About the Project
The impact of climate change on agricultural production will be greatest in the tropics and subtropics, with South Asia projected to be particularly vulnerable from multiple stresses and low adaptive capacity (IPCC, 2007; Rodell et al., 2009; Niyogi et al., 2010; ADB, 2009). Many climate modeling studies suggest that high day- and night-time temperatures will become more common in the future and may represent a tremendous environmental hurdle to global food production (Lobell et al., 2011; Stebbins, 2011; Cairns et al., 2012). Maize is particularly vulnerable to the reproductive stage heat stress (Cairns et al., 2012). A recent study showed that each degree day spent above 30°C reduced the final yield of maize by 1% under favorable growing conditions and 1.7% under drought stressed environments (Lobell et al., 2011b). Most of the tropical maize growing areas in South Asia are highly vulnerable to drought and high temperature stress. Spring maize is an important option for intensifying and diversifying cropping systems in South Asia, especially in the in the upper and middle Indo-Gangetic plains, but is prone to severe heat stress during flowering/early grain filling stages (Prasanna, 2011).
Systematic efforts to develop maize cultivars with high temperature tolerance have only recently been initiated. Initial experiments undertaken by the CIMMYT-Asia team to identify heat stress tolerant tropical maize lines among the elite, drought tolerant (DT) maize germplasm developed in Mexico, Asia and Africa revealed: (a) high vulnerability of most of the tropical maize germplasm, including commercial cultivars in South Asia, to reproductive stage heat stress; and (b) poor correlation between drought and heat tolerance, indicating that physiological mechanisms that contribute to heat stress tolerance in maize may be different from those that contribute to drought tolerance (Zaidi and Cairns, 2011; Cairns et al., 2012). However, CIMMYT-Purdue University collaborative studies in the last two years showed considerable genetic variation for the target trait, including identification of some highly promising Asia-adapted, tropical maize lines developed by CIMMYT with tolerance to high temperature.
Accelerated development and deployment of heat stress resilient maize varieties requires: (a) carefully undertaken field-based phenotyping in several relevant sites as well as under technically demanding managed-stress screens, both of which are often beyond the capacity of individual breeding programs; (b) an understanding of the genetic architecture of the target trait, coupled with application of modern molecular breeding tools, including genome-wide association studies (GWAS), genomic selection (GS), and doubled haploid (DH) technology for rapid development of improved products; and (c) effective partnerships with committed seed companies in the target regions for sustainable delivery of climate resilient cultivars.
The proposed outputs of the project are: (a) generation of knowledge about the genetic architecture of heat stress tolerance in tropical maize germplasm, including biomarkers and bioassays for heat tolerance for utilization in breeding strategies; (b) elite heat stress tolerant tropical donors with/without drought tolerance identified and shared with the public and private partners; (c) South Asia-adapted maize lines with enhanced levels of heat stress tolerance, coupled with other adaptive traits, developed using molecular marker-assisted breeding through GWAS and Genomic selection GS; (c) best-bet heat stress-resilient maize hybrids with high yield and other adaptive traits for potential deployment by NARS and private seed partners; and (d) well-trained human resources in precision phenotyping and selection for heat stress tolerance, and (e) application of modern tools (GWAS, GS and DH technology) for accelerated development of abiotic stress resilient crop varieties.