Evaluation of Cold Resistance and Semi-lethal Low Temperature(LT_(50))of Nine Pear Cultivars

[Objectives]To evaluate the cold resistance and semi-lethal temperature of pear cultivars,and provide a theoretical basis for the regional extension and breeding of cold-resistant pear cultivars.[Methods]Nine pear cultivars were used to study the changes in relative conductivity and cell injury rate of pear branches under low temperature stress,and the semi-lethal temperature(LT_(50))of pear branches was analyzed by fitting Logistic equation.[Results]The relative conductivity and cell injury rate of pear branches took on the trend of slow increase,rapid increase,and slow increase the decrease of treatment temperature.The LC_(50) of the nine pear cultivars were as follows:Nanguo pear-33.9℃,Wanyu-32.3℃,Red D Anjou-31.8℃,Jinfeng-31.3℃,Wujiuxiang-29.2℃,20 th Century Pear-29.1℃,Hanxiang-35.1℃,Yuluxiang-27.9℃ and Korla Fragrant Pear-29.2℃.[Conclusions]The semi-lethal temperature could reflect the cold resistance of pear trees,and Wanxiang had better cold resistance.The evaluation of cold resistance and semi-lethal temperature of pear cultivars can provide theoretical basis for regional extension and breeding of cold-resistant pear cultivars.

Effects of Cold Acclimation on Several Enzyme Activities in Euonymus radicans ‘Emorald & Gold’and Its Relation to Semi-lethal Temperature

The changes in activities of superoxide dismutase (SOD), peroxidase (POD) and ATPase in the leaves of Euonymus radicans were studied when seedlings were cold-acclimated (at 4 ℃) for 1 week, 2 weeks, 3 weeks and then treated for 1 d under low temperature stress (at 5 ℃). The semi-lethal temperatures of acclimated and unacclimated seedlings were also investigated. The results indicated that the activities of the three enzymes in the leaves of the seedlings treated at 4 ℃ for 1, 2 and 3 weeks were all higher than those of unacclimated seedings (treated at 22 ℃ as controls). The activities of SOD and POD increased continuously with the prolongation of the time of cold acclimation, but stepped up to summits then down to the levels of the controls. The activities of SOD culminated at the first week, and the activities of POD at the second week. When acclimated and unacclimated seedlings were both treated at 5 ℃ for 1 d, the activities of the three enzymes in the leaves of acclimated seedlings were a little lower than those before stress, but higher than those of the controls. Moreover, the decrease rate of enzyme activities was greatly lower than that of the controls. The results showed that cold acclimation could enhance the stability of the three enzymes in the leaves of seedlings under low temperature stress; the semi-lethal temperature was 19.1 ℃ when the seedlings were treated at 4 ℃ for 3 weeks, but it was 5.4 ℃ when the seedlings were treated at 22 ℃. The decline of the semi-lethal temperature caused by the adaptive changes of enzyme activities was one of the foundations of enhancing the cold tolerance.

10个红掌品种的抗寒性与耐热性评价

采用低温半致死温度(LT50)评价低温条件下10个红掌(Anthurium andraeanum Lind.)品种的抗寒性;并在测定高温(39℃)处理48 h后各品种叶片生理指标的基础上,对这些指标的耐热系数和相关系数进行分析,采用主成分分析和隶属函数法综合评价了10个红掌品种的耐热性。结果表明:经过-1℃、-3℃、-5℃、-7℃和-9℃的低温处理,10个品种的叶片相对电导率(REC)均逐渐增大,其中,品种‘阿拉巴马’(‘Alabama’)的REC值呈"缓慢升高—迅速升高"的趋势,其他品种的REC值均呈"缓慢升高—迅速升高—平稳升高"的趋势;依据Logistic方程获得的各品种的LT50值,10个红掌品种的抗寒性由强至弱依次排序为‘阿拉巴马’,‘皇冠’(‘Royal champion’),‘马都拉’(‘Madural’),‘甜冠军’(‘Sweet champion’),‘特伦萨’(‘Turenza’),‘阿瓦托’(‘Avento’)、‘阿瑞博’(‘Arebo’)和‘粉冠军’(‘Pink champion’),‘白冠军’(‘White champion’),‘骄阳’(‘Sierra’)。高温处理48 h对各品种叶片的生理指标均有一定影响,其中,REC值和CAT活性明显高于对照(室温)、MDA含量高于或等于对照,它们的耐热系数均大于100%;相对含水量、叶绿素和类胡萝卜素及脯氨酸含量均低于对照,它们的耐热系数均小于100%;多数品种叶片的SOD和POD活性及可溶性蛋白质含量(SPC)低于对照,耐热系数也小于100%;仅品种‘阿拉巴马’叶片的SOD和POD活性及SPC值略高于对照,耐热系数大于100%;各指标的耐热系数间均存在一定的相关性。主成分分析结果显示:前3个主成分的累计贡献率达到91.50%,其中,第1主成分定义为酶活性和渗透调节物质含量,第2主成分定义为光合色素含量,第3主成分定义为膜透性。根据耐热性综合评价值,10个红掌品种耐热性由强至弱依次排序为‘阿拉巴马’、‘皇冠’、‘阿瓦托’、‘阿瑞博’、‘马都拉’、‘骄阳’、‘特伦萨’、‘粉冠军’、‘甜冠军’、‘白冠军’。研究结果表明:品种‘阿拉巴马’的抗寒性和耐热性均较强,可以在不同气候区推广种植。

不同桉树品种在低温胁迫下的生理反应

为探讨引种桉树抗寒适应性,以1年生离体枝条为试材,研究不同低温(0℃、-5℃、-10℃、-15℃和-20℃)处理对4种桉树电解质外渗率、可溶性糖、游离脯氨酸(Pro)及叶绿素荧光参数的影响,以及在0℃(CK)低温胁迫下不同处理时间(2 d、4 d、6 d)对4种桉树叶绿素荧光参数的影响。结果表明,随着处理温度降低4种桉树叶片的电解质外渗率呈上升趋势,拟合Logistic方程得出4种桉树的半致死温度(LT50),表明河红桉LT50最低;可溶性糖含量随着温度的降低先升高后降低,各品系间可溶性糖含量表现显著差异;游离脯氨酸(Pro)含量随着温度的降低而上升;叶绿素荧光参数分析显示,随着处理温度下降及0℃下胁迫时间延长,初始荧光(Fo)逐渐上升,PSⅡ最大光化学效率(Fv/Fm)、实际光化学效率(ФPSⅡ)、光化学猝灭系数(qP)逐渐下降。根据隶属函数法,求出隶属函数值,综合各指标,得出4种桉树抗低温胁迫能力强弱的排序为:河红桉﹥DH-32﹥U-6﹥广林9。

乌塌菜新种质的抗冻性鉴定

为提高‘上海小八叶’乌塌菜在北方地区的抗冻性和露地越冬能力,采用抗冻性强的‘平度薹菜’与乌塌菜进行变种间杂交,以‘上海小八叶’乌塌菜为轮回亲本进行4代回交,从自交后代中选出抗冻性强的乌塌菜新品系‘5-15’和‘6-9’。本试验测定了新品系和亲本材料的露地越冬存活率、低温半致死温度以及叶绿素荧光参数综合性能指数PI_(total),以期了解新品系的抗冻性及露地越冬性。试验结果表明,乌塌菜新品系的露地越冬成活率显著高于‘上海小八叶’,2年平均存活率分别达到83%(‘5-15’)和90%(‘6-9’),与父本‘平度薹菜’无显著差异。室内抗冻性鉴定结果显示,乌塌菜材料‘5-15’和‘6-9’和‘平度薹菜’的低温半致死温度LT_(50)均达到-7℃以下,低于‘上海小八叶’;叶绿素荧光参数中的综合性能指数PI_(total)也反映出低温下乌塌菜材料‘5-15’和‘6-9’的光合性能要显著高于‘上海小八叶’。以上结果均表明乌塌菜新种质的抗冻性较其亲本‘上海小八叶’乌塌菜显著增强,通过对抗冻种质资源的杂交利用,可有效提高乌塌菜的越冬能力。

电导法对32个辣椒品种组合抗寒性的测定及配合力分析

为了比较辣椒品种的抗寒性,以32个线椒杂交组合为试材,在人工气候箱下进行低温处理,应用电导法测定叶片相对电导率(REC)。通过Logistic曲线方程拟合求出拐点温度(即半致死温度)(LT50),作为各试材抗寒性评价的参考指标,并将32个线椒组合的半致死温度(LT50)进行比较。结果表明:随处理温度的降低,相对电导率不断升高,变化过程呈"S"型曲线。32个线椒组合抗寒性顺序依次为:H2>H13≈H28>H31≈H1≈H23>H24>H26>H30>H8>H27≈H19>H5≈H12>H21>H3>H18>H15≈H14>H22>H17>H7≈H29>H4>H11>H10≈H16>H20>H6>H9>H25>H32。配合力分析表明,相对电导率的GCA效应值以亲本P1和P2最低,SCA效应值以P1×P2最低。

Hypocotyl elongation based on HY5 transcription factor in cold resistant winter rapeseed(Brassica napus L.)

Winter rape(Brassica napus L.)is better than other edible oil crops in China,but poor cold resistance is the key factor restricting its development.Hypocotyl length was found closely related to cold tolerance.The correlation between hypocotyl length and semi-lethal low temperature was significant,and the highest correlation between hypocotyl length and LT50 of autumn sowing was 0.9557.When the hypocotyl were treated at low temperature,the cells were seriously damaged and formed cavity structures,with cell walls seriously damaged or merged into each other.The positive regulation gene of hypocotyl length in resistant line of VHTSG 10 was identified as HY5(transcription factor HY5-like)by qPCR,and bZIP transcription factor was found to be its conserved domain.Fused gene by GFP and HY5 from VHTSG 10 was transient transferred into Nicotiana benthamiana cells.Corresponding to the 35S:GFP widely distributed in plasma membrane of leaf epidermis,the fusion protein 35S:HY5-GFP was mainly distributed in nucleus.Thus we regarded BnHY5 gene is a key gene related to cold tolerance and hypocotyl length in B.napus.