Stress-resilient maize for climate-vulnerable ecologies in the Asian tropics

Abstract

Most parts of the Asian tropics are hotspots of climate change effects and associated weather variabilities. One of the major challenges with climate change is the uncertainty and inter-annual variability in weather conditions as crops are frequently exposed to different weather extremes within the same season. Therefore, agricultural research must strive to develop new crop varieties with inbuilt resilience towards variable weather conditions rather than merely tolerance to individual stresses in a specific situation and/or at a specific crop stage. C4 crops are known for their wider adaptation to range of climatic conditions. However, recent climatic trends and associated variabilities seem to be challenging the threshold limit of wider adaptability of even C4 crops like maize. In collaboration with national programs and private sector partners in the region, CIMMYT-Asia maize program initiated research for development (R4D) projects largely focusing on saving achievable yields across range of variable environments by incorporating reasonable levels of tolerance/resistance to major abiotic and biotic stresses without compromising on grain yields under optimal growing conditions. By integrating novel breeding tools like - genomics, double haploid (DH) technology, precision phenotyping and reducing genotype × environment interaction effects, a new generation of maize germplasm with multiple stress tolerance that can grow well across variable weather conditions were developed. The new maize germplasm were targeted for stress-prone environments where maize is invariability exposed to a range of sub-optimal growing conditions, such as drought, heat, waterlogging and various virulent diseases. The overarching goal of the stress-resilient maize program has been to achieve yield potential with a downside risk reduction.

Genomic regions associated with heat stress tolerance in tropical maize (Zea mays L.)

“…South Asia region has been identified as one of the hot-spot regions for climate change effects; therefore, without sufficient adaptation measures, the region is likely to suffer negative impacts of the climate change 5 . During the past 2 decades, Asian tropics have experienced frequent episodes of extreme weather events including increased day/night temperatures, apart from scattered drought/heat stress periods almost every year in one or another country of South Asia 6 . Impact assessment of climate change effects on maize in South Asia showed that heat stress affected areas of South Asia will increase significantly under future climates, especially in the pre-monsoon season (spring) and in monsoon season 7 .…”

“…The temperatures above 40 °C during the reproductive stage can cause irreversible physiological damage and severely affect grain yield 8 , 9 . In view of recent climate change patterns in the lowland tropics, heat stress alone and in combination with drought, has emerged as one of the major production constraints for maize in several maize-dependent countries 6 , 10 . Lobell and Burke 11 showed that an increase of 2 °C temperature would result in a greater yield penalty in maize crop than a 20% decrease in precipitation.…”

Impact of weather parameters on maize agroecosystem and adaptation strategies under changing climatic conditions: A review: Sustainable and climate-resilient adaptation strategies in maize agroecosystem

“…In central India, sowing of maize crops between the 7th and 14th of July could reduce the impact of temperature on maize grain and biomass yield. The new maize germplasm is targeted for stress-prone environmental conditions (11).…”

“…The optimization of the planting window (changing planting dates, selection of cultivars) for utilizing solar radiation is an eco-friendly and low-cost adaption strategy (9,10). Similarly, stressresilient new germplasm of maize is discovered to achieve yield potential with a reduction in the risk concerning climate change (11). This review presents the latest systematic data published between 2000-2022 based on planting dates and climate change strategies for maize.…”

Genomic Regions Associated With Salinity Stress Tolerance in Tropical Maize (Zea Mays L.)

“…Maize, a widely adopted crop under a range of climatic conditions, is often planted on salt-affected fields, as many farmlands are salinized ( Zaidi et al, 2020 ; Prasanna et al, 2021 ). Analyzing the salt tolerance mechanism in maize by studying the diverse maize germplasm and understanding the genetic architecture of salinity tolerance can guide breeding programs aimed at developing salt-tolerant maize varieties ( Luo et al, 2017 ).…”