Screening Of Potato Breeding Parents Of Stable Food And Establishment Of Shade Tolerance Evaluation System

China is the largest country at consumption and production of potato in the world.China is promoting the stable food of potato vigorously,which could improve the economy development for local industrial.However,the development of potato is hindered because of the lack of specialized breeds.The southwestern region is the second area that produces potato in China.The potato/maize intercropping is the main cultivation mode in this area.However,potato is mainly suffered from shade stress by taller maize at tuber bulking stage in relay intercropping system,which induced yield and quality reduction which reduced the economic benefits of potato.Therefore,we need screening the specialized breeds of potato for stable food and the breeds that have better shading tolerance.It is significant to promote the developmeng and increase the economic benefits of potaot in outhwestern region.Firstly,we evaluated the genetic background through SSR molecular markers and analyzed the main characteristics of photosynthetic,yield,and quality of 198 potato materials.Secondly,35 potato genotypes were treated under shading and natural light conditions in a field experiment.The plants were shaded with black nets which had 77% shading rate of natural light from bulking to harvest.The natural light plants were used as the control.Photosynthetic physiological and stress resistance indexes measured after 15 days with shading.Yields and main qualities of each genotype and were tested after harvest.Shade tolerance coefficients of all indexes from both treatments were analyzed by using principal membership function method,component analysis,hierarchical cluster analysis and stepwise regression analysis.The main results are as follows:The polymorphism of 198 potato resource materials was analysied by SSR.A total of 159 polymorphic bands were detected,and 1-11 polymorphic bands were obtained for each pair of primers.4.82 polymorphic bands were detected for the primers average.The polymorphism information content ranged from 0.1964 to 0.9791,with an average of 0.6696.These materials were clustered into fiver types where the genetic similarity coefficient was 0.65.The clustering results were revised to be divided into 4 types according to the analysis of the population structure.(2)The main traits including yield,dry rate,protein contents and photosynthetic rate of 198 potato materials were evaluted.Firstly,we screened 26 materials from the first category and the first sub-genus in the first subcategory of the second largest category,including Lishu 6,Fengshenyangyu and Huayu 5 etc.according to yield.Secondly,26 materials were chosed from the first category and the first sub-genus in the first subcategory of the second category,including Qingshu 2,Zhongshu 2 and Liangshu 6 etc.according to photosynthetic rate.Thirdly,we screened 7 and 30 materials from the first category according to dry rate and protein content respectively.That included S03-2744,S14A53-13 and Deshu 3 etc.and B2,K103 and Eshu 10 etc.respectively.And the dry rate of the first class of materials is above 26%.Finally,we screened 71 potato materials totaly that performed well in one or more aspects according to above 4 traits.(3)In the shading tolerance evaluation,six independent comprehensive components were obtained from 13 single indexes by principal component analysis,and 35 potato genotypes were divided into four shade tolerance types by cluster analysis.Eshu10 and LiShu6 were screened as a shade tolerance genotype and a shade sensitive genotype,respectively according to the result.A mathematical evaluation model for potato shade tolerance was stablished by stepwise regression equation: D=0.060+0.106Gs+0.214qP+0.143 NPQ.(R2=0.93,p = 0.0001),which indicated that three indexes were feasible to predict the shade tolerance in potato at tuber bulking stage.In summary,we screened high-dry or high protein nutritional content materials with different genetic backgrounds,and provided parental materials for potato breeding of staple food in the present study.A comprehensive evaluation system was established based on parameter values of photosynthetic systems by multivariate statistics for the buiking stage of potato,which could be used to predict shade tolerance at potato tuber bulking stage simply and efficiently,and have potential application value in practical.