Genetic parameters for agronomic characteristics: II: intermediate and advanced stages in a Open Access potato seed breeding population

The aim of this research was to determine the genetic variation available in some important characteristics for true potato seed breeding in intermediate and advanced stages of a breeding population developed by the Centro Internacional de la Papa. A factorial mating design was used to calculate variance components and heritability at both selection stages. Four males were crossed with four females within each set (4 for intermediate stage and 5 for advanced stage) and their resulting offspring tested across two contrasting locations. Tuber yield and set were the only common characteristics recorded in both selection stages. In the intermediate stage early development characteristics (seed germination plus root and internode length) were also measured. In the advanced breeding material, vine earliness and other reproductive traits (days to flowering, flowering intensity, style length and pollen production) were scored. The heritability for tuber yield (0.35) and tuber set (0.32) in the advanced selection stage was higher than in the intermediate stage (0.26 and 0.13 respectively), which suggest that recombination through more cycles of recurrent selection brought untapped variation for both characteristics in this breeding material. Significant additive genetic variation, and thereby high heritability, was observed for internode length (0.52) in the intermediate selection stage, and for days to flowering (0.53) in the advance stage. Progress through selection may be expected for both characteristics. The heritability for pollen production was intermediate (0.23), while it was low (i.e. 0.10) for the other characteristics recorded in both populations

Genetic parameters for agronomic characteristics: 1: early and intermediate breeding populations of Open Access potato seed

The original variation in the source population as well as the selection method may influence the genetic variation in further cycles of genetic improvement. Therefore, the objectives of this research were to determine genetic parameters (variance components and heritability) in source and intermediate stages of a true potato seed (TPS) breeding population and to calculate the genetic and phenotypic correlations in this breeding material developed by the Centro Internacional de la Papa (CIP). The intermediate stage was derived from a source population adapted to the warm lowland tropics plus introduction of exotic germplasm from North America and Europe. Non-additive genetic variation was almost nil for plant survival, tuber yield and tuber shape uniformity in both stages of the breeding population and no quantitative genetic variation for uniformity of tuber color was observed in both source and intermediate breeding materials. Heritability was higher in the intermediate stage than in the source population for plant survival (0.86 vs 0.66), tuber yield (0.30 vs 0.14) and tuber shape (0.77 vs 0.51), but it was the reverse for tuber uniformity (0.11 vs 0.72). These results suggest that potato breeders at CIP were able to keep enough genetic variation for most important characteristics for potato production from true seed in their intermediate breeding materials by adding new sources of variation to the original breeding population. Additive genetic and phenotypic correlations were significant and positive between plant vigor after transplanting and tuber yield, and tuber shape and tuber uniformity, which suggest that high yielding offspring result from early vigorous growth, and that tuber uniformity could depend on tuber shape uniformity in this breeding materia

Application of Biotechnology for Conservation and Utilisation of Andean Root and Tuber Crops and Biosafety Guidelines

The International Potato Centre (CIP) recognizes the value of biotechnology in the conservation and use of solanum potato and sweet potato germplasm. Biotechnological development and utilisation at CIP is currently at the transgenic plant production and gene mapping stages. CIP complies with international standards regarding biosafety guidelines to ensure biotechnology products without adverse environmental effects, and to prevent unintentional release of hazardous organisms. CIP preserves thousands of potato and sweet potato accessions and other Andean root and tuber crops in-vitro, a biotechnology technique, as opposed to risky field conditions. The paper highlights the value of the in-vitro technique in storing and distributing pathogen-tested clonal accessions of potato and sweet potato. Aspects of germplasm characterization, genome modification and manipulation, and biosafety guidelines are discussed

Cybrids and tetrad sterility for developing true potato seed hybrids

Potato cybrids result from the fusion between cytoplasm and nuclear gene donors. Such genetic materials are an alternative means to broaden the breeding pool by non-sexual gene transfer. Tetrad pollen sterility provides also another source of male sterility with some potential for true potato seed breeding. The objective of this research was to investigate cybrid-derived offspring for both agronomic and reproductive characteristics in two contrasting Peruvian locations, and to examine new exotic germplasm for tetrad sterility, with the aim of broadening the breeding pool available at the Centro Internacional de la Papa (CIP). The cybrids were derived from fusions between Y-245.7, a clone with tetrad sterility, and Atzimba. These cybrids were crossed with selected male parents from the CIP breeding population, and their hybrid offspring were tested in La Molina (coastal desert) and Huancayo (cool highlands). In addition, other clones with tetrad sterility were also crossed with selected testers to determine their breeding value. There were significant differences for tuber yield, style length, and berry number among the hybrid offspring, and the genotype by environment interaction was significant for tuber yield and berry number. The top 25% highest yielding cybrid-derived offspring across both locations showed the same tuber yield although they were significantly different for some of the reproductive characteristics. With the exception of one cybrid, the others did not exhibit segregation for tetrad sterility in their hybrid offspring, which were male fertile. However, the offspring derived from crosses between other sources of tetrad sterility and the same testers all showed tetrad sterility, and some of them had outstanding tuber yield at La Molina. The lack of segregation for tetrad sterility in these new crosses suggests that the non-cybrid, male sterile, female parents are triplex or quadriplex for the Tr nuclear locus, which interacts with a sensitive cytoplasm (e.g. Trs from S. verrucosum or S. stoloniferum) to produce tetrad sterility in potato