Potato Germplasm Research And Genome-wide EST-SSR Markers Development

Potato (Solanum tuberosum L.) is the most important non-cereal crops, all through the world, and is essential to global food security. It is clonally reproduced, has a genetic composition of autotetraploid, is highly heterozygous, and suffers acute filial generation depression. Thus the progress and achievements of potato genetics and breeding are far behind those of other crops. Lacking of resources, and restricted by scale, Chinese potato breeding procedure is more difficult to produce outstanding varieties, especially varieties for processing. That has been the primary restricting factor of china’s development of potato production and industry. Cross-breeding is the most commonly used and realistic breeding method of potato at home and abroad.Focusing on the need for screening and combining of parents in cross-breeding, the following experiments were conducted:1) Flowering, yield and quality traits of tested potato resources, under field condition, were investigated and analysed.2) Genetic diversity and relationship of germplasm and 30 varieties used in Sichuan’s virus-free seed potato propagating procedure were analysed by RAPD and SSR markers.3) SSR loca distribution in potato genome were analysed based on the next-generation sequencing data and EST data; single-copy SSR loca revealed were selected to develop new EST-SSR markers. The results and related conclusions as follows:1. Flowering and fruiting data of 97 germplasm resources in spring and autumn indicated that:1) the flowering and fruiting rates in spring are higher than autumn and it’s suitable for crossing and anther culture in spring rather than autumn under local eco-climatic donditions.2) Reffering their relationship, the budding and flowering rates in autumn is valid indicater for screening parents for cross-breeding.3) Most of the lines need appropriate treatments for using as parents in cross-breeding.4) 40 available cross-breeding parents were revealed.2. Yield components traits in spring and autumn field conditions and their relationships indicated that:1) 97 tested potato lines are of different season adaptabilities referring to their yield components traits, thus they might be used for season-specific variety breeding.2) Weight of large tuber is the most important and direct component of yield per plant, and should be taken as major indicator in selection for yield and certification of potato variety.3) Weight of large tuber is also more reliable indicator for economic tuber output than the rate of economic potato.4) The tight, but not simply component corresponding, relationship between yield components of different planting seasons indicate that 2 seasons (eg. spring and autumn) selection breeding procedure might lead to lose of season-spicific genetic types.5) Yield data of tested lines are useful information for cross parents’selection and combination, also.3. Quality data investigated and further analyses showed that:1) there is no significant correlation relationship among 4 major quality traits and between quality traits and yield traits, except for the significant correlation between starch and dry matter content.2) It is feasible for yield, quality and specific processing potato varieties, by giving specific breeding objectives and selecting through breeding procedure.3) Quality data investigated can be used for cross parents’selection.4. Genetic distances and cluster analyses of potato germplasm lines based on RAPD and SSR indicated that:1) the potato germplasm resources are of lower genetic diversity. So it’s necessary to explore and create germplasm, and broaden genetic basis of potato, for further achivements of potato cross breeding.2) Eco-genetic similarity might be main restrictive factor of genetic diversity among resources tested.3) Some of the valuable lines, such as 80-2, U4 etc. were indentified by the genetic differences revealed by RAPD and/or SSR markers.4) Genetic distances among tested lines also provided information for further crossing combination.5. RAPD analyses of 30 varieties from Sichuan’s virus-free seed potato propagating procedure showed that:1) Genetic diversity among these varieties are higher than genetic diversity among germplasm resources tested.2) The higher genetic diversity might be explained by the eco-genetic diversity among 30 varieties, thus using different eco-genetic parents in cross breeding should be an effective way to broaden genetic basis of potato.3) Some of the same-named varieties from different location, such as D29 and D30 (Zhongshu 2), D22 and D23 (Mira), were proved to be the same varieties, while the others might be different varieties.4) Presumably, some different-named varieties were the same varieties.5) It is suggested that identification of varieties should be emphasized in virus-free seed potato propagating procedure.6. It also can be concluded that:1) the results revealed by RAPD and SSR in our experiments confirmed each other generally. Both of them are applicable for genetic diversity and related research.2) SSR is more reliable and operability for identification of varieties. It is suggested that more expression sequences related SSR markers (and primers) should be developed based on the next-generation sequencing data and EST data.7. Genome-wide analysis of simple sequence repeats showed that:1) there are abundant overall SSRs and unique SSRs within the genome of potato.2) Unique SSRs revealed were aligned within ESTs of potato,2036 SSRs with products were screened, 1848 of them were proved to be polymorphic EST-SSRs, and 465 of them were identified giving products with more than 3 bp length differences.3) Further application of polymorphic EST-SSR markers developed was discussed.8. Two-factor test, seed-tuber size and planting density, showed that:1) Growth of tuber size and weight, accumulation and distribution of dry matter, propagation coefficient and other indicators were influenced by the size of the seed-tuber and planting density significantly.2) Increasing in the size of the seed-tuber extended the period of growthing, tuber size and weight, which was helpful to the transportation of dry matter and it’s accumulaton in tuber, and reduced the propagation coefficient of tuber weight, but improved the propagation coefficient of tuber number.3) Both lower and higher planting density shorten the period of tuber growth, but enhanced the speed of growth.4) Higher density bounded the tranportation of matter to tuber and decreased the propagation coefficient of tuber weight and number.