Indexes screening and comprehensive evaluation of low nitrogen tolerance of hybrid maize cultivars at seedling stage

To develop a better screening and identification method of low nitrogen resistant hybrid maize cultivars at the seedling stage, and obtain low nitrogen tolerant maize cultivars applicable in production, 51 commercial hybrid maize cultivars were two-year treated under low nitrogen stress by the vermiculite and pearlite pot culture with Hoagland nutrient solution. The results showed that low nitrogen stress had a significant impact on the main morphological and physiological indexes of different maize cultivars at the seedling stage and the degrees of effect among the indexes and cultivars were significantly different. Based on the coefficients of variation of relative values of different indexes, total of 7 indexes including leaf area, nitrogen accumulation, root-shoot ratio, dry shoot weight, root volume, dry root weight and dry biomass weight were selected as indexes for screening and evaluation of the degree of low nitrogen tolerance of hybrid maize. The low nitrogen tolerability of hybrid maize was evaluated by using the method of the fuzzy membership function with the normalized coefficients of variation as weight of the selected 7 indexes. The evaluation result was compared with the results of the fuzzy membership function and principal component analysis using 13 indexes for the first year and 25 indexes for the second year. The comparison showed that the evaluation results of 7 screening indexes and all the indexes were largely identical. The coincidences rates of low nitrogen tolerance and sensitivity of the first 10 cultivars were 90% and 80%, proving the representativeness of the screening indexes and the feasibility of the evaluation method. The study showed that the above 7 indexes may be used to evaluate low nitrogen resistance of maize at seedling stage and to screen hybrid maize cultivars with low nitrogen resistance. In the study, 'Zhenghong 311', 'Chengdan 30', and 'Qianbei 2' were identified as low nitrogen resistant cultivars and to be suitable for the southwestern hill and mountain areas of china.