system and related plant responses will vary in different plant-fungus combinations (Smith and Read, 1997). Nevertheless, study of host response to inoculation with a single fungus isolate can provide useful information. This is particularly true where the inoculating fungus exhibits a broad host range, as is the case for the G. mossea and G. etunicatum isolate used in this study. Mycorrhizae species to be different in root colonization and dependence ratio in a low-fertility soil with increased P and Zn application (Ortaş et al., 2001). This may be the effect of soil ecological parameters on root infection. Very high and very low phosphorus levels may reduce mycorrhizal infection/colonization (Koide, 1991). It is well established that infection by mycorrhizal fungi is significantly reduced at high soil phosphorus levels (Amijee et al., 1989; Koide and Li, 1990). The level of phosphorus in the plant has also been shown to influence the establishment of a mycorrhizae with high levels inhibiting colonization by mycorrhizae (Menge, et al. 1978; Graham et al., 1981; de Miranda et al., 1989; Asimi et al., 1989). However no information related to the mycorrhizal dependence about excess Zn application on root infection was obtained. It has been hypothesized that mycorrhizal dependence is largely controlled by root architecture system (Baylis, 1975) and nutrient requirement (Ortaş et al., 2001). Plants with coarsely branched roots and with few or no root hairs are expected to be more dependent on mycorrhiza than are plants with finely branched root systems (Smith and Read, 1997). Menge et al. (1978) defined mycorrhizal dependence as the degree to which a plant species is dependent on the mycorrhizal condition to produce its maximum growth at a given soil fertility. This definition mostly pronounced for P requirement but not for other nutrients such as Zn (Ortas et al., 2001). Plenchette et al. (1983) suggested a new definition of mycorrhiza dependence by expressing the dry mass of a mycorrhizal plant as the dry mass of a non-mycorrhizal plant at a given level of soil fertility. An earlier definition of mycorrhiza dependence (Menge et al. 1978) is expanded and modified to give a percentage increase of yield relative to that of mycorrhizal plants. In this definition the range is between zero and 100% rather than an unlimited percentage increase. The result is likely to vary depending on the nutrient status of the soil, so it is suggested that the relative mycorrhizal dependence should be subscribed with the level of available phosphorus. Sylvia (1986) tested mycorrhizal dependence by using two arbuscular mycorrhizal fungi, identified as Glomus intraradices and G. etunicatum, at three different levels of available phosphorous and mycorrhizal inoculation increased flowering dogwood seedling survival, root length, root fresh mass, shoot dry mass, shoot height and the proportion of roots colonized. Azcon and Barea (1997) suggested that mycorrhizal dependence for a representative plant species in Mediterranean shrublves (Lavandula spica L.) as a key factor to its use for re-vegetation strategies in desertification-threatened areas. The degree of plant dependence is of great practical and ecological interest for plant nutrition. In the present study we attempted to study the mycorrhizal dependence of several plants grown under field and green house condition. Materials and Methods Field Experiment Soils The experiment was carried out on Menzilat soil series (Entic Chromoxerert), which is located in Research Farm of the University of Çukurova, Turkey. The soil chemical and physical properties are given on Table 1. Soil Fumigation Methyl bromide (60 g/m2) exploited under the plastic polyethylene sheet. One week after the application, the plastic sheet was removed from the surface. Following this, soil was aerated for a five-day period before sowing. Experimental Design The experiment was conducted in two blocks with and without soil fumigation. In each block, main treatments P0 (0 kg P2O5 ) and P1 (100 kg P2O5 /ha) were applied with and without mycorrhizae inoculation. The plots were 3 x 5 m wide equal to 15 m2. For eggplants and tomatoes there were four rows, with each row 60 cm away from the next. For peppers, there were six rows with 50 cm interrows. Inoculum of Glomus mosseae ((Nicolson and Gerdemann) isolated from Rothamsted, UK) 1000 spores/plant mix of source (soil, sand and organic matter mix), chopped roots and mycorrhiza spores were placed 30 mm below the seedlings. The non-mycorrhizal plants received the same amount of mycorrhiza free-inoculum (containing the same microbes). Seedling production For Eggplants (Pala), Tomatos (SC2121) and Peppers, Local variety (Kahramanmaras) seeds were sown on a mix of sand: soil: organic matter (7:2:1 v/v) growth medium. Seeds were treated with and without mycorrhizal inoculation. Water was added daily to maintain moisture near field capacity. The seedlings were grown in a greenhouse for 32 days before being transferred to main field plots. Pot experiment Two widely distributed Zn and P-deficient calcareous soils from the Central Anatolia were used in the experiment. Concentration of NaHCO3 extractable P and DTPA-extractable Zn were very low, and below the critical deficiency level (i.e., 32 kg P2O5 ha-1 and 0.15 mg Zn kg-1 soil). Maize, green pepper and bean were grown in two soils low in phosphorus (P) and Zinc (Zn) and fertilized with 3 levels of P (P0=0, P1=25, P2=125 mg P kg-1 soil and 2 level of Zn (Zn0=0 and Zn1=5 mg Zn kg-1soil) in 2 kg soil. Plants were inoculated with G. Mossea and G. Etunicatum (1000-spore per plant, 3 cm below seeds). Non-inoculated pots received the same amount of non-mycorrhizal spore inoculums. G. Mossea (Nicolson and Gerdemann) Rothamstedt Isolate, UK) and G. etunicatum (Becker and Gerdemann) Nutri-Link Isolate, USA) were used as mycorrhizal inoculum. Mycorrhizal Dependence was calculated according to the following formula  Mycorrhizal infection Before plant flowering, two plants per plot were killed off, and plant root were collected from the soil. The Roots of the plants were washed carefully for mycorrhizal infection. The root clearing and staining procedure followed the method described by Koske and Gemma, (1989). The percentage of AM infection was calculated as a number of 10 mm long root segments out of 100 identified as infected under a stereo microscope at a magnification of X 20 (Giovannetti and Mosse, 1980). All statistical analyses were performed using the Statistical Analysis System (SAS). Results and Discussion Under the field conditions, tomato, eggplant and green pepper plants were grown and plants responses to mycorrhizae were investigated. Fruits were harvested several times (weekly) and finally total yield was recorded. It has been observed that mycorrhizal inoculation increased fruit yield of three vegetable plants significantly compared to non-inoculated ones. The effect of mycorrhizal inoculation on plants in control plots (0 P) yield was higher than yield increase with additional P application. When zero P was applied, mycorrhizal inoculation increased tomato yield up to 52%, eggplants up to 28% and pepper up to 36 %, but with P addition, mycorrhizal inoculation increased yield up to 28 %, 14 % and 21 % respectively, compared to non inoculated ones (Table 1).  Mycorrhizal dependence was calculated. It was found that in 1997 all three plants give high MD especially green peppers and eggplants. Mycorrhizal dependence was higher in P0 than P 1 treatment. In 1998 mycorrhizal dependence was lower in general but in 1999 again microbial response was high. The reason is not known why some year it is non-responding to the mycorrhizal inoculation. Even in 1998 there was a negative response to mycorrhizal inoculation (Table 1). Under field conditions, mycorrhizal inoculation increased eggplant, tomato and pepper plants fruit yields, especially under the low P supply conditions. Although during the vegetative growth mycorrhizae inoculated eggplants were larger and grew earlier, but this was not been reflected in the yield increase. Al-Raddad (1987), also used eggplant, tomato and pepper plants with inoculation of G. Fasciculatum, G. Monosporum and G. Mossea under greenhouse conditions and found that eggplant dry weight increased significantly. In Japan under greenhouse conditions, the effect of mycorrhizal fungus inoculation on seedling of 17 species of vegetable crops were investigated and it was reported that growth was noticeably enhanced by AMF inoculation (Matsubara et al., 1994). In greenhouse experiments, mycorrhizal inoculation of G. Etunicatum and G. Mosseae significantly increased plant growth in Sultanönü soil but did not so in Konya soil. Mycorrhizal species were different in their effect on plant growth; in Sultanönü soil, G. Mossea was much more effective than G. Etunicatum, but in Konya soil G. Etunicatum was more effective than G. Mossea. Since beans are sensitive to salt effect in Konya soil, the plant did not grow in a proper way. Consequently been plant is less mycorrhizal dependent (Table 2). Sultanönü and Konya soils had different responses to the P and Zn application. In Sulatanönü soil, mycorrhizae inoculation without P addition, both mycorrhiza species increased plant growth. Addition of Zn application increased plant growth as well. But in the Konya soil, there was less effect.  Without mycorrhizal inoculation, shoot and root dry matter productions were affected by P and Zn deficiency, and increases in supply of adequate amounts of P and Zn significantly enhanced plant growth, especially for Sultanönü soil. When the soil was inoculated with mycorrhizal species, P and Zn fertilization could only slightly increase plant growth. Mycorrhizal species were different in their effect on nutrient uptake; G. Mossea was little higher than G. Etunicatum. There were small differences in plant growth between the doses of P fertilization. By contrast, Zn addition significantly increased plant growth, irrespective of P addition. Compared to P supply, the effect of Zn on plant growth was much greater, especially at higher P rates in Sultanönü soil. But Konya soil because of high B concentration, mycorrhizal inoculation and nutrient supply did not make a significant contribution. In this case mycorrhizal inoculation had a slightly higher effect than the nutrient supply. High P is known to depress mycorrhiza formation (Amijee et al. 1989; Ortaş et al., 1996) consequently the plant gets less P, but in the present study such an effect was not uniform among mycorrhizae species for both soils. Therefore, mycorrhiza formation, response to added P, host nutrient requirement, and mycorrhiza responsiveness are all interrelated. Janos (1996) stated that host independence of AM is a consequence of low nutrient requirement or the ability of roots alone to take up all required mineral nutrients. In the present experiment mycorrhizal inoculation regarding P addition significantly increased the P uptake even in Konya soil. The results obtained indicate that peppers, maize and beans are mycorrizal-dependent plant with under low P and Zn supply, and therefore inoculation of mycorrhizae in soil with P and Zn deficiency is a critical factor in crop production as well as in P and Zn uptake of plants. Phosphorus treatments generally reduced mycorrhizal dependence. But Zn application did not lead to any differences. In general, G. Etunicatum inoculated plant had high mycorrhizal dependence compared to the G. Mossea inoculation. In the present experiment although mycorrhizal inoculation increased plant Zn uptake, yet the plant was found to be much more mycorrhizal dependent on P nutrition. It seems that mycorrhizal dependence is an inherent characteristic for which plant nutrient requirement and uptake efficiency are important parameters, especially for P requirement. Considering the importance of mycorrhiza dependence for plant survival, it is of great interest to categorize species according to this characteristic. Conclusions Under field condition plant depend on mycorrhizal inoculation but also depend on P supply and year differences. With high P application, mycorrhizal dependence significantly reduces. nder green house conditions, irrespective of P and Zn treatments, mycorrhizal inoculation increases shoot, and increasing P and Zn supply also significantly response to plant growth. Although plant growth is strongly affected by the P and Zn supply, mycorrhizal inoculation increases P and Zn uptake, but this is strongly dependent on the P supply rather than the Zn supply. Results obtained support the hypothesis that pepper, maize and bean are mycorrhizal dependent, nevertheless with increasing P and Zn this is gradually reduced. But mycorrhizal dependence (MD) decreases more pronouncedly for the P requirement rather than the Zn requirement. References . Al-Raddad, A.M., 1987. Effect of VA mycorrhizal isolates on growth of tomato, eggplant and pepper in field soil. Dirasat (Jordan). 14, 161-168. . Matsubara, Y., Harada, T. & Yakuwa, T., 1994. Effect of vesicular-arbuscular mycorrhizal fungi inoculation on seedling growth in several species of vegetable crops. J. Japan. Soc. Horti. Sci. 63, 619-628. . Amijee, F., Tinker P.B. & Stribley D.P., 1989. The development of endomycorrhizal root systems. VII. A detailed study of effects of soil phosphorus on colonization. New Phytol 111, 435-446 . Asimi, S. Gianinazzi-Pearson, V. & Gianinazzi, S., 1980. Influence of increasing soil phosphorus levels on interactions between andsicular-arbuscular mycorrhizae and Rhizobium in soybeans. Canadian Journal of Botany 58, 2200-2205. . Azcon, R. & Barea, J. M., 1997. Mycorrhizal dependence of a representative plant species in Mediterranean shrublands (Lavandula spica L.) as a key factor to its use for renegotiation strategies in desertification-threatened areas. Applied Soil Ecology. 7, 83-92. . Baylis, G.T.S., 1975. The magnolioid mycorrhiza and mycotrophy in root systems derived from it. In: Sanders FE, Mosse B, Tinker PB (eds) Endomycorrhizas. Academic, London, pp 373-389 . De Miranda, J.C.C., Harris, P.J. & Wild, A., 1989. Effects of soil and plant phosphorus concentrations on vesicular-arbuscular mycorrhizae in sorghum plants. New Phytologist 112, 405-410. . George, E., Marschner, H. & Jakobsen, I., 1995. Role of arbuscular mycorrhizal fungi in uptake of phosphorus and nitrogen from soil. Critical Reviews in Biotechnology 15(3-4), 257-270, . Giovannetti, M. & Mosse, B., 1980. An evaluation of techniques for measuring andsicular-arbuscular mycorrhiza in roots. New Phytologist 84, 489-500. . Graham, J. H., Leonard, R.T. & Menge, J. A., 1981. Membrane-mediated decrease in root exudation responsible for phosphorus inhibition of vesicular-arbuscular mycorrhiza formation. Plant Physiology 68, 548-552. . Janos, D.P. 1996., Mycorrhizas, succession and the rehabilitation of deforested lands in the humid tropics. In: Frankland JC, Nagun N, Gadd GM (eds) Fungi and environmental change. British Mycology Society Symposium, vol 20. Cambridge Uniandrsity Press, Cambridge, pp 129-162 . Koide, R.T. & Li, M., 1990. On host regulation of the andsicular-arbuscular mycorrhizal symbiosis. New Phytologist 114, 59-65. . Koide, R.T., 1991. Nutrient supply, nutrient demand and plant response to mycorrhizal infection. New Phytologist 117, 365-386. . Koske, R.E. & Gemma, J.N., 1989. A modified procedure for staining roots to detect VAM. Mycological Research 92, 486-505. . Kothari, S.K., Marschner, H. & Romheld, V., 1991. Contribution of the VA mycorrhizal hyphae in acquisition of phosphorus and zinc by maize grown in a calcareous soil. Plant and Soil. 131(2), 177-185. . Lambert, D.H., Baker, D.E. & Cole, H., 1979. The role of mycorrhizae in the interactions of phosphorus with zinc, copper and other elements. Soil Science Society of America Journal. 43,976-980. . Menge, J.A. Steirle, D., Bagyaraj, D.J., Johnson, E.L.V. & Leonard, R.T., 1978. Phosphorus concentrations in plants responsible for inhibition of mycorrhizal infection. New Phytologist 80,575-578. . Ortas, I., Harris P.J. & Rowell, D.L., 1996. Enhanced uptake of phosphorus by mycorrhizal sorghum plants as influenced by forms of nitrogen. Plant and Soil 184, 255-264. . Ortas, I., Kaya, Z. & Çakmak, I., 2001. Influence of VA-Mycorrhiza Inoculation on Growth of Maize and Green Pepper Plants in Phosphorus and Zinc Deficient Soils. In plant Nutrition- Food security and sustainability of agro-ecosystems. Pp.632-633. . Plenchette, C, Fortin J.A. & Furlan, V., 1983. Growth responses of several plants species to mycorrhizae in a soil of moderate P fertility. I. Mycorrhizal dependence under field conditions. Plant Soil 70,199-209 . Smith, S.E. & Read, D.J., 1997. Mycorrhizal symbiosis, 2nd edn. Academic, San Diego . Sylvia, D., 1986. Effects of andsicular-arbuscular mycorrhizal fungi and phosphorus on the survival and growth of flowering dogwood (Cornus florida). Canadian Journal of Botany, 64, 950-954. |