Breeding for Fusarium wilt resistance in pigeonpea: From landraces to molecular techniques

Abstract

Fusarium wilt, caused by Fusarium udum Butler, is a devastating disease of pigeonpea (Cajanus cajan) that causes 30-100% yield losses in affected fields (Kannaiyan et al., 1984). Breeding for Fusarium wilt resistance in pigeonpea has evolved from simple field selection of landraces to advanced molecular breeding and biotechnology. Early efforts (1970s-1980s) focused on screening thousands of germplasm accessions in “wilt-sick” fields, yielding a handful of resistant lines such as ICP 8863 (released as ‘Maruti’ in 1986) which revolutionized pigeonpea cultivation in wilt-endemic regions (ICRISAT, 1986). Conventional breeding strategies including pure-line selection, hybridization, pedigree breeding, and induced mutation produced numerous wilt-resistant cultivars (e.g. ‘Bahar’, ‘Pusa 9’, ‘Sharad’, ‘Durga’, ‘BDN-2004-1’) adapted to different Indian agro-ecologies (Singh et al., 1990; Choudhary et al., 2013). Since the 1990s, breeding programs (notably at ICRISAT and Indian national institutes) achieved milestones such as the variety ‘Asha’ (ICPL 87119), the first pigeonpea combining high yield with dual resistance to Fusarium wilt and sterility mosaic disease (Saxena et al., 2010). In the 2000s, attention turned to molecular approaches: genetic studies revealed both dominant and recessive genes for wilt resistance (Parupalli et al., 2017) and molecular markers were developed to tag resistance loci (e.g. RAPD markers linked to a wilt-resistance gene by Kotresh et al. (2006)). The pigeonpea genome sequence was completed in 2012, enabling mapping of quantitative trait loci (QTLs) for wilt resistance and marker-assisted selection (MAS) in breeding (Varshney et al., 2012; Saxena et al., 2017). Advanced genomics tools high-density SNP arrays, QTL mapping via genotyping-by-sequencing and comparative transcriptomics have identified several genomic regions and candidate genes associated with wilt resistance (Singh et al., 2016; Purohit et al., 2021). However, breeding remains challenging due to the pathogen’s high variability and the need to pyramid multiple disease resistances (Saxena et al., 2020; Purohit et al., 2021). Recent breakthroughs include diagnostic DNA markers for Fusarium wilt resistance (Saxena et al., 2020) and transgenic pigeonpea lines expressing antifungal genes (e.g. rice chitinase, plant defensins, oxalate oxidase) that show enhanced wilt resistance in experimental trials (Kumar et al., 2004; Choudhary et al., 2013). This review traces the global progression of Fusarium wilt resistance breeding in pigeonpea with special emphasis on India from traditional methods to modern molecular techniques. It discusses historical milestones, key resistant varieties and breeding programs, and the latest advances in genomics-assisted breeding, gene discovery and biotechnology. Challenges and future prospects are analyzed, highlighting integrated strategies to develop durable Fusarium wilt resistance in pigeonpea.