Eun Ui Oh

Characterization of microspore development and pollen tube growth response to self and cross-pollination in Jeju old local citrus species

This study was conducted to investigate the seed formation potential by the evaluation of microspore development and self- and cross-compatibility through their pollen tube growth response to self and cross pollination in Jeju old local citrus species. Anther and pollen histological analyses were done to observe microspore development for three species including byungkyul, sadoogam, and dangyooza. Pollens of ten citrus species were tested for pollen viability by staining with Lugol’s solution and fluorescein diacetate. Flowers of all species were emasculated and self- and cross-pollinated just before anthesis. Pistils of nine pollinating combinations between the listed three species were collected at 1, 3, 5, 7, and 9 days after pollination for evaluation of a growth pattern of the pollen tube. Pistils of the other combinations were collected at 9 days after pollination for self- and cross-compatibility evaluation. Pistils were prepared by squashing and staining method with aniline blue. Eight pollen developmental stages were recognized and indicated normal development of microspore. These ten citrus species produced high percentage of viable pollens. Pollen tube behavior in compatible and incompatible pollination was distinguished. Pollen tube performance was largely depended on male-female combination. All of these Jeju old local citrus species were male fertile and have the ability to produce enough viable pollens for self- and cross-pollination. All evaluated citrus species were self- and cross-compatible to each other except dangyooza which was self-incompatible.

Effect of artificial defoliation on cane regrowth and fruit development in ‘Jecy Gold’ kiwifruit

Leaves of kiwifruit have long petiole and large size, so that they are easily damaged by strong wind. This study was performed to evaluate the effect of leaves loss by typhoon damage on fruit quality and yield and new cane growth with artificial defoliation. Five-year-old ‘Jecy Gold’ kiwifruit vines grown in a plastic house were used in this study. Artificial defoliation was done on August 23 (100 days after anthesis) at the different defoliation levels, such as 0 (control), 50, 75, and 100%. Cane regrowth by axillary bud burst, cane bark carbohydrate reserve, and fruit quality and yield were investigated. Severe defoliation at 75 and 100% level showed significantly higher axillary budburst than the control and the 50% defoliation. Especially, the 100% defoliation induced a few abnormal off-season flowering. Starch and sucrose contents were significantly declined during the first 2 weeks after defoliation at the 75 and 100% defoliation. However, other soluble carbohydrate reserves including fructose, glucose, and myo-inositol were not affected significantly. Fruit drop was promoted and the mean fruit weight, firmness, and soluble solid concentrations were lower by the defoliation. Our results indicated that the loss of leaves above 50% would induce a transient shortage of assimilate supply and reduce fruit quality and yield significantly.

Defoliation time influences vine regrowth, off-season flowering, and fruit quality in ‘Jecy Gold’ kiwifruit vines

Abrupt and severe loss of leaves caused by a typhoon disrupts physiological development and metabolism in kiwifruit vines. The aim of this study was to evaluate the effects of time of defoliation on off-season flowering, vine regrowth, and fruit quality in ‘Jecy Gold’ kiwifruit. ‘Jecy Gold’ kiwifruit vines were subjected to artificial 100% defoliation on July 28 and August 29, 2014. In October, the occurrence of off-season flowering was observed only on vines that were defoliated on August 29. There was no significant difference in vine regrowth between defoliation on July 28 or August 29. However, defoliation on August 29 showed a significant reduction in soluble solid content in fruits at harvesting time. Furthermore, there was no significant difference in starch and sugar content of cane bark between the different times of defoliation. The results indicate that the floral evocation of ‘Jecy Gold’ kiwifruit might occur in August and that fruit maturation is delayed after defoliation on August 29 in comparison to defoliation on July 28.