Jin Hee Lim

Genetic variation of flower characteristics in a population derived from a cross between the chrysanthemum cultivars ‘Falcao’ and ‘Frill Green’

Chrysanthemum is a major floriculture species and a breeding goal is to develop cultivars with unique flower forms and colors. This study was conducted to investigate the genetic basis of six flower traits including petal color, flower shape, ray floret length, the level of ray floret twisting, the shape of the ray floret tips, and the attitude of the basal part of the ray florets. A pseudo-testcross population derived from a cross between the ‘Falcao’ and ‘Frill Green’ cultivars was used. The female parent ‘Falcao’ is a popular pompon type that has an orange-pink color and lacks twisted ray florets. The male parent ‘Frill Green’ is a single type with green twisted ray florets. For color, six different colors were observed in 130 progeny: white, yellow, green, orange, orange-pink, and pink and 52 (40%) and 52 (40%) progeny showed green and yellow colors, respectively. The progeny was grouped into 4 classes based on flower form. The semi-double class was the most frequent (70%) in the population, suggesting an incomplete dominance for the double and single flower. Among four ray floret traits, the shape of the ray floret tips seems to be controlled by a single gene, while the level of twisting of the ray floret showed a significant deviation from the expected 3:1 or 1:1 ratio (p < 0.05). The progeny were divided into three classes in terms of the attitude of the basal part of the ray florets (ascending, descending, and horizontal). Four and three progeny for green pompon or green double flowers were selected, respectively. Two of the four green pompon selections have twisted ray florets. These results will help breeders for developing new chrysanthemum cultivars with unique flower forms and colors.

Preharvest Environmental Conditions Affect the Vase Life of Winter-Cut Roses Grown under Different Commercial Greenhouses

The vase life of cut flowers is not only determined by differences between cultivars, but also by growth conditions. For instance, the vase life of cut roses that are grown hydroponically during the winter period often ends at an early stage of maturation due to petal wilting or neck bending. In addition, the vase life of cut roses from different growers varies markedly despite identical postharvest conditions. To elucidate the underlying mechanisms, the relationship between preharvest environmental factors, postharvest morphological and physiological factors, and the vase life of cut roses were determined. Cut roses (Rosa hybrid L. cv. Fuego) that were grown hydroponically during winter were harvested from three commercial greenhouses in Korea, and the interrelations between the above-mentioned factors and the vase life of the cut flowers were analyzed using principal component analysis (PCA). The vase life of roses varied by 70% among growers in January when the vapor pressure deficit (VPD) differed the most. PCA revealed that preharvest environmental conditions strongly correlated with changes in morphological and physiological characteristics and the vase life of the cut roses. Roses grown under high relative humidity (RH) and low VPD during the winter had less functional stomata and, consequently, higher transpiration from leaves after harvest. This increased transpiration caused shorter vase life in the cut roses. In addition, supplementary lighting, high photosynthetic photon flux, and CO2 supplementation also increased transpiration and, consequently, shortened vase life, although these conditions improved the external quality of the cut roses. Thus, the external quality, i.e., the appearance of the cut flowers, did not directly correspond with the length of vase life of the flowers. This study improves our understanding of the relationship between preharvest conditions and morphological and physiological characteristics and vase life of winter-cut roses.

Conditions during export affect the potential vase life of cut roses (Rosa hybrida L.)

We determined the longevity (i.e., potential vase life) of cut roses across seasons and identified key factors during export that affect vase life. We obtained cut Rosa hybrida L. ‘Lovely Lydia’ roses harvested at an identical stage of maturity from commercial rose growers in Jeonju and Jangsu, Korea, in December 2014 and in April, July, and December 2015. We randomly divided the roses into two groups, which were transported to Seoul or Japan, and assessed their vase life in a controlled environment room (standard conditions) at Sejong University or in test rooms (export conditions) in flower markets in Japan. We regarded vase life under standard conditions as potential vase life and vase life under export conditions as consumer-level vase life. Overall, export-environmental conditions and vase life varied greatly across seasons. A seasonal variation in vase life was observed in both groups of flowers, and the difference between potential vase life and vase life increased as the potential vase life increased. Multiple regression analysis indicated that vase life is negatively correlated with flower auction temperature but positively correlated with potential vase life, RH during loading, and RH in the warehouse. Furthermore, the vase life of cut roses depends primarily on potential vase life, indicating that potential vase life, which is determined by the time of harvest, is modified by environmental conditions during export.