Breeding is more than genetics: a non-genetic toolkit to improve hybrid potato breeding

Abstract

For potato, diploid hybrid breeding is a novel technology that has recently been developed. The implementa8on of this technology in an efficient breeding programme raised new ques8ons. Besides the gene8c varia8on that is present in a breeding programme, breeders have to deal with environmental varia8on in all stages of the breeding process. Partly, this environmental varia8on can be used to assess genotypic varia8on under specific condi8ons.For another part, varia8on is a nuisance that needs to be dealt with, to limit its effect on the outcome of variety trials where the goal is to evaluate different genotypes and select for the best inherent performance.To decrease unwanted varia8on in breeding trials two approaches were used. On the one hand, to assess to varia8on due to star8ng material differences. Therefore, we determined the effect of the seedling tuber quality traits tuber weight and number of eyes on the performance of plants grown from these seed tubers in the field as well as on their yield.Large varia8on in single-tuber weight was found in a seedling tuber batch of size class 35-45 mm, with up to a factor 4.6 difference in weight between the highest and lowest sizes. A higher seedling tuber weight resulted in higher yield. With the varia8on in weight found in the seedling tuber batch, this trait can result in unwanted varia8on in breeding trials. The number of eyes of seedling tubers affected plant growth rather than yield. A higher number of eyes led to more stems per plant, however, this was compensated by fewer tubers per stem, resul8ng in no effect on yield.On the other hand, to decrease unwanted varia8on in breeding trials we determined the effect of plot size and develop models to calculate varia8on when using different plot sizes and shapes. This was done for the following relevant traits: total tuber weight, number of tubers, tuber shape, standard devia8on of tuber shape, tuber volume, and standard devia8on of tuber volume. The developed models can be used to determine the plot size that is needed for the required degree of precision in a trial.Environmental varia8on can also be applied to determine how genotypes respond in different environments in fewer cycles of selec8on and tes8ng. In climate room trials we found that increasing air temperature decreases number of tubers and weight per tuber, while increasing the day/night difference in temperature led to an increase in weight per tuber. Increasing light intensity and increasing the percentage of far-red light in the spectrum led to increases in number of tubers. For these responses, we found varia8on among the used parent lines, and one rela8vely heat-tolerant line was iden8fied. This line can be used to develop heat-tolerant hybrids.Environmental varia8on was also applied by performing variety trials in different loca8ons, in which genotype ´ environment interac8on and yield stability of a large set of hybrid materials and standard commercial cul8vars was determined. Experimental test-hybrids only slightly underperformed compared to comme...