Summer squash (Cucurbita pepo L.) cultivars were compared for ability to set parthenocarpic fruit. Some cultivars set no parthenocarpic fruit and others varied in the amount of fruit set when not pollinated. The degree of parthenocarpy varied with season, but the relative ranking of cultivars for parthenocarpy was generally similar. Cultivars with the best parthenocarpic fruit set were of the dark green, zucchini type, but some cultivars of other fruit types also set parthenocarpic fruit. A summer squash cultivar was developed that combines a high rate of natural parthenocarpy with multiple disease resistance. Yield of summer squash plants grown under row covers that excluded pollinating insects was as much as 83% of that of insect-pollinated plants in the open.
Environmental parthenocarpy leading to seedless fruits is a well-known phenomenon in pepper, particularly when the crop is exposed to low temperatures before and during anthesis. The resulting fruits show large variation in fruit deformation and are of low marketable value. Genetic parthenocarpy controlling even shape may be useful for fruits for both home use and industrial processing. However, parthenocarpic pepper cultivars are an attractive goal that is still far from realization. From greenhouse pot experiments (2) carried out over 3 years with ‘California Wonder’, fruit weights of up to 150 g were obtained with a high correlation between seed number and fruit weight. Linear regression from this study demonstrated that parthenocarpic fruit of ‘California Wonder’ weigh 60–70 g, about half that of the largest-seeded fruit. Fruit of greenhouse plants weigh about half that of field-grown fruit. It is expected that the parthenocarpic fruits in the field will weigh more than 60–70 g. Moreover, in cultivars with “giant” fruits, in which the realization of large fruit weight depends on the genetic potential for weight and seed number, the parthenocarpic fruits are expected to be heavier than in the parthenocarpic Belltype cultivars.
Methyl-2-chloro-9-hydroxyfluorene-(9)-carboxylate (chlorflurenol) effectively promoted parthenocarpic fruit development in gynoecious pickling cucumbers, Cucumis sativus L. Treatment with chlorflurenol increased yields of fruits under both greenhouse and open-field conditions. Yields were dependent on the degree of genetic parthenocarpy for each cultivar. Parthenocarpic yields following chlorflurenol treatment were higher with night temperatures of 16° and 21°C than with 27°.
Parthenocarpy in pepino (Solanum muricatum Aiton) can overcome poor fruit set caused by pollination deficiencies. In two families involving a parthenocarpic parent (Pp), a nonparthenocarpic parent (Pnp), and the generations Pp⊗, Pnp⊗, F1, BCp, BCnp, and F2, we studied three traits that are often confused: parthenocarpy, efficiency of parthenocarpy over seeded fruit set, and the degree of facultative parthenocarpy. Plants were trained to two stems (A and B). On stem A we emasculated six flowers per truss; three were pollinated and the other three were left unpollinated. We considered that a plant was parthenocarpic if it set one or more seedless fruit similar in size and shape to those seeded, and nonparthenocarpic if it only set seeded fruit. The efficiency of parthenocarpy over seeded fruit set was measured with a parthenocarpic fruit set index (PFSI), defined as twice the ratio of seedless to total fruit on stem A. In stem B all flowers were left to self-pollinate naturally. We quantified the degree of facultative parthenocarpy as the percentage of seedless fruit of the total. Parthenocarpy is controlled by one dominant gene for which we propose the symbol P. Parthenocarpic fruit set in the homozygote PP was as efficient as the seeded one (PFSI ≈ 1); in the heterozygote Pp it was less efficient (PFSI ≈ 0.6). The dose of gene P explained the differences found between generations for the PFSI and made it possible to predict the PFSI of a given generation from the proportions of PP and Pp genotypes. Although for the Pp hybrids parthenocarpic fruit set was less efficient than the seeded one, their ability to set seedless fruit in conditions of deficient pollination, together with their high degree of heterosis, makes them agronomically useful. The degree of facultative parthenocarpy seemed to be a complex trait with low heritability. In environments unfavorable for pollination, parthenocarpic genotypes set seedless fruit, thus ensuring crop production and yield stability. Using the degree of facultative parthenocarpy to classify plants for parthenocarpy is not recommended. Developing parthenocarpic cultivars can help spread this crop and stabilize yields.
characteristic for fresh market fruit, including citrus. Parthenocarpy Parthenocarpy, literally meaning virgin fruit, is the natural, artificially induced, or genetically modified production of fruit without fertilization. In the absence of pollination
as the pollen, covered the stigma surface, and blocked the interface between the pollen and the papillae cells ( Fig. 3C ). In pistachios, pollen-induced parthenocarpy, fruit set without fertilization, produces a fully expanded pericarp (shell
seeded and small seedless fruit may result from double fertilization, stenospermocarpy, and parthenocarpy simultaneously within different fruits of a cluster, but the causative factors for the various seed in this cultivar are still poorly understood
T 286, a rabbiteye blueberry selection from a `Delite' × `Tifblue' cross, generally has been regarded as producing semi-seedless fruit. A comparison of nonpollinated flowers of T 286, `Delite', and `Tifblue' showed no differences in ovule count, and comparisons of ovules at 10, 20, and 40 days from manual cross-pollination showed no obvious evidence of embryo abortion. Manually cross-pollinated flowers contained 85, 60, and 38 seeds per fruit for `Delite', `Tifblue', and T 286, respectively. Open-pollinated fruit of T 286 had a seed count similar to that of open-pollinated `Tifblue' but possessed significantly heavier fruit. The number of seed in T 286 and `Tifblue' indicates a tendency toward parthenocarpy.
During a 4-year period, ‘Kerman’ pistachio trees (Pistacia vera) produced an average of 26% blank nuts. Production of blanks by individual trees remained relatively constant from year to year and was not associated with yield or position of the trees in relation to pollinators. Blank production was also found to be a characteristic of P. atlantica Desf. and P. chinensis Bunge. Results demonstrated that production of blanks, at least in ‘Kerman’, is partly the result of parthenocarpy.
A hypothesis is proposed and tested for the mechanism of action of parthenocarpy induction in cucumber (Cucumis sativus L. cv. ‘GY3’) by the potent inhibitors of auxin transport 3,3a-dihy dro-2-(p-methoxy phenyl)-8H-pyrazolo [5,1-a] isoindol-8-one (DPX1840), methyl-2-chloro-9-hydroxyfluorene-9-carboxylate (morphactin), N-l-naphthylphthalamic acid (naptalam), and 2,3,5-triiodobenzoic acid (TIBA). The transport of NAA-l-14C in 5-mm peduncle sections was strongly polar in the basipetal direction (i.e., out of the ovary toward the stem) and was inhibited within 0.5 hr by each transport inhibitor when applied at 500 to 1000 mg/1 to intact plants. Ether extractions of ovary tissue from plants treated in a similar manner contained significantly greater auxin activity as determined by the Avena coleoptile straight growth bioassay.
These results are compatible with the hypothesis that auxin transport inhibitors induce parthenocarpy in cucumber by rapidly blocking the natural outward flow of auxin from the ovary thereby resulting in an accumulation of auxin within the ovary sufficient to trigger parthenocarpy.