Developmental program impacts phenological plasticity of spring wheat under drought

Marwa N. M. E. Sanad, Kimberley Garland Campbell, Kulvinder S. Gill

Developing drought-tolerant crops critically depends on the efficient response of a genotype to the limited water availability, a trait known as phenological plasticity. Our understanding of the phenological plasticity remains limited, in particular, about its relationships with plant developmental program. Here, we examined the plastic response of spring wheat at tillering, booting, heading, and anthesis stages to constant or periodic drought stress. The response was assessed by morphological and physiological parameters including symptoms. The dynamics of morphological symptoms were indicators of the plasticity identification of drought. We found that spring wheat exhibits higher phenological plasticity during tillering stage followed by the heading stage, while booting and anthesis stages are the most sensitive. Also, the adaptive response is thought to be influenced with the plant height genes. Furthermore, periodic stress caused more pronounced inhibition of yield than the constant stress, with limited resistance resolution under long period. Our study shows the importance of considering the phenological plasticity in designing screens for drought tolerance in spring wheat and proposes tillering as the most informative stage for capturing genotypes with tolerance to limit water availability.