橡胶树种质的分子量与分布差异及年度变化研究

Difference and annual change of molecular weight and distribution in Hevea germplasm

【目的】对橡胶树种质的分子量与分布差异及其年度变化进行研究,为橡胶树优异种质挖掘、优良新品种选育和天然橡胶加工提供参考依据。【方法】以18份橡胶树的野生种质和栽培种质为研究对象,采取非刺激割制,在割胶期间的上中下旬采割胶乳,应用凝胶渗透色谱(GPC)进行分子量测定,分析分子量大小及其年度变化情况。【结果】18份橡胶树种质的数均分子量(Mn)、重均分子量(Mw)在种质间和年度内达极显著差异(P<0.01,下同),Mn年平均值为272414~764161,变异系数为0.09~0.37,Mw年平均值为2769600~3561437,变异系数为0.06~0.15;Z均分子量(Mz)在种质间差异不显著(P>0.05),但年度内差异达极显著水平,年平均值为7220414~7697966,变异系数为0.07~0.11;多分散系数(PDI)为4.7~8.8,栽培种质较野生种质具有更宽的分布。在年度变化上,大部分种质的Mn在开割前2个月较高,7月下降后并保持平稳,PDI则相反;Mw和Mz全年呈规律性波动态势,且均在7月中旬有明显的上升趋势。对测试月份分析发现,Mn、Mw和PDI年平均值与每月的上中下旬、代表性月份(5、7和10月或6、8和10月)测定平均值的相关系数均在0.950以上;Mn和PDI在代表性月份各测定1次,与年平均值的相关系数也在0.950以上(除6月上旬外),Mw则是5月下旬和7月、10月任一旬,以及6月下旬和8月、10月任一旬的平均值与年平均值的相关性更好,分别达0.927和0.913。18份橡胶树种质的GPC曲线各自呈现出一定特征,根据低峰情况可初步分为单峰和高低双峰分布2种类型,高峰大多出现在logMw为6.5处,低峰大多出现在logMw为5.4处。【结论】Mn、Mw和PDI可作为橡胶树种质胶乳特性的遗传指标,Mz不适合作为遗传指标。Mn、Mw和PDI年度内存在一定变化,可采取代表性月份测定或每月测定。

【Objective】The differences and annual change of molecular weight and distribution of Hevea germplasm were studied,to provide a basis for excellent germplasm exploration,breeding and natural rubber(NR)processing.【Method】A total of 18 Hevea germplasms including wild and cultivated germplasms were selected as research materials.Latex was collected in the first,middle and last ten days during tapping period and non-stimulus tapping was chosen.Molecular weight was determined by gel permeation chromatography(GPC).Analysis of molecular weight and annual changes were conducted.【Result】The difference in number-average molecular weight(Mn)and weight-average molecular weight(Mw)among 18 germplasms and within a year was extremely significant(P<0.01,the same below).Mn had an annual average of 272414-764161 and a coefficient of variation(CV)of 0.09-0.37.Mw had an annual average of 2769600-3561437 and CV of 0.06-0.15.The difference of Z-average molecular weight(Mz)between germplasm was not significant(P>0.05),yet the annual difference was significant,with an annual average of 7220414-7697966 and CV of 0.07-0.11.The polydispersity indexes(PDI)of 18 germplasm ranged from 4.7 to 8.8 and cultivated germplasm had a wider distribution than wild germplasm.In terms of annual change,Mn of most germplasms was higher in the first two month of tapping,and remained generally stable after falling in July.The annual change of PDI was opposite to Mn.Mw and Mz showed regular fluctuation throughout the year,and both increased in the middle ten days of July.It was found that the annual mean values of Mn,Mw and PDI were significantly correlated with the mean values in the first/middle/last ten days of each month,the representative months of May,July,October or the representative months of June,August,October.The correlation coefficient(CC)was all above 0.950.Further analysis found that Mn and PDI were measured once in representative months,and the correlation with the whole year was also above 0.950(except the first the days in June).For Mw,the average of three tests of the last ten days in May with any ten days in July,October,or the last ten days in June with any ten days in August,October had better correlation,reaching 0.927 and 0.913 respectively.The GPC curve of 18 germplasms showed their own characteristics.According to the low peak curve,the 18 gemplasms could be divided into two types:unimodal and bimodal.Most of the high peak appeared at logMw=6.5,and the low peak appeared at logMw=5.4.【Conclusion】Mn,Mw and PDI can be used as latex genetic indexes in Hevea germplasm,while Mz is not suitable.Although Mn,Mw and PDI vary within a year,it can be measured monthly or in representative months.