Phenotyping ripe rot resistance in the <i>Actinidia chinensis</i> (kiwifruit) mapping population

Abstract

Resistance to ripe rot (Cryptosporiopsis actinidiae) in kiwifruit is likely to be controlled by quantitative trait loci (QTL) Accurate phenotyping of ripe rot resistance is crucial to locating QTL on the kiwifruit genomic linkage map and may facilitate identification of candidate genes for breeding A detached fruit assay was developed to compare resistance to ripe rot in the mapping population Fruit at or near eating ripeness were inoculated by inserting mycelial plugs (3 mm diameter) under shallow skin flaps and then lesion development was monitored at 20C Results suggested that resistance was quantitative Assay variability was reduced by pipetting spore inoculum into uniform wounds (5 mm) in the fruit surface Preliminary analysis using single marker ttests showed that marker Ke316 which may be involved in acyl lipid metabolism/transfer was associated with ripe rot susceptibility The association weakened as more genotypes were tested and more analyses are necessary to determine whether Ke316 detects an actual QTL and/or if further QTLs are detectable