EFFECT OF RHIZOBIUM, VAM AND ROCK PHOSPHATE INOCULATION ON GROWTH, PRODUCTIVITY AND NUTRIENTS ACQUISITION OF SOME SELECTED LEGUMES

Abstract

Microorganisms and their interactions in soil play a critical role in nutrient transformations and cycling, and in sustaining soil productivity. Arbuscular mycorrhizal fungi (AMF) are a keystone group of fungi influencing nutrient cycling. In turn, the activity and composition of microorganisms in soil are influenced by management practices such as the choice of crop species and fertilization. Biofertilizer has been identified as an alternative source for chemical fertilization to increase soil fertility and crop production. Arbuscular mycorrhizal (AM) fungi and rhizobia are two of the most important plant symbionts in natural habitats. Many leguminous plants have the ability to associate with the two microbial symbionts, which yield arbuscular mycorrhizae and root nodules. Moreover, AM fungi, rhizobia and leguminous plants are able to form a tripartite symbiosis. It has demonstrated that the intimate association is determined by the mutual recognition and subsequently the penetration of plant tissues in the establishment stage. A pot experiment was conducted in a net house in the University of Peshawar Pakistan, investigate the effect of seed inoculation with Rhizobium and/or soil inoculation with the vesicular-arbuscular mycorrhizal fungus Glomus mosseae, Glomus fasciculatum and G. aggregatum under different levels of RP fertilization. A pot experiment was conducted in 2010-2011 to investigate the arbuscular mycorrhizal (AM) status of Vigina radiate (NAIB-92, NAIB-98, NAIB-2006), Macroptilum bracteatum, Pisum sativum, Desmodium adscendens and Lens culinaris (NARC-2008-2, NARC-2008-3, NARC- 2008-4, NARC-2002) its relationship with plant vegetative, flowering and fruiting stages. The different inoculations (single and dual) of Rhizobium and VAM fungi mostly Glomus msesea, Glomus fasciculatum and G. aggregatum were incorporated under deficient P soil (1.13%). The growth and yield responses of studied legumes to co-inoculation with AMF and Rhizobium strains depended on the particular AMF-Rhizobium strain combination. In some cases, the productivity of studied legumes inoculated with an effective Rhizobium strain was reduced by an apparently incompatible AMF species compared to the Rhizobium treatment. In contrast, the yield of studied legumes inoculated with some ineffective Rhizobium strains was enhanced by an apparently compatible AMF species compared to the Rhizobium treatment. However, maximum Lens culinaris productivity was achieved only in treatments with effective Rhizobium strains or co- inoculation treatments with effective Rhizobium strains and a compatible AMF species. Plants were analysed for growth parameters (plant height, number of leaves, number of flowers/plant, number of pod/plant, number of seeds/pod, length of pod), dry weight of plant, nutrient uptake (Mg, Ca, K,Cu, Mn, Fe and Zn), proximate composition (crude protein, ash, crude fiber, fat and carbohydrate), percent VAM infection and spore density. Plant were analyzed for proximate composition and mineral composition. Results showed significant at (p>0.05) increase in the moisture and carbohydrate contents the fat, ash, crude fiber and protein content treated plants. Mycorrhizal colonization gradually increased with the increase in plant age from early vegetative to fruiting stage. Plants colonized by arbuscular mycorrhizal (AM) fungi have been shown to respond positively to the application of insoluble forms of inorganic phosphorus (P) such as rock phosphates (RPs) that responses to RP by mycorrhizal (MRP 1 and MRP 2 ) plants more pronounced than RP alone. The results revealed that dual inoculation of Rhizobium with VAM (Glomus msesea, Glomus fasciculatum and G. aggregatum) enhanced seed yield of legume. Varieties were single or dual inoculated with different AM fungus and different Rhizobium strains the dual symbiosis formed by AM fungi and Rhizobium depending on the plant variety and the symbionts involved. Influence of VAM fungus, Rhizobium and Rock phosphate inoculation on lentil,green mung bean, pea, desmodium and burgundy growth response in relation to growth parameters, yield and productivity , dry weight of plants , grains, roots colonization was studied in pot studies. The treatments consisted of inoculation with VAM fungus only, Rhizobium, dual inoculation with VAM fungus and Rhizobium. Rock phosphate alone and dual with VAM and control. Seeds concentrationof VAM used as inoculum was 290 spores per pot. Rhizospheric soil from wheat field having high spores number of different AMF i-e Glomus fasciculatum, G. mosseae and G. aggregatum and roots of wheat and maize infected with Arbuscular mycorrhiza were used as rhizobase inoculum . Roots were cut into 1cm pieces. These root pieces along with soil base inoculum (rhizospheric soil) were spread uniformly in layers at a depth of 3cm and 6cm before sowing. Inoculum for each pot consisted of 180 gm of mycorrhizal infected roots and adhering soil. The spore density was found to be 290 spores per 100g of soil. A synergistic relationship dependent on N and P status exists between rhizobia and AM fungi on growth. Co-inoculation with rhizobia and AM fungi significantly increased. Studied legumes growth under low P.