Chlorpyrifos enrichment enhances tolerance of Anabaena sp. PCC 7119 to dimethoate.

Organophosphorus (OP) insecticides are widely used for on-field pest control, constituting about 38% of global pesticide consumption. Insecticide tolerance has been recorded in microorganisms isolated from the contaminated soil. However, the cross-tolerance of laboratory-enriched cultures remains poorly understood. A chlorpyrifos tolerant (T) strain of Anabaena sp. PCC 7119 was developed through continuous enrichment of the wild strain (W). The cross-tolerance of the T strain to the OP insecticide dimethoate was assessed by measuring photosynthetic performance, key enzyme activities and degradation potential. The presence of dimethoate led to a significant reduction in the growth and pigment content of the W strain. In contrast, the T strain demonstrated improved growth and metabolic performance. Chl a and carotenoids were degraded faster than phycobiliproteins in both strains. The T strain exhibited superior photosynthetic performance, metabolic efficiency and photosystem functions, than of W strain, at both the tested dimethoate concentrations (100 and 200 µM). The treated T strain had more or less a normal OJIP fluorescence transient and bioenergetic functions, while the W strain showed a greater fluorescence rise at ≤ 300 µs indicating the inhibition of electron donation to PS II, and at 2 ms due to reduced electron release beyond QA. The T strain had significantly higher levels of esterase and phosphatases, further enhanced by insecticide treatment. Dimethoate degradation efficiency of the T strain was significantly higher than of the W strain. T strain also removed chlorpyrifos more efficiently than W strain at both the tested concentrations. The BCFs of both chlorpyrifos and dimethoate were lower in the T strain compared to the W strain. These findings suggest that the enriched strain exhibits promising results in withstanding dimethoate toxicity and could be explored for its potential as a bioremediating organism for OP degradation.

Chemopriming for induction of disease resistance against pathogens in rice.

Rice is an important grain crop of Asian population. Different fungal, bacterial and viral pathogens cause large reduction in rice grain production. Use of chemical pesticides, to provide protection against pathogens, has become incomplete due to pathogens resistance and is cause of environmental concerns. Therefore, induction of resistance in rice against pathogens via biopriming and chemopriming with safe and novel agents has emerged on a global level as ecofriendly alternatives that provide protection against broad spectrum of rice pathogens without any significant yield penalty. In the past three decades, a number of chemicals such as silicon, salicylic acid, vitamins, plant extract, phytohormones, nutrients etc. have been used to induce defense against bacterial, fungal and viral rice pathogens. From the detailed analysis of abiotic agents used, it has been observed that silicon and salicylic acid are two potential chemicals for inducing resistance against fungal and bacterial diseases in rice, respectively. However, an inclusive evaluation of the potential of different abiotic agents to induce resistance against rice pathogens is lacking due to which the studies on induction of defense against rice pathogens via chemopriming has become disproportionate and discontinuous. The present review deals with a comprehensive analysis of different abiotic agents used to induce defense against rice pathogens, their mode of application, mechanism of defense induction and the effect of defense induction on grain yield. It also provides an account of unexplored areas, which might be taken into attention to efficiently manage rice diseases. DATA AVAILABILITY STATEMENT: Data sharing not applicable to this article as no datasets were generated or analysed during the current study.

Biopriming for induction of disease resistance against pathogens in rice.

MAIN CONCLUSION: Rice is attacked by an armada of pathogens. Present review provides a critical evaluation of the potential of different biotic agents used to protect rice yield drop from pathogenicity and an account of unexplored areas, which might be taken into consideration to manage rice diseases. Rice (Oryza sativa L.), is the most important staple food of Asian countries. Rice production is significantly limited by a diversity of pathogens, leading to yield loss and deficit in current rice supply. Application of agrochemicals of diverse types has been considered as the only option to control pathogens and enhance rice production, thereby causing environmental concerns and making the pathogens resistant to the active ingredients. Increase in population and resistance of pathogen towards agrochemicals put pressure on the agronomists to search for safe, novel, eco-friendly alternative ways to manage rice pathogens. Inducing resistance in rice by using different biotic/abiotic agents provides an environmental friendly alternative way to effectively manage bacterial, fungal, and viral rice pathogens. In recent years, a number of protocols have been developed for inducing pathogen resistance by bio-priming of rice. However, a comprehensive evaluation of the potential of different biotic agents to protect rice crop loss from pathogens is hitherto lacking due to which the research on induction of defense against pathogens in rice is discontinuous. This review deals with the detailed analysis of the bacterial and fungal agents used to induce defense against rice pathogens, their mode of application, mechanism (physiological, biochemical, and molecular) of defense induction, and effect of defense induction on the yield of rice. It also provides an account of gaps in the research and the unexplored areas, which might be taken into consideration to effectively manage rice pathogens.