Drought resistance of maize hybrids and their parent inbred lines during germination stage in southwestern China

【Objective】To study the effects of drought on agronomic traits and physiological and biochemical indexes of tropical and subtropical maize hybrids and their parent inbred lines during germination stage,which could provide theoretical reference for the germplasm utilization of drought resistant maize inbred lines and breeding of drought resistant new varieties in southwestern China. 【Method】The study used maize hybrid varieties Guidan 686（GML9616×ZNC442）,Guidan 689（GML1003×CML2020）,Guidan 662（GuiA10341×GML906） and their parent inbred lines as experimental materials. 20% polyethylene glycol（PEG-6000）solution was used to simulate drought stress, with an equal amount of sterilized distilled water treatment as control, to analyze the effects of drought on the main agronomic traits and physiological and biochemical indexes during the germination stage. The drought resistance differences of different maize varieties and their parent inbred lines were evaluated by drought resistance coefficient and membership function method, and the relationship between drought resistance of maize hybrids and their parent inbred lines was explored through heterosis analysis. 【Result】The analysis of variance results showed that the differences in various agronomic traits and physiological and biochemical indexes between treatments and materials were extremely significant（P＜0.01, the same below）. Except for plumule length and plumule dry weight, the differences in other indexes between treatments and materials were extremely significant. Drought stress simulated by PEG solution led to a decrease in germination energy,germination rate,germination index,radicle length, plumule length,radicle dry weight, plumule dry weight,storage material transfer rate and superoxide dismutase（SOD） activity in maize varieties and their parent inbred lines. Meanwhile,malondialdehyde（MDA）,soluble sugar and soluble protein content,peroxidase（POD） and catalase（CAT）activity increased. The coefficient of variation of agronomic traits and physiological and biochemical indexes during germination stage of maize ranged from 6.08% to 34.05% and 30.73% to 64.65% respectively,accounting for 38.16% and 61.84% of the total weight coefficient of membership function evaluation respectively. The evaluation results using the membership function method showed that the comprehensive membership function D values for Guidan 689 and Gui A10341,GML9616,ZNC442,GML2020 and GML1003 were 0.5-0.7,belonging to drought resistant varieties or inbred lines. The D values of Guidan 686 and Guidan 662 were 0.4-0.5,belonging to medium drought resistant varieties. The D value of GML906 was less than 0.4,belonging to the weak drought resistant inbred line. No strong drought resistant varieties or inbred lines with D values greater than 0.7 were found. The analysis of heterosis showed that the number of drought resistance coefficient indexes with high parent advantage for Guidan 686,Guidan 689 and Guidan 662 were only 1,5 and 5 respectively. 【Conclusion】Drought stress during germination stage disrupts the redox balance within maize cells,exacerbates lipid peroxidation of membranes,hinders the generation of substances,suppresses growth vitality,and ultimately leads to a decline in germination capacity,with reduced germination energy and germination rate. In southwestern region of China,where maize sowing often encounters drought,drought resistant varieties such as Guidan 689 can be selected for planting to improve the adaptability of seeds to drought. In the breeding of drought resistant maize varieties,attention should be paid to the utilization and improvement of southwestern tropical and subtropical germplasms such as Gui A10341,GML9616 and ZNC442,and further create new germplasms with outstanding drought resistance. Meanwhile,in breeding practice,the heterosis of drought resistance of maize hybrids can not be simply predicted based on the drought resistance of their parents.