Identification Of Heat Tolerance And Heat Resistant Material Screening In Chinese Kale

Abstract:Chinese kale（Brassica oleracea Bailey var.chinensis Lei）belongs to cool vegetables.In summer and autumn season,the common limiting factor of C hinese kale is high temperature adversity.It is difficult for C hinese kale to grow under high temperature.Under high temperature stress,the changes of physiological and biochemical indexes at seed germination stage and seedling stage were studied to evaluate the heat tolerance of15 Chinese kale cultivars from our research group aiming to provide theoretical reference for screening heat-resistant materials and breeding of Chinese kale.1.Identification of heat resistance at seed germination stage35℃treatment could best reflect the heat tolerance of the varieties at the germination stage,and could be used as the stress temperature at germination stage.At germination stage,the cluster based on germination rate,vigor index,root length and hypocotyl length were analyzed.E,L,C,K,G were extremely heat-resistant varieties.J,N,M,F were heat-resistant varieties.H,D,B,A were heat sensitive varieties.I,O were extremely heat sensitive varieties.Forecast model was established for tolerance to 35℃at the germination.The stepwise regressive function was as following:U=-0.09+0.03X₁+0.161X₂+0.435X₃+0.409X₄（X₁:germination rate;X₂:vigor index;X₃:root length;X₄:hypocotyl length）.2.Identification of heat tolerance at seeding stageAt the seedling stage,the heat damage index,relative conductivity,chlorophyll,proline,MDA,and the variations of antioxidant enzymes（SOD,POD,C AT）were analyzed.The order of heat resistance of 15 C hinese kale strains was identified:O>K>B>A>G>J>C>E>H>M>F>D>L>N>I.Forecast model was established for tolerance to high temperature at seedling stage.The stepwise regressive function was as following:U=-0.415+0.002X₁+0.005X₂+0.002X₃-0.004X₄+0.12X₅（X₁:CAT;X₂:Proline;X₃:SOD;X₄:Relative Conductivity;X₅:Soluble protein）.3.Comprehensive evaluation of heat toleranceWith the combination of the germination stage and seedling stage,identification of 15Chinese kale cultivars could result:heat tolerance of C,D,E,F,G,H,I,J,K,M in the two stages was more consistent and heat tolerance of K and G were best.