Identification Of Dry-hot Wind Resistance Of Wheat Cultivars And Gene Expression Of SHSPs Related To Heat Stress

Dry-hot wind is a kind of unpredictable weather disaster, it is too late to prevent and control when it comes, therefore, breeding and planting dry-hot wind resistant wheat varieties is beneficial to resisting dry-hot wind stress and is the best way to reduce production losses. The study aimed to identify and select the most important indices for evaluating and screening the dry-hot wind resistant cultivars, which provided the foundation for the genetic improvement of relevant traits of the dry-hot wind resistance as well as for the cultivars distribution.Kinds of natural catastrophes are occured during the growth stage of winter wheat, dry-hot wind is a kind of natural catastrophes which will cause severe loss in yield and quality at medium-late stage. It is an important subject in the study of raising output of wheat to research the prevention of dry-hot wind and how mitigate such disasters from dry-hot wind. Choosing the right wheat cultivars is the key to prevent dry-hot wind, therefore, it has great significance to identify dry-hot wind resistance and analyze expression of small heat shock protein genes(sHSPs) related to heat stress in resistant and susceptible wheat cultivars to explore new index of resistance identification.98 Wheat cultivars were used as materials and treated by simulating dry-hot wind after anthesis from tenth days. We aimed to study the changes of spike traits(sterile spikelet number per spike and single kernel weight at different positions), morphological characteristics(chlorophyll), yield traits(1000- kernel weight) and quality traits(starch and protein) after dry-hot wind in different wheat cultivars. Grain quality and thousand-kernel weight were tested, the effects of dry-hot wind resistance on wheat cultivars was studied. The expression of sHSPs in 15-day-old seeding of resistant and susceptible wheat cultivars which were subjected to continuous heat stress of 38 ℃ for 4.5 h was tested by Real-time quantitative PCR. This study aims to identify dry-hot wind resistance of 98 wheat cultivars and analyze expression of small heat shock protein genes(sHSPs) related to heat stress in resistant and susceptible wheat cultivars, and provide basises for rational distribution of wheat cultivars and dry-hot wind resistance evaluation of wheat cultivars in filling period. The main findings were as follows:1. The chlorophyll content in flag leaf of 8 wheat cultivars decreased gradually during the treatment of dry-hot wind and decreased much more in susceptible wheat cultivars than in resistant cultivars.2. The seed building was affected by the period at which dry-hot wind occurred. The study indicated that the percentage of sterile spikelet number per spike increased greatly when dry-hot wind occurred at 5~10 days after flowering. While dry-hot wind had little influence to sterile spikelet number per spike when it occuerred after 10 days.3. The single grain weight of the grains at different positions decreased greatly after dry-hot wind. Besides the single grain weight of middle position of the grain decreased much more than the base spikelet grains and the top spikelet grains.4. Thousand-seed weight of all cultivars was reduced after dry-hot wind treatment and some cultivars which were identified showed the same resistance to dry-hot wind in 2 years replications,such as Shannong 23 showed steadily resistant to dry-hot wind, whereas Shiluan 02-1 was sensitive to dry-hot wind in 2 years replications.5. Protein content significantly increased while the starch content significantly decreased. Besides, the percentage of decreased starch content of wheat cultivars with high adversity resistance index(AI) was lower than the cultivars with low AI.6. TaHsp16.9, TaHsp17.7, TaHsp23.6 and TaHsp26.6 in wheat seeding were highly expressed and the expression trends of sHSPs were first increasing and then decreasing during heat stress at 38℃. In addition, the gene expression of sHSPs was different between resistant and susceptible wheat cultivars. For TaHsp16.9, the up-regulated extent of gene expression in resistant wheat cultivars was bigger than in susceptible wheat cultivars. For TaHsp17.8, the up-regulated times of gene expression in resistant wheat cultivars was higher than in susceptible wheat cultivars under heat stress at 0.5 h. Cultivars like Shannong 23 which were heat tolerant, the up-regulated times of them were higher than 590, whereas the cultivars like Shiluan 02-1 which were heat susceptible only reached 300. For TaHsp23.6, the peak of the heat tolerant cultivar Shannong 23 was four times higher than other cultivars. For TaHsp26.6, the up-regulated times of gene expression in susceptible wheat cultivars were higher than resistant wheat cultivars under heat stress at 4.5 h. Cultivars like Shiluan 02-1 which were heat susceptible, the up-regulated times of them were higher than 4000, whereas the cultivars like Shannong 23 which were heat tolerant only reached 3000.