Rice brown spot (BS) is a chronic disease that affects millions of hectares of rice every growing season, grown by some of the most resource-poor farmers. Despite its widespread occurrence and impact, much still needs to be understood about BS. Reported yield losses in relative terms vary widely from 4 to 52 %. However, accurate, systematic estimates are lacking. BS is conventionally perceived as a secondary problem that reflects rice crops that experience physiological stresses, e.g. drought and poor soil fertility, rather than a true infectious disease. Much remains to be understood about the mechanisms leading to epidemics and crop losses. Quantitative and qualitative knowledge gaps exist in our understanding of the epidemiological processes, sources of resistance and biocontrol methods. In this review we identify several of these gaps, which if filled, could lead to a strong impact on the management of brown spot. We also use the architecture of a simulation model to position and prioritize these knowledge gaps, assess the epidemiological consequences of disease management options on
The application of Trichoderma strains with biocontrol and plant growth-promoting capacities to plant substrates can help reduce the input of chemical pesticides and fertilizers in agriculture. Some Trichoderma isolates can directly affect plant pathogens, but they also are known to influence the phytohormonal network of their host plant. In the current study, we evaluated the production of potential growth-promoting metabolites (IAA and phosphate) for eight isolates of Trichoderma collected from different geographical locations of Chhattisgarh and some isolates were procured from STRASA-BMGE using 83 elite rice lines. All the eight isolates assessed their growth response onrice. All the Trichoderma isolates were able to release inorganic phosphorus from tri-calcium phosphate and showed consistent ability to produce indole-3-acetic acid (IAA). The production of these metabolites varied greatly within species. Confrontation assays of Trichoderma isolates against two soil borne plant pathogens (Scelrotium rolfsii and Rhizoctonia solani) expressed varying degrees of antagonistic responses, In-vitro antagonism being more effective against R. solani than S. rolfsii. The production of metabolites in all the Trichoderma isolates did not correlate with enhanced root growth in rice lines and bio control efficacy. However, one of the Trichoderma viride isolate (T 14) was identified as highest producer of inorganic phosphate, IAA exhibited high antagonistic and plant growth promoting ability. A characteristic aromatic odor resembling coconut in T 14 isolate was observed which we speculate is due to 6-Pentylpyrone (one of the best studied secondary metabolites having both antifungal and plant growth-promoting activities. Besides the T 14 isolate isolates designated as IRRI-2, IRRI-3 and IRRI-4 were the promising inducer of plant growth.
The Pseudomonas fluorescens a major Rhizobacteria encourage the plant growth through producing yellowish green fluroscent siderophore involve in high affinity transport of iron into the cell. The P. fluorescens isolates grow in iron deficient media because of production capacity of siderophore depends on iron content. Fifty nine Pseudomonas fluorescens were isolated in King's B media under 260 nm wavelengths from the rhizosphere and non-rhizospheric soil of cave, forest, fellow land and agriculture field in Chhattisgarh region. The amounts of siderophore produce by P. fluorescens isolates were screen in iron deficient succinate media and most of them were found positive for the production of much siderophores. One of the isolate from Pakhanjore area "P3" produce highest siderophore, which further assessed for plant growth promotion activities of crops rice, urd, mung and arhar. The study showed significantly higher increase in root length over control plants was observed in Rice (68.45%) followed by Urd (40.1%), Mung (33.71%) and Arhar (29.53%). Similarly, significantly higher increase in shoot length over control plants was observed in Rice (68.925%) followed by Urd (43.42%), Mung (39.96%) and Arhar (19.45%). It has been shown that these bacteria competively colonize plant roots and cause the plant statistically significant root and shoot increases by stimulating plant growth and reduce the incidence of plant disease of above mention crops under green house of tray culture conditions.
Highlights• There were 59 isolates of pseudomonas fluorescens isolated from rhizosphere and non-rhizospheric soil.• P. fluorescens isolates were screen in iron deficient succinate media for amount of siderophore production.• One of isolate highest siderophore producing further assessed for PGPA.• The study showed significantly higher increase in shoot length and root length by P. fluorescens
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