Integrated management of root-rot of guar using biological agents along with neem and fungicids Bohra Burhanuddin, Mathur Kusum1, Trivedi P.C.2, Vyas B.N. Research Centre, Godrej Agrovet Limited, Pirojshanagar, Eastern Express Highway, Vikhroli (East), Mumbai-400 079, India 1Department of Plant Pathology, Rajasthan College of Agriculture, Udaipur-313 001, India 2Department of Botany, University of Rajasthan, Jaipur-302 004, India Online published on 30 November, 2019. Abstract In order to ecofriendly management of root rot of guar, biocontrol agents, oil based neem formulation and carbendazim were evaluated in various combinations as seed and seed + soil treatments in field condition. The seed treatment with T. harzianum Gn1+B. subtilis Ch-Kp-b-1 resulted in highest seed germination and dry biomass of plants and lowest disease incidence as compared to untreated control where seed germination and dry biomass were lowest and root rot incidence was highest. The combination of T. harzianum with oil based neem formulation and the combinat ion of B. subtilis with both oil based neem formulation and carbendazim also proved better resulting in higher seed germination and dry biomass and reduced disease incidence as compare to control. In case of soil + seed treatment T. harzianum soil treatment & carbendazim seed treatment was found higher effective followed by the combination of T. harzianum Gn1+B. subtilis Ch-Kp-b-1 where disease incidence were less dry biomass were high. It has been observed that the over all disease incidence was lower and dry biomass of guar plants was higher in the treatments specially BCAs which were applied as seed treatments compared to their soil treatments. The integrated treatments were significantly superior over the individual treatment. All the treatments significantly suppressed the inoculum density of F. solani and R. solani over the untreated control. The studies on population densities of the BCAs and the two pathogens revealed that the BCAs established and multiplied well in guar rhizosphere and could also effectively suppress the pathogens. The effective BCAs- T. harzianum Gn1 and B. subtilis Ch-Kp-b-1, were further evaluated in micro plots by integrating the host plant resistance, chemical fungicide carbendazim, and oil based neem formulation. These were tested in different combinations with guar root-rot tolerant cultivar ‘Swati-55’ and highly susceptible cultivar ‘Pusa Nav Bahar’. Highest seed germination was recorded in tolerant cultivar where combination of T. harzianum Gn1 and B. subtilis Ch-Kp-b-1 was applied. This was followed by carbendazim seed treatment + drench. Combination of T. harzianum Gn1 and B. subtilis Ch-Kp-b-1 also resulted in lower disease (ranging from 4.4 to 14.9 per cent during 30–70 days of sowing) and highest yield of green pod and dry biomass of guar plants followed by carbendazim (seed treatment + soi l drench) and T. harzianum Gn1+B. subtilis Ch-Kp-b-1+ oil based neem formulation. Similar trend of the efficacy of combined treatments were also observed with susceptible cultivar ‘Pusa Nav Bahar’. In this seed treatment with oil based neem formulation along with BCAs was significantly superior in suppressing the disease and higher yield of green pod and dry biomass weight of plants over control. All the treatments resulted in significant suppression of the guar root-rot pathogens as compared to untreated control in both the cultivars. The population densities of F. solani and R. solani was considerably less in tolerant cultivar “Swati-55” (42 and 22 x 105 c.f.u./g soil, respectively) than in the susceptible cultivar “Pusa Nav Bahar”, where these were 60.3 and 30.8 x 105 c.f.u./g soil, respectively. In Pusa Nav Bahar also, the integrated treatments resulted in significantly low inoculum densities of the 2 root-rot pathogens as compared to control. The lower population densities of these two guar root -rot pathogens as observed in the pot experiment was further confirmed in micro plot testing. Though the effects of the treatments were consistent in both, tolerant and susceptible culti vars, their effects were bet ter realized in tolerant cultivar. This shows the effectivity of the selected strains of the BCAs. The integration of fungal and bacterial BCAs as seed treatment proved highly effective than fungicide (carbendazim) seed treatment plus drench, and the individual BCAs were almost at par with it. Integration of BCAs with oil based neem formulation was also quite effective. Top Keywords Guar, Root rot, Fusarium solani, Rhizoctonia solani, Biocontrol, Integrated disease management, Neem formulation, Trichoderma harzianum, Bacillus subtilis. Top |