Inheritance of Resistance to Colletotrichum gloeosporioides and C. acutatum in Strawberry

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Abstract
Information on the inheritance of resistance to Colletotrichum gloeosporioides and C. acutatum hemibiotrophic infections (HBI) in strawberry leaf tissue and the genetic control of anthracnose crown rot (ACR) in crown tissue are relatively unknown. Six parental genotypes were crossed in a half-diallel mating design to generate 15 full-sib families. HBI and ACR experiments were conducted concurrently. Both seedlings and parental clones were inoculated with 1 × 106 conidia/ml of C. gloeosporioides or C. acutatum. Percent sporulating leaf area, wilt symptoms, and relative area under the disease progress curve were calculated to characterize resistance among genotypes and full-sib families. Low dominance/additive variance ratios for C. acutatum HBI (0.13) and C. gloeosporioides ACR (0.20) were observed, indicating additive genetic control of resistance to these traits. Heritability estimates were low for C. acutatum HBI (0.25) and C. gloeosporioides HBI (0.16) but moderate for C. gloeosporioides ACR (0.61). A high genetic correlation (rA = 0.98) between resistance to C. acutatum HBI and C. gloeosporioides HBI was observed, suggesting that resistance to these two Colletotrichum spp. may be controlled by common genes in strawberry leaf tissue. In contrast, negative genetic correlations between ACR and both HBI traits (rA = −0.85 and −0.61) suggest that resistance in crown tissue is inherited independently of resistance in leaf tissue in the populations tested. Overall, these findings provide valuable insight into the genetic basis of resistance, and the evaluation and deployment of resistance to HBIs and ACR in strawberry breeding programs.

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