Crop genetics, climate change and maize stability

American Society of Agronomy: Climate change is an ever-present threat to agriculture. Many experts predict sudden and unexpected changes in climatic conditions will bring new stresses to the environment. Ensuring the stability of crop varieties across environments and conditions is a critical breeding goal when dealing with the uncertainty of climate change.

Maize is one of three primary crops worldwide. Slight changes in climatic conditions may cause substantial yield losses, resulting in great food shortages and economic losses. Consequently, numerous breeding programs are currently evaluating maize stability under different climatic stress conditions. However, many breeders design yield improvement programs without first conducting preliminary studies to determine which environmental factors actually limit the crop and which genetic parameters are essentially affected.

Scientists in northwestern Spain, from the Spanish National Council (CSIC), have investigated the effects of multiple climatic stresses on maize grain yield. The study, which was funded by the Spanish Plan of Research and Development, evaluated 76 Spanish populations of maize, along with five commercial hybrids. Research was conducted at three distinct locations over three years, for a total of nine environments. Evaluations were made under multiple stress conditions, including a shortage of water, cold temperature, and low nutrient availability. No pesticide or herbicide treatments were applied during the growing cycle, and weeding was limited in order to allow competition. Data on several traits related to plant development and yield were collected on each plot. Environmental variables were also recorded to monitor variations in temperature and rainfall during the growth season.

The results of the study, which are published in the January/February 2010 issue of Crop Science, illuminate the effect of genotype and environment on yield stability, as well as the magnitude of genotype-environment interactions. Researchers determined that commercial hybrids had higher yield and stability than most populations, suggesting that breeding programs focusing on yield have released hybrids with high yield and stability under different stress conditions. Some non-hybrid populations also produced a reasonable compromise between yield and stability. If yield stability under stress conditions is a breeding goal, researchers recommended that several climatic variables, especially those related to high temperatures, and genotypic traits, such as kernel depth and ear length, be considered.

Although hybrids are more stable under diverse climatic conditions, it is important to remember that old populations are the reservoirs of genes from which these hybrids have been developed. In order to continue the development of improved hybrids, research with populations must also be emphasized. However, old populations need to be intensely improved for yield if they are going to be used for future breeding programs.

Multicolored corn cobs, shot by Waugsberg, Wiikimedia Commons, under the Creative Commons Attribution Share-Alike license version 2.0