|QU, XINSHUN - Pennsylvania State University|
Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2015
Publication Date: 1/7/2016
Citation: Haynes, K.G., Qu, X. 2016. Late blight and early blight resistance from Solanum hougasii introgressed into Solanum tuberosum. American Journal of Potato Research. 93(1):86-95.
Interpretive Summary: Late blight, the cause of the Irish potato famine in the 1840s, is still a serious disease of potato worldwide. The organism responsible for the disease has been able to overcome many resistance genes; therefore, plant breeders are always looking for new sources of resistance. Another important disease of potato worldwide that causes crop loss is early blight. Plant breeders previously identified late blight resistance in a Mexican wild potato species. We crossed this wild species with the cultivated potato and identified high levels of resistance to both late blight and early blight arising from this wild species. In addition to high levels of resistance to both diseases, the hybrids developed from this cross had favorable combinations of traits including yield plus attributes important for potato chip producers. The hybrids that we developed will be valuable for breeders in developing improved potato varieties with desirable combinations of disease resistance and quality attributes.
Technical Abstract: Late blight, caused by Phytophthora infestans, and early blight, incited by Alternaria solani,are the two most widely occurring foliar diseases of potato in the U.S. Resistance to both diseases is necessary if growers are to reduce fungicide applications. Field resistance to late blight has previously been reported in an accession of Solanum hougasii (2n=72). The putative aneuploid clone E53.61, derived from (S. hougasii x S. tuberosum) x S. tuberosum was obtained from C.R. Brown and crossed with three S. tuberosum clones. Thirty-five hybrid clones were evaluated for foliar late blight resistance in Rock Springs, PA along with the susceptible check ‘Atlantic’ and for foliar early blight resistance in Presque Isle, ME along with the susceptible check ‘Harley Blackwell’ for three years (2012-2014). The experimental design was a randomized complete block design with two to three replications each year. The US23 genotype of P. infestans occurred naturally and/or was used in inoculations in PA and plants were infected naturally with A. solani in ME. Relative area under the disease progress curve (RAUDPC) was calculated based on visual assessment of foliar disease 4-5 times late in the season each year and subjected to statistical and stability analyses. There were significant differences among clones and the clone x environment interaction was significant for both diseases. Of the 35 hybrid clones evaluated for late blight, 16 were more resistant and 7 were more susceptible than Atlantic, and 12 were as susceptible. Of the 35 hybrid clones evaluated for early blight, 23 were more resistant than Harley Blackwell; the rest were as susceptible. Late blight resistance or susceptibility was independent of the stability of resistance, however, early blight resistance was associated with greater stability. Fourteen clones were more resistant than the check varieties for both late blight and early blight, suggesting that resistance genes for both late blight and early blight have been combined in this genetic material.