How to improve drought tolerance in popcorn maize?

Water scarcity has become a critical constraint on global agricultural production. Particularly in tropical and subtropical regions, major crops such as maize frequently face the dual threats of drought and high temperatures. Climate change has further exacerbated this issue, leading to a significant increase in the frequency and intensity of droughts. In Brazil, recent droughts have severely impacted water, food, and energy security, making the development of crop varieties adapted to water-deficient environments an urgent priority in agricultural research. As a specialty maize variety, popcorn maize is particularly sensitive to water conditions in terms of yield and quality. However, research on the genetic mechanisms underlying its morphophysiological and agronomic traits under water stress remains limited. How can we optimize breeding strategies by dissecting genetic effects to enhance the yield stability of popcorn maize under drought conditions?

Valter Jário DE LIMA and colleagues from Universidade Estadual do Norte Fluminense Darcy Ribeiro (UENF), Brazil, evaluated the genetic effects of 25 traits in 10 popcorn inbred lines and their 45 diallel hybrids under water-stressed (WS) and well-watered (WW) conditions using diallel analysis. This study systematically revealed the genetic control mechanisms of key traits in popcorn maize under water stress, providing precise guidance for the breeding of drought-tolerant varieties. The relevant article has been published in Frontiers of Agricultural Science and Engineering, volume 13, Issue 2 (DOI: 10.15302/J-FASE-2025647).

The study found that the Normalized Difference Vegetation Index (NDVI) and relative chlorophyll content (SPAD) effectively reflected phenotypic differences in crops during critical growth stages under water stress, while Canopy Temperature Depression (CTD) served as an important indicator of stomatal closure. These indices provide reliable physiological markers for drought tolerance screening. Through genetic effect analysis, dominance effects dominated most traits, such as grain yield, plant height, and ear length, while popping expansion (PE) and stem diameter (SD) were mainly controlled by additive effects. This pattern remained stable under both water-stressed and well-watered conditions.

The study also identified inbred lines (L76, L61, and P3) with high General Combining Ability (GCA), which exhibited outstanding performance in yield and drought tolerance-related traits. The hybrids L61 × L76 and L71 × L76 performed excellently under both water regimes, demonstrating strong heterosis. Some genotypes maintained high chlorophyll levels through the stay-green trait, extending the duration of photosynthesis and thereby sustaining biomass accumulation under drought conditions.

Under water stress, the yield of popcorn maize decreased by an average of 39.8%. However, the drought tolerance of varieties can be significantly improved through optimized breeding strategies. The results of this study provide a scientific basis for drought-tolerant breeding in popcorn maize. In the next step, emphasis can be placed on developing new varieties with both high yield and drought tolerance to address the agricultural challenges posed by climate change.