MARKER ASSISTED SELECTION FOR RESPONSE ATTACK OF VENTURIA INAEQUALIS IN DIFFERENT APPLE GENOTYPES

Abstract

Apple scab caused by Venturia inaequalis, is an important disease, spread worldwide, having a major negative impact in apple production. In this study, there were analyzed four apple cultivars (Liberty, Florina, Starkrimson, Golden Spur), used as genitors in a diallel cross, and their seedlings. In the field, plants selection was done after presence or absence of the scab on leaves, and afterwards, phenotipically selection was completed by marker assisted selection. The molecular analysis conducted with the markers AL-07, AM-19 and U1400, detects the presence of the Vf gene, introgressed from Malus floribunda 821, which confers resistance to the pathogen, in the parental cultivars Liberty and Florina, and in all the F1 hybrids belonging these two genitors. Starkrimson and Golden Spur were susceptible scab parents with recessive homozygous genotype (vfvf), while Liberty and Florina were identified as heterozygous scab resistant parents with genotype (Vfvf). From the 60 apple seedlings analyzed, grouped in six combinations after their genitors (in each combinations were selected ten hybrids, among them five resistant and five susceptible to apple scab attack) 28 were resistant and heterozygous for Vf gene (Vfvf) and 32 were susceptible to scab with recessive homozygous genotypes (vfvf), being obtained almost Mendelian ratio for response to the pathogen, 50% resistant: 50% susceptible. Seedlings belonging to Starkrimson x Golden Spur were only recessive homozygous genotype (vfvf), and in combination resistant x resistant (Liberty x Florina) were identified susceptible and resistant offspring, but at last, only with heterozygous for Vf gene (Vfvf) and no one with dominant homozygous genotypes (VfVf).