effect has been produced. The flowering of C. oleifera occurs mostly in cold seasons (autumn and winter), and insects are required for cross-pollination. When the temperature during the flowering period is low, insects do not move frequently, and the
Hongli Wei, Chao Gao, Jie Qiu, Li Long, Biao Wang, Lu Yang, and Yang Hu
Thomas L. Davenport, Zhentu Ying, and Raymond J. Schnell
The synchronously dichogamous flowering behavior of avocado has historically been assumed to promote cross-pollination. Preliminary studies in southern California have revealed that self-pollination is more typical. The primary objective of the California research is to determine the paternity of individual fruit sampled during early and late fruit development using SSR markers. Cultivars included Hass as the primary cultivar and Bacon, Ettinger, Fuerte, Harvest, Lamb Hass, Marvel, Nobel, SirPrize, and Zutano serving as cross-pollinizing cultivars. We were able to: 1) estimate proportions of self- and cross-pollinated `Hass' fruit with cultivars planted in rows of varying proximity to the `Hass' rows; determine if the proportion of outcrossed fruit increased during maturity due to preferential abscission of self-pollinated fruit; and 2) determine if there is preferential retention of fruit cross-pollinated by a specific cultivar during maturation. On average, cross-pollination by any individual cultivar in 2004 was 6% or less in marble-sized fruit. Over 70% of the fruit were self-pollinated. This is greater than the proportion of self-pollination (about 30%) observed in near-mature fruit harvested in the previous year, 2003. Proportions of marble-sized fruit pollinated by each cultivar within each row were compared to the proportions of self or cross-pollinations in fruit harvested from the same trees at near-maturity. We observed about a 10% increase in proportion of self-pollinated fruit and a concomitant decrease in retained fruit derived from cross-pollination. Self-pollination appears to be the dominant mode of pollination. These preliminary results indicate that trees benefit from it, perhaps in preference over cross-pollination.
Christopher S. Cramer
This research was funded by the NMSU Agricultural Experiment Station and the New Mexico Dry Onion Commission. Thanks to Petoseed Co., Rio Colorado Seed Co., and Shamrock Seed Co. for the contribution of open-pollinated and hybrid onion
Blair Sampson, Steve Noffsinger, Creighton Gupton, and James Magee
Fruit set in the muscadine grape (Vitis rotundifolia Michx.) depended on insect cross-pollination, although flowers were well adapted for selfing. Pollinizer cultivars produced about half of their optimal fruit set when selfed, but cross-pollination was needed to reach an optimal fruit set of 33.7%. Eighty-one percent of the overall fruit set in pistillate vines was attributed to insect cross-pollination; wind played only a small role. Diminished fruit set and fewer seeds per berry occurred in cultivars receiving no effective cross-pollination. Components of fruit quality were not profoundly affected by the pollination treatments, although seed set and berry weight in pistillate cultivars was lower in the absence of cross-pollination. Parthenocarpy was rare, except in `Fry Seedless'. Muscadine production throughout the southeastern United States depends on cross-pollination by indigenous insects, particularly bees. To ensure consistently high yields, bees must have safe access to flowers and their nesting sites must be preserved.
Rakesh Kumar, Mahendra Dia, and Todd C. Wehner
Watermelon [ Citrullus lanatus (Thunb.) Matsum. & Nakai var. lanatus ] has been improved for yield and other traits as part of the process of plant breeding. Knowledge of the rate (percentage) of self- or cross-pollination is useful for watermelon
The seed producing system in viola (Viola ×cornuta) was investigated to improve seed yield and to save labor. In a flower five anthers sequentially dehisced; pollen grains were continuously supplied to the anterior petal, which played a significant role in pollination, throughout the flowering period. Evidence from pollen and ovule number suggests that the species is facultative autogamy. Each flower opened more than 10 days was independent of the success in fertilization and kept seed producing ability during the flower longevity period. Pollen grains also maintained viability during the flower longevity period. Pollinators were indispensable for pollination of viola, but pollination in viola was done by a different mechanism from the typical insect-mediated pollination that sticky pollen grains adhere to the exposed stigmas. Pollen grains, accumulated around the entrance of the stigmatic cavity, entered into the cavity by the movement of pollinators. Although the visitation of pollinators was occasional, solitary bees primarily contributed to the pollination of viola. On the other hand, germination of pollen grains on the stigmatic surface was under 50%. Seed set was much lower than the germination percentage of pollen grains. A viola flower had the ability for additional pollinations and fertilization for some days after the fertilization success in some ovules in the flower. This characteristic suggested that repeated pollination is effective to increase the number of mature seeds in a capsule.
Richard W. Robinson
Bumblebees are commercially used to improve fruit set of greenhouse tomatoes, but they seldom pollinate tomatoes outdoors if not confined in a no-choice situation. Bumblebees frequently pollinated L. peruvianum and other self-incompatible (SI) Lycopersicon species, but not tomato plants, in the field at Geneva, N.Y. Bumblebees were very efficient pollinators of Sl Lycopersicon species, averaging only 5 s to pollinate one flower and fly to the next. Transfer of this attractiveness to pollinating insects to the tomato could improve fruit set of tomatoes grown in greenhouses with introduced bumblebees. It could also improve fruit set in the field, especially when conditions are poor for pollination. It has potential use for producing F1 hybrid seed, but associated problems make hybrid tomato seed production by insect pollination impractical now. Attractiveness to pollinating insects is being introgressed from L. peruvianum, L. hirsutum, and L. pennellii in the tomato breeding program at Geneva, N.Y. Several floral characteristics were found to be of importance for attracting pollinators, including the reaction to ultraviolet light. Flowers of SI species absorbed UV, whereas tomato flowers reflected UV light.
Chitose Honsho, Masami Kotsubo, Yuri Fukuda, Yosui Hamabata, Yoshikazu Kurogi, Aya Nishiwaki, and Takuya Tetsumura
commercial value of a fruit. Gibberellic acid during the early stages of fruit development ( Yamamoto and Iwasaki, 1994 ) and pollination with pollens from 4× citrus trees ( Imai et al., 2007 ; Yamashita, 1976 ; Yamashita et al., 1990 ) have been
Ramesh R. Sagili, Carolyn R. Breece, Rhonda Simmons, and John H. Borden
., 2004 ). In seed crops, adequate pollination is the key for high seed quality and yield. Many hybrid seed crops are not very attractive to honeybees and they may be easily lured to alternative flowering plants that are more attractive ( Delaplane and
Bernadine C. Strik and Amanda J. Vance
In blueberry ( Vaccinium spp.), issues related to poor pollination are considered as important production problems in many regions (e.g., Oregon Blueberry Commission, 2018 ; Northwest Center for Small Fruits Research, 2018 ; Washington Blueberry