Bisexual Flowers Research Articles

Phylogenomics of the aquatic plant genus Ottelia (Hydrocharitaceae): Implications for historical biogeography

Ottelia Pers. is the second largest genus of the family Hydrocharitaceae, including approximately 23 extant species. The genus exhibits a diversity of both bisexual and unisexual flowers, and complex reproductive system comprising cross-pollinated to cleistogamous flowers. Ottelia has been regarded as a pivotal group to study the evolution of Hydrocharitaceae, but the phylogenic relationships and evolutionary history of the genus remain unresolved. Here, we reconstructed a robust phylogenetic framework for Ottelia using 40 newly assembled complete plastomes. Our results resolved Ottelia as a monophyletic genus consisting of two major clades, which correspond to the main two centers of diversity in Asia and Africa. According to the divergence time estimation analysis, the crown group Ottelia began to diversify around 13.09 Ma during the middle Miocene. The biogeographical analysis indicated the existence of the most recent common ancestor somewhere in Africa/Australasia/Asia. Basing on further insights from the morphological evolution of Ottelia, we hypothesized that the ancestral center of origin was in Africa, from where the range expanded by transoceanic dispersal to South America and Australasia, and further from Australasia to Asia. We suggested that the climatic change and global cooling since the mid-Miocene, such as the development of East Asian monsoon climate and tectonic movement of the Yunnan-Guizhou Plateau (YGP), might have played a crucial role in the evolution of Ottelia in China.

Stigma receptivity in Cashew nut (Anacardium occidentale L.)

The cashew is widely and commercially cultivated throughout the nation for its nut. Cashew is a polygamo – monoecious plant with both male and bisexual flowers developing in same inflorescence. Experimental study was conducted at Kesiary Cashew Plantation Sector, Medinipur as per the guidelines Regional Research Station, Jhargram and National Research Centre of Cashew, Karnataka (2014 – 2018). Changes in stigma receptivity were studied by over 100 panicles chosen at random taken from the commercially cultivated germplasms (WBDC – 4, Kottakerala – 2/97, Dicherla – 2/9, Vetore – 56 and Ullal – 2). The study was continued as for one day before, on the day of flower opening, one day & two days after flowering. It indicates that one day prior to opening & two days after of flowering, stigma receptivity was maximum in the plants of Vetore – 56. But on the day & one day after of flowering it was highest in Dicherla – 2/9. The optimum period of receptivity was at 12 noon on the day of anthesis.

Discovery of a millennial androecious germplasm and its potential in persimmon (Diospyros kaki Thunb.) breeding

Persimmon (Diospyros kaki Thunb.) can produce unisexual (male and female) and bisexual (hermaphrodite) flowers, showing relatively complex sexuality at the species level. In China, there are more than 1000 persimmon germplasms, but most are gynoecious cultivars that bear female flowers only. To date, few germplasms have been reported to generate male flowers, until seven androecious persimmons were recently found in the Dabieshan Mountains at the juncture of Hubei, Anhui and Henan Provinces in central China. Here, we report a new androecious germplasm located in Jiangxi Province that was cultivated by the first generation of the Luo family in the Song Dynasty nearly for a thousand years ago. Up to now, the millennial androecious germplasm has continuously borne only male flowers and the seeding plant still has a strong growth vigor. Investigation of the leaf and pollen morphology showed that this androecious germplasm is similar to ‘Male 2’ (androecious, discovered in Dabieshan Mountains) but different from two Japanese cultivars (‘Taishuu’ and ‘Zenjimaru’). Polymerase chain reaction (PCR) detection of the sex-linked marker DlSx-AF4S verified that the millennial androecious germplasm carries this sex-linked marker. Moreover, the RO2 marker, linked Chinese pollination constant non-astringent (C-PCNA) locus, was also present in the millennial androecious germplasm. Additionally, the genetic relationships between SSR markers showed that the millennial androecious germplasm is related to Dabieshan’s androecious genotypes and some persimmon cultivars of Chinese origin. Collectively, our results revealed that the ancient androecious persimmon found in Jiangxi Province is distinguished from previously reported androecious germplasms and has the potential to serve as a breeding resource for selecting sex-linked PCNA persimmons in the future.

PENGGUNAAN KOMPOS BAGASE UNTUK MENGOPTIMALKAN PRODUKSI TANAMAN TERUNG (Solanum melongena L.)

Eggplant (Solanum melongena L.) is a plant species that is known as the fruit and vegetables grown for use as a food ingredient. These plants belong to one group of plants that produce seeds Eggplant Trunk divided into two kinds, namely the main stem and branching. Eggplant leaf consists of a petiole and the leaf blade. Eggplant flowers are hermaphrodite flowers, or better known as the bisexual flowers, the flowers are one of the stamen to the pistil. Eggplant fruit is the fruit of a true single.. Cultivation of eggplant in the Project of Independent Business is using composting technology bagase. Bagase compost is compost that comes from bagasse or the rest of the sugar mill. Bagase own compost organic matter content of about 90%, N content of 0,3%, 0,02% P2O5, K20 0,14%, Ca 0,06% and 0,04% Mg. The project goal independent business is the use of compost bagase on the cultivation of eggplant to reduce the use of chemical fertilizers and optimize plant production eggplant, farming systems semi-organic environmentally sustainable and analyze the feasibility of cultivation of eggplant with market potential in Payakumbuh and the District Fifty City. Independent business projects implemented during the four months from September to December 2015 and conducted experiments dikebun State Agricultural Polytechnic Payakumbuh with total area of ​​300 m2. Eggplant crop production on the independent business projects with the use of compost bagase treatment that is 575 Kg/300 m2, a profit of Rp. 835.310, the profitability of 92% and RC Ratio of 1,92.

Cryptic diversity within the African aquatic plant Ottelia ulvifolia (Hydrocharitaceae) revealed by population genetic and phylogenetic analyses.

Revealing cryptic diversity is of great importance for effective conservation and understanding macroevolution and ecology of plants. Ottelia, a typical example of aquatic plants, possesses extremely variable morphology and the presence of cryptic diversity makes its classification problematic. Previous studies have revealed cryptic Ottelia species in Asia, but very little is known about the molecular systematics of this genus in Africa, a center of species diversity of Ottelia. In this study, we sampled Ottelia ulvifolia, an endemic species of tropical Africa, from Zambia and Cameroon. We used six chloroplast DNA regions, nrITS and six polymorphic microsatellite markers to estimate the molecular diversity and population genetic structure in O. ulvifolia. The phylogenetic inference, STACEY and STRUCTURE analyses supported at least three clusters within O. ulvifolia, each representing unique flower types (i.e., bisexual yellow flower, unisexual yellow flower and bisexual white flower types). Although abundant genetic variation (> 50%) was observed within the populations, excessive anthropogenic activities may result in genetic drift and bottlenecks. Here, three cryptic species of O. ulvifolia complex are defined, and insights are provided into the taxonomy of Ottelia using the phylogenetic species concept.

Gynodioecy in the common spindle tree (Euonymus europaeus L.) involves differences in the asymmetry of corolla shapes between sexually differentiated flowers.

Gynodioecy is typically associated with a smaller perianth size in purely pistillate flowers than in hermaphrodite flowers. However, it is unclear whether this size differentiation is associated with any differences in flower shape between the two sexual groups. A geometric morphometric analysis of the symmetry of tetrameric corolla shapes was used in the study of Euonymus europaeus L., Darwin’s classical system of floral sexual differentiation. I investigated whether there are any shape differences between the female and bisexual flowers, with respect to both purely symmetric variation involving coordinated shape changes of the four petals and asymmetry among petals within flowers. The corolla shapes of the female and bisexual flowers and the variability among flowers within each sexual group were very similar in the purely symmetric components of shape variation. However, the female flowers were significantly more asymmetric with respect to both the lateral and transversal asymmetry of their corolla shapes. This is the first study to apply geometric morphometrics in the analysis of morphological patterns in a sexually differentiated gynodioecious plant system. The results showed that subtle shape differences in corolla asymmetry differ between the sexual groups and indicate diverging developmental or selection signals between the sexes.

Sex-specific floral attraction traits in a sequentially hermaphroditic species.

●Many angiosperms are hermaphroditic and produce bisexual flowers in which male (pollen export) and female (stigma receptivity) functions are separated temporally. This sequential hermaphroditism may be associated with variation in flower size, color, or pattern, all of which may influence pollinator attraction. In this study, we describe variation in these traits across discrete functional sex stages within and between 225 greenhouse‐grown individuals of Clarkia unguiculata (Onagraceae). In addition, to identify the effects of floral phenotype on pollinator attraction in this species, we examine the effects of these floral traits on pollen receipt in ~180 individuals in an experimental field array.●Petal area, ultraviolet (UV)‐absorbing nectar guide area, and blue and green mean petal reflectance differ significantly across the functional sex stages of C. unguiculata. Male‐ and female‐phase flowers display significantly different pollinator attraction traits. Petal and UV nectar guide area increase as flowers progress from male phase to female phase, while blue reflectance and green reflectance peak during anther maturation.●In field arrays of C. unguiculata, female‐phase flowers with large UV nectar guides receive more pollen than those with small nectar guides, and female‐phase flowers with high mean blue reflectance values are more likely to receive pollen than those with low blue reflectance. Female‐phase flowers with green mean reflectance values that differ most from background foliage also receive more pollen than those that are more similar to foliage. These findings indicate that components of flower color and pattern influence pollen receipt, independent of other plant attributes that may covary with floral traits. We discuss these results in the context of hypotheses that have been proposed to explain sex‐specific floral attraction traits, and we suggest future research that could improve our understanding of sexual dimorphism in sequentially hermaphroditic species and the evolution of features that promote outcrossing.

Flower-Specific Overproduction of Cytokinins Altered Flower Development and Sex Expression in the Perennial Woody Plant Jatropha curcas L.

Jatropha curcas L. is monoecious with a low female-to-male ratio, which is one of the factors restricting its seed yield. Because the phytohormone cytokinins play an essential role in flower development, particularly pistil development, in this study, we elevated the cytokinin levels in J. curcas flowers through transgenic expression of a cytokinin biosynthetic gene (AtIPT4) from Arabidopsis under the control of a J. curcas orthologue of TOMATO MADS BOX GENE 6 (JcTM6) promoter that is predominantly active in flowers. As expected, the levels of six cytokinin species in the inflorescences were elevated, and flower development was modified without any alterations in vegetative growth. In the transgenic J. curcas plants, the flower number per inflorescence was significantly increased, and most flowers were pistil-predominantly bisexual, i.e., the flowers had a huge pistil surrounded with small stamens. Unfortunately, both the male and the bisexual flowers of transgenic J. curcas were infertile, which might have resulted from the continuously high expression of the transgene during flower development. However, the number and position of floral organs in the transgenic flowers were well defined, which suggested that the determinacy of the floral meristem was not affected. These results suggest that fine-tuning the endogenous cytokinins can increase the flower number and the female-to-male ratio in J. curcas.

Small RNA and mRNA Sequencing Reveal the Roles of microRNAs Involved in Pomegranate Female Sterility.

Female sterility is a key factor restricting plant reproduction. Our previous studies have revealed that pomegranate female sterility mainly arose from the abnormality of ovule development. MicroRNAs (miRNAs) play important roles in ovule development. However, little is known about the roles of miRNAs in female sterility. In this study, a combined high-throughput sequencing approach was used to investigate the miRNAs and their targeted transcripts involved in female development. A total of 103 conserved and 58 novel miRNAs were identified. Comparative profiling indicated that the expression of 43 known miRNAs and 14 novel miRNAs were differentially expressed between functional male flowers (FMFs) and bisexual flowers (BFs), 30 known miRNAs and nine novel miRNAs showed significant differences among different stages of BFs, and 20 known miRNAs and 18 novel miRNAs exhibited remarkable expression differences among different stages of FMFs. Gene ontology (GO) analyses of 144 predicted targets of differentially expressed miRNAs indicated that the “reproduction process” and “floral whorl development” processes were significantly enriched. The miRNA–mRNA interaction analyses revealed six pairs of candidate miRNAs and their targets associated with female sterility. Interestingly, pg-miR166a-3p was accumulated, whereas its predicted targets (Gglean012177.1 and Gglean013966.1) were repressed in functional male flowers (FMFs), and the interaction between pg-miR166a-3p and its targets (Gglean012177.1 and Gglean013966.1) were confirmed by transient assay. A. thaliana transformed with 35S-pre-pg-miR166a-3p verified the role of pg-miR166a-3p in ovule development, which indicated pg-miR166a-3p’s potential role in pomegranate female sterility. The results provide new insights into molecular mechanisms underlying the female sterility at the miRNA level.

Studies on flowering induction, sex ratio and fruit set improvement in pomegranate

The present study was conducted to induce flowering at the desired period with higher percentage of bisexual flowers and fruit set to improve yield and minimize fruit cracking through withholding of irrigation, pruning and ethrel application. Pooled data analysis revealed that horticultural interventions, chemical treatments and their interactions significantly affected sex ratio and fruit set. Among horticultural interventions, earliest defoliation (10.47 days), highest defoliation (81.25%), shortest flowering period (64.46 days), minimum male flowers (58.59%), maximum bisexual flowers (27.43%), maximum fruit set (25.84%) and fruit retention (82.23%) were recorded in withholding of irrigation during June + pruning and thinning as compared to control natural flowering. Among chemical treatments, earliest defoliation (7.59 days), highest defoliation (93.35%) and shortest flowering period (61.07 days) were recorded in ethrel 3 ml/l + DAP 5 g/l application while minimum male flowers (59.21%), maximum bisexual flowers (25.51%), maximum fruit set (25.16%) and fruit retention (80.74%) were recorded in ethrel 2 ml/l + DAP 5 g/l treatment as compared to control. Among interactions, earlier defoliation (6.78 days), highest defoliation (95.72%) and shortest flowering period (55.42 days) were observed in withholding of irrigation during June + pruning and thinning + ethrel 3 ml/l + DAP 5 g/l treatment. The minimum male flowers (57.78%), maximum bisexual flowers (28.22%), maximum fruit set (26.39%) and fruit retention (83.34%) were recorded in withholding of irrigation during June + pruning and thinning + ethrel 2 ml/l + DAP 5 g/l treatment as compared to maximum male flowers (66.36%), minimum bisexual flowers (22.03%), fruit set (22.19%) and fruit retention (75.28%) recorded in natural flowering without chemical treatment. Therefore, it can be concluded that withholding of irrigation during June + pruning and thinning + ethrel 2 ml/l + DAP 5 g/l treatment induced flowering during optimal climatic conditions and significantly improved sex ratio and fruit set of pomegranate.

Ampelographic description, ampelometric screening and agrobiological characteristics of the Donus grape variety

The agrobiological and ampelographic characteristics of the Donus interspecific grape variety are given. A variety of universal use, average ripening period, the duration of the production period for 2010-2019 was 146 days with the sum of active temperatures 3297 0C. The variety is characterized by high winter hardiness. With a sum negative temperature of 586 0C and an absolute minimum of minus 25 0C, the live buds from 49% to 72.8%. Fruit shoots 90-100%, fruitfulness ratio 1.8. Yield / bush ≥ 6.9 kg with a planting pattern of 3 m × 1.5 m. It has bisexual flower, clusters of medium density, cylindro-conical with 1 -2 wings, weighing 212 g. The berry is oval, greenish-yellow, weighing about 3 g. The parameters of the berry are 14.6 × 13.4 mm. The pulp is juicy with muscat aroma. Differs in moderate sugar accumulation with moderate acidity. Resistance to mildew and oidium is high. The variety has been defined as a donor of mildew resistance. It is used for the production of juices, dry and sparkling wines, fresh consumption. The wine degustation evaluation is on average 8.5 points on a ten-point scale. The Donus is a perspective variety for commercial vitiviniculturel.

О ПОЛОВОМ ПОЛИМОРФИЗМЕ В РОДЕ PRUNELLA L.

We studied sexual structure, anthecology and seed production in natural populations of two gynodioecic species: Prunella vulgaris L. and P. grandiflora (L.) Jacq. The population of Prunella grandiflora had a small part of female plants (less than 1%). The part of female plants in the population of Prunella vulgaris varied from 1% (in forest steppe Chernozemie) to 1% - 25% (in Priuralie). Bisexual flowers of these species had a weak proterandria and probability of combination of allogamy and autogamy. The evidence is the probability of seed formation while isolation of generative shoots. This experiment showed varying degrees of self-compatibility of these plants. Such difference result in different seed production in natural and experimental conditions. Prunella grandiflora is recommended for landscaping in Priuralie.

Varate Giduga (Acc. No. 21067; IC No. 418238) : A unique mango (Mangifera indica L.) variety

Varate Giduga is one of the unique variety from Sirsi region of Karnataka. The tree is Semi-circular shaped with dense foliage, leaves about 25cm long; dark green in colour with wavy margin. It is a very consistent and heavy producer. The fruit of this tree matures by mid-April and fruit has a distinctive yellow skin color on fruit exposed to the sun. The fruit shape is round, fruit weight ranged from 350-400 g, fruit length was 9.8 cm, fruit diameter was 9.2 cm, fruit thickness was 8.0cm and bisexual flowers were 16.53%. Biochemical constituents such as the total phenols (317.50 mg/100 g), flavonoids (5.79 mg/100g), carotenoids (1.46 mg/100 g) and acidity (0.19%) were recorded which suggests that these characters are unique as compared to other varieties. The fruit skin is rough and glossy in appearance and the fruit has little or no fiber. It is very delicious in taste with high pulp percentage (74.0%) and high TSS (23.4º B). The flesh color is orange. The fruits have deep orange firm pulp and very sweet with pleasant flavor. Besides,several other traits have drawn special attention to this mango variety as it has large sized fruits (Fig-1), late variety with very good taste, fruit can be cut into two halves by retaining the stone in one half, regular bearer and fruit fly resistant genotype because of its thick peel and high phenolic content in pulp (317.50 mg/100 g).

Varate Giduga (Acc. No. 21067; IC No. 418238) : A unique mango (Mangifera indica L.) variety

Varate Giduga is one of the unique variety from Sirsi region of Karnataka. The tree is Semi-circular shaped with dense foliage, leaves about 25cm long; dark green in colour with wavy margin. It is a very consistent and heavy producer. The fruit of this tree matures by mid-April and fruit has a distinctive yellow skin color on fruit exposed to the sun. The fruit shape is round, fruit weight ranged from 350-400 g, fruit length was 9.8 cm, fruit diameter was 9.2 cm, fruit thickness was 8.0cm and bisexual flowers were 16.53%. Biochemical constituents such as the total phenols (317.50 mg/100 g), flavonoids (5.79 mg/100g), carotenoids (1.46 mg/100 g) and acidity (0.19%) were recorded which suggests that these characters are unique as compared to other varieties. The fruit skin is rough and glossy in appearance and the fruit has little or no fiber. It is very delicious in taste with high pulp percentage (74.0%) and high TSS (23.4º B). The flesh color is orange. The fruits have deep orange firm pulp and very sweet with pleasant flavor. Besides,several other traits have drawn special attention to this mango variety as it has large sized fruits (Fig-1), late variety with very good taste, fruit can be cut into two halves by retaining the stone in one half, regular bearer and fruit fly resistant genotype because of its thick peel and high phenolic content in pulp (317.50 mg/100 g).

Anatomy and development of gynoecium in Tapiscia sinensis Oliv. and its implications for the origin of carpels

Tapiscia sinensis Oliv. (Tapisciaceae) is a rare tree endemic in China. Characteristic of its androdioecy is the coexistence of male and hermaphroditic flowers. Its bisexual flower bears five stamens surrounding the gynoecium, which is composed of a terminal style and an ovary at the base. The style has a bifid stigmata, which is hollow and longer than stamens. The ovary is syncarpous, unilocular, formed by two fused carpels, with a basal or subbasal placenta. Ovule is bitegmic, anatropous, borne on the placenta and supplied by an amphicribral vascular bundle arising directly from receptacle. The carpel wall is supplied by a collateral vascular bundle. The ovule’s position changes from initially inserted on the ovary base to later attached to the middle of the ovary wall due to unequal growth of the embryo sac. Based on the present observation and others, the implications of vascular system in Tapiscia for the evolution of carpel are discussed.

Zulustylis (Abildgaardieae, Cyperaceae) – a new genus from sub-Saharan Africa

The generic placement of two African species currently included in the genus Fimbristylis, F. hygrophila and F. variegata, has been contentious. These two species, which have been known for the past half century, are glabrous tufted perennials whose spikelets have semi-distichous to spiral glume arrangement, bisexual flowers, and a pistil with an enlarged and deciduous style base. While the two species fit the gross morphology of Fimbristylis, they differ in lacking the characteristic Kranz anatomy. We present phylogenetic inference of the Abildgaardieae based on DNA sequence data and map photosynthetic type. C4 photosynthesis has arisen twice in Abildgaardieae, in the Bulbostylis and the Fimbistylis clades, with a C3 clade (including Arthrostylis) sister to rest of tribe and a C3 grade (the two African Fimbristylis species, Trachystylis, Actinoschoenus) separating the two C4 clades. The new genus Zulustylis is described here, to segregate the two aberrant African Fimbristylis species, and its taxonomy presented.

Differential Expression Pattern Of MADS Box Genes in Floral Whorls of Garcinia indica

Flower formation is one of the main developmental stages in the life cycle of flowering plants that can be used as a model system to elucidate the molecular mechanics that control the developmental process in plants. In the present study, we investigated the floral homeotic and MADS box genes in the polygamadioecious tree Garcinia indica. The differential gene expressions of floral homeotic and MADS box genes in male, female, bisexual flowers, and floral organs such as sepal, petal, stamen, and carpel were studied by employing quantitative real-time, PCR-based assays. Of nine differentially expressed floral genes of the MADS box class, AGL11, the master control gene of ovule identity was found to be expressed 2-fold higher in female carpel whereas the ribosome protein involved in ovule development showed 2×106-fold high expression in the female carpel. The hierarchical clustering grouped these genes into four major clusters: cluster I comprised AGL11, AG, and PMADS2, cluster II comprised AP3 and AGL9, cluster III comprised SEP1 and ELFB, and cluster IV comprised AG pathway and ribosome protein. The clustering found was correlated with the quantitative and qualitative expression of genes.

Gene Interactions Regulating Sex Determination in Cucurbits.

The family Cucurbitaceae includes many economically important crops, such as cucumber (Cucumis sativus), melon (Cucumis melo), watermelon (Citrullus lanatus), and zucchini (Cucurbita pepo), which share homologous gene pathways that control similar phenotypes. Sex determination is a research hotspot associated with yield and quality, and the genes involved are highly orthologous and conserved in cucurbits. In the field, six normal sex types have been categorized according to the distribution of female, male, or bisexual flowers in a given plant. To date, five orthologous genes involved in sex determination have been cloned, and their various combinations and expression patterns can explain all the identified sex types. In addition to genetic mechanisms, ethylene controls sex expression in this family. Two ethylene signaling components have been identified recently, which will help us to explore the ethylene signaling-mediated interactions among sex-related genes. This review discusses recent advances relating to the mechanism of sex determination in cucurbits and the prospects for research in this area.

Inducing Sterility in Carolina Laurel Cherry Using Gamma Irradiation

Carolina laurel cherry (Prunus caroliniana) is native to the U.S. southeastern coastal plain from North Carolina westward to eastern Texas. The species has been planted extensively in the southeast as an ornamental tree or hedge. Unfortunately, carolina laurel cherry naturalizes readily and is now found in a variety of habitats, both natural and disturbed. Flowering occurs in the late winter/early spring before new leaves emerge and fruit ripens in the fall/winter. Fruit is eaten by migratory birds and seed is dispersed. Seedlings readily germinate in the understory of forests and landscapes in the spring. As there are a limited number of cultivars available, selections with improved form and sterility are needed for the landscape trade. In 2008, seed was collected and treated with Cobalt-60 gamma irradiation at rates ranging from 0 to 150 Gy. The lethal dose killing 50% of the seedlings (LD50) was between 50 and 100 Gy. Three sterile plants were selected in 2012 from the M1 (first generation of mutagen-treated seedlings) population totaling 62 seedlings. M2 (second-generation seedlings from M1 parents) seed was collected Fall 2012, and 1509 seedlings were grown to flowering size in containers. In 2014–15, 120 seedlings that showed no fruit production were planted in the field in Watkinsville, GA, for further evaluation. Ratings on field-grown plants in Dec. 2017 and 2018 showed that 73% and 78% of the plants, respectively, produced no fruit, whereas the remaining plants had minimal to heavy fruit set. Because carolina laurel cherry is andromonoecious, production of male and bisexual flowers was evaluated on 17 selections in 2018. Of 500 flowers evaluated per selection, the number of male flowers per plant ranged from 22 to 415 (4.4% to 83%). The number of racemes with all-male flowers on each selection ranged from 1 to 32. There were no significant correlations between the number of male flowers or number of all-male flowered racemes per plant and production of fruit. Approximately 5% of M2 seedlings remain seedless after 6 years of growth.

The ethylene receptors CpETR1A and CpETR2B cooperate in the control of sex determination in Cucurbita pepo

High-throughput screening of an ethyl methanesulfonate-generated mutant collection of Cucurbita pepo using the ethylene triple-response test resulted in the identification of two semi-dominant ethylene-insensitive mutants: etr1a and etr2b. Both mutations altered sex determination mechanisms, promoting conversion of female into bisexual or hermaphrodite flowers, and monoecy into andromonoecy, thereby delaying the transition to female flowering and reducing the number of pistillate flowers per plant. The mutations also altered the growth rate and maturity of petals and carpels in pistillate flowers, lengthening the time required for flowers to reach anthesis, as well as stimulating the growth rate of ovaries and the parthenocarpic development of fruits. Whole-genome sequencing allowed identification of the causal mutation of the phenotypes as two missense mutations in the coding region of CpETR1A and CpETR2B, each one corresponding to one of the duplicates of ethylene receptor genes highly homologous to Arabidopsis ETR1 and ETR2. The phenotypes of homozygous and heterozygous single- and double-mutant plants indicated that the two ethylene receptors cooperate in the control of the ethylene response. The level of ethylene insensitivity, which was determined by the strength of each mutant allele and the dose of wild-type and mutant etr1a and etr2b alleles, correlated with the degree of phenotypic changes in the mutants.