Relative performance of strawberry genotypes over four cycles of cultivation on fumigated and nonfumigated soils

Yield and fruit size were determined for 49 strawberry (Fragaria xananssa ouch,) genotypes during a 7 gear period, in soils prepared with and without preplant soil fumigation using 2 methyl bromide : 1 chloropicrin (wt/wt). Strawberries were grown in alternate years, with the nonfumigated treatment representing the first, second, third, and fourth strawberry crop cycles initiated without soil fumigation, Highly significant (P < 0.01) effects of soil fumigation treatment were present for yield in a combined analysis ol er all Sears; fumigation increased yield by 41% over nonfumigated soils in the first nonfumigated cultivation cycle and by 68% to 74% for subsequent nonfumigated cycles. Fruit size was less affected by soil treatment but increases due to fumigation (2% to 18%) were significant (P < 0.05) in the third or fourth nonfumigated crop cycle. Genotypic variances were highly significant in the combined analysis, whereas genetic x fumigation interaction variances were significant only for fruit size and contributed < 8% of the total phenotypic variance for either trait. Genetic correlations were r(g) = 0.77 and 0.92, respectively, for yield and fruit size treated as independent traits across soil fumigation environments. There was no evidence for genes that confer specific adaptation to nonfumigated soils, or that these genes emerge as important contributors to the phenotypic variation as the soil environment deteriorates with repeated cultivation of strawberry in nonfumigated soil, Chemical names used: trichloronitromethane (chloropicrin).