Associative transcriptomic analysis of defensive responses of Brassica juncea (L.) Czern to Alternaria brassicae

Pooja Bharmera; Lenka Havlickova; Anna Goyal; Zhesi He; Pankaj Sharma; Harjeevan Kaur; Chhaya Atri; Lihong Wang; Andrea L Harper; Ian Bancroft; Javed Akhatar; Mehak Gupta; Gurpreet Kaur; S.S. Banga; Prabhjodh Singh Sandhu

Just Accepted

This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.

Associative transcriptomic analysis of defensive responses of Brassica juncea (L.) Czern to Alternaria brassicae

Pooja Bharmera, Lenka Havlickova, Anna Goyal, Zhesi He, Pankaj Sharma, Harjeevan Kaur, Chhaya Atri, Lihong Wang, Andrea L Harper, Ian Bancroft, Javed Akhatar, Mehak Gupta, Gurpreet Kaur, S.S. Banga, Prabhjodh Singh Sandhu

Abstract

Context: Periodic outbreaks of Alternaria leaf blight (ALB) or brown spot caused by Alternaria brassicae results in significant production losses in mustard crops globally. Understanding the genetic basis of resistance to ALB is crucial for developing stable, resistant cultivars. Aims: This study is aimed to evaluate defensive responses to a purified isolate of A. brassicae in a diverse germplasm collection of B. juncea and to identify candidate genes associated with resistance. Methods: A germplasm collection comprising 261 lines of B. juncea was assessed for resistance to A. brassicae. Phenotypic variation was analyzed to determine inheritance patterns, and associative transcriptomics was used to identify candidate genes involved in the defense response. Key Results: Resistance responses exhibited a near-normal distribution, suggesting quantitative inheritance. Wild Brassicaceae introgression lines, such as IM-152, IM-87, J-8, and the exotic germplasm line ZEM-3356, consistently displayed resistance. Among them, J-8 and ZEM-3356 showed the lowest disease severity. Thirteen candidate genes were identified, with TSD2 emerging as a strong candidate, specifically linked to resistance against Alternaria brown spot. Other key genes, including ADT5, CBF2, and DUF677, were also implicated in fungal resistance. Conclusions: Resistance to ALB is quantitatively inherited, and specific candidate genes were identified as critical for defence. Incorporating these genes into mustard cultivars may improve resistance. Implications: Strategies such as pyramiding these genes, marker-assisted recurrent selection, and interspecific hybridization could enhance genetic resistance in mustard and related crops like canola rapeseed, ultimately reducing losses caused by ALB.

CP25018 Accepted 06 June 2025