Il Rae Rho

Chlorophyll Fluorescence as a Diagnostic Tool for Abiotic Stress Tolerance in Wild and Cultivated Strawberry Species

Chlorophyll (Chl) fluorescence analysis was used to assess stress tolerance in wild and cultivated strawberry species. We found that the parameters, photochemical quenching (1-qP), non-photochemical quenching (qN), and maximum quantum yield (Fv/Fm), can serve as stress indicators because they are sensitive to early responses to stress. The most sensitive region used for measuring Chl fluorescence in strawberry leaves was the upper surfaces of leaflets located in the middle of new leaves. An analysis of the Chl fluorescence characteristics of strawberry species showed that octoploid species had greater stress tolerance than diploid species. The ‘Whiteberry’ maintained high levels of 1-qP and qN through the dissipation of excess excitation energy as heat during early stress treatment. These results suggest that ‘Whiteberry’ has a photoinhibition system that allows it to respond to stress in a more sensitive manner than other cultivars. Therefore, among the Chl fluorescence parameters examined, 1-qP and qN, can serve as good indicators for comparing stress tolerance, and they can be used to simultaneously screen many plants for stress tolerance in strawberry breeding programs.

Effects of backcrossing on quality of strawberry fruit

American/European strawberry cultivars are morphologically different from Asian cultivars with American cultivars generally having higher yields, fruit weight, and fruit hardness and Asian cultivars tending to have higher sugar content. In this study, we performed backcrossing to improve the fruit qualities of Asian varieties of strawberries using American cultivars as the donor parent. The F1 progeny derived from crosses between Asian and American cultivars tended to have lower sugar content and higher fruit weight and yield than Asian cultivars, but fruit hardness did not differ between the Asian cultivars and the progenies. The percent germination and survival ratio were not significantly different between the BC1F1 and BC2F1 generations, whereas the percent germination decreased rapidly with advancing backcross generations. The BC1F1 generation had slightly higher sugar content and the sugar content of the BC2F1 generation increased significantly over the BC1F1 generation, but fruit weight and yield decreased. However, there was variability among individual progeny from the same cross. With advancing generations of backcrossing (BC3F1, BC4F1, BC5F1), sugar content tended to improve while fruit weight and yield tended to decrease, and hardness tended not to change. Therefore, to develop new cultivars with the combined qualities of Asian and American cultivars, we concluded that generations beyond the BC2F1 are not necessary, and that the selection efficiency of superior individual plants can be improved if the number of seedlings is increased in generations before the BC1F1 or BC2F1.

Evaluation of bioactive compounds in different tissues of sprouting okra

The levels of major bioactive compounds, such as amino acids and antioxidants, were investigated in okra sprouts and seeds of the varieties ‘Green Sword’ and ‘Benny’. Total polyphenol content was the highest in ‘Benny’ cotyledons, followed by ‘Benny’ hypocotyls and ‘Green Sword’ cotyledons. Polyphenol and flavonoid content in the two varieties were approximately 5- to 6-fold higher in sprouts than in seeds, and were higher in the cotyledons than in other tissues within the sprout. Activity of the radical scavenger DPPH was the highest in ‘Benny’ cotyledons, and mean values were 7.3-fold higher in sprouts than in seeds. Total amino acid content in both varieties was the highest in hypocotyls, followed by cotyledons and seeds. This content was about 40-fold higher in hypocotyls than in seeds. Alanine and Glycyrrhizin were the most abundant amino acids. Total vitamin C content was the highest in ‘Benny’ cotyledons, followed by ‘Green Sword’ cotyledons, and the lowest in hypocotyls of both varieties. In ‘Green Sword’ seeds, the levels of vitamins B1, B3, B5, and B6 were higher than the levels of B2 and B9. In ‘Benny’, B1 and B3 content were higher in the cotyledon, while B2, B5, and B9 content were higher in the hypocotyl. This study demonstrates the potential of okra sprouts to be used as a functional food ingredient and as a source of antioxidants.