|Keywords (Extracted from title, table of contents and abstract of thesis)
rhizosphere mycofoora, rhizoplane mycofoora, soybean, fungi, aspergillus, penicillium, fusarium, h. phaseolina.. r. solani, drechslera sp., fungicides, biological antagonists, triohoderma harzianum, paeoilomyces lilaoinus, gliocladium virens, bacillus subtilis, rhizobium meliloti, streptomyces sp
Studies on quantitative mid quantitative changes in the rhizosphere and rhizoplane mycoflora of soybean showed the occurrence of greater number of fungi in the rhizosphere as compared to rhizoplane. Species of Aspergillus, Penicillium and Fusarium were most frequently isolated from the rhizosphere with a. predominant population of H. phaseolina.. R. solani, Fusarium sp., and Drechslera sp., in the rhizoplane. Microbial population gradually increased with age of plant which attained a. peak at the flowering and fruiting stage. Population of fungi showed an increase in the rhizosphere of soybean during the summer season as compared to plants grown in winter.
Among the five soybean cultivars viz., AGS, Improved Pelican, Steel 5/1, Amsoy and Columbus, the number of rhizosphere fungi varied with lowest fungal population found in soybean cv. Improved Pelican and highest. in cv. Amsoy. R/N ratio increased at fruiting period in all the varieties. Soybean seeds grown in garden loam soil showed greater fungal population in the rhizosphere and rhizoplane as compared I to' sandy clay loam or clay. Changes in soil pH between 7 and 8.5 showed no significant changes in .the rhizosphere/rhizoplane with Urea, NPK, DAP and mycoflora of soybean. Soil amendment SP04 showed significant suppression in root colonization of soybean by H. phaseolina, R. solani and Fusarium sp. Use of fertilizers showed an increase in fungal population both in rhizosphere and non-rhizosphere regions with higher counts at flowering and maturation period of soybean plants. Organic fertilizers viz., Higro, Fish meal, Plant food and FYM significantly suppressed H. phaseolina and R. solani infection on rhizoplane of soybean. Population of Fusarium sp., in the where Higro, Plant food and FYI! Were rhizosphere decreased used. Use of organic and inorganic fertilizers mixed with microbial antagonists showed significant reduction in population of rhizosphere and rhizoplane than their separate use.
Amendment of soil with oil cakes of neem, cotton and mustard alone or in combination with Bradyrhizobia showed an increase in the total fungal population in the rhizosphere with significant reduction in infection by H. phaseolina, R. solani andFusarium sp. Low dosages of neem, cotton and mustard cake stimulated the soil mycoflora in the non-rhizosphere soil, but in the presence of higher dosages, the growth of fungi in soil was inhibited. Soil amendment with wheat straw alone or with microbial antagonists showed significant reduction in H. phaseolina and R. solani infection on soybean. Plants treated with P. lilacinus showed highest RIM ratio as compared to control. Greater infection of soybean root with H. phaseolina.. R. solani and Fusarium sp., was observed in: plants subjected to water stress or grown in soil with low moisture. mycoflora in plants subjected to water stress increased with qualitative and quantitative changes in the rhizosphere. Significant changes in rhizosphere and rhizoplane mycoflora were produced' by P. lilacinus, T. harzianum, G. virens and Streptomyces sp., at 25 and 50% MHC and by R. me1i10ti and B. subti1is at 75% MHC.
Of the fungicides used, Benomyl, Bavistin and Dithane used RS soil drench were found more effective in controlling the infection of R. solani whereas seed treatment with Benomyl, Vitavax, Captan, Dithane and Bavistin showed significant reduction in infection of H. phaseolina, R. solani and Fusarium sp. Fungicide used as seed dressing or soil drench inhibited rhizosphere and non-rhizosphere fungi. Germination and nodulation on soybean plants increased by seed treatment with fungicide and Dithane showed better seed germination. Benomyl and Dithane showed complete control of H. phaseolina. R. solani and Fusarium sp., plants as compared to regularly watered plants. in stressed
Seed coating with biological antagonists viz., Triohoderma harzianum, Paeoilomyces lilaoinus, Gliocladium virens, Bacillus subtilis, Rhizobium meliloti and Streptomyces sp. controlled the infection of H. phaseolina, R. solani and Fusarium sp., whereas soil drenching decreased the fungal population in the rhizosphere and root colonization of root infecting fungi. Inoculation of microbial antagonists reduced fungal population in the rhizosphere of ; saline 'soil than in rhizoplane whereas pathogenic fungi viz., F. solani, H. phaseolina and R. solani showed an increase on th£ root system in soil at high salinity level.