Phenological Characterization of Near‐Isogenic Sunflower Families Bearing Two QTLs for Photoperiodic Response

Abstract

Understanding the effects of environment and genotype on crop phenology is critical to achieving appropriate adaptation of cultivars to targeted production areas. The main objective of this work is to examine the phenology of near‐isogenic sunflower (Helianthus annuus L.) families bearing all combinations of alleles for quantitative trait loci (QTLs) A and B associated with photoperiodic response growing in controlled environment chambers under short and extended photoperiods. Plants were harvested at intervals, the apices dissected out, and apex development from the start (apex transformation) to the end of floral differentiation scored using a 10‐point scale of floral stages. Parental lines showed significant (p < 0.05) contrasting responses to photoperiod. The genotypes exhibited significant (p < 0.0001) effects of photoperiod, QTL, QTL × photoperiod, and QTL × QTL interactions for the timing of apex transformation (B0) and for the inverse of rate of development during floral differentiation (B1). The strong QTL A × QTL B interaction for both B0 and B1 reflects the much greater delay in development under both photoperiods when QTL A was derived from HA89 and QTL B from ZenB8. This effect on B1, but not on B0, increased under extended photoperiod in the same family, reflecting a three‐factor (QTL A × QTL B × photoperiod) interaction acting on rate of development during the floral differentiation process. Given the weight of direct and interaction contributions associated with the two QTLs to the nonerror variability of both B0 and B1 across genotypes and photoperiods, we conclude both QTLs are important effectors in the photoperiodic control of flowering in sunflower.