Evaluation On Genetic Diversity And Genetic Analysis Of Important Traits For Potato Germplasm

Along with the frequent cooperations with other countries,the condition for China’s potato germplasm has been greatly improved.Institute of Vegetables and Flowers Chinese Academy of Agriculture Sciences conserve possession of huge diversity of potato materials,which reflects of the structure and composition of potato germplasm nationwide.In this study,we did pedigree analysis,cytoplasm genotyping,phenotype trait clustering,genetic diversity analysis by SSR,combining ability and heritability analysis,using approximate 600 potato accessions including cultivars bred inland and materials introduced from Europe,North America,International Potato Center（CIP）et al.The results achieved pave the way for researches working on germplasm use,parent selection,enriching parent resources and broadening the hereditary basis of potato cultivars in China.The main conclusions are summarized as follows:1.The hereditary basis of approved potato cultivars in China was analysed.By 2012,there were436 potato cultivars have been authorized.It was found that there were 423 parents involved in the breeding progress of 379 cultivars.In total,the 423 parents were utilized for 724 times and can be classified into 8 groups:cultivars inland,breeding lines inland,indigenous breeds,Neo-tuberosum,materials introduced from North America,Europe,CIP and others.Their corresponding nuclear and cytoplasmic germplasm genetic contribution from these eight groups was 97.5,107,10.5,16,27.5,71,33 and 16.5,respectively.The results indicatie that the cultivars and breeding lines inland always play the major role.Indigenous breeds are mainly used as female.Neo-tuberosum&materials introduced from Europe,North America et al are more frequently used as male.Based on the pedigree data and consanguinity composition analysis,potato cultivars Epoka,Jubel,Industrie,Bintje and Early Rose were classified into parents generation 1（G1）while Irish Cobbler,Triumph,Schwalbe,Anemone,Mira,292-20,Katahdin and B76-16 the parents generation 2（G2）.2.Using multiplex marker system developed by Hosaka,the cytoplasm of 608 potato accessions tested were grouped into T-,D-,P-,A-,M-and W-type,with the respective quantity and ratio being 303（49.8%）,243（40%）,2（0.3%）,15（2.5%）,6（1%）and 39（6.4%）.No additional new types were detected.3.Based on sixteen phenotype traits,UPGMA clustering analysis was performed using 454potato accessions.It showed that all accessions can be grouped into two clusters A₁ and A at the Euclidean distance of 14.66.The cluster A₁ can be further grouped into two subclusters A₁₁1 and A₁₂ at the Euclidean distance of 12.74.In total,all the accessions can be grouped into 9 clusters,including four small ones（A,B,C and H）and five big ones（D,E,F,G and I）.And the cluster I was the biggest one,accounting for 57.5%of all the accessions.4.Thiry-six of 332 pairs of SSR primers were screened out,which covered all the 12chromosomes of potato.In total,244 polymorphic alleles were amplified in the 559 accessions with the36 pairs of primers.Polymorphic alleles were amplified by each pair of primer ranged from 1（STM1049 and SSR15406）to 7（PM0890）,with a mean of 3.72.The fragment sizes amplified varied from 106bp to 308bp.The polymorphic information content values（PIC）spread from 0.1545（SSR15406）to 0.7743（PM0890）,with a mean of 0.5783.With primers of higher PIC value,more polymorphic alleles were amplified and vice versa.Based on the Neighbor-Joining tree constructed with software PowerMarker V3.25,all the 559 accessions tested were clusterd into 3 general groups（Group1,Group 2 and Group 3）.Group 1 is a mixed one,containing 133（23.8%）materials from almost all the regions.Group 2 is one mostly gathered by accessions from Europe,North America,Northeast and Northwest regions in China.There were 187 materials including in this group,accounting for 33.5%of all.Group 3 held 239 out of 559 accessions（42.8%）,mainly focus on North America,South America,Northeast and Southwest regions in China.These three groups could be further divided into small group:Group 11 and Group 12;Group21,Group22 and Group23;Group31,Group32 and Group33,respectively.5.Combining ability analysis was performed for the eight potato cultivars/breeding lines used for processing or early-maturing growing according to incomplete diallel cross.The result indicated that Atalantic and GT12867-02 was low in GCA for tuber set.The relative effect of the GCA was-9.89 and-15.43 for Atlantic,-9.11 for GT12867-02 in 2010.Atalantic and Lenape was high in GCA for dry matter.For Atalantic,the relative effect was 4.50 in 2009,Atalantic,GT12867-02 and Lenape was high in GCA for chipping color and the corresponding relative effect was 11.90 and 12.45 for Atalantic,5.02and 4.75,for GT12867-02 and Lenape in 2009,respectively.6.Heritability was estimated and analysed for chipping qualities and important agronomic characters.The results showed that broad heritabilities were above 62%for tuber yield,dry matter,tuber size,tuber set and chipping color,indicating that these five characters were determined by genetic factors to a great extent.The narrow sense heritabilities of chipping color were both above 50%in two years,indicating that the additive effect plays the major role and is tolerant to surroundings.So it is feasible to select lines with good chipping color quality in earlier generations.Meanwhile,the heritability in the narrow sense of tuber yield and tuber size were relatively low,so the selection should be conducted in higher generation.