Apricot breeding for resistance to Sharka

V. Bozhkova, S. Milusheva
Abstract. The Sharka disease caused by Plum pox virus (РРV) was found for the first time in Bulgaria more than 80 years ago and it is an endemic disease for our country, as is for all the East European countries. Like all plant viruses, PPV could not be controlled with treatments and that makes breeding of resistant cultivars and rootstocks a significant tool for limiting its spread. The investigation was carried out in the period 2009–2012 in the collection plantations of the Fruit-Growing Institute, Plovdiv in the frames of FP7 project of the EU „Sharka Containment (SharCo)”. The aim set in one of the work packages of the project was to carry out accelerated breeding activities of apricot cultivars resistant to Sharka by using MAS (marker-assisted selection). The hybridization programme included 24 parental combinations with 12 633 pollinated flowers and as a result 1661 hybrid stones (seeds) were obtained. The molecular marker analysis of the leaf samples from 39 hybrid plants obtained from 7 crossings showed that 8 of the hybrids contained a gene for resistance to PPV. Those were plants of the parental combinations ‘Harcot’ х ‘Lito’, ‘Lito’ х ‘SEO’ and ‘Harlayne’ х ‘Harcot’. Data showed that all hybrids obtained from crossing of two resistant cultivars (‘Lito’ х ‘SEO’) have a gene for resistance. If only one of the parental cultivar is resistant, part of the hybrids have gene for resistance to PPV and in our case it is 50% of all analyzed hybrids.