Impact of AM Fungi and Rhizobial Isolates for Improvement of certain Tree Legumes in Tamil Nadu Lalitha S.1,*, Santhaguru K.2 1Department of Microbial Biotechnology, PSGR Krishnammal College for Women, Peelamedu, Coimbatore-641004, India 2Department of Botany, Thiagarajar College, Madurai-9, India *Corresponding author: Email: lara9k@yahoo.co.in
Online published on 11 June, 2014. Abstract Nitrogen is one of the major elements available to plants through biological nitrogen fixation, which has received much attention in recent years. The present study aims at improving tree legumes viz., Albizzia lebbeck, Pithecolobium dulce, Sesbania grandiflora, Albizzia amara, Enterolobium saman, Erythrina indica, Leucaena leucocephala, Acacia mellifera, Pongamia glabra and Acacia auriculiformis through dual inoculation with arbuscular mycorrhizal fungi and suitable rhizobial isolates. Dual inoculation with five arbuscular mycorrhizal fungi namely Glomus mosseae, Glomus fasciculatum, Acaulospora morrowae, Glomus ambisporum and Scutellospora heterogama and rhizobial isolates increased the dry matter yield compared with uninoculated control plants, or single inoculation with either rhizobial or arbuscular mycorrhiza fungal inoculated tree legume species. Based on the biochemical characterization of rhizobial isolates and dry matter yield of test tree legume species, strain AcM05 and Glomus fasciculatum were scored as the most efficient strain and these two were used to inoculate Acacia mellifera. Dual inoculation with Rhizobium and Glomus fasciculatum increased the nodule nitrogenase activity (36–213%), dry matter yield (156–279%), total nitrogen content (12–159%) and total chlorophyll content of leaves of Acacia mellifera (125–395%) compared to the uninoculated control or single inoculation with either Rhizobium or Glomus fasciculatum alone. Initially the soil had high potassium content (115mg/Kg soil) and low nitrogen (14mg/Kg soil) and phosphorous (1.1mg/Kg soil) content. In contrast, dual inoculation significantly enhanced the nitrogen (60.0mg/Kg soil) and phosphorous (24.3mg/Kg soil) contents of soil, but to a lesser extent with respect to potassium content (155mg/Kg soil). The per cent increase of the activity of soil enzymes amylase, protease, phosphatase and chitinase was more upon dual inoculation. Higher percent mycorrhizal root colonization was found in Acacia mellifera with dual inoculation than compared with plants inoculated with either Rhizobium or Glomus fasciculatum alone. In conclusion, it may be stated that tripartite association not only enhances plant growth but also improves the nutrient status and activities of soil enzymes. Top Keywords Glomus fasciculatum, Rhizobium, Acacia mellifera, tree legumes, soil enzymes. Top |