Molecular Breeding Strategy and Challenges Towards Improvement of Downy Mildew Resistance in Cauliflower (Brassica oleracea var. botrytis L.)

Abstract

Cauliflower (Brassica oleracea var. botrytis L.) is one of the important, nutritious and healthy vegetable crops grown and consumed worldwide. But its production is constrained by several destructive fungal diseases and most importantly, downy mildew leading to severe yield and quality losses. For sustainable cauliflower production, developing resistant varieties/hybrids with durable resistance against broad-spectrum of pathogens is the best strategy for a long term and reliable solution. Identification of novel resistant resources, knowledge of the genetics of resistance, mapping and cloning of resistance QTLs and identification of candidate genes would facilitate molecular breeding for disease resistance in cauliflower. Advent of next-generation sequencing technologies (NGS) and publishing of draft genome sequence of cauliflower has opened the flood gate for new possibilities to develop enormous amount of genomic resources leading to mapping and cloning of resistance QTLs. In cauliflower, several molecular breeding approaches such as QTL mapping, marker-assisted backcrossing, gene pyramiding have been carried out to develop new resistant cultivars. Marker-assisted selection (MAS) would be beneficial in improving the precision in the selection of improved cultivars against multiple pathogens. This comprehensive review emphasizes the fascinating recent advances made in the application of molecular breeding approach for resistance against an important pathogen; Downy Mildew (Hyaloperonospora parasitica) affecting cauliflower and Brassica oleracea crops and highlights the QTLs identified imparting resistance against this pathogen. We have also emphasized the critical research areas as future perspectives to bridge the gap between availability of genomic resources and its utility in identifying resistance genes/QTLs to breed downy mildew resistant cultivars. Additionally, we have also discussed the challenges and the way forward to realize the full potential of molecular breeding for downy mildew resistance by integrating marker technology with conventional breeding in the post-genomics era. All this information will undoubtedly provide new insights to the researchers in formulating future breeding strategies in cauliflower to develop durable resistant cultivars against the major pathogens in general and downy mildew in particular.

Establishment of a stable, effective and universal genetic transformation technique in the diverse species of Brassica oleracea

“…Since then, the research on important gene mining and their regulatory mechanism of B. oleracea crops has entered a period of rapid development. A series of genetic loci or genes controlling plant growth, resistance to biotic and abiotic stresses, quality composition and fertility, etc., have been excavated ( Li et al., 2021 ; Shaw et al., 2021 ; Zhang et al., 2021 ; Han et al., 2021 ; Ren et al., 2022 ; Alemán et al., 2022 ). Therefore, the effective transformation method established in this study will greatly accelerate the functional validation and regulatory mechanism study of the target genes controlling important agronomic traits of B. oleracea crops and promote rapid gene pyramiding to develop excellent target materials.…”

Harnessing adult-plant resistance genes to deploy durable disease resistance in crops

“…In addition to resistance against biotrophic fungi, such as rust and powdery mildew, studies have reported the involvement of APR genes in resistance against hemibiotrophic and necrotrophic diseases, such as tan spot [ 27 ], Septoria nodorum blotch [ 28 ] and Fusarium head blight/crown rot [ 29 ] of wheat. Outside the cereals, APR genes are also known globally for their involvement in resistance against important diseases of other crops, such as maize northern leaf spot [ 30 ], canola blackleg [ 31 ], Brassica downy mildew [ 32 ], chickpea Fusarium wilt and Ascochyta blight [ 33 ], and soybean powdery mildew [ 34 ]. Beside conveying resistance against multiple pathogen strains, these APR genes play a vital role in prolonging the durability of frequently used major or seedling resistance genes when deployed along with them.…”

Editorial: Genetic and epigenetic regulation of disease resistance in horticultural plants

“…Unfortunately, disease outbreaks and an overuse of pesticides are impeding the expansion of the horticultural business. Effective disease prevention techniques must address these issues by choosing germplasm that is resistant to disease and creating resilient plant varieties through breeding and genetic modification ( Zahoor et al, 2020 ; Shaw et al, 2021 ).…”