Screening Of Drought-tolerant Maize Varieties And Water Stress And Rehydration Responses Of Their Seedlings

In this study, polyethylene glycol (PEG-6000) was used to simulate osmotic stress conditionand comprehensive drought resistance evaluation was made on the seedlings of22maize hybrids,then the tested maize varieties were classified as strong drought-tolerant, moderatedrought-tolerant, and drought-sensitive. Repeated dehydration/rehydration survival tests wereconducted on the seedlings of three drought-tolerant varieties and three drought-sensitivevarieties, and finaly screened out two maize varieties as the top drought-resistance anddrought-sensitive ones, respectively. The selected drought-tolerant and drought-sensitivevarieties were used as study materials, and the polyethylene glycol (PEG-6000) was used tosimulate water stress condition to investigate the impacts of water stress and subsequentrehydration on physiological characteristics of maize varieties with different drought tolerance.The main results are as following:1. Relative germination potential, relative germination rate, relative storage materialtransformation rate, relative radicle length, relative radicle dry weight and germination-droughtindex were significantly correlated; these parameters could be used as identification indicators ofmaize drought resistance capacity. Through the comprehensive evaluation method–five-gradescoring system, higher scores were observed on Zhengdan958, Qingdan6, Haihe558and Xinyu9among the22maize germplasms tested, which suggested that they were drought-tolerant;while Hongyu319, Qingdan11, Longdan46and Jidan522were drought-sensitive; and othervarieties were of moderate drought tolerance.2. Correlation analysis showed the maize seedling survival rate under repeateddehydration/rehydration treatments and maize seeds germination-drought index were closelyrelated, and intergrated analysis of drought resistance capacity at these two different stages wasconducted, and ultematly determined that Zhengdan958was the most drought-tolerant varietyand Jidan522was the most drought-sensitive variety.3. Under conditions of water stress and rehydration, both Zheng958and522Jidanexhibited a decline on net photosynthetic rate (Pn), stomatal conductance (Gs), transpirationrate(Tr), intercellular CO2concentration (Ci), chlorophyll content and relative water content (RWC),then all above mentioned parameters demonstrated an increasing trend during the subsequent rehydration process; all parameters reached the lowest level the on the3rdday after dehydrationexcept the Ciand chlorophyll content of Jidan522, which reached the lowest level on the2nddayafter dehydration and the1stday after rehydration respectively; greater decline on all theparameters were observed for Jidan522when stressed/dehydrated, which also experienced aslower recovery after rehydration, but the differences of RWC between Zhengdan958and Jidan522were not significant under water stress. For both varieties, the relative electric conductivity,malondialdehyde (MDA), the activities of superoxide dismutase (SOD), catalase (CAT),peroxidase (POD), soluble sugar content, soluble protein content and proline content alsofollowed a first-increase-then-decrease pattern, and reached the highest level on the3rdday afterdehydration; a greater increase on the relative electric conductivity and MDA were observed forJidan522over Zhengdan958, while Zhengdan958exhibited a greater increase for all otherparameters. The results showed that less damage was made to Zhengdan958under water stressthan that of Jidan522, and Zhengdan958also showed better recovery ability and physiologicalcompensation effects in the process of subsequent rehydration.