Genetic analysis of strawberry root system traits in fumigated and nonfumigated soils II. Relationships among root system and above-ground traits of strawberry seedlings

Genotypic and phenotypic relationships among root system and above-ground traits of strawberry (Fragaria xananassa Duch.) mere evaluated for seedlings grown in annual hill culture, with soil treatments consisting of 1) preplant fumigation with methyl bromide and chloropicrin or 2) nonfumigation, Seedlings were from crosses among 10 genotypes within the University of California strawberry improvement program that had been selected previously for yield and other production traits. Root mass had positive genotypic correlations with plant diameter 5 months after planting in both fumigated (r = 0.58) and nonfumigated (r = 0.69) soils, Genotypic correlations between root mass and two production traits, yield and fruit size, were nonsignificant. However, plant diameter had positive genotypic correlations with yield (r = 0.36 to 0.51) and negative genotypic correlations with fruit size (r = -0.47 to -0.60). In general, root appearance scores were uncorrelated with production traits, but their genotypic correlations with vegetative traits were occasionally strong. Genotypic path coefficient analyses conducted separately for fumigated soils and nonfumigated soils both indicated that plant diameter had positive direct effects on yield that were twice the magnitude of that for any other trait. Root mass had a small negative direct effect on yield in each fumigation environment, while root appearance scores had small to moderate direct effects on yield that were more positive for samples obtained after fruiting (in April) versus before fruiting. Pleiotropic relationships appear to exist between root traits and plant diameter, but plant diameter is the best single predictor of genotypic variation for yield in both soil fumigation environments.