The effect of chemical properties of soil on symbiosis of apple and grape with arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF), are natural obligate root symbiont of 80 percent of plants, and play a key role in water and some nutrients, particularly phosphorus, absorption and sustainable production of field crops and fruit trees. Some of these fungi reported from grape's rhizosphere, and some species increased apple seedlings growth. This research was conducted to investigate the presence of these fungi in apple and grape orchards of Boyer-Ahmad and Dena areas, southwest Iran, and the impact of soil chemical properties on their symbiotic relationships.
Sixty samples were collected from the rhizosphere of apples and grapes in this region. Spores of AMF were isolated by wet sieving and decanting method and then centrifuged in sugar solution, and spores population of these fungi estimated at 100 grams of each samples. The trap pot culture for each sample was established with maize in the greenhouse, for 14 weeks. AMF species were identified with study the morphological characteristics of isolated spores from the samples and trap pot cultures. Root length colonization was measured in each sample, after discoloring roots with 10% KOH, and their staining with Lactophenol-Anilinblue solution. Soil texture, pH, EC and soil phosphorus, were appointed, for each sample. The correlation coefficients of soil chemical properties with AMF spores population, and root length colonization were measured, for each plant.
AMF were present in all samples. The mean of the spores population, species richness, and root length colonization in apple were 1474, 3.3 and 67.28; and in grape were 1045, 2.8 and 40.41. Fourteen species of these fungi belong to the 8 genera were identified as follow: Funneliformis constrictum, F. caledonium, F. mosseae, F. geosporum, Glomus deserticola, G. microaggregatum, Rhizophagus fasciculatus, R. clarus, Claroideoglomus claroideum, C. etunicatum, Scutellospora calospora, Entrophospora infrequens, Ambispora gerdemannii, Acaulospora bireticulata. F. mosseae had the highest frequency by 76.6%. The soil texture of samples were varied from clay to loamy. Soil pH, EC and phosphorus, had negative correlations with AMF spores population and root length colonization. The correlation coefficient of AMF spores population with soil pH, EC and phosphorus was -0.02, -0.42 and -0.04 in apple, and -0.45, -0.30 and -0.01 in grape respectively. Also correlation coefficients of the root length colonization with soil pH, EC and phosphorus were -0.22, -0.19 and -0.38 in apple, and -0.44, -0.15 and -0.16 in grape respectively.
The presence of AMF in all samples indicated that these plants need to this symbiosis for their natural growth and development. AMF spores population, species richness and root length colonization in apple samples were greater than the grape. More frequency of F.mosseae, reflects its ability to establish symbiotic relationship with these plants and the impact on their growth. The negative correlation between the amount of phosphorus, pH and electrical conductivity of soil with a spores population of AMF and root length colonization indicate that the ability of AMF symbiosis with these plants and their propagation are higher in soils with low phosphorus, pH and salinity. Therefore the use of AMF to improve the growth of these plants can be suggested in such soils.