Impact of edapho-climatic factors on the dynamics of VAM root colonization and spore density in three forest tree species of Western Ghats, India

A survey was carried out to evaluate the diversity of VAMfungi associated with three exotic forest tree species, Eucalyptus grandis Hill ex. Maid, Grevillea robusta A. Cunn. and Tectona grandis Lf in the Western Ghats ecosystem, South India. The samples were collected from two locations, Kodaikanal (1500 m A.S.L.) and Siruvani (700 m A.S.L.) from January 1992 to June 1993. Climatic factors, physico-chemical properties of rhizosphere soils and VAMF spore counts and root colonization were recorded. Species isolated were Acaulospora, Gigaspora, Glomus, Sc1erocystis and Scutellospora with Glomus constituting 73% of the total species recorded. The mycorrhiza spore density was maximum from January to June in all samples collectedfrom all three tree species at both sites. High root colonization was recorded between the months of September and November. In both sites, the spore density was positively correlated with temperature and negatively with rainfall and soil moisture. The reverse was recorded for root colonization. There was positive correlation between vesicle number and spore number

Effect of interactions of three growth-promoting microorganisms on VAM colonization, spore density, plant growth and nutrient accumulation in tomato (lycopersicon esculentum) seedlings

Interactions of Azospirillum brasilense and Bacillus megaterium var. phosphaticum and Glomus fasciculatum in the rhizosphere of tomato plants were studied. There was no significant difference in plant growth parameters between YAM-inoculated treatments. Plants inoculated with the phosphobacteria had significantly higher shoot length, which was equivalent to VAM and other VAM + phosphobacteria combinations. Azospirullum or phosphobacteria alone increased plant biomass compared with the uninoculated control. VAM index was significantly reduced with the addition of phosphobacteria. There was no difference in tissue nutrient concentrations between treatments

Effects of Formaldehyde Fumigation and Fytolan Drench on VAM fungi and nodulation in some Leguminous forest Tree Seedlings in India

Seedlings of 12 legume tree species (Acacia caesia, A. catechu, A. farnesiana, A. holosericea, A. leucocephala, A. nilotica, Albizia lebbeck, Dichrostachys cinerea, Leucaena latisiliqua, Prosopis cineraria, Dalbergia latifolia and Pterocarpus marsupium) were raised informaldehyde-fumigatedf Fytol and renched beds in a nursery. Seedlings in the formaldehyde fumigated beds had stunted growth and were chlorotic; had poor VAM root colonization (18-25.3%) and spore density (3.1 - 10.6 g. soil-1 ) and lower nodule number (3 - 8 plant-1 ) and nodular biomass (100 - 870 mg plant-1 ); the total biomass (15.5 - 72 g plant-1 ) and field survival rate (31.2 - 40.4%) of the seedlings were very low. The mycorrhizal species isolated were Acaulospora bireticulata, Glomus fasciculatum and G. geosporum. In contrast, seedlings form Fytolan-drenched beds showed normal growth, enhanced biomass (18 - 83.21g plant-1 ) and higher field survival rate (71 - 86%); intense VAM root colonization (53.4-100%) and higher spore density (36 - 82.8 g soil-1 ) and higher module number (7.4 - 17.6 plant-1 ) and nodular biomass (195 - 950 mg plant ) compared with the control seedlings. Roots of these plants exhibited extensively developed arbuscular and vesicular structures. Ofthe seven VAMF species recordedfrom the rhizosphere soils of control and Fytolan-drenched beds, A. bireticulata, G. fasciculatum and G. geosporum were the dominant species. The differences between treatments were statistically significant (P < 0.05)

Role of edaphic factors on VAM fungal colonization and Spore populations in certain tropical wild legumes

Four nodulating annual tropical wild legumes, viz., Alysicarpus monilifer, Desmodium triflorum, Indigofera linnaei and Tephrosia purpurea from three different regions in the Western Ghats ecosystem were investigated to assess their mycorrhizal status. The response ofvesicular-arbuscular mycorrhizal (VAM) root colonization and spore number to edaphicfactors such as soil moisture, pH and available Nand P was analysed. Though the spore number varied significantly both within and between sites, a uniformly high degree ofroot colonization was observed for all the plants in the present study. The spore number recorded was high, rangingfrom 15 to 165 spores gl soil. Spores of sixteen VAM fungal species belonging to Acaulospora, Glomus and Scutellospora were isolated from the rhizosphere soils. Soil moisture generally had a positive influence on VAM colonization and sporulation except in I. linnaei. The pH correlated negatively with root infection in I. linnaei and T. purpurea, but had no influence in the other two species. The effect of 2-pH on sporulation varied with host species and sites. No general correlation existed between available soil nutrients, root colonization and spore number but the influence ofNand P was counteractive on VAM infection. The present study indicates that the response of root colonization and spore number to edaphic factors is a localised rather than a generalised phenomenon

Vesicular-Arbuscular Mycorrhizal colonization and growth of tomato (Lycopersicon esculentum) in autoclaved soil

The effect of autoclaving soil an uesicular-arbuscular mycorrhizal (VAAl) Jungal colonization and biomass production of tomato (Lycopersicon esculentum Mill) was assessed in pot experiments under greenhouse conditions. Four treatments were given viz., (1) VAM-free plants in autoclaued soil, (2) VAM plants in autoclaued soil, (3) VAM plants in autoclaved soil amended with VAM-free filtrate of non-autoclaved soil, and (4) VAM plants in non-auloclaved soil. The VAM plants grown in non-autoclaued soil showed the highest root colonization of 87.78% while those under (2) and (3) showed only 55.11 % and 56.94% respectiuely. On the other hand, significantly higher shoot length (105.4 cm2/plant), wtal kaJ area (740.3 cm2/plant) and biomass (8.43 g/plant) were obtained in VAM plants grown in autoclaved soiL VAM-free plants in autaclaved sail had reduced growth. In treatments 3 and 4 plant growth was intermediate. The results indicate that VAM colonization and sporulation were favoured under natural conditions, but VAM plants under autoclaved soil conditions produced maximum growth

Mycorrhizal Dependency in Certain Indian Cotton Cultivars

Mycorrhizal dependencies of ten cotton cultivars were evaluated in the green houseusing completely randomized block design model. Acid-delinted seeds were sown inpolybags containing natural black soil. Plant growth, nutrient content and mycorrhizalcolonization levels were studied. Cotton cultivars exhibited mycorrhizal colonizationranging from 36.52 to 73.5 %. Plant dry weight and tissue Nitrogen content were positivelycorrelated whereas tissue Potassium was not correlated with the mycorrhization. Rootdiameter, number of root hairs and root length were varied among the cultivars. Rootdiameter was highest in the cultivar NHH 44, whereas root hair number was more in Suvin.Root hair length was maximum in the cultivar Suvin. Mycorrhizal dependency wasnegatively correlated with root hair number and root hair length. Maximum mycorrhizaldependency was exhibited by the cultivar Surya. The results showed the existence of strongmycorrhizal dependency in the cotton cultivars

Early Establishment of Native Vesicular-Arbuscular Mycorrhizas in Three Vegetable Crops of South India - A Comparative Study

The vesicular-arbuscular mycorrhizal (VAM) status of three vegetable crops viz., tomato, brinjal and chilli was assessed during the initial establishment period in natural field conditions as well as in pot culture using nonsterile soil. The soil had low nutrient status and no manurial application was made during the 60 d course of the study. VAM fungal colonization in the roots was maximum at 45, 50, and 60 d after the respective germination of brinjals, tomato and chilli seeds under field conditions, and on the 60th d in the pot culture experiment. In no case was 100 per cent root colonization obtained. Ascending and descending trends in colonization were observed. In all cases, the original spore count of3.90 (±0.30) g dry soil increased markedly in the rhizosphere soil after plant growth. Spore number was more pronounced in pot than in field culture

Mycorrhizae in sedges as related to root character and its ecological significance

Twenty four sedges were examined to assess the role of root characters on mycorrhizal status. Vesicular-arbuscular mycorrhizal (VAM) injection was positively related to root thickness and negatively to root hair number and length. Dried mycorrhizal roots of Bulbostylis barbata, Cyperus cyperinus. C. kyllingia and Fimbristylis ovata served as inocula oj VAMJungi in pot culture study indicating that mycorrhizal sedge roots could act as inocula in initiating and reviving mycorrhizae in natural soils

Response of Siratro (Macroptilium atropurpureum Urb. Rabaceae) to Vesicular-arbuscular Mycorrhizal Fungi and Rhizobium sp. in Sterilized Soil

The effect of inoculation of six species of vesicular-arbuscular mycorrhizal fungi viz., Gigaspora margarita, Glomus mosseae, G. monosporum, G. versiformis, G. fasciculatum, G. deserticola and Rhizobium sp. on growth and NPK content in siratro (Macroptilium atropurpureum) was studied. The mycorrhizal species were isolated from the rhizosphere forest soils of the Western Ghats and multiplied in pot culture with Sorghum bicolor as the host plant. Rhizobium sp. isolated from fresh nodules of siratro was cultured and maintained in yeast extract mannitol broth. The influence of VAM fungi and Rhizobium sp. either singly or in combination on growth and nutrient contents of siratro showed statistically significant increase after only 60 days of plant growth. Dual inoculation with VAM fungi and Rhizobium increased plant nodule number and tissue NPK content. Highest growth and nutrient content were exhibited by plants inoculated with Rhizobium together with multiple VAM fungi

Biochemical changes in cotton plants by Arbuscular Mycorrhizal colonization

Biochemical changes in ten cultivars of cotton (Gossypium hirsutum L. Merr. ) in relation with arbuscular mycorrhizal (AM) colonization was studied.  Proteins, sugars, amino acids and phenols in both leaves and roots were quantified and compared with the mycorrhization levels of the cultivars. Cultivars showed varying levels of mycorrization which correlated with the biochemical levels of the plants. It is concluded that cultivars which are more mycorrhizal do show increased levels of phenols and proteins which in turn help them to resist pathogenesis