Assessment of lima bean genotypes for high-temperature cultivation based on physiological and agronomic traits

Abstract

ABSTRACT Rising temperatures resulting from climate change present a significant limitation to lima bean (Phaseolus lunatus L.) production, especially in hot and semiarid regions. This study evaluated lima bean genotypes under elevated-temperature conditions to identify heat-adapted lines based on vegetative, physiological, and yield-related traits. Measurements included vegetative growth parameters, gas exchange, photosystem II quantum efficiency, photosynthetic pigments, agronomic traits, and grain yield across 16 genotypes, encompassing both improved lines and landrace varieties. Significant differences were observed among genotypes for all evaluated characteristics, demonstrating considerable genetic variability. Lines H25-64, H94-31, and H25-54 exhibited superior physiological performance, as indicated by higher photosynthetic efficiency and favorable agronomic traits under elevated temperatures. Notably, line H81-32 displayed low growth and physiological performance but achieved the highest grain yield and hundred-grain weight, suggesting efficient allocation of photoassimilates to reproductive sinks. In contrast, lines H25-56 and H25-67 demonstrated high CO2 assimilation and stomatal conductance, yet this physiological advantage did not translate into increased grain yield. Landrace varieties exhibited traits linked to rusticity and morphological adaptation, such as larger pod dimensions, underscoring their value as sources of adaptive alleles. Multivariate analyses revealed that productivity under elevated temperatures is more closely associated with physiological efficiency than with vegetative biomass accumulation. The identified lines constitute promising parental materials for breeding programs targeting the development of heat-tolerant lima bean cultivars suited to warming environments, thereby supporting the sustainability of production systems under climate change.