|Santa Cruz, Jose|
Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2009
Publication Date: 11/1/2009
Publication URL: http://hdl.handle.net/10113/41616
Citation: Santa Cruz, J., Haynes, K.G., Chris, B.J. 2009. Effects of one cycle of recurrent selection for early blight resistance in a diploid hybrid solanum phureja-S. stenotomum population. American Journal of Potato Research. 86:490-498. Interpretive Summary: Genetic resistance to a disease called early blight in potatoes has been hard to find in potatoes that have good levels of other traits. We found resistance to early blight in a related non-commercial potato species that we thought would work in commercial potatoes. We tried to breed the non-commercial potato species for early blight resistance and other important traits. Unfortunately, we found that this resistance also carried along with it some undesirable traits that are not acceptable. This information will be used by potato breeders to look for sources of resistance to this disease.
Technical Abstract: Early blight, caused by Alternaria solani, is the second most important foliar disease in potatoes, after late blight, around the world. Heritable early blight resistance was previously identified in a diploid hybrid population of Solanum phureja-S. stenotomum (phu-stn). Seventy-two clones, consisting of the most early-blight resistant clone from each of the 72 phu-stn families in this population, were randomly intermated and four horticulturally good clones from each family were selected to constitute the second cycle population. The objective of this study was to determine if this recurrent selection strategy would result in improved levels of early blight resistance in the second cycle population. Approximately 288 clones, derived from these 72 half-sib phu-stn families, were evaluated in a replicated field trial for two years, along with the control cultivar ‘Atlantic’, in Pennsylvania. Area under the disease progress curve (AUDPC) was calculated from estimates of the percentage of necrotic lesions and defoliation. Broad-sense heritability for resistance was 0.75, with a 95% confidence interval of 0.69-0.81. Narrow-sense heritability was 0.63 ± 0.29. Although these two estimates of heritability were high in both the first and second cycle populations, no genetic gain in early blight resistance was made with this recurrent selection approach. The second cycle population was more susceptible and later in maturity than the first cycle population. Because of the negative association between earliness and resistance to early blight, it is likely that selecting horticulturally good clones to constitute the second cycle population also resulted in selection in favor of susceptibility. An alternate breeding strategy to improve early blight resistance in this population will have to be devised.