Parthenocarpic Cultivars Research Articles

Yields, Postharvest Storage, and Response to Pruning of Eggplant Cultivars Grown in High Tunnels in New Hampshire, USA

We grew eight cultivars of eggplant (Solanum melongena) over 2 years in four experiments conducted in high tunnels located in Durham, NH; North Haverhill, NH; and Ossipee, NH, USA. The marketable yields of eggplant harvested over 14 to 15 weeks ranged from 925 to 3269 g per plant (2.5–8.8 kg⋅m–2), depending on year and cultivar. Significant differences in marketable yield among cultivars were observed in three of the four experiments, but trends were not consistent. Parthenocarpic cultivars developed for greenhouse production, including Angela, Annina, Aretussa, Jaylo, and Michal, did not produce significantly greater yields than the cultivars developed for field production (Nadia, Traviata, and White Star). In two experiments, using a subset of cultivars, we explored the effects of training plants to four leaders compared with the standard practice of no pruning. Pruning treatment did not impact significantly the number or weight of marketable fruit, or the percentage of cull fruit, and there was no cultivar-by-pruning treatment interaction. In three separate experiments in Durham NH, USA, weight loss, browning, and softness were evaluated after 2 weeks of storage in one of three conditions: within the ideal range of temperatures (average of 50–64 °F), too warm (63–73 °F), and too cool (38–49 °F). Overall, responses to conditions that were warmer or cooler than ideal were as predicted, and weight loss, softness, and browning were all minimized when fruit were stored at 50 or 60 °F. We did, however, see some differences among cultivars in susceptibility to common postharvest storage problems. In conclusion, we found that cultivar choice can be important for high-tunnel eggplant producers, especially if postharvest storage conditions are not ideal. We also found that pruning and parthenocarpy did not enhance marketable yields, allowing growers to reduce labor and seed costs without impacting yield or fruit quality negatively.

Transcriptomic, Hormonomic and Metabolomic Analyses Highlighted the Common Modules Related to Photosynthesis, Sugar Metabolism and Cell Division in Parthenocarpic Tomato Fruits during Early Fruit Set

Parthenocarpy, the pollination-independent fruit set, can raise the productivity of the fruit set even under adverse factors during the reproductive phase. The application of plant hormones stimulates parthenocarpy, but artificial hormones incur extra financial and labour costs to farmers and can induce the formation of deformed fruit. This study examines the performance of parthenocarpic mutants having no transcription factors of SlIAA9 and SlTAP3 and sldella that do not have the protein-coding gene, SlDELLA, in tomato (cv. Micro-Tom). At 0 day after the flowering (DAF) stage and DAFs after pollination, the sliaa9 mutant demonstrated increased pistil development compared to the other two mutants and wild type (WT). In contrast to WT and the other mutants, the sliaa9 mutant with pollination efficiently stimulated the build-up of auxin and GAs after flowering. Alterations in both transcript and metabolite profiles existed for WT with and without pollination, while the three mutants without pollination demonstrated the comparable metabolomic status of pollinated WT. Network analysis showed key modules linked to photosynthesis, sugar metabolism and cell proliferation. Equivalent modules were noticed in the famous parthenocarpic cultivars ‘Severianin’, particularly for emasculated samples. Our discovery indicates that controlling the genes and metabolites proffers future breeding policies for tomatoes.

First RNA-seq approach to study fruit set and parthenocarpy in zucchini (Cucurbita pepo L.)

BackgroundZucchini fruit set can be limited due to unfavourable environmental conditions in off-seasons crops that caused ineffective pollination/fertilization. Parthenocarpy, the natural or artificial fruit development without fertilization, has been recognized as an important trait to avoid this problem, and is related to auxin signalling. Nevertheless, differences found in transcriptome analysis during early fruit development of zucchini suggest that other complementary pathways could regulate fruit formation in parthenocarpic cultivars of this species. The development of next-generation sequencing technologies (NGS) as RNA-sequencing (RNA-seq) opens a new horizon for mapping and quantifying transcriptome to understand the molecular basis of pathways that could regulate parthenocarpy in this species. The aim of the current study was to analyze fruit transcriptome of two cultivars of zucchini, a non-parthenocarpic cultivar and a parthenocarpic cultivar, in an attempt to identify key genes involved in parthenocarpy.ResultsRNA-seq analysis of six libraries (unpollinated, pollinated and auxin treated fruit in a non-parthenocarpic and parthenocarpic cultivar) was performed mapping to a new version of C. pepo transcriptome, with a mean of 92% success rate of mapping. In the non-parthenocarpic cultivar, 6479 and 2186 genes were differentially expressed (DEGs) in pollinated fruit and auxin treated fruit, respectively. In the parthenocarpic cultivar, 10,497 in pollinated fruit and 5718 in auxin treated fruit. A comparison between transcriptome of the unpollinated fruit for each cultivar has been performed determining that 6120 genes were differentially expressed. Annotation analysis of these DEGs revealed that cell cycle, regulation of transcription, carbohydrate metabolism and coordination between auxin, ethylene and gibberellin were enriched biological processes during pollinated and parthenocarpic fruit set.ConclusionThis analysis revealed the important role of hormones during fruit set, establishing the activating role of auxins and gibberellins against the inhibitory role of ethylene and different candidate genes that could be useful as markers for parthenocarpic selection in the current breeding programs of zucchini.

Efficacy of Foliar Application of Ga3 and K on Growth and Biochemical Parameters of Two F1 Hybrid Parthenocarpic Cultivars of Cucumber

Abstract The experiment was conducted in anti-insect net house for three consecutive years (2013–2016) with the goal of improving the growth and biochemical contents in two F1 cultivars of cucumber, ‘Sevenstar’ and ‘KUK 9’. Treatment was given in the form of foliar spray containing different concentrations of gibberellic acid (GA3) [0.005 g·dm−3 (G1), 0.01 g·dm−3 (G2), and 0.015 g·dm−3 (G3)] and potassium [1.0 g·dm−3 (K1), 2.5 g·dm−3 (K2), and 5.0 g·dm−3 (K3)] alone and as combinations. All the treatments significantly enhanced plant growth and yield over control. The combination K2G2 showed a marked increase in growth parameters (leaf area, flower number, total dry matter production, growth rate, net assimilation rate) and biochemical attributes (total sugar content, starch, protein). The cultivar ‘KUK 9’ had more increased parameter values than the ‘Sevenstar’. This study provides a direct evidence of the beneficial role of the application of potassium and gibberellic acid on growth, biochemical attributes, and yield of cucumber.

Expression and functional analysis of apple MdMADS13 on flower and fruit formation.

Apple MdMADS13 has a transcription factor with MADS domain. Moreover, it is expressed specifically at petals and carpels. The product forms a dimer with MdPISTILLATA (MdPI) protein as a class B gene for floral organ formation. Reportedly, in parthenocarpic cultivars of apple (Spencer Seedless, Wellington Bloomless, Wickson and Noblow) the MdPI function is lost by genome insertion of retrotransposon, which cultivars show a homeotic mutation of floral organs, petals to sepals and stamens to carpels. Apple fruit is pome from receptacle tissue, and MdSEPALLATA (MdMADS8/9) and AGAMOUS homologues MdMADS15/22 involved in the fruit development, the transgenic apple suppressed these gene showed poor fruit development and abnormal flower formation. This article describes that the MdMADS13 retained expression after blossom and small fruits of parthenocarpic cultivars. Yeast two-hybrid experiment showed specific binding between MdPI and MdMADS13 proteins. Furthermore, transgenic Arabidopsis with 35S::MdMADS13 have malformed stamens and carpels. These results suggest strongly that MdMADS13 is related to flower organ formation as a class B gene with MdPI.

Biomarkers for selection of parthenocarpic zucchini cultivars

Biomarkers for selection of parthenocarpic zucchini cultivars

Exploring an East Asian melon (Cucumis melo L.) collection for parthenocarpic ability

In melon (Cucumis melo L.), the amount of fertile pollen decreases at low temperature during winter and early spring and thereby restricts fertilization. A promising way to overcome this problem is to develop parthenocarpic cultivars. Parthenocarpic cucumber and squash, but not melon cultivars are available. In this study, we explored 172 accessions from an East Asian melon collection and identified accessions that exhibited strong parthenocarpic ability throughout the year. Crosses between parthenocarpic accessions and a non-parthenocarpic cultivar, and among parthenocarpic accessions indicated that parthenocarpy may be inherited in a recessive manner and is likely controlled by the same gene or genes in these accessions. The parthenocarpic indices, such as the size and number of parthenocarpic fruits, differed among the cultivation periods, indicating the importance of environmental factors for parthenocarpic fruit development. We conclude that it is possible to breed new cultivars with stable parthenocarpic ability throughout the year by using the identified accessions.

Auxin signalling regulation during induced and parthenocarpic fruit set in zucchini

Fruit set and fruit development can be limited due to ineffective pollination in off-season crops of Cucurbita pepo. To avoid this problem, parthenocarpy, the natural or artificial fruit development without fertilization, is required. The application of synthetic growth regulators is a common practice for inducing stimulative parthenocarpy in zucchini cultivars, but this method increases production costs and may cause other fruit defects. The disadvantages associated with this can be overcome through the use of vegetative parthenocarpic cultivars, which allow fruit set without any external stimuli. Three zucchini cultivars have been studied and differences have been found in parthenocarpic fruit development. Ethylene release of unpollinated fruit has corroborated the parthenocarpic fruit development. Vegetative parthenocarpy was observed in the Whitaker cultivar. Furthermore, the involvement of the auxin signalling pathway in controlling fruit set and parthenocarpy have been studied. Transcriptome analysis of auxin signalling genes, CpARF8, CpIAA9 and CpTIR1, have shown tissue-specific expression and have revealed a decrease in the expression levels of these genes in pollinated fruits after the fertilization signal, indicating their role in the transition from ovary to fruit. Nevertheless, it has also been shown that expression of these genes can be different between parthenocarpic cultivars.

QTL mapping of parthenocarpic fruit set in North American processing cucumber.

Through a novel phenotyping method, four QTLs were consistently associated with increased parthenocarpic fruit set in North American processing cucumber that accounted for over 75% of observed phenotypic variation. Parthenocarpy is a desirable trait with potential for increasing yield and quality in processing cucumber production. Although many successful parthenocarpic fresh market cucumber varieties have been developed, the genetic and molecular mechanisms behind parthenocarpic expression in cucumber remain largely unknown. Since parthenocarpy is an important yield component, it is difficult to separate the true parthenocarpic character from other yield related traits. In the present study, we developed a novel phenotypic approach for parthenocarpic fruit set focusing on early fruit development. Two hundred and five F3 families derived from a cross between the highly parthenocarpic line 2A and low parthenocarpic line Gy8 were phenotypically evaluated in three greenhouse experiments. Seven QTLs associated with parthenocarpic fruit set were detected. Among them, one each on chromosomes 5 and 7 (parth5.1 and parth7.1) and two on chromosome 6 (parth6.1 and parth6.2) were consistently identified in all experiments, but their relative contribution to the total phenotypic variation was dependent on plant growth stages. While each of the four QTLs had almost equal contribution to the expression of the trait at commercial harvest stage, parth7.1 played an important role in early parthenocarpic fruit set. The results suggested that parthenocarpic fruit set can be accurately evaluated with as few as 20 nodes of growth. The QTLs identified in this study for parthenocarpic fruit set are a valuable resource for cucumber breeders interested in developing parthenocarpic cultivars and to researchers interested in the genetic and molecular mechanisms of parthenocarpic fruit set.

The analysis of transgenic apples with down-regulated expression of MdPISTILLATA.

In parthenocarpic cultivars of apple (Malus×domestica Borkh.), MdPISTILLATA (MdPI) expression has been suppressed by retrotransposon insertion into the MdPI genome. In this study, transgenic apple lines were produced that exhibited the same level of MdPI depression. The 1P-2 promoter from the MdPI genome, which specifies its expression in the petals and stamens, was used for antisense-MdPI expression, and rolC:AtFT was included to accelerate flowering. The transgenic apple with rolC:AtFT/1P-2:antisense-MdPI showed homeotic changes in the floral organs, whereby petals and stamens were replaced with sepals and pistils, respectively. Line 9-2 of this transgenic apple also showed strong suppression of MdPI. Some individuals from this line had deformed floral organs, suggesting that the homeotic changes were incomplete. Other transformants of line 9-2 that had double sepals in the first and second whorls, and many pistils in the third and fourth whorls, as seen in apple cultivars with class B mutations, which demonstrated MdPI functioned for floral organs formation same as Arabidopsis PISTILLATA gene. The transgenic apples set parthenocarpic fruits (15.7%). However, precocious transgenic apples with rolC:AtFT exhibited more parthenocarpy (14-27%). This indicates that MdPI depression cannot explain fruit formation in parthenocarpic cultivars of apple, and so some other as yet unidentified genes must be responsible.

Gibberellic Acid Reduces Flowering Intensity in Sweet Orange [Citrus sinensis (L.) Osbeck] by Repressing CiFT Gene Expression

In Citrus, gibberellic acid (GA3) applied at the floral bud inductive period significantly reduces flowering intensity. This effect is being used to improve the fruit set of parthenocarpic cultivars that tend to flower profusely. However, the molecular mechanisms involved in the process remain unclear. To contribute to the knowledge of this phenomenon, adult trees of ‘Salustiana’ sweet orange were sprayed at the floral bud inductive period with 40 mg L−1 of GA3 and the expression pattern of flowering genes was examined up to the onset of bud sprouting. Trees sprayed with paclobutrazol (PBZ, 2,000 mg L−1), a gibberellin biosynthesis inhibitor, were used to confirm the effects, and untreated trees served as control. Bud sprouting, flowering intensity, and developed shoots were evaluated in the spring. GA3 significantly reduced the number of flowers per 100 nodes by 72% compared to the control, whereas PBZ increased the number by 123%. Data of the expression pattern of flowering genes in leaves of GA3-treated trees revealed that this plant growth regulator inhibited flowering by repressing relative expression of the homolog of FLOWERING LOCUS T, CiFT, whereas PBZ increased flowering by boosting its expression. The activity of the homologs TERMINAL FLOWER 1, FLOWERING LOCUS C, SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1, and APETALA1 was not affected by the treatments. The number of flowers per inflorescence, in both leafy and leafless inflorescences, was not altered by GA3 but increased with PBZ; the latter paralleled LEAFY relative expression. These results suggest that GA3 inhibits flowering in Citrus by repressing CiFT expression in leaves.

Parthenocarpic genetic resources and gene expression related to parthenocarpy among four species in pear (Pyrus spp.)

Parthenocarpy—the production of seedless fruits without fertilization—is very useful for fruit cultivation, especially in self-incompatible species such as pears. To search for parthenocarpic genetic resources in pear, 31 pear accessions [20 Chinese pears (13 Pyrus bretschneideri, seven Pyrus ussuriensis), five European pears (Pyrus communis), two Japanese pears (Pyrus pyrifolia), and four interspecific hybrids] were subjected to flower emasculation and left unpollinated, and then the fruit-set ratio and fruit enlargement were investigated. All European pears examined had a stable and high degree of fruit set, and ‘La France’ had high fruit enlargement. The possibility of stenospermocarpy was ruled out, because the emasculated flowers were left unpollinated in paper bags and the absence of seed was confirmed in the enlarged fruits. Neither Chinese nor Japanese pears treated with emasculation and no pollination showed consistently stable fruit set and fruit enlargement. An analysis of parthenocarpy in the offspring of ‘La France’ suggested that both high fruit set and fruit enlargement were inherited and that it should be possible to introduce parthenocarpy into Japanese pears. Although parthenocarpic ‘La France’ fruits weighed slightly less than those from cross-pollinated flowers, their cortex enlargement compared favorably with that seen with cross-pollinated ones. By using a customized pear cDNA microarray, we compared the gene expression profiles of highly and weakly parthenocarpic cultivars before flowering. Expression of several phenylpropanoid-related genes and photosystem-related genes differed significantly between the two groups. Some of these genes were putatively encoded in the chloroplast genome. These genes might be candidates of DNA markers for achievement of parthenocarpy in Japanese pear breeding.

Development of the Parthenocarpic Eggplant Cultivar 'Anominori'

Using pollinator insects or treating flowers with phytohormones is necessary for stable fruit setting in forcing culture of eggplant using plastic houses. However, these means are costly and/or labor-intensive. Use of parthenocarpic cultivars is considered to be the most cost-effective solution for stable fruit setting under sub-optimal environmental conditions such as lower temperature in forcing culture. ‘Anominori’, a parthenocarpic eggplant cultivar, was developed by the National Institute of Vegetable and Tea Science in 2006. This cultivar is the F1 hybrid between two parthenocarpic inbred lines, ‘AE-P08’ and ‘AE-P01’. ‘AE-P08’ was selected from the cross between an F3 plant derived from ‘Nakate Shinkuro’ × ‘Talina’ and an F4 plant derived from ‘Talina’ × ‘Nasu Chuukanbohon Nou 1’. ‘AE-P01’ was selected from the cross between ‘Talina’ and ‘Nasu Chuukanbohon Nou 1’. ‘Anomi-nori’ can produce sufficient yields for commercial use without treating with phytohormones or using pollinator insects in forcing culture. The plant characteristics of ‘Anominori’ are the following: high plant height, long internode, thick stem and large leaves. The fruit of ‘Anominori’ at harvest stage is long egg-shaped and glossy dark purple. The flesh of fruit is very dense.

Seed Formation is Affected by Uniconazole, an Inhibitor of Gibberellin Biosynthesis, in a Parthenocarpic Cultivar Severianin of Tomato (Lycopersicon esculentum Mill.)

In order to increase seed production of a pat-2 parthenocarpic tomato cultivar, we attempted to enable fertilization by applying an inhibitor of gibberellin (GA) biosynthesis to the whole plant to prevent pseudoembryo formation prior to anthesis. The pat-2 parthenocarpic tomato cultivar ‘Severianin’ was cultured with hydroponics, and the GA biosynthesis inhibitor, uniconazole-P, (E)-(S)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pent-1-en-3-ol, was added to the culture solution at 0, 0.01, 0.05, and 0.25 mg·L-1 about two weeks before the first flower anthesis. Stigmata were removed to prevent pollination from half of the plants of each concentration before anthesis, and the other half were tapped by a finger at anthesis for pollination. For pollinated fruits, there were no differences in fruit weight and seed number between the different concentrations of uniconazole-P. A significant positive correlation was observed between seed number and fruit weight in pollinated fruits treated with uniconazole-P that was not observed in the absence of uniconazole-P. There were no significant differences in the germination rate at any concentrations tested compared to the control. Seedlings grown from uniconazole-P-treated plants appeared to develop normally and did not differ from the control. Hence, uniconazole-P treatment of the whole plant was useful for increasing the efficiency of seed production for a parthenocarpic pat-2 cultivar. This was augmented by choosing large fruits at harvest, which contain sufficient amounts of true seeds based on the strong positive correlation between seed number and fruit weight.

SELECTION OF SWEET PEPPER (CAPSICUM ANNUUM L.) GENOTYPES FOR PARTHENOCARPIC FRUIT GROWTH

Yield irregularity and blossom-end-rot are major problems in sweet pepper production, which can be reduced by parthenocarpy. However no commercial parthenocarpic cultivars are available. The purpose of this study was to find parthenocarpic genotype(s) of sweet pepper with the ability to produce good quality fruits without seeds. Eleven genotypes of sweet pepper were studied at normal (20/20°C D/N) and at low night temperature (20/10°C D/N), in two greenhouse compartments from January till May. Fruit length, diameter, fresh and dry weight and number of seeds per fruit were measured. A higher percentage of parthenocarpic fruits was observed for all genotypes at low night temperature compared to normal temperature. Within the genotypes which showed at least 60% parthencarpic fruit growth at low night temperature, two groups were distinguished, which showed a different expression of parthenocarpy in response to the environment. In one set of genotypes (Line 1 and Line 3) high expressivity for parthenocarpy was found irrespective of night temperature. In another set of genotypes (Gen A, Gen B, Gen C, Lamuyo A, Lamuyo B and Bruinsma Wonder), a high level of parthenocarpy was expressed at low night temperature only, which may be due to non-viable pollen at low night temperature. Further evaluation of the latter six genotypes resulted in one genotype (Bruinsma Wonder) for which the absence of seeds only marginally influenced shape and size of fruits. These selected genotypes may eventually lead to an exploitation of parthenocarpy in sweet pepper breeding.

Fruit set and embryo rescue in crosses using parthenocarpic ‘Mopanshi’ persimmon

The ‘Mopanshi’ persimmon is a seedless, astringent parthenocarpic cultivar that does not produce male flowers. After pollination using four non-astringent cultivars (‘Zenjimaru’, ‘Nishimurawase’, ‘Okugosho’ and ‘Hanagosho’), seeds were produced to different degrees. ‘Mopanshi’ fruits pollinated with ‘Zenjimaru’ produced far more seeds than those pollinated with the other three cultivars. The ratio of abnormal seeds obtained from the fruits pollinated with ‘Hanagosho’ was higher than that obtained from the fruits pollinated with the other three cultivars. Most embryos degenerated in the early to late stages of seed development. Immature embryos were cultured in a modified MS medium (half of NO 3 in MS medium + 0.4 μM BA + 0.1 μM IBA) with the greatest success (52–80%) from embryos taken from fruits 60–80 days after pollination. Seedlings failed to initiate radicles so they were transferred to dark culture conditions for 8 days or to a rooting media that contained 3% sucrose and 1% Chinese ink. The seedlings on the medium darkened with ink rooted at greater than 90.83% compared to 75.83% for dark cultured seedlings. This study demonstrated that ‘Mopanshi’ persimmon could be used as a female parent in crosses, but embryos needed to be moved to tissue culture conditions to continue to develop and form plantlets.

Effect of fruit-load on growth patterns of fruit at the middle nodes of gynoecious-type cucumbers

SummaryThe effects of different timings of fruit thinning at the lower nodes (nodes 4 to 7) on fruit growth and abortion at higher nodes were investigated in a gynoecious, parthenocarpic cultivar of cucumber (Cucumis sativus L.), ‘NK x AN8’. Fruits at the lower nodes were removed 0, 5, 10, 15 and 20 d after anthesis of flowers at node 8 (DAA8).Total leaf areas and growth patterns of individual fruit were then monitored. When fruits at nodes 4 to 7 were thinned 0 or 5 DAA8, all fruits at nodes 8 to 12 grew to commercial size, without fruit abortion. When fruits were thinned 10 DAA8, the fruits at nodes 8 to 12 ceased to grow after anthesis, but growth was restored a few days after fruit thinning. Fruit thinning at 15 or 20 DAA8 forced most fruits at nodes 8 to 12 to abort, while fruits at node 13 and above ceased to grow for a while, but resumed growth after fruit thinning. In all treatments, total leaf area increased with time throughout the experiment. High fruit load depressed the rate of growth of leaf area slightly, 65 to 75 d after sowing. Fruit load (fresh weight) per leaf area was about 50 mg cm–2 just before fruits at nodes 4 to7 were thinned at 20 DAA8.These results suggest that fruit abortion occurs if fruits at the lower nodes persist for a long period, and fruits at the middle nodes senesce before enlargement. Fruit thinning at the lower nodes can restore the growth of fruits in the stagnant growth phase within 10 d.

Grapevine productivity and yield components: A case study using field vines of Zante currant

Yield components of the parthenocarpic cultivar Zante were analysed for five vineyards of diverse age and management. The data was obtained as part of an experiment to improve fruit set and yield by applying combinations of gibberellin and 2-chloroethyltrimethyl ammonium chloride or 4-chlorophenoxyacetic acid. Four of the vineyards were located in the Brockman valley north of Perth, Western Australia, two of these were irrigated, one was rain fed and one received supplementary flood irrigation. The fifth lay in an adjacent area of coastal sand plain, at the foot of the Darling scarp, and was irrigated. The vines were aged from 6 to 50 years. Principal component analysis showed that vine age was negatively correlated with vigour (pruning weight) and with berry number per bunch. Vine age however was not strongly related to either yield or yield components (bunch number and berry volume). Sugar concentration was negatively correlated with all yield components but imprecisely modelled based on any combination of the measured variables. Berry number per vine appeared to be the underlying factor determining 'sink' strength though this was inextricably confounded with bunch number per vine. Interpretation of the data leads to the conclusion that increased berry volume is an inefficient means of increasing dried yield. This conclusion argues for caution in the application of plant growth regulators that act primarily to increase berry volume. Yield of sugar per vine was accurately modelled based on second order relationships with bunch number per vine, berry number per bunch, berry volume and pruning weight. Vine age also showed a second order relationship to yield although the range was relatively small. The observations are considered in terms of developing strategies for maximising dried yield and devising mathematical models to account for photoassimilate (dry matter) partitioning in Vitis.

Reassessment of Seed Influence on Return Bloom and Fruit Growth in 'Bartlett' Pear

In a simple, yet elegant experiment conducted 30 years ago, Chan and Cain (1967) using 'Spencer Seedless', a facultatively parthenocarpic apple (Malus×domestica Borkh.) cultivar, proposed that seeds inhibited flowering and accentuated biennial bearing in apple. Their conclusions have been extrapolated widely to include apple and other species. We have tested the universality of their conclusions using 'Bartlett' pear (Pyrus communis L.), a commercially important, facultatively parthenocarpic cultivar. Unlike 'Spencer Seedless' apples and seedless 'Bartlett' pear grown in France, California-grown seedless 'Bartlett' pear fruit strongly inhibited flowering the following year. However, the presence of seeds increased 'Bartlett' pear fruit size relative to seedless fruit by 13% and 20% in nonthinned and heavily-thinned pear trees, respectively, indicating that seeds increased fruit sink strength.

Transgenic parthenocarpic eggplants: superior germplasm for increased winter production

Winter production of three eggplant hybrids transgenic for the parthenocarpic gene DefH9-iaaM was compared, in an unheated greenhouse, to the performance of two untransformed control hybrids and the commercial parthenocarpic cultivar Talina. Each hybrid was either treated or untreated with a commercial formulation of phytohormones to induce fruit set and growth. The productivity of the transgenic parthenocarpic hybrids was not influenced by the hormonal treatment. On the contrary, the productivity of untransformed hybrids was significantly improved by hormonal treatment of the flower buds. The yield of the transgenic hybrids was significantly higher than that obtained in the corresponding untransformed hybrids, even when the latter were treated with phytohormones. The yield increment due to the parthenocarpic trait was particularly evident when compared to the yield of the two corresponding hybrid combinations, which are identical except for the presence of the DefH9-iaaM gene. The transgenic hybrids allowed an increase in productivity of ca. 25%. This increment coincided with a 10% reduction in cultivation cost, mainly due to the labour needed for the hormonal sprays, and to the production of fruits of better quality. Thus, the DefH9-iaaM gene is a biotechnological tool superior to both agronomic and traditional genetic parthenocarpic mutants.