Effect of Acute Heat Stress During Pod Filling on Seed Quality Traits in Lentil (Lens culinaris Medikus)

Abstract

Heat stress is an increasing threat to lentil production systems, yet its effects on seed quality traits remain poorly understood. This study evaluated seed quality responses of lentil genotypes grown under control and heat stress conditions across three seasons (2022–2024), with acute heat stress applied during the pod-filling stage for 3 days. Across seasons, heat stress consistently reduced 100-grain weight (100GWT), seed size index (SSI) and seed coat redness (a*), with the extent of reduction increasing under higher heat loads. In contrast, seed plumpness (SP), lightness (L*) and yellowness (b*) stayed largely stable. Protein concentration increased by 3.8%–6.0% under heat stress, indicating a compositional shift linked to reduced starch accumulation during seed filling. Trait relationships remained consistent across seasons with different environmental conditions, with larger seeds generally associated with lower protein levels and lighter seed coat colours. Despite notable genotype × environment interactions, consistent response patterns emerged, highlighting significant genetic variation in heat tolerance associated with seed quality traits. Several genotypes, including ILL 512/70951, GIA Metro, GIA Thunder, PBA Bolt, PBA Hallmark XT and PBA Jumbo 2, showed stable seed quality across seasons, whereas others demonstrated specific trait advantages such as stable seed size, colour or protein concentration under heat stress. These findings show that acute heat stress during pod filling affects lentil seed quality in a trait-dependent manner and highlight opportunities to select genotypes with reliable performance under higher temperatures, thereby advancing understanding of heat tolerance mechanisms in lentil and supporting the development of climate-resilient cultivars through informed trait-based selection.