Genome editing for banded leaf and sheath blight resistance in Indian maize genotypes

Abstract

Maize is the third most significant grain crop in India and is used as food, feed, and industrial raw material. Banded Leaf and Sheath Blight (BLSB) disease of maize caused by the necrotrophic fungal pathogen Rhizoctonia solani causes significant yield losses frequently between 10-40 per cent. To date, a few maize genotypes having mild/partial resistance to this destructive fungus have been reported. Additionally, a small number of quantitative trait loci (QTLs) for resistance to BLSB have been identified globally; yet, none of these QTLs have been found to confer strong resistance to BLSB. Therefore nonavailability of completely field-resistant or immune maize genotypes is of great concern and poses a major challenge for plant breeders. To manage this disease, a variety of agrochemicals, agronomic practices, and integrated pest management strategies are being used; nonetheless, sufficient and sustainable control could not be achieved. Further, there are negative ecological effects from the widespread usage of fungicides. Moreover, the management of BLSB is highly ineffective because of the broad host range of R. solani, the great genetic heterogeneity of the pathogen, the long survival ability in the form of sclerotia, and the lack of stable resistant maize cultivars against this disease. This implies that novel strategies should be used to develop BLSB-resistant Indian maize genotypes. In view of the above facts, developing a transgene-free genome-edited Indian maize genotype resistant to BLSB via the CRISPR/Cas- mediated targeted mutagenesis of major regulator gene i.e. the F-box proteinencoding gene, ZmFBL41 would be a viable approach. It is anticipated that precise editing of this key gene would potentially address a major factor causing yield penalty in Indian maize i.e. BLSB disease.