黄瓜苗期耐热种质筛选与耐热性评价体系构建

Screening of cucumber germplasms in seedling stage and the construction of evaluation system for heat tolerance

构建耐热性评价体系是选育耐热新品种以及研究作物耐热机制的重要前提。评价植物耐热性多采用综合评价法,然而鲜有报道此方法用于黄瓜(Cucumis sativus)苗期耐热种质筛选和评价。本文以12份不同生态类型的黄瓜自交系为材料,在人工模拟自然高温条件下,研究了高温胁迫对黄瓜幼苗生长和生理指标的影响,并利用多元分析方法对其耐热性进行综合评价。结果表明:高温胁迫下,大部分黄瓜自交系生长受阻,株高、茎粗、节间长和叶面积显著降低;少数自交系的株高、节间长有所增加,茎粗、叶面积下降,表现为徒长趋势。高温处理后,12份黄瓜自交系的丙二醛(MDA)含量和相对电导率较对照显著增加,叶绿素a、叶绿素b、总叶绿素含量以及净光合速率(Pn)和光系统II最大光化学效率(Fv/Fm)较对照显著降低,大部分自交系叶绿素a/b升高,不同材料之间差异显著。综合不同自交系各性状的相关性分析、主成分分析和隶属函数分析结果,将12份黄瓜材料划分为强耐热、中等耐热、不耐热和热敏感4种类型。通过逐步回归分析建立预测方程,筛选出节间长、相对电导率、叶绿素a含量、叶绿素a/b、Pn和Fv/Fm作为黄瓜耐热性鉴定指标。利用该方程对供试材料进行耐热性预测,其结果与耐热性综合评价值(D值)的结果完全一致,表明综合评价法可用于黄瓜苗期耐热种质的筛选和评价。

Establishing an effective and efficient method for scoring heat tolerance is a prerequisite for breeding of heat-tolerant varieties and investigating the mechanisms of heat tolerance in crops.However,the comprehensive evaluation of heat tolerance in cucumber(Cucumis sativus)was seldom reported.Here we examed the morphological and physiological impacts of heat stress on 12 cucumber inbred lines of different ecological types under controlled artificial high temperature conditions,and scored the heat tolerance by multiple analysis methods.The results show that the growth of most cucumber inbred lines was inhibited under high temperature stress.The plant height,stem diameter,internode length and leaf area were decreased significantly.Strikingly,a few inbred lines showed excessive physiological growth,with increased plant height and internode length,and decreased stem diameter and leaf area.Under high temperature,the malondialdehyde(MDA)content and relative conductivity of 12 cucumber inbred lines were significantly higher than those of control;while the contents of chlorophyll a,chlorophyll b and total chlorophyll,net photosynthetic rate(Pn),and photochemical maximum efficiency of photosystem II(Fv/Fm)were significantly lower,but chlorophyll a/b of most cucumber inbred lines was higher than those of control.However,significant differences were also found among different cucumber inbred lines.Based on correlation analysis,principal component analysis and subordinate function analysis,the 12 cucumber inbred lines were differentiated into four types:strong heat resistance,moderate heat resistance,non-heat resistance and heat sensitivity.Through stepwise regression analysis,we developed a prediction equation,which employs internode length,relative conductivity,chlorophyll a content,chlorophyll a/b,Pn and Fv/Fm as selection indices of heat tolerance in cucumber.The rankings of prediction values were consistent with that of the D value.The result indicates that the comprehensive evaluation system is capable to screen and evaluate heat tolerance of cucumber germplasm in seedling stage.