Genetic Parameter Estimates for Resistance to Colletotrichum gloeosporioides and Comparisons with Production Traits in Strawberry

The fungus Colletotrichum gloeosporioides infects the crowns of strawberry plants, causing wilting and death that may result in significant losses in the field. Cultivars developed at the University of Florida show variable levels of resistance to this disease. Thus, genetic parameters for resistance to C. gloeosporioides were estimated in this study to aid in the selection of breeding practices that would improve resistance. About 13 seedlings were randomly selected from each of 76 families obtained from a circular diallel mating design, with one runner plant per seedling in each of four blocks. Plants in two of the blocks were inoculated by spraying the crowns with 2 mL of a spore suspension of C. gloeosporioides. The remaining two non-inoculated blocks were utilized for measuring production traits including average fruit weight, marketable yield, proportion of unmarketable fruit, and soluble solids content.  Broad-sense heritability for resistance to crown rot was estimated as 0.38 ± 0.05 suggesting moderate genotypic control. Improvement in resistance to crown rot will be possible through recurrent selection, as narrow-sense heritability was also moderate (0.49 ± 0.12), suggesting a lack of non-additive variance for this trait.  For production traits, narrow-sense heritability estimates ranged from 0.12 ±0.04 to 0.53 ±0.04 whereas broad-sense heritabilities ranged from 0.19 ± 0.03 to 0.67 ± 0.03. Estimates for the production traits were similar to those obtained in previous studies, except those for soluble solids content (h²= 0.12 ± 0.04, H² = 0.19 ± 0.03) which were lower than in previous reports. Broad-sense heritability estimates for all traits except soluble solids were moderate to high, suggesting that gains can be obtained from clonal selection in this population