Institut für Züchtungsforschung an landwirtschaftlichen Kulturen
The overall objective of this project is the creation of methodological foundations to optimize breeding for diploid hybrid potato varieties (“DHP”). The transition from traditional breeding of tetraploid clonal varieties towards diploid, true-potato seed (TPS)-based varieties offers several quantitative genetical and methodological advantages, which promise a higher selection gain and a faster adaption of new varieties, in particular to changing climatic conditions. A central problem of DHP breeding is currently inbreeding depression, which limits the success rates for the development of inbred lines, the parents of hybrids. The main objective of this project is the development of a strategy to overcome inbreeding depression of diploid potato in an efficient way. Moreover, the test-cross hybrid testing scheme shall be optimized to maximize overall selection gain.Work package A - Development of genomic predictive methods to increase tolerance to inbreeding: Each of the two companies provides 500 S0 genotypes, which possess the Sli-gene and which are therefore self-compatible. The S0 genotypes will be characterized phenotypically and genotypically and will be selfed. The inbreeding depression of resulting S1 genotypes will be quantified by survival rate of S1 plants in the field, as well as by a vigor and by a fertility trait for which each S1 plant is scored. Generations of higher inbred level (S2, S3) will be characterized phenotypically and genotypically and a second cycle consisting of S0, S1 and S2 material will be generated. Based on this data, inbreeding depression will be associated with genomic features and the potential of “genomic prediction” for selecting for inbreeding tolerance will be assessed. Work package B - Investigation of „early selection“ based on test-cross performance of hybrids derived from parents of low degree of inbreeding: Additionally to the efficient creation of germplasm with high level of tolerance to inbreeding, it is important to know in which generation test-crosses should be generated for selection decisions. The higher the degree of inbreeding of the parental lines is, the more precise is the selection decision, but also the later the information is obtained. Therefore, there may be an optimum intermediate level of inbreeding which generates the highest selection gain in the DHP program. Studies with corn did not lead to clear results. To investigate this aspect experimentally with diploid potato, 20 sequences of S0-S1-S2 genotypes from work package A will be used and will be crossed to the same tester. The correlation of the performance of S0-TC and S1-TC and S2-TC combinations will be investigated. A high phenotypic correlation would indicate that a strategy of “early testing”, that is using S0-TC or S1-TC data for selection decisions would be appropriate.
Federal Ministry of Food and Agriculture
