Inbreeding depression for seed germination and seedling vigor in strawberry (Fragaria × ananassa Duch.)

Experiments leading to the procurement of subsequent inbred generations were conducted in the years 2006- 2013. Seeds obtained from open pollination and after self-pollination of four strawberry cultivars (Teresa, Senga Sengana, Kent and Chandler) and clone 1387 were used. These genotypes were evaluated for their tolerance to strong inbreeding under in vitro culture conditions. The aims of this study were to estimate the inbreeding depression of each of the progenies. During the investigation, the germination percentage as well as seedling viability were evaluated. The highest seed germination was shown for populations derived from ‘Teresa’ × open pollination (82%) and ‘Kent’ (7) S₄ (78%). Seeds derived from self-pollination resulted in the lowest germination - an average of 16.8%. Generally, seed germination was significantly lower for the five S₁ offspring, whose depression was 0.62, in comparison with the S₄ seedlings, whose depression was 0.31. Inbred offspring showed a depression in relation to the average weight of a single seedling of 0.08 in the case of S₁ progeny, whereas in the case of S4 progeny it was 0.23. The highest germination energy was shown by ‘Kent’ (7) S₄ seeds (74%) and hybrids of ‘Teresa’ derived from open pollination (75%); whereas seeds obtained at the same time from self-pollination germinated 10.8% on average.