| Litchi chinensis Sonn is native to China and ranking first in the world in terms of cultivated area and variety types.It is an important tropical and subtropical fruit tree,which is known as the "Lingnan Fruit King".In order to make the similar variety selection in DUS testing more accurate and efficient,42 basic characteristics 74 litchi varieties were observed according to the agricultural industry standard NY/T2564-2014 "Guidelines for the conduct of tests for distinctness,uniformity and stability—Litchi",and the genotypes of the 74 litchi varieties were also studied by SSR molecular markers.The main results are as follows:1.The qualitative and psuedo-qualitative characteristics in the 42 basic characteristics were assigned notes directly.Nine quantitative traits including leaf length,leaf width,internode length,leaf axis length,petiole length,branch thickness,flower spike length,flower spike width,and edible rate of fruit were measured,and the original data was recorded and classified: the data of leaf length,internode length,leaf axis length,branch thickness,flower spike length,flower spike width,and fruit edible rate was in accordance with normal distribution or approximate normal distribution and these seven characteristics were classified by the least significant difference method;the data of leaf width and petiole length did not conform to the normal distribution and they were classified according to the grade difference method.2.In order to eliminate the effects of ecological environment and observation errors when using the note method to screen similar varieties,GAIA method was initially used for phenotypic distance anlysis in litchi varieties.According to the basic principles proposed in UPOV technical document TGP/8-3,the field testing experience and the suggestions from relevant experts,the GAIA weight was assigned to the note difference of each characteristic of litchi,and the GAIA phenotypic distance of some litchi varieties was obtained.The results of cluster analysis showed that 42 lichi varieties could be divided into 3 categories at a distance of 12,and into 6 categories at the distance of 10.3.From the 129 SSR primers collected from published literature,20 primers with high polymorphism were obtained.Using these 20 SSR primers,PCR amplification of 74 litchi varieties was carried out,and then capillary electrophoresis analysis was performed.84 bands were amplified in total with 2 to 7 bands for each pair of primers,4.2 bands on average,and the polymorphic band rate reached 96.43%.The results of cluster analysis using the UPGMA method showed that 74 litchi varieties can be divided into 4 main categories at the genetic similarity coefficient of 0.71.The 74 lichi varieties were also into4 categories by using the genetic structure analysis of the STRUCTURE population,which implied that the extensive gene exchange existed in each group.4.74 litchi varieties could be completely divided by using only 6 out of the 20 pairs of primers,such as LZ63,LZ20,LZ11,LZ17,LZ74 and LZ42.These 6 primers were used as the core primers for the construstion of the molecular fingerprint and a unique “molecular ID card”for each of the 74 lichi varieties were obtained.5.The correlation between molecular distance and phenotypic GAIA distance reached a very significant level.The genetic similarity coefficient 0.89 and phenotypic GAIA distance threshold 5 were established primarily and the molecular distance and phenotypic GAIA distance can be used together to improve the accuracy of similar varieties selection in DUS test.6.Make corrections to some errors in "Guidelines for the conduct of tests for distinctness,uniformity and stability—Litchi";put forward suggestions for reclassification of some trait expression states. |
PDF Full Text Request