General combining ability and heterosis regarding the phytochemical properties in strawberry (Fragaria × ananassa) hybrids

Strawberries are a common and important fruit in human diet because of their high content of essential nutrients and beneficial phytochemicals, which have relevant biological activity in human health. In this study, six cultivars and 15 selected F₁ hybrids between S₄ inbred lines and tester (cv. ‘Dukat’) were evaluated in a field trial over a period of two consecutive years. The amounts of total anthocyanin, phenolics and vitamin C in fruits and antiradical activity were analysed. General combining ability (GCA) and mid‐parent heterosis were also determined for those characteristics. Among all the genotypes tested, the inbred lines of ‘Senga Sengana’ 17 showed the highest breeding value based on GCA for all studied traits. Estimated heterosis varied among genotypes tested. The highest heterosis in terms of vitamin C occurred in the offspring of clone 1387 18‐15 × ‘Dukat’, but with regard to phenols and antiradical activity in hybrid ‘Teresa’ 18‐15 with cv. ‘Dukat’. This study revealed that the differentiation in chemical composition of strawberry fruits between genotypes is clearly dependent on individual genotype combinations and demonstrated the presence of heterosis in phytochemical contents in some specific genotypic combinations.     

A diallel crossing approach aimed on selection for ripening time and yield in breeding of new strawberry (Fragaria × ananassa Duch.) cultivars

The extension of the ripening season in open field production is of high economic interest for strawberry growers. Therefore, targeted breeding for extreme early or late ripening cultivars with high yield potential is of particular interest. Thirteen strawberry cultivars were crossed in a reciprocal way without selfing, and the 144 resulting F₁ populations were evaluated in a field trial over a period of two consecutive years. The data were analysed using a mixed‐model approach adapted for diallel crossing designs using SAS 9.3. The variability in the crossing approach is mainly based on the general combining ability (GCA) of the cultivars (additive effects). Specific and reciprocal combining abilities (non‐additive effects) appear less important. The highest GCAs for the trait Marketable Yield were found for the cultivars ‘Polka’ and ‘Yamaska’. The trait Earliness is bilateral with significantly low GCAs for early ripening in ‘Clery’ and ‘Daroyal’ and significantly high GCAs for late ripening in ‘Yamaska’ and ‘Florence’. Crosses with these cultivars are likely to deliver populations with both high yield and an extended ripening period.     

Mapping quantitative trait loci (QTLs) underlying seed vitamin E content in soybean with main,epistatic and QTL × environment effects

Soybean (Glycine max (L.) Merr.) seed contains small amounts of tocopherol, a non‐enzymatic antioxidant known as lipid‐soluble vitamin E (VE). Dietary VE contributes to a decreased risk of chronic diseases in humans and has several beneficial effects on resistance to stress in plants, and increasing VE content is an important breeding goal for increasing the nutritional value of soybean. In this study, quantitative trait loci (QTLs) underlying VE content with main, epistatic and QTL × environment effects were identified in a population of F_5 : 6 recombinant inbred lines from a cross between ‘Hefeng 25’ (a low‐VE cultivar) and ‘OAC Bayfield’ (a high‐VE cultivar). A total of 18 QTLs were detected that showed additive main effects (a) and/or additive × environment interaction effects (ae) in different environments. Moreover, 19 epistatic pairs of QTLs were found to be associated with α‐tocopherol (α‐Toc), γ‐tocopherol (γ‐Toc), δ‐tocopherol (δ‐Toc) and total VE (TE) contents. The QTLs identified in multienvironments could provide more information about QTL by environment interactions and could be useful for the marker‐assistant selection of soybean cultivars with high seed VE contents.