Flowering Time Response of Diverse Lentil (Lens Culinaris Medik.) Germplasm Grown in Multiple Environments

Abstract

Adaptation of lentil (Lens culinaris Medik.) germplasm from one environment to another is a complex process and days to flower (DTF) is considered as the primary phenological stage determining the adaptation of genotypes. Studies revealed that temperature and photoperiod are major environmental factors defining DTF. This research was conducted with the objective of understanding the variation of DTF governed mainly by temperature and photoperiod and their interactions and identifying genomic regions and candidate genes or markers associated with DTF in specific environments. To accomplish this, 324 lentil genotypes were grown in three replications at ten field locations over two seasons in three major lentil growing macro-environments (Northern temperate, Mediterranean and South Asian). Results showed significant variation (p<0.001) in DTF among the genotypes (G), site-years (E), and genotype by site-year interaction (G × E). However, site-years was by far the most important determinant of DTF. In temperate site-years, the DTF variation occurred mainly because of the genotypic variability. Temperature was observed as the major factor defining DTF variation in Mediterranean site-years, whereas, the interaction between temperature and photoperiod was observed to be the determinant factor in South Asia. The effect of temperature on DTF variation was better described in the form of thermal flowering time (TFT) by considering 5°C base temperature in long day environments. A complete model to analyze the interaction effect of temperature and photoperiod in DTF variation could not be confirmed due to constraints associated with the critical photoperiod calculation. To identify candidate genes or genomic regions associated with DTF to a specific environment, association studies were conducted using a mixed linear model that included both relative kinship and population structure using 255,714 markers derived from an exome capture array, and phenotypic data of the same 324 genotypes. Association studies detected three quantitative trait loci (QTLs) for DTF on chromosome 2 and one on chromosome 5. A flowering time related candidate gene ELF4 was identified at QTL qDTF.2-1 from the Bardiya 2016 and Jessore 2016 site-years. This gene may serve as a promising target for flowering time related studies in lentil in South Asia and may assist in improving the adaptation of lentil germplasm from a long day to short day situations.