Response of different maize germplasms to drought stress and heat stress at anthesis period

【Objective】The responses of agronomic and photosynthetic physiological traits of different maize germplasms to drought stres and heat stress were studied in order to provide theoretical basis for the screening of drought and heat tolerant maize germplasm and the utilization of tropical germplasm.【Method】 A total of 25 tropical germplasms， 25 temperate germplasms and 25 mix germplasms were used as the experimental materials. Drought treatment and high temperature treatment were carried out before and after the flowering and powder stage respectively，the normal management of local maize planting was as control. The plant height， ear height， tassel branch numbers， anthesis-silking interval， ear length， ear rows， kernels per row， 100-kernel weight， yield per plant， chlorophyll content were measured under three treatments，and calculated the PSⅡ potential activity（F_v/F_o）and the PSⅡ maximum photochemical efficiency （F_v/F_m）. Comprehensive evaluation of drought tolerance and heat tolerance of different germplasms was conducted.【Result】 The results of the joint analysis of variance for 12 traits among different maize germplasm showed extremely significant differences （P＜0.01，the same below）between germplasm and environment（stress）. The results showed that the change trend of drought stress response among three types germplasms at anthesis stage were consistent. The yield per plant and anthesissilking interval were affected by drought stress the most， and the ear rows was the least affected by drought stress. The change trend of heat stress response among three types germplasms at anthesis stage were consistent. The yield per plant was the most affected by heat stress， and the ear height was the least affected by heat stress. The drought tolerance coefficients of chlorophyll content，F_v/F_o and F_v/F_m performed the best in tropical germplasms，the drought tolerance coefficients of tassel branch numbers performed the best in mix germplasms，and the drought tolerance coefficients of plant height and ear height performed the best in temperate germplasms. Heat tolerance coefficients like ear length，yield per plant，chlorophyll content，F_v/F_o and F_v/F_m performed the best in tropical germplasms. Comparative analysis of the inbred lines which with medium or high drought tolerance among three types of germplasms showed tropical germplasms （11） ＞mix germplasms （9） ＞temperate germplasms （7）. Comparative analysis of the inbred lines which with medium or high heat tolerance among three types of germplasm showed tropical germplasms（10） ＞mix germplasms（3） ＞temperate germplasms（2）. The comprehensive evaluation results of drought and heat tolerance of different germplasm were highly consistent with their cluster analysis results. There was extremely significant correlation between the weighted membership values of drought tolerance and heat tolerance in different germplasms. The results of cluster analysis showed that the yield per plant，chlorophyll content，F_v/F_m，plant height and ear length of the strong drought tolerant inbred lines were better，and the yield per plant，ear length，row number，chlorophyll content and F_v/F_m of the strong heat tolerant inbred lines were better. The weighted membership value showed that plant height，yield per plant，chlorophyll content and F_v/F_m were highly correlated with drought tolerance，while row number，yield per plant，chlorophyll content and F_v/F_m were highly correlated with heat tolerance.【Conclusion】Different maize germplasms had the same response trend to drought stress and heat stress at anthesis stage. Tropical germplasms are more likely to screen inbred lines with better drought tolerance or heat tolerance performance. Yield per plant， chlorophyll contentand F_v/F_m have fine evaluation effects on drought and heat tolerance.