Background
Fusarium wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici (FOL) is a serious disease that causes significant economic losses in tomato production. Seventeen endophytic Bacillus isolates from tomato roots of Meghalaya were tested for antagonistic and plant growth promotion activities. Dominating arbuscular mycorrhiza fungi (AMF) spores were isolated from the rhizosphere soils of tomato grown in Meghalaya. The effect of different combinations of AMF and endophytic Bacillus on Fusarium wilt severity and growth of tomato plant under pot and field conditions was studied.
Results
The endophytic Bacillus isolates ERBS51 and ERBS10 showed a maximum inhibition against FOL, with 58.43 and 55.68%, respectively, in a dual culture experiment. ERBS51 and ERBS10 were identified as Bacillus velezensis and Bacillus sp., respectively, based on 16s rRNA sequencing. Both isolates were found positive for iturin A, surfactin, bacillomycin D, protease, cellulase, pectinase, alpha-amylase, siderophore, ammonia production and ZnCO3 solubilization. Funneliformis mosseae and Glomus fasciculatum were the dominating AMF species in tomato rhizosphere of Meghalaya. The result of pot and field experiments revealed that out of all the treatments, combination of Funneliformis mosseae + Glomus fasciculatum + Bacillus velezensis + Bacillus sp. was shown to be the best in reducing the severity of Fusarium wilt to 77.44 and 66.74%, respectively. F. mosseae + G. fasciculatum + B. velezensis + Bacillus sp. also recorded the highest in most growth attributes and yield.
Conclusions
Endophytic Bacillus (B. velezensis and Bacillus sp.) and AMF (F. mosseae and G. fasciculatum) were safe and effective biocontrol agents against Fusarium wilt of tomato.
This investigation was carried out to assess the combined effect of salt stress and drought on physiological and biochemical traits in wheat (Triticum aestivum L.) varieties so as to deduce the probable mechanism of stress tolerance in these varieties. Two salt tolerant (Kharchia 65 and KRL 210) and two salt sensitive (HD 2851 and HD 2009) wheat varieties were subjected to salt (50 mM and 100 mM NaCl) and drought (25% and 50% water deficit) stresses alone as well as in combination to study the interactive effects of salt × drought stresses under pot house conditions at seedling stage. The data recorded on physiological (membrane injury, relative water content, chlorophyll content, Na+, K+, Cl- and K+/Na+), biochemical (total soluble sugars and proline) and yield (number of tillers, productive tillers, biomass, and 1000 seed weight) attributes indicated the effect of salt and drought stresses in the studied varieties. These stresses caused a significant decline in chlorophyll content, K+ content, number of tillers, number of productive tillers, biomass and yield in sensitive varieties, while the tolerant ones were least affected. The sensitive varieties HD 2851 and HD 2009 accumulated the highest Na+ and Cl+ content, whereas Kharchia 65 (tolerant) accumulated the lowest amount of these ions. All the varieties, however, showed increased accumulation of compatible solutes (total soluble sugars and proline) with inclined stress which helped in osmotic adjustment. Consistent and significant reductions were observed in number of tillers as well as in productive tillers with every successive increase in salt and drought stresses. Yield in terms of 1000 seed weight followed the trend: 34.51 g in Kharchia 65>28.52 g in KRL 210>24.89 g in HD 2009>24.55 g in HD 2851.
A canker disease of broad bean (Vicia faba L.) pods was observed annually from February to April every year since 1995. Disease incidence ranged from 45 to 100% in commercial fields and experimental plots at the Central Agricultural University, Imphal, Manipur. Initial symptoms on young pods appeared as bright yellow, scattered spots 1 to 2 mm in diameter that later became raised, black, and corky within 12 days. As the disease progressed, the lesions coalesced and formed large cankers, which resulted in unmarketable pods. Surface-sterilized symptomatic tissues were plated on potato-dextrose agar (PDA) and the fungus that grew out was identified as Pestalotiopsis disseminata. One culture was deposited at the Indian Type Culture Collection, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi. Pathogenicity of the fungus was determined by pipetting two drops of a 3 × 103 conidia/ml spore suspension on each of five healthy young pods and repeating on each of 10 plants. A similar five pods inoculated with sterile water served as controls. Inoculated broad bean plants were covered with plastic bags for 48 h and placed into the open under shade having a temperature range of 25 to 28°C. Corky lesions similar to those originally observed developed within 16 days on inoculated pods. Symptoms did not appear on control pods. Necrotic tissues from artificially induced broad bean cankers were plated on PDA and consistently yielded P. disseminata. This is the first report of P. disseminata on broad bean in India.
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