Improve Fruit Set Research Articles

In vitro fruiting and seed set of Capsicum annuum L. CV. Sweet banana

Plantlets of Capsicum annuum L. ev. Sweet Banana regenerated via somatic embryogenesis from immature zygotic embryos were capable of producing flower, fruit, and seed when cultured in small tissue culture containers. In vitro floral buds were first formed on plantlets that grew on plantlet development medium [agar-gelled Murashige and Skoog (MS) basal medium containing 1 mgl−1 (5.3 μM) α-naphthaleneacetic acid (NAA)] in a growth room at 22°C and continuous illumination. However, floral buds rarely developed further into mature flowers. This problem was overcome using the vented autoclavable plant tissue culture containers. In vitro fruit formation and ripening was observed when liquid half-strength MS basal medium supplemented with 5 μg ml−1 silver thiosulfate, 1 mg l−1 (5.3 μM) NAA, and 3% sucrose was added to the surface of the plantlet development medium. Hand-pollination improved fruit set. Further research in needed to determine why the pepper seeds formed in vitro failed to germinate.

Boron Improves Growth, Yield, Quality, and Nutrient Content of Tomato

Boron deficiency in fresh-market tomatoes (Lycopersicon esculentum Mill.) is a widespread problem that reduces yield and fruit quality but is often not recognized by growers. Tomatoes were grown in field and hydroponic culture to compare the effects of foliar and soil applied B on plant growth, fruit yield, fruit quality, and tissue nutrient levels. Regardless of application method, B was associated with increased tomato growth and the concentration of K, Ca, and B in plant tissue. Boron application was associated with increased N uptake by tomato in field culture, but not under hydroponic culture. In field culture, foliar and/or soil applied B similarly increased fresh-market tomato plant and root dry weight, uptake, and tissue concentrations of N, Ca, K, and B, and improved fruit set, total yields, marketable yields, fruit shelf life, and fruit firmness. The similar growth and yield responses of tomato to foliar and root B application suggests that B is translocated in the phloem in tomatoes. Fruit from plants receiving foliar or root applied B contained more B, and K than fruit from plants not receiving B, indicating that B was translocated from leaves to fruit and is an important factor in the management of K nutrition in tomato.

Effects of Aminoethoxyvinylglycine and High Temperatures on Fruit Set and Fruit Characteristics of Heat-cultured Satsuma Mandarin.

The effects of temperature and aminoethoxyvinylglycine (AVG), an ethylene synthesis inhibitor, on fruit set and growth of satsuma mandarins (Citrus unshiu Marc.), using 6- and 14- year-old potted trees in a temperature-controlled growth chamber and in a greenhouse, respectively, were studied. Trees, kept at 30°C in the daytime from bloom to the physiological fruit drop, resulted in severe fruit abscission more than did those kept at 25°C. Application of 200 ppm AVG at the start of blooming reduced ethylene production from flower and young fruit, and improved fruit set at 30°C. Fruit size, rind color, and juice characteristics indicated that high temperature and treatment with AVG advanced fruit growth and maturity, compared to temperatures presently used commercially. Therefore, the combination of AVG, which promotes fruit set, and heating to 30°C are useful management tools to accelerate fruit growth and quality.

Reproductive growth of grapevines in response to nitrogen supply and rootstock

Nitrogen fertiliser was applied at two rates (0 or 100 kg N/ha) to field-grown Muller-Thurgau grapevines grafted onto six rootstocks (Kober 5BB, Teleki 5C, Teleki 8B, Selection Oppenheim 4, Couderc 3309, Ruggeri 140). Half the nitrogen was applied four weeks pre-flowering and half at the end of flowering. Nitrogen supply reduced symptoms of inflorescence necrosis and improved fruit set, but increased bunch-stem necrosis, Botrytis cinerea bunch rot and yield. This was associated with reduced grape sugar, higher acidity and lower pH. Rootstocks had no significant effect on inflorescence necrosis, bunch-stem necrosis and bunch rot, but vines grafted on C-3309 and Ru-140 had both lowest yields and highest fruit quality. Nitrogen ¥ rootstock interactions were rare and contributed little to total variance, suggesting that rootstock-induced differences in scion performance were, except for SO4, largely independent of soil nitrogen level.

Pollination biology and breeding system of Acacia senegal

Phenology, pollination biology and breeding system were investigated in three populations of Acacia senegal located in Delhi and Rajasthan. Flowers emit a mild fragrance and produce a minute quantity of nectar. The stigma is wet non-papillate, cup-shaped and generally accommodates one polyad with 16 pollen grains. The style is solid. The mass effect created by the brush type of blossoms attracts a wide variety of insects, of which the giant Asian honeybee, Apis dorsata, is the effective pollinator. Manual in vivo pollination studies have shown that the species is self-incompatible. Self-incompatibility appears to operate inside the embryo sac. Under natural conditions fruit set is as low as 0.36%. Insufficient pollination is the main cause of low fruit set. Manual xenogamous pollinations substantially improve fruit set to 30%.

Pollination biology and breeding system of Acacia senegal

Phenology, pollination biology and breeding system were investigated in three populations of Acacia senegal located in Delhi and Rajasthan. Flowers emit a mild fragrance and produce a minute quantity of nectar. The stigma is wet non-papillate, cup-shaped and generally accommodates one polyad with 16 pollen grains. The style is solid. The mass effect created by the brush type of blossoms attracts a wide variety of insects, of which the giant Asian honeybee, Apis dorsata, is the effective pollinator. Manual in vivo pollination studies have shown that the species is self-incompatible. Self-incompatibility appears to operate inside the embryo sac. Under natural conditions fruit set is as low as 0.36%. Insufficient pollination is the main cause of low fruit set. Manual xenogamous pollinations substantially improve fruit set to 30%.

Frutificação e crescimento de frutos em abóbora híbrida 'Tetsukabuto' tratada com alfa-naftalenoacetato de sódio

A abertura de flores femininas na abóbora híbrida 'Tetsukabuto' concentra-se num período de três a quatro semanas. Este curto período de florescimento indica que uma polinização deficiente pode ocasionar grande comprometimento da produção de frutos. Este trabalho foi conduzido com o objetivo de avaliar o efeito de concentrações do fitorregulador alfa-naftalenoacetato de sódio (ANA-Na), pulverizado em flores abertas femininas, na frutificação e crescimento de frutos da abóbora 'Tetsukabuto'. O experimento foi conduzido em Lages, SC, na safra 1992/1993, seguindo o delineamento em blocos casualizados, com três repetições. A parcela foi constituída de cinco covas de 'Tetsukabuto' e uma da polinizadora Cucurbita maxima, em espaçamento de 3 x 1 m, com duas plantas/cova. Os tratamentos utilizados foram testemunha (polinização natural) e 150, 300, 450, 600 e 750 mg·L-1 de ANA-Na. Nos tratamentos com ANA-Na, evitou-se a polinização natural isolando-se as flores com sacos de papel. Avaliou-se percentagem de frutificação, peso, comprimento e diâmetro dos frutos e peso, espessura, rendimento e sólidos totais da polpa. Apenas a dose de 750 mg·L-1 do hormônio reduziu a percentagem de frutificação. Os frutos obtidos por tratamento com ANA-Na apresentaram crescimento similar ao dos frutos obtidos por polinização.

Patterns of fruit and seed set within inflorescences of Pancratium maritimum (Amaryllidaceae): nonuniform pollination, resource limitation, or architectural effects?

We investigated patterns of fruit and seed production on inflorescences of a population of Pancratium maritimum in northwest Spain over a 2-yr period. Initial findings showed that the earliest opening flowers on an inflorescence are more likely to set fruit and produce more seeds than later opening flowers and that this pattern is maintained throughout the flowering season. Supplementary pollination and flower-removal experiments were performed to investigate whether the observed pattern is attributable (a) to variation in pollen receipt, (b) to sequestration of resources by the earliest flowers on an inflorescence, and/or (c) to "architectural" limitations on the fruit/seed production of later flowers. Supplementary pollination did not improve fruit or seed production by late flowers in either of the 2 yr of study. In flower-removal experiments, the remaining flowers showed improved fruit set and mean number of seeds per flower, by comparison with flowers in the same position on control inflorescences. When all flowers except the latest third were removed, these showed fruit set and seed production similar to those of early flowers on control inflorescences. These results strongly suggest that the observed within-inflorescence patterns of fruit and seed production in P. maritimum are mainly attributable to competition for resources (i.e., explanation b), though other adaptive explanations cannot be ruled out.

Parthenocarpy induced by N-(2-chloro-4-pyridyl)- N′-phenylurea (CPPU) prevents flower abortion in Chinese white-flowered gourd ( Lagenaria leucantha)

Flower abortion under unfavorable weather conditions is a serious problem in commercial production of cucurbitaceous crops in spite of artificial pollination. The effects of naphthaleneacetic acid (NAA), gibberellic acid (GA 3), N-(2-chloro-4-pyridyl)- N′-phenylurea (CPPU), 6-benzylaminopurine (BA), N, N′-diphenylurea (DPU) and N-(4-pyridyl)- N′-phenylurea (4-PU) on fruit set in unpollinated and pollinated ovaries of Chinese white-flowered gourd ( Lagenaria leucantha) were studied with the aim of increasing fruit set. Among the tested compounds, only CPPU showed high activity in inducing parthenocarpy and all the parthenocarpic fruit developed to normal size. The parthenocapy percentage induced by CPPU was as high as 100% within the tested concentration (10–100 mg l −1) and was not significantly altered by application time from 2 days before anthesis to two days after anthesis. NAA and GA 3 induced parthenocarpic fruit set in 37.5% and 45.5% of treated ovaries respectively, however, they could not induce parthenocarpic fruits of normal size. DPU, 4-PU and BA treatments had little effects on unpollinated ovaries. NAA, however, improved fruit set of pollinated ovaries but did not accelerate fruit growth. A contrary trend was observed in GA 3 treatment. CPPU also increased fruit set and fruit growth of pollinated ovaries. Treating all ovaries on a plant or alternate ovaries increased fruit yield by 91.3% and 83.3%, respectively, but reduced fruit size.

From flowering to dispersal: reproductive ecology of an endemic plant, Astragalus australis var. olympicus (Fabaceae)

Astragalus australis var. olympicus is an endemic plant of the Olympic Mountains, Washington. It is considered a Species of Concern by the U.S. Fish and Wildlife Service. This study focused on the reproductive biology of the plant from flower production through seed germination to identify possible weak points that might contribute to its rarity and impede its conservation. Most plants produced a large mean number of flowers and ovules (314.8 and 4106, respectively), but relatively few of these formed fruits and seeds (25.8 and 3.8%, respectively). In decreasing importance, ovules in fruits were lost to predation, seed abortion, and lack of fertilization. The percentages of these fates differed among sites and years. Excluding pollinators by bagging flowers reduced fruit set by ∼50%, but seed set per fruit and seed mass were unaffected. Germination was affected by scarification, temperature, and moisture availability. About 11% of seeds damaged by predispersal seed predators (weevil larvae) remained viable and were released from dormancy. I hypothesize that predispersal seed predation (over 80% at one site) has a negative effect on population growth. Conservation of this species could benefit from improved fruit set and decreased seed predation.

Grapevine fruiting cuttings: validation of an experimental system to study grapevine physiology. II. Study of grape development

<p style="text-align: justify;">The study was carried out in order to compare the development of berries growing on fruiting cuttings and on vines from the field, and to evaIuate this experimentaI system for grapevine physiology studies. The results show that the main developmental characteristics of the berries are close to those of berries from the vineyard. Fruit set is good and berry growth follows a double sigmoid curve. Final size is smaller than usual, even if seed number is higher for fruiting cuttings. The evolution of organics acids, sugar and mineral content is classical. At maturity, the berries from fruiting cuttings reach the same sugar content, but are less acidic, because the components of acid equilibrium are slightly modified. At flowering polyamine content is higher in the cluster of fruiting cutting but the variations aIong cluster development is the same than in the vineyard. Finally the application of exogenous putrescin on fruiting cuttings at flowering time improves fruit set, as in the field. Our data allow to conclude that fruiting cuttings behave mostly as bigger vines and could be a usefull tool for grapevine physiology studies.</p>

Relative Effects of Growth Retardant (Paclobutrazol) and Water Stress on Tree Growth and Photosynthesis in Ponkan (Citrus reticulata Blanco).

The effects of water stress and/or chemical growth retardant, paclobutrazol, applied either as foliar spray or soil drench, on photosynthesis, tree vegetative and reproductive growth in young ponkan trees (Citrus reticulata Blanco cv. Yoshida) were evaluated. Paclobutrazol was applied when spring shoots were about 5 mm in length, either as an 840 ppm foliar spray or as a soil drench (0.5 g active ingredient per tree). Soil water stress of up to pF 2.95 was gradually imposed on the trees before re-watering. Water stress improved fruit set, whereas paclobutrazol reduced it. The proportion of abnormal flowers was increased by applying paclobutrazol without water stress. Abnormal flowers were reduced when paclobutrazol was applied in combination with water stress. Tree height increased about 14% for soil drench and 60% for foliar applied paclobutrazol based on initial heights at beginning of the experiment. Water stress caused up to 20% reduction in leaf expansion, reduced photosynthesis, and moderately reduced tree growth. Application of paclobutrazol ameliorated photosynthetic reductions associated with water stress, by maintaining higher photosynthetic and transpiration rates during water stress and ensuring quicker recovery after re-watering.

The role of ethylene in apple fruit set

SummaryApplication of branch sprays of silver thiosulphate (STS) and of aminooxyacetic acid (AOA) did not affect fruit set or fruit size in three apple cultivars. In contrast, sprays of aminoethoxyvinyl glycine (AVG) (100 and 200 ppm) improved fruit set of open-pollinated flowers. Ethephon (40 to 100 ppm) did not affect fruit set significantly, yet at 100 ppm it eliminated the promotive effect of AVG. In two experiments, AVG tended to reduce ethylene production from flowers excised 1–10 d after treatment, but variability was high and the differences were not statistically significant. In an additional experiment, AVG inhibited ethylene production by all portions of dissected flowers (pedicels, receptacle, petals), with least effect on peduncles/pedicels. The peduncle/pedicels produced 5 to 25% of the total ethylene evolved by the flower cluster, the receptacle 20 to 50% and the petals approximately 50%.

Breeding Tomatoes for Attractiveness to Pollinating Insects

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.

Pollination ecology of Petrocoptis grandiflora Rothm. (Caryophyllaceae); a species endemic to the north-west part of the Iberian Peninsula

Abstract Petrocoptis grandiflora Rothm. is a species endemic to the Iberian Peninsula with restricted distribution. We studied various aspects of its pollination ecology: nectar characteristics and standing crop, pollinators and nectar-robbers, and the effects of nectar robbing and supplementary pollination on fruit set. The nectar is moderately rich in saccharose (saccharose/hexose ratio 0.54), and is largely consumed by long-tongued bees (Anthophoridae). The incidence of nectar robbing by Xylocopa violacea differed between the four plant populations studied, and it had significant effects on fruit set when the population was simultaneously considered. Supplementary pollination did not improve fruit set significantly.

Pollination ecology of Petrocoptis grandiflora Rothm. (Caryophyllaceae); a species endemic to the north-west part of the Iberian Peninsula

Petrocoptis grandiflora Rothm. is a species endemic to the Iberian Peninsula with restricted distribution. We studied various aspects of its pollination ecology: nectar characteristics and standing crop, pollinators and nectar-robbers, and the effects of nectar robbing and supplementary pollination on fruit set. The nectar is moderately rich in saccharose (saccharose/hexose ratio 0.54), and is largely consumed by long-tongued bees (Anthophoridae). The incidence of nectar robbing by Xylocopa violacea differed between the four plant populations studied, and it had significant effects on fruit set when the population was simultaneously considered. Supplementary pollination did not improve fruit set significantly.

EFFECTS OF GIBBERELLIN AND GIRDLING ON THE YIELD OF “NOVA” (CLEMANTINE × ORLANDO TANGELO) AND “NIVA” (VALENCIA × WILKING)

GA3 and/or girdling half of the main branches significantly increased both fruit set and yield, but caused the highest rate of fruitlet drop. Spraying GA3 at mid-anthesis is the best treatment to improve fruit set and yield. Yield loss of up to 48% was due to rind-splitting-induced fruit abscission in August and mid-October. Morphological study of splitting revealed that this phenomenon occurred at the stylar end starting at the flavedo, progressing into the albedo and leaving the vascular bundles intact, although they separated later. Spraying Nova trees with different growth regulators in July, failed to reduce splitting. Reducing water supply by 35 or 50% from August onward, reduced rind splitting by up to 35% accompanied by a decrease in fruit size and yields. Internal quality was not affected when water supply was reduced by 35%. Reducing water supply by up to 50% decreased TSS/acid ratio and percent of juice. It is therefore, questionable whether reduced water supply is an effective treatment for limiting rind splitting and premature fruit drop.

Suppression of Frankliniella bispinosa (Thysanoptera: Thripidae) and the Fungal Pathogen Colletotrichum gloeosporioides, with Pesticides During the Bloom Cycle and Improved Fruit Set on ‘Navel’ Orange in Florida

Four field experiments were conducted in two ‘Navel’ orange groves in southwest Florida between 1988-1990. Insecticides were applied alone, in combination with the fungicide benomyl, or benomyl was applied alone during ‘Navel’ orange flowering cycles between February and April. The duration and intensity of flowering differed each year. Population densities and peak activity of Frankliniella bispinosa (Morgan) differed by year and by site during the same year. Fifty-unit samples of small (5-9 mm), medium (10-13 mm), and large (≥14 mm) floral buds, open flowers, and fruitlets were evaluated to determine the optimal stage of floral development for sampling adults and larvae of F. bispinosa . All floral stages were infested but open flowers consistently had the highest numbers of both adults and larvae and were used to assess treatment differences in thrips populations after 1988. Results showed a positive relationship between population suppression of F. bispinosa during the flowering cycle and subsequent ‘Navel’ orange fruit set in late June or early July. Chlorpyrifos, dimethoate, and formetanate hydrochloride were effective in suppressing numbers of F. bispinosa , with activity lasting 3-7 dafter application. Two or more applications of benomyl resulted in fruit set increases each year in the four field experiments compared with fruit set increases in three of four experiments where insecticides only were applied. The fungal pathogen, Colletotrichum gloeosporioides Penzig, was identified previously as the causative organism for postbloom fruit drop disease on citrus. This study demonstrated that there are two potential factors ( F. bispinosa and C. gloeosporioides ) involved in reduced fruit set on ‘Navel’ orange during the flowering cycle in Florida.

CULTURAL MODIFICATION TECHNIQUES FOR ALLEVIATION OF HEAT STRESS IN BELL PEPPERS

Bell pepper (Capsicum annuum L.) was grown in 1989, 1990, and 1991. Cultural modifications were used in an effort to alleviate heat stress, improve fruit set, reduce sunscald, and improve yield quantity and quality. Treatments included bare soil, plastic mulch (both black and white), straw mulch, living rye (Secale cereale) mulch, and row covers (white and black) suspended above the foliage. Soil temperature at 2.5, 10, and 20 cm, soil moisture at 20 cm, and yield parameters were recorded. In general, plots containing white rowcovers produced good yields each year, straw mulched plots produced good yields two out of three years, plots with black plastic mulch gave poor yields two out of three years, and plots with living rye gave consistently poor yields. Yield inconsistency from year to year was correlated with, and can be explained by, soil temperatures. Sunscald was reduced by rowcovers.

Alternative rest-breaking agents to DNOC/oil for apples

Rest-breaking agents less toxic than the commercially-used DNOC/winter-oil and less expensive than hydrogen cyana- mide were tested on Golden Delicious in a high density planting in a region of warm winters. Some combinations of mineral oil and cyanamide were as effective in promoting budbreak as both DNOC/oil and cyanamide but neither treatment improved fruit set or fruit size 12 weeks after treatment, relative to the control. Rest-breaking treatments are seen as one aspect of tree manipulation rather than a direct means of increasing production.