Assessment Of The Ability Of Secondary Laticifer Differentiation And Efficiency Of Rubber Biosynthesis In Relation To Rubber Yield Of Rubber Tree

In natural rubber production, latex flows out of the severed secondary laticifers by cutting the trunk bark of rubber trees and is collected as the raw material for refining rubber. Thus, it is difficult to disect the component traits of rubber yield and subsequently to develop a technique suitable for yield early selection, which is primarily ascribed to the time-consuming and low efficient selection in traditional breeding processes.The number of the secondary laticifers and latex regeneration between successive tapping has long been believed to be the key factors that determine rubber yield. In the present study, these two factors are further to dissected by the ability of the secondary laticifer differentiation and efficiency of rubber biosynthesis, respectively. Moreover, the correlation between either the ability of the secondary laticifer differentiation or the efficiency of rubber biosynthesis and rubber yield was analysized. The main results as follows:1. There was an evident difference in the ability of the secondary laticifer differentiation of the1-year-old epicormic shoots among Wickham'germplasm (the cultivated varieties) upon mechanical wounding. The ability of the secondary laticifer differentiation could be roughly divided into four types:sensitive, sensitive superposition, torpid and torpid superposition. Of which, either the sensitive or torpid superposition occurred in most of the rubber tree clones that are used in large scale.2. The difference in the ability of the secondary laticifer differentiation of the forth-and fifth extension units of2-year-old epicormic shoots among Wickham'germplasm was also evident under natural conditions. The ability of the secondary laticifer differentiation under natural conditions was generally in accordance with the case upon mechanical wounding.3. The ability of the secondary laticifer differentiation of hybrid offsprings was different upon test tapping, which was positively correlated to the rubber yield.4. Nine polymorphic loci in the promoter and one Indel sequence in the first intron of HbFDPS gene were correlated to rubber yield. And also, one polymorphic locus in3' non coding region of HblMYCl, HbREF and HbHMGS2was associated with rubber yield, respectively.5. The level of expression of HblCOI1?HblMYC1?HblMYC3?HblJAZ2?HblJAZ3and HblHRT2in mature germplasms with high-yield potential was significantly higher than that with low-yield potential. The similar expression pattern of HblCOI1? HblMYC1?HblMYC3and HblHRT2occurred in the corresponding immature trees.According to the results, the ability of rubber tree germplasm to produce rubber can be early predicted by evaluating their ability of the secondary laticifer differentiation at three stages within three years. The correlation between the polymorphism in gene structure or gene differential expression need to be further verified in large-scale germplasm population. The evaluation of the efficiency of rubber biosynthesis in rubber tree germplasm is in progress by an experimental system for rubber biosynthesis in vitro with the labeled MVA as substrate. All these data should be necessary for using the genomic data of rubber tree to develop an accurate and simplified technique for early selecting ability of rubber tree germplasm to produce rubber.