Tropentag, September 10 - 12, 2025, Bonn "Reconciling land system changes with planetary health"

Heat stress response and genome-wide association mapping in global leaf mustard (Brassica juncea) accessions

¹Tokyo University of Agriculture , International Agricultural Development , Japan
²Tokyo University of Agriculture, International Agricultural Development
³Tokyo University of Agriculture, Bioresource Development
⁴Tokyo University of Agriculture, Bioresource Development, Japan
⁵Tokyo University of Agriculture, Bioresource Development, Japan

Abstract

In recent years, heat stress caused by global warming has become a major threat to sustainable agriculture and global food security. The use of diverse genetic resources is critical for developing heat-tolerant crop varieties. Leaf mustard (Brassica juncea L.), cultivated widely across countries such as Vietnam, Myanmar, and Japan, exhibits high genetic diversity due to its complex cross-pollination nature. This study aims to evaluate the heat tolerance of 116 leaf mustard accessions collected worldwide and identify accessions with potential for breeding programs, along with genetic markers associated with heat stress. Heat-induced cellular damage was assessed via electrolyte leakage, expressed as relative injury (RI%) (Orvar et al., 2000). In addition, pungency was quantified through allyl isothiocyanate (AITC) content, and a genome-wide association study (GWAS) was conducted. Based on RI%, accessions were classified into three categories: heat-tolerant (RI% < 50%, n = 12), moderately tolerant (50% ≤ RI% < 70%, n = 56), and heat-sensitive (RI% ≥ 70%, n = 26). Four elite heat-tolerant accessions were identified: two from Myanmar (270163, 261431), one from China (37392), and one from Japan (‘Irakabu’), with RI values ranging from 40.4% to 44.7%. Additionally, three accessions—Japanese ‘Akaōbatakana’ (RI 46.5%, AITC 0.67 mg/g), Myanmar 261454 (47.2%, 0.85 mg/g), and Myanmar 270127 (48.2%, 0.82 mg/g)—were notable for their combination of heat tolerance and high pungency. Correlation analysis showed a negative relationship between RI% and AITC content, indicating that higher pungency may be associated with greater heat tolerance. GWAS revealed significant SNPs associated with heat tolerance on chromosomes AA_09 and BB_04. These findings provide valuable insights for breeding B. juncea cultivars with improved resilience to heat stress under climate change.

Keywords: Brassica juncea, GWAS, heat tolerance, leave mustard, relative injury (RI%)

Contact Address: Chau Tran Thi Ha, Tokyo University of Agriculture , International Agricultural Development , Nozawa, 1540003 Setagaya, Japan, e-mail: chautran654gmail.com