| As the main food crop in China,people pursue rice varieties with good taste,good quality and high yield,pursue authenticity when they buy rice seeds,and breeders hope their varieties bred could be protected.Constructing fingerprints,analyzing genetic diversity and genetic similarity,screening specific markers of rice varieties are necessary,which could provide a theoretical basis for parent selection,variety identification and classification evaluation of rice varieties to achieve the purpose of breeding high quality and high yield varieties.When farmers cultivate rice plant,artificial weeding is costly and time-consuming.The use of chemical herbicides can effectively reduce the cost and the excellent weeding effect of glyphosate is widely recognized.The QTL location of glyphosate tolerance lays a foundation for the cloning of genes and the analysis of its tolerance mechanism.By crossing glyphosate resistant rice varieties with high-quality and high-yield varieties,we can select varieties that are both glyphosate resistant and high-quality and high-yield,improving farmers’ income,reducing farmers’ production costs and promoting the development of modern agriculture.This study consists of two parts: firstly,genetic diversity,genetic similarity,constructing fingerprint and screening specific marker were be done for 67 japonica rice varieties in the middle and lower reaches of the Yangtze River and northeast rice regions;The other is to select glyphosate sensitive Zhejing 22 from 67 japonica rice varieties and glyphosate resistant CA19 to construct a recombinant inbred population,to locate the glyphosate resistant QTL and screen the tolerant lines to analyze the mechanism of glyphosate tolerance1.The genetic diversity of 67 Japonica Rice Varieties in the middle and lower reaches of the Yangtze River and Northeast China were analyzed by 190 polymorphic markers.The variation range of number of alleles was 26,with an average of 2.79;the variation range of Shannon index was 0.091.39,with an average of 0.52;the variation range of Nei’s gene diversity was 0.030.76,with an average of 0.29.Among the 67 japonica rice varieties tested,the results of diversity analysis showed that there were some differences between the japonica rice varieties in the middle and lower reaches of the Yangtze River and those in the northeast,Zhejiang and Jiangsu,but the number of alleles,Shannon index and Nei’s gene diversity have little difference and they all showed low genetic diversity.The variation range of genetic similarity was 0.530.96.Among the 67 japonica rice varieties tested,the rice varieties in the middle and lower reaches of the Yangtze River can be distinguished from those in the northeast by using genetic similarity coefficient and UPGMA cluster analysis.24 polymorphic markers were selected to construct fingerprints and 33 specific markers were used for variety identification.The construction of fingerprints and the selection of specific markers can help variety right protection,rice quality supervision and management.2.158 Lines of CA19/Zhejing 22 inbred population F4:5 were used as materials,spraying glyphosate solution with concentration of 2 g/L at three leaf stage,and QTL mapping was carried out according to the statistics of three characters: dead time,survival rate and dead index.The genotypes of 158 lines were detected by 95 polymorphic markers selected from 750 markers,and the genetic map was constructed.The threshold value of LOD was 2.5.One QTL was detected for each of the three traits,which were located between RM1370 and RM3765 on chromosome 6 with a genetic distance of 5.79 c M.Taking Zhejing 22 as a control,the tolerance mechanism of glyphosate resistant line 5396 was analyzed.The leaves of Zhejing 22 turned yellow on the third day after spraying glyphosate,and withered on the fifth day.The cell structure of Zhejing 22 was seriously damaged.The activity of 5-enolpyruvylshikimate-3-phosphate synthetase in the leaves decreased significantly,the content of shikimic acid increased significantly,the expression of EPSPS gene in rhizome and leaf did not change significantly,the content of active oxygen ions increased more,and the distribution range was wide.After treatment,the leaves of line 5396 had no obvious change on the 3rd day,but part of the leaves turned yellow on the 5th day,stagnating growth,but did not wither and die;at this time,the cells were damaged,but the overall structure,chloroplast and mitochondria were relatively complete,the activity of EPSPS enzyme and the content of shikimic acid had no significant change,the expression of EPSPS gene in roots and stems had no significant change,and the expression of EPSPS gene in leaves was increased 475.89 times and 520.34 times respectively on the 3rd and 5th days,the content of active oxygen ions increased little,and the distribution range was small.On the 32 nd day,the new tillers of line 5396 began to grow,and the new tillers grew on the 39 th day.The expression of EPSPS gene in the leaves increased significantly.line 5396 had strong tolerance to glyphosate,and the expression of EPSPS gene in leaves increased to cope with the inhibition of glyphosate on EPSPS activity,and the growth was restored by tillering again. |
