Recurrent maternal half-sib selection improves resistance to foliar late blight in a diploid hybridSolanum phureja-solanum stenotomum population

Abstract

Foliar late blight, caused byPhytophthora infestans, is a devastating disease of potatoes worldwide. In 1996 we initiated a breeding strategy to improve the levels of resistance to late blight in a diploid hybrid population ofSolanum phureja-Solanum stenotomum. The purpose of this study was to determine if resistance to late blight in this diploid potato population could be improved by recurrent maternal half-sib selection. Four clones from each of 72 maternal half-sib families were evaluated for late blight resistance in replicated field trials in Pennsylvania in 1996 and 1997 (cycle 1) and in 2003 and 2004 (cycle 2). ‘Atlantic’ was included as a check cultivar at all sites. Percentage of infected foliage was recorded three times towards the end of the growing season each year and was used to compute area under the disease progress curve (AUDPC). Mean AUDPC for Atlantic in cycle 1 and 2 was 863 and 854, respectively. Mean AUDPC of the cycle 1 and cycle 2 diploid clones was 652 and 556, respectively. Narrowsense heritability for resistance in cycle 1 and cycle 2 was estimated as 0.78 and 0.77, respectively; additive genetic variance was estimated as 10960 and 12636, respectively; phenotypic variance was estimated as 14088 and 16375, respectively. Predicted and realized genetic gain from cycle 1 to cycle 2 was −80 and −96, respectively. Recurrent maternal half-sib selection is an effective way to improve resistance to late blight in this population and to maintain adequate genetic diversity for further enhancement efforts.