Identification And Evaluation Of Gene Resources For Drought Resistance In Maize

Drought is one of the main factors that influence maize production in China. Drought tolerant breeding of maize is an effective way to reduce the yield loss under drought stress. Since the conventional improvement of maize drought tolerant is quite difficult and slow, the use of biotechnology is proved to be an alternative approach to improving the efficiency of breeding for drought tolerance. Therefore, identification and evaluation of gene resources for drought tolerance in maize have a great significance for transgenic breeding for stress tolerance.The present study used maize inbred lines and transgenic materials to establish the methodology of identification and evaluation for drought tolerance in maize, screen promising transgenic events in future breeding and fine evaluate drought tolerance-related traits in the field of these promising events. The results are as follows:1. Ten maize inbred lines and their diallel hybrids were used to invesigate the contribution of parents to the performance of drought tolerance of their hybrid combinations. The results showed that the drought tolerance of maize hybrids depends on drought tolerance of the female and male parents significantly, especially on that of the female parent. The sum of drought tolerance coefficients of the reciprocal crosses of F1 generation was basically equal to the sum of those of their parents.2. Drought tolerances of 61 transgenic maize materials were evaluated in the field at Urumqi of Xinjiang. The results showed that under the normal irrigation the corn plant had appropriate plant architechture and high yield. Most of the transgenic maize materials were influenced by drought stress, but the materials with less decreasing plant height and small anthesis silking interval (ASI) had stronger drought tolerance. Whether or not there is drought, there was a significant positive relationship between ear diameter and cob diameter, ear weight and grain weight,100-grain volume and 100-grain weight.3. Eight LOS5-overexpressing transgenic maize events and their donor of genetic background, Zheng58, were fine evaluated for drought tolerance in the field, with the irrigation treatment of 150,225, 300,375,450 and 600 mm (CK), respectively. The irrigations were applied at different developmental stages. The results showed that the yield of the eight lines of transgenic maize under irrigation with the range of 225-450 mm were significantly higher than Zheng58, due to higher ear length, more kernels per row and longer stay green. However, the degrees of drought tolerance were significantly different among the transgenic lines. Moreover, since a half of normal irrigation applied could maximize the difference of drought tolerance among the materials, it seemed that the water stress treatment could be used in evaluation for drought tolerance of transgenic maize and in elucidating the stage(s) a given material has the strongest or weakest drought tolerance.4. A simple mathematics model was developed based on the relationship between crop yield and irrigation quantity. The model could fit the S curve or the saturation curve between the yield and the cumulative irrigation amount. All of the three parameters in the model, production capacity (Ym), half owned water (Wh) and water sensitivity coefficient K, had specific biological meanings. The model was validated by five other models and two gradient irrigation experiment data, and the calculated results were fitted with the test results. The model could be used to analyze the water use efficiency and drought tolerance of maize.5. A total of 24 transgenic maize materials and their corresponding donor of genetic background were treated with drought at different growth stages for four years. Using the proposed model described above to fit between the calculated values and experimental values, the water requirements of the 24 transgenic maizes with half of yield under normal irrigation were less than those of the corresponding donors, suggesting the improvement of drought tolerance in the transgenic materials. The model could be effectively used in precision evaluation for drought tolerance of transgenic maize, especially phenotypic effects at different stages.