Genetic control of stomatal pattern in common bean

Abstract

Common bean (Phaseolus vulgaris) is an important legume crop in many low-income countries and a major source of protein and micronutrients. In recent years, increasing temperatures and drought stress have decreased global bean production, with approximately 60% of current cultivations experiencing yield loss. The intake of carbon dioxide is done through stomata, microscopic pores on the leaf epidermis. However, stomata also serve as the primary pathway for water vapor loss through transpiration. Stomatal conductance is tightly regulated by stomatal traits, and identifying traits associated with improved drought tolerance and water use could support selective breeding of more resilient bean cultivars. To investigate a genetic basis of stomatal traits a multiparent advanced generation intercross (MAGIC) population of common bean was used. The population consisted of 500 inbred MAGIC lines containing recombined founder genotypes of eight parent lines with the aim to identify lines with enhanced drought tolerance. In this study microscopy was conducted on the eight parent lines and 200 MAGIC lines. Stomatal area, length and density were measured, and the theoretical maximal stomatal conductance was calculated for each line. A quantitative trait locus (QTL) analysis identified a significant peak for stomatal area on chromosome 1. No significant QTL-peaks were identified for the remaining stomatal traits. Within the QTL interval, 95 candidate genes were identified, including leucine-rich repeats, receptor-like kinases as well as other genes potentially involved in the regulation of stomatal area. Furthermore, a clear negative correlation between stomatal density and area was identified in both parent and MAGIC populations, with the MAGIC population displaying a broader variation. These findings improve our understanding of the genetic and phenotypic regulation of stomatal traits, and the detected QTL-region provides a foundation for future research of stomatal regulation and adaptation to drought in common bean.