Root response to temperature extremes: association mapping of temperate maize (Zea mays L)

Abstract

Little is known about the genetic control of the root architecture of maize (Zea mays L) and its response to temperature extremes. An association mapping panel, including 32 flint and 42 dent inbred lines, was characterized for root traits. The growth of axile and lateral roots was assessed non-destructively in growth pouches at 16°C (chilling), 28°C (control) and 36°C (heat). Association mapping was done using the PKOpt mixed-model associationmapping approach. Heat slowed down the development of seedling roots to a lesser extent than chilling, but differences between the heterotic groups were observed mainly at optimal temperature. Of 1,415 AFLP markers, 70 showed significant marker-trait associations and 90 showed significant marker-trait associations with temperature interaction effects. Compared to the flint lines, the dents showed stronger growth of axile roots, especially under optimal conditions, and carried more of the trait-increasing alleles for the length of axile roots. In contrast, Benjamin the flints accumulated more root dry weight at low temperature and exclusively carried the alleles favoring tolerance to chilling. A combination of inbreds carrying alleles positive for performance under contrasting temperature conditions should lead to a complementary effect in the hybrid and would increase adaptation to a wider range of temperature.