Moving the corn belt northward: identifying key ultrastructural and physiological markers which provide chilling and frost stress resistance to enhance the breeding process

点击翻译按钮获取中文摘要

Corn (Zea mays L.) is a chilling and frost sensitive crop of significant economic value. Corn is the number one crop worldwide (over 980,000,000 million metric tonnes in 2014) followed by paddy rice, wheat and soybeans (http://www.statcan.gc.ca/pub/96-325-x/2014001/article/11913-eng.htm). In the USA alone (accounting for about one-third of world production), the farm gate value of corn was $52 billion in 2014. Corn prices have more than doubled in the ten years since 2004. In 2014, Canada was ranked 9th in corn production worldwide (USDA). In Canada, corn is the third most valuable crop and production area doubled from 1971 to 2011. However, the necessity of warm temperatures and a long growing season are the main determinants of its production area and thus regions such as Saskatchewan, which has over 40% of the arable land in Canada, has only 0.3% of Canada's corn production area. Accordingly, lack of both chilling and frost stress resistance are the primary perpetual constraints limiting grain corn production across the prairies. In spite of a large research effort, significant advancements in elevating low temperature stress tolerance (chilling and freezing) in corn have not been achieved. This may be related to the focus on the early stage of growth (few days old seedlings), lack of incorporation of contrasting genotypes into experimental systems and method of stress application (cold shock exposure without prior cold acclimation). Night temperatures during the growing season in the prairies are typically 10C and plants have potential to cold acclimate under these conditions. Grain filling is the stage of highest risk to low temperature stress in the fall and has the greatest impact on yield. The goal of this study is to identify key ultrastructural and physiological markers which are linked to chilling and frost stress resistance during both the vegetative and grain filling stages in stress sensitive and tolerant grain corn lines with and without prior acclimation to cold. These identified markers can then be used to enhance the efficiency of the breeding process through targeted selection. This study builds upon and complements two ongoing research projects on chilling and frost resistance in corn.