The potential of brassinosteroids to alleviate the effect of mesotrione residue on three legume crops
Mota, Maipato Margaret
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Legume crops are warm climate crops with the potential of improving soil fertility, by fixing atmospheric nitrogen in the soil, utilizing the Rhizobium bacteria and after harvest the roots of the crop is left in the soil to decompose, which results in improved soil fertility. They are very important to both smallholder and commercial farmers, because they provide a source of income and food for both humans and animals. Due to their importance in increasing soil fertility it is economically viable to plant them in a crop rotation system. However, despite their importance, production can be low if weed competition is not eliminated and due to their sensitivity to certain herbicides. Mesotrione is a selective herbicide that is normally used to control annual broad weeds and grasses in maize production, and it can be used as a preemergence or post-emergence application in the field. However due to legume’s sensitivity to this herbicide it can have a huge impact on the production in a rotation system. To enable assessment of these impacts, the three legumes required testing with scenarios involving different levels of mesotrione residues in interaction with different application methods of brassinosteroids interactions. It is hypothesized that negative consequences of mesotrione on plant productivity would be mitigated by the application of brassinosteroids. This mitigation may be ascribed to BRs increasing both morphological, physiological and yield parameters and increased resistance or tolerance, which may buffer transient periods of herbicide stress. Under glasshouse conditions over two seasons, again BRs in combination with three concentrations of mesotrione residue have been shown to ameliorate damages caused by mesotrione residue on crops and all the morphological, physiological and yield parameters were significantly increased after treatment with BRs. The study confirmed the potential of BRs to counteract the possible negative effects of the mesotrione residue on morphology, physiology and yield of the three legumes. Further studies need to explore the effect of residual activities using different herbicides and to determine the alleviating effect of brassinosteroids. This will enable more precise exploration of legume plant response to herbicide stress scenarios.