Nursery production of Mountain Laurel (Kalmia latifolia L.) often involves manual disbudding or deadheading flower clusters immediately after flowering, to stimulate the formation of one or several new shoots. Experiments were initiated on populations of K. latifolia `Angel' (41 plants), `Snowdrift' (17 plants), and `Hoffman's Pink' (37 plants) to test the effectiveness of single applications of 0 (water control), 500, 1000, and 2000 ppm ethephon in reducing seed set and stimulating new shoot formation. Ethephon was applied on 9 June 1995 when an average of 52.9%, 53.4%, and 27.3% of the flowers were open in each flowering cluster of `Angel', `Snowdrift', and `Hoffman's Pink', respectively. On 17 to 19 July 1995, data were collected for numbers of green seed capsules per flower cluster and the number of new shoots per plant. One way analysis of variance showed the treatments had highly significant effects on seed capsule numbers per flower cluster and in stimulating the production of new shoots per plant in the three cultivars. The average number of green capsules per flower cluster and new shoots per plant for each cultivar treated with 2000 ppm ethephon were: 2.2 capsules and 57.2 shoots in `Angel', 1.1 capsule and 40 shoots in `Snowdrift', and 6.6 capsules and 39.3 shoots in `Hoffman's Pink'. In contrast, the controls had 20.1 capsules and 2.8 shoots in `Angel', 22.9 capsules and 8 shoots in `Snowdrift', and 27.3 capsules and 2 shoots in `Hoffman's Pink'.
Richard K. Kiyomoto
Li Jiang, Yun-wen Wang, and Bruce L. Dunn
(data not shown). Table 2. Flower pollination, seed set, and germination for intraspecific crosses as seed parent within Lychnis . Table 3. Flower pollination, seed set, and germination for intraspecific crosses as pollen parent within Lychnis
Mark W. Farnham
Using anther culture to generate doubled-haploid (DH) homozygous lines for use as parents in F1 hybrid crosses has become a common practice in breeding broccoli (Brassica oleracea L. Italica Group). During anther culture and subsequent embryogenesis and plant regeneration, polyploidization of microspore-derived embryos may not occur or it may occur accompanied by a doubling, tripling, quadrupling, octupling, or irregular polyploidization of the genome. Thus regenerants from the process can be haploids, diploids, triploids, tetraploids, octaploids, or aneuploids. The objectives of this research were to 1) conduct repeat cycles of broccoli anther culture using a group of F1 hybrids as anther donors and develop populations of regenerants; 2) analyze resulting populations using DNA flow cytometry and determine the influence of F1 source on frequency of different ploidy levels among regenerants; and 3) compare seed set in broccoli inbreds developed in a traditional selfing program compared to seed set in DH broccoli derived from anther culture. In two cycles (1994 and 1995) of anther culture, anther-derived populations of regenerants were developed using the F1 hybrids `Marathon', `Everest', `High Sierra', and `Futura' as sources of anthers. In 1994, `Everest', `High Sierra', and `Futura' yielded populations that included 2% to 7% haploids, 53% to 56% diploids, 32% to 38% tetraploids, and 5% to 6% other types. `Marathon'-derived regenerants were 5% haploid, 78% diploid, 15% tetraploid, and 2% other, showing significantly more diploids. In 1995, `Marathon' regenerants again included significantly more diploids and fewer tetraploids than those derived from other F1 sources, confirming that the genotype of the anther source affects the frequency of a particular ploidy level among regenerants derived from culture. In manual self-pollinations of 1994 regenerants, only diploids and rare tetraploids set seed. When plants that set no seed were discounted, seed production following manual self pollinations of 1995 regenerants was not significantly different from that of traditional inbreds derived from the same F1 sources.
Chun-Qing Sun, Zhi-Hu Ma, Guo-Sheng Sun, Zhong-Liang Dai, Nian-jun Teng, and Yue-Ping Pan
a study of the factors that affect seed set in several chrysanthemum crosses, it was found that a low number of germinated pollen grains and the abnormal growth of most pollen tubes were the main causes of the failure of the cross between D
Neil O. Anderson and Peter D. Ascher
Commercial chrysanthemums are short day (SD) plants. Recently, several day neutral (DN) garden genotypes have been identified. Both glasshouse and garden cultivars vary in heat delay insensitivity (HDI). This research analyzed yield components (seed set, germination, yield potential) and tested a DN/HDI ideotype for its effectiveness. Progeny from a 6 × 6 diallel were embryo rescued, clonal ramats were grown in two environments (glasshouse—long days; field—long to short days) and evaluated for flowering, early flowering response groups, thermozero temperature response, low long day leaf number (LDLN), high leaf initiation rates, and low mean stem lengths of the terminal shoot. Self seed set ranged from 0% to 8% while outcross seed set was 0% to 92%. General and specific combining ability were highly significant for seed set, the reciprocals, and their interactions. Germination averaged 67%, while yield potential was 44%. Cotyledon pigmentation in embryo rescued seedlings was 7% albinos, 15% anthocyanin (transposable elements), and 78% normal (green). SD parents did not flower in either photoperiod although PPSL-10 carried alleles for DN. SD x DN crosses produced some DN progeny and fit a 1:3 chi square ratio (DN:SD), indicating DN to be recessive. However, DN x DN crosses also fit a 3:1 chi square ratio, due to HDI. No progeny flowered within the 3 to 6 week ideotype; visible bud date had a heritability of h 2 = 0.50. Most progeny were within the LDLN range (h 2 = 0.72). Several leaf initiation rates exceeded the ideotype (h 2 = 0.003); plant height also matched the ideotype (h 2 = 0.66). Both visible bud and flowering dates require significant improvement before progeny match the DN/HDI ideotype.
Bernadine C. Strik and Amanda J. Vance
Commission, 2018 ). In particular, growers are concerned with poor fruit set (the proportion of flowers that become berries), but seed set (the proportion of ovules that become seeds) and fruit size at harvest are also important. Commercial growers in the
Yu-Chun Chu and Jer-Chia Chang
bloomed. Fig. 2. Floral morphology and anatomical structure of ‘Da Hong’ pitaya. Non-ovary organs (NO); ovary (O). NO was comprised of sepal (S), petal (P), stamen (STM), stigma (STG), and style (STY). Fruit and seed set, fruit development and
S. Wolf, Y. Lensky, and N. Paldi
Fruit and seed set in insect-pollinated agricultural crops rely primarily on honeybees because of their ease of management and transportation. In many fruit and vegetable crops, the number of bee visitations can be the limiting step in obtaining optimal yield. Increasing the attractiveness of flowers to honeybees could, therefore, provide a useful means of improving fruit yield and seed production. Genetic variability in attractiveness to honeybees was found within the genus Citrullus. The number of daily visits per flower ranged from six to 12 among cultivars. Moreover, most of the visits to the more attractive cultivars occurred in the first hour of bee activity, whereas visits to the less attractive cultivars started later in the morning. A positive relationship was found between the frequency of bee visitations and seed number per fruit. Analyses of floral attributes indicated no genetic variability in flower size, amount of pollen grains, or nectar volume; however, differences were observed in the concentration of sucrose and total sugars in the nectar. A positive relationship was found between attractiveness to bees and nectar sugar concentration, suggesting that this characteristic is one of the parameters responsible for variability in attractiveness to honeybees.
Doron Schneider, Raphael A. Stern, and Martin Goldway
Apple (Malus domestica) has a gametophytic self-incompatibility (GSI) system. Consequently, fertilization is achieved by cross-pollination with a compatible pollinator. Compatibility is governed by a multiallelic S locus. Cultivars are fully compatible when both of their S-loci differ and are semi compatible when one locus is identical and the other differs. In a previous study we found that the fruit set and yield of the apple cultivar `Topred' was reduced when it was pollinated by a semi compatible cultivar. To examine if this occurrence is a general feature in apples grown under suboptimal conditions, three additional cultivars, `Golden Delicious', `Granny Smith' and `Royal Gala', were studied as pollen recipients of semi and fully compatible pollinators. Based on PCR analysis of the S-RNase allele, it was determined that the pollination rate of the semi compatible was significantly lower than that of the fully compatible pollinator in all cases. This was reflected by the lower fruit set and seed set of `Golden Delicious' and `Royal Gala', but not of `Granny Smith'. In hand pollination experiments, where pollen was in excess, no difference was found between the semi and fully compatible pollinators in all three cases. These results indicate that the low yield, conferred by semi compatible pollinators, is due to insufficient cross-pollination (and not to cultivar characteristics). Thus, low yields due to semi compatibility may be avoided by appropriate honeybee management that will increase pollination. Still, under suboptimal conditions, for growth and pollination, full compatibility is preferable.
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.