Gynoecious Lines Research Articles

Breeding of some cucumber hybrids according to some water stress criteria under plastic houses conditions

The study was conducted at the College of Agriculture - University of Anbar during three agricultural seasons, the autumn of 2021 and the spring and autumn of 2022, with the aim of producing F1 hybrids of cucumbers for greenhouses that are resistant to drought stress. Four Gynoecious lines were used, which were planted in the autumn season 2021, and 12 reciprocal and reverse hybrids were produced by full Diallel-crosses, and then planted in the spring season 2022 for the purpose of performance evaluation. Three hybrids were selected that were superior in characteristics of growth and yield with the best parents and a certified hybrid for comparison (Kanz) planted in the autumn season 2022 in an experiment carried out within the design of split plots with two factors according to the randomized complete block design (RCBD) and with three replications. The first factor included 6 genotypes and the second factor included two levels of moisture depletion at 25% and 50% of the available water calculated on the weight method, and the results were as follows. The results of evaluating the performance of the produced combinations showed the superiority of three hybrids, 4×1, 4×3, and 1×4, as they recorded distinct yields of 4.97, 4.38, and 4.20 kg plant-1 respectively. The same hybrids recorded a significant positive hybrid vigor of 34.84%, 18.91% and 14.03%, respectively. The same hybrids were introduced into the third season experiment with the two best parents, 4 and 1, and it appeared that the 4×1 hybrid excelled in plant yield, amounting to 4.06 kg plant-1, and recorded the best values in all studied stress tolerance criteria, as it reached 4.06 and 4.05 in MP and GMP criteria respectively, and in SSI, YR and TOL criteria, it recorded values of 0.70, 0.10 and 0.42, respectively, and in STI, HM, YI, and DI criteria, values of 1.22, 4.05, 1.22, and 0.94, respectively while the parent P1 recorded the lowest values in stress tolerance criteria. From study concluded that the differences in the chemical responses and the amount of production of cucumber, due to the genetic variation of the genotypes under study. Three locally produced hybrids achieved superiority in yield during high moisture depletion. We recommend preserving parents 1 and 4 due to their distinctiveness and using them to produce distinctive hybrids.

A point mutation in MC06g1112 encoding FLOWERING LOCUS T decreases the first flower node in bitter gourd (Momordica charantia L.).

In Cucurbitaceae crops, the first flower node (FFN) is an important agronomic trait which can impact the onset of maturity, the production of female flowers, and yield. However, the gene responsible for regulating FFN in bitter gourd is unknown. Here, we used a gynoecious line (S156G) with low FFN as the female parent and a monoecious line (K8-201) with high FFN as the male parent to obtain F1 and F2 generations. Genetic analysis indicated that the low FFN trait was incompletely dominant over the high FFN trait. A major quantitative trait locus (QTL)-Mcffn and four minor effect QTLs-Mcffn1.1, Mcffn1.2, Mcffn1.3, and Mcffn1.4 were detected by whole-genome re-sequencing-based QTL mapping in the S156G×K8-201 F2 population (n=234) cultivated in autumn 2019. The Mcffn locus was further supported by molecular marker-based QTL mapping in three S156G×K8-201 F2 populations planted in autumn 2019 (n=234), autumn 2020 (n=192), and spring 2022 (n=205). Then, the Mcffn locus was fine-mapped into a 77.98-kb physical region on pseudochromosome MC06 using a large S156G×K8-201 F2 population (n=2,402). MC06g1112, which is a homolog of FLOWERING LOCUS T (FT), was considered as the most likely Mcffn candidate gene according to both expression and sequence variation analyses between parental lines. A point mutation (C277T) in MC06g1112, which results in a P93S amino acid mutation between parental lines, may be responsible for decreasing FFN in bitter gourd. Our findings provide a helpful resource for the molecular marker-assisted selective breeding of bitter gourd.

Genetic Diversity and Population Structure Analyses in Bitter Gourd (Momordica charantia L.) Based on Agro-Morphological and Microsatellite Markers.

Bitter gourd (Momordica charantia L.) is an important vine crop of the Cucurbitaceae family and is well known for its high nutritional and medicinal values. However, the genetic variation remains largely unknown. Herein, 96 diverse bitter gourd genotypes were undertaken for diversity analysis using 10 quantitative traits, and 82 simple sequence repeat (SSR) markers. Out of 82 SSRs, 33 were polymorphic and the mean polymorphism information content (PIC) value was 0.38. Marker, JY-003 revealed a maximum (0.81) PIC value and, the number of alleles per locus ranged from 2 to 7 (average 3.46). The value of gene diversity showed the presence of a significant level of polymorphism among these genotypes. The unweighted pair group method (UPGMA) cluster analysis grouped the genotypes into two major clusters of which Cluster I comprised mostly small and medium-fruited genotypes of both M. charantia var. charantia and M. charantia var. muricata, whereas Cluster II included mostly long and extra-long fruited genotypes. Furthermore, these genotypes were divided into six distinct groups based on population structure analysis. The diversity analysis based on 10 quantitative traits revealed that earliness and high-yielding ability were exhibited by the predominantly gynoecious line DBGS-21-06 followed by DBGS-48-00. The principal component analysis (PCA) revealed that the first two components exhibited more than 50% of the total genetic variation. The present study deciphered a higher magnitude of agro-morphological and genetic diversity in 96 bitter gourd genotypes. Therefore, trait-specific genotypes identified in this study could be utilized in breeding programmes directed towards the development of improved cultivars and hybrids of bitter gourd.

Fine mapping and candidate gene analysis of gynoecy trait in chieh-qua (Benincasa hispida Cogn. var. chieh-qua How).

Gynoecy demonstrates an earlier production of hybrids and a higher yield and improves the efficiency of hybrid seed production. Therefore, the utilization of gynoecy is beneficial for the genetic breeding of chieh-qua. However, little knowledge of gynoecious-related genes in chieh-qua has been reported until now. Here, we used an F2 population from the cross between the gynoecious line 'A36' and the monoecious line 'SX' for genetic mapping and revealed that chieh-qua gynoecy was regulated by a single recessive gene. We fine-mapped it into a 530-kb region flanked by the markers Indel-3 and KASP145 on Chr.8, which harbors eight candidate genes. One of the candidate genes, Bhi08G000345, encoding networked protein 4 (CqNET4), contained a non-synonymous SNP resulting in the amino acid substitution of isoleucine (ATA; I) to methionine (ATG; M). CqNET4 was prominently expressed in the female flower, and only three genes related to ethylene synthesis were significantly expressed between 'A36' and 'SX.' The results presented here provide support for the CqNET4 as the most likely candidate gene for chieh-qua gynoecy, which differed from the reported gynoecious genes.

Fine-mapping and candidate gene analysis of the Mcgy1 locus responsible for gynoecy in bitter gourd (Momordica spp.).

The Mcgy1 locus responsible for gynoecy was fine-mapped into a 296.94-kb region, in which four single-nucleotide variations and six genes adjacent to them might be associate with sex differentiation in bitter gourd. Gynoecy plays an important role in high-efficiency hybrid seed production, and gynoecious plants are excellent materials for dissecting sex differentiation in Cucurbitaceae crop species, including bitter gourd. However, the gene responsible for gynoecy in bitter gourd is unknown. Here, we first identified a gynoecy locus designated Mcgy1 using the F2 population (n = 291) crossed from the gynoecious line S156G and the monoecious line K8-201 via bulked segregant analysis with whole-genome resequencing (BSA-seq) and molecular marker linkage analysis. Then, a large S156G × K8-201 F2 population (n = 5,656) was used for fine-mapping to delimit the Mcgy1 locus into a 296.94-kb physical region on pseudochromosome MC01, where included 33 annotated genes different from any homologous gynoecy genes previously reported in Cucurbitaceae species. Within this region, four underlying single-nucleotide variations (SNVs) that might cause gynoecy were identified by multiple genomic sequence variation analysis, and their six neighbouring genes were considered as potential candidate genes for Mcgy1. Of these, only MC01g1681 showed a significant differential expression at two-leaf developmental stage between S156G and its monoecious near-isogenic line S156 based on RNA sequencing (RNA-seq) and qRT-PCR analyses. In addition, transcriptome analysis revealed 21 key differentially expressed genes (DEGs) and possible regulatory pathways of the formation of gynoecy in bitter gourd. Our findings provide a new clue for researching on gynoecious plants in Cucurbitaceae species and a theoretical basis for breeding gynoecious bitter gourd lines by the use of molecular markers-assisted selection.

A novel mutation in ACS11 leads to androecy in cucumber

Sex determination in plants gives rise to unisexual flowers. A better understanding of the regulatory mechanism underlying the production of unisexual flowers will help to clarify the process of sex determination in plants and allow researchers and farmers to harness heterosis. Androecious cucumber (Cucumis sativus L.) plants can be used as the male parent when planted alongside a gynoecious line to produce heterozygous seeds, thus reducing the cost of seed production. The isolation and characterization of additional androecious genotypes in varied backgrounds will increase the pool of available germplasm for breeding. Here, we discovered an androecious mutant in a previously generated ethyl methanesulfonate (EMS)-mutagenized library of the cucumber inbred line ‘406’. Genetic analysis, whole-genome resequencing, and molecular marker-assisted verification demonstrated that a nonsynonymous mutation in the ethylene biosynthetic gene 1-AMINOCYCLOPROPANE-1-CARBOXYLATE SYNTHASE 11 (ACS11) conferred androecy. The mutation caused an amino acid change from serine (Ser) to phenylalanine (Phe) at position 301 (S301F). In vitro enzyme activity assays revealed that this S301F mutation leads to a complete loss of enzymatic activity. This study provides a new germplasm for use in cucumber breeding as the androecious male parent, and it offers new insights into the catalytic mechanism of ACS enzymes.

Genetic assessments, dominance estimates of economic traits of gynoecious cucumber (Cucumis sativus) under Himalayas

In India generally monoecious and cross-pollinated cucumber (Cucumis sativus L.) hybrids/varieties are grown. The use of stable gynoecious cucumber varieties/hybrids would increase the productivity of cucumber in India. In the past, despite improvement in monoecious cucumber varieties/hybrids, little effort has been done into the development of stable gynoecious hybrids. To address this issue 3 genetically diverse gynoecious lines and improvement, and 6 testers were crossed in line × tester fashion to develop 18 crosses during 2017. These 18 crosses along with 9 parents evaluated at the Krishi Vigyan Kendra, Kandaghat, Himachal Pradesh and Dr. YSPUHF, Solan, Himachal Pradesh during pre-kharif season 2018–19 to determine the mode of gene action, combining ability, extent heterosis and potence ratio for 12 quantitative traits. Experimental results depicted that the dominant component of variance (σ2S) was found higher than the additive component of variance (σ2S) for all the traits indicating a predominant role of non-additive gene action governing yield and its contributing traits during both the years. Gynoecious inbred lines KTG-40, 2870G and testers K-90, UHF-16 were found most promising general combiners for fruit yield. The cross combination KTG-40 × K-90 and 2870G × K-90 isolated based on heterosis manifested and SCA effects. Further, the performance of top 7 heterotic crosses illustrate the presence of overdominance in most of the crosses for traits under study, suggesting the importance of heterosis breeding for the development of early, high-yielding, disease tolerance stable gynoecious hybrids in cucumber.

Evaluation of various monoecious and gynoecious genotypes of bitter gourd (Momordica charantiaL.) for yield and attributing traits

Bitter gourd is one of the significant cucurbitaceous crops with high economic importance. Exploitation of novel traits like gynoecism in particular and yield in general can substantially contribute to the future crop improvement programmes in bitter gourd. In the present investigation, 38 monoecious lines and 6 gynoecious lines were evaluated pertaining to 9 important quantitative morphological traits at the experimental farm of ICAR-Indian Institute of Vegetable Research, Varanasi across two seasons of spring-summer and kharif. From the mean performance analysis of all the accessions under study, VRBTG-5 was found to be the best performer among the monoecious lines, whereas, Gy-323 was the best peforming gynoecious line concerning the yield per plant (g). Moreover, for all other major yield-contributing traits, both of these lines have exhibited superior performance over all other accessions across the seasons and can be exploited further in crop improvement programmes.

Candidate gene based SSR and SNP markers for gynoecy in bitter gourd (Momordica charantia L.).

Even though the bitter gourd hybrids are shown to have significant heterosis for many of the economic traits, processes such as manual bagging and hand pollination make the hybrid seed production labour-intensive. Use of gynoecious line as female parent makes hybrid seed production more economical. This work was performed with the objective to identify the candidate gene based molecular markers for gynoecy in bitter gourd. Seven putative genes for flowering and sex expression, isolated from the monoecious (MC-136) and gynoecious (KAU-MCGy-101) bitter gourd accessions, were sequence characterized. MADS-box transcription factor genes AG6 and McAG2 had nucleotide polymorphisms at five sites each and were potential candidates for marker development. An In/Del polymorphism of 48bp ([TC]24) in AG6 gene was used to develop an SSR marker and a transition mutation of [A/G] in this gene was used to develop a set of SNP markers. These markers have developed distinct polymorphism between the monoecious and gynoecious genotypes and were found suited for the marker assisted selection. MADS box transcription factor genes AG6 and McAG2 are identified as candidates for sex expression in bitter gourd. Based on the InDels and transition in the intronic region of AG6, SSR marker BGAG6 and an SNP marker set segregating with the sex forms were developed. The markers have been validated using four other monoecious lines and are routinely used in our bitter gourd hybrid seed production programmes.

Integrated transcriptome and hormone analyses provide insights into silver thiosulfate-induced "maleness" responses in the floral sex differentiation of pumpkin (Cucurbita moschata D.).

The perfect mating of male and female flowers is the key to successful pollination. The regulation of ethylene with chemicals is a good option for inducing staminate or female flowers. Silver thiosulfate is often used to induce the formation of male flowers in subgynoecious and gynoecious crops, which is important to maintain their progenies. However, its effects on flower sex differentiation in pumpkin (Cucurbita moschata Duch.) and the underlying mechanism remain unclear. In this study, the application of silver thiosulfate to pumpkin seedlings significantly delayed the occurrence of the first female flower and increased the number of male flowers. We next investigated the underlying mechanism by employing transcriptome and endogenous hormone analyses of the treated plants. In total, 1,304 annotated differentially expressed genes (DEGs)were identified by comparing silver thiosulfate-treated and control plants. Among these genes, 835 were upregulated and 469 were downregulated. The DEGs were mainly enriched in the phenylpropanoid biosynthesis and metabolism pathways (phenylalanine ammonia-lyase, peroxidase) and plant hormone signal transduction pathways (auxin signaling, indole-3-acetic acid-amido synthetase, ethylene response factor). Silver thiosulfate significantly reduced the levels of 2-oxindole-3-acetic acid, para-topolin riboside, dihydrozeatin-O-glucoside riboside, and jasmonoyl-l-isoleucine but increased the levels of trans-zeatin-O-glucoside, cis-zeatin riboside, and salicylic acid 2-O-β-glucoside. The levels of auxin and jasmonic acid were decreased, whereas those of salicylic acid were increased. Different trends were observed for different types of cytokinins. We concluded that silver thiosulfate treatment not only affects the expression of auxin synthesis and signaling genes but also that of ethylene response factor genes and regulates the levels of auxin, salicylic acid, jasmonic acid, and cytokinins, which together might contribute to the maleness of pumpkin. This study provides useful information for understanding the mechanism underlying the effect of silver thiosulfate on floral sex differentiation in pumpkin, a widely cultivated vegetable crop worldwide, and gives a production guidance for the induction of maleness using STS for the reproduction of gynoecious lines of Cucurbitaceae crops.

Generation mean analysis of important yield traits in Bitter gourd (Momordica charantia)

Generation mean analysis study in bitter gourd was undertaken using six basic generations viz. P1, P2, F1, F2, B1 and B2 population derived from crossing gynoecious line (IIHRBTGy - 491) with two monoecious lines (IIHR Sel -19 -1 and IIHR Sel-78-4). The gynoecious parent was superior for node for first female flowering, number of fruits and yield/plant whereas the monoecious parents were superior for fruit length, fruit diameter and fruit weight. The superior performance of F1 over better parent indicated over-dominance of these traits. F2 plants were significantly diverse. B1 and B2 population exhibited mean value closure to their recurrent parents. Significance of one or more scaling tests, i.e. A, B, C and D in most of the traits revealed the presence of epistasis in both the crosses except for node bearing 1st male flower. Days to 1st female flower opening, node bearing 1st female flower, fruit diameter and yield showed presence of duplicate epistasis whereas days to 1st male flower opening, number of fruits per plant, fruit length and fruit weight showed complimentary epistasis in IIHRBTGy - 491 × IIHR Sel -19 -1 cross. Node bearing 1st female flower, fruit length, fruit diameter and yield showed presence of duplicate epistasis whereas days to 1st female flower opening, days to 1st male flower opening, number of fruits and fruit weight showed complimentary epistasis in IIHRBTGy - 491× IIHR Sel-78-4 cross. Additive gene action may be predominant for inheritance of node bearing 1st male flower.

Potential of Gynoecious Line in Generating Superior Heterotic Hybrids in Bitter Gourd (Momordica charantia L.)

An experiment was designed to find out the extent of heterosis in bitter gourd using gynoecious line, KAU- MCGy-101 and three monoecious lines viz., Preethi, Priyanka, and MC133. Hybrids were generated by both direct and reciprocal crosses. All the hybrids exhibited earliness in terms of days to first female flower opening, node bearing first female flower, and days to first harvest. The hybrid KAU-MCGy-101 × Priyanka exhibited significantly higher heterosis with regard to heterobeltiosis (-16.03 %) and standard heterosis (-18.63 %) for days to first female flower opening. All the six hybrids manifested significant standard heterosis for sex ratio in the desirable negative direction, ranged from 44.25 to -55.52 %. The highest yield was recorded in the hybrid KAU-MCGy-101 × Priyanka (22.88 t/ha) and was followed by KAU-MCGy-101 × Preethi (20.42 t/ha) and KAU-MCGy-101 × MC 133 (20.05 t/ha). Heterobeltiosis for yield (t/ha) varied from 14.72 to 57.85 % and the standard heterosis ranged between 37.59 to 89.31 %. The best performing hybrids were KAU-MCGy-101 × Preethi, KAU-MCGy-101 × Priyanka, and KAU-MCGy-101 × MC 133 with respect toearliness, number of fruits per plant, and yield. Thus, the superiority of hybrids having gynoecious line as a maternal parent is prominent in the present study.

Characterization and maintenance of promising gynoecious bitter gourd line through hormonal regulation and micropropagation

New gynoecious bitter gourd line, KAU-MCGy-101 identified from Kerala Agricultural University, India, was morphologically characterized. Silver thiosulphate (STS) was used for altering the sex expression of gynoecious line. STS induced hermaphrodite flowers in gynoecious plants and maximum number of hermaphrodite flowers was in plants receiving single spray at 200 ppm after emergence of first female flower. F1 was generated by crossing with monoecious variety Preethi and all the hybrids were monoecious in nature. Expression of gynoecious character in the sib-mated gynoecious inbred and monoecy in F1 hybrids, indicate the recessive nature of gynoecy in bitter gourd. Gynoecious inbred was also maintained through micropropagation. The shoot tip explants cultured on MS medium supplemented with 2.0 mgL−1 BA followed by 1.5 mgL−1 BA have given the highest shoot initiation response in 20.75 days. Multiple shoots, up to 5.50 per explant, were induced on MS medium with 2.0 mgL−1 BA and microshoots elongated best with 0.5 mgL−1 IAA + 0.5 mgL−1 NAA. Best in vitro rooting was on half strength MS medium with 3.0 gL−1 activated charcoal and 1.0 mgL−1 IBA. The gynoecious expression was found to be stable in tissue culture regenerated progenies.

Floral biology studies in cucumber (Cucumis sativus L.)

Artificial pollination of vegetable crops necessitates the knowledge of crop's floral biology. In this aspect present investigations were carried out, to gather the information on the floral biology of monoecious (K-75 and UHF-CUC-101) and gynoecious (GYNO-1 and GYNO-2) varieties of cucumber at the Experimental Research Farm, Department of Vegetable Science, Dr. YSPUHF Nauni, Solan (HP) during Kharif, 2016. The experiment was laid out in a RCBD with three replications. The observations were recorded on time of anthesis, dehiscence, pollen viability (%), stigma receptivity and node number bearing first female flower. The experimental results showed that anthesis started at 6AM and completed by 8AM with the maximum anthesis between 6AM to 7AM in monoecious varieties whereas, in gynoecious varieties it was maximum upto 6:00AM in both open and controlled conditions and similar pattern was observed for dehiscence. Dehiscence occurs soon after anthesis. Maximum pollen viability was recorded on the day of anthesis and viability of pollen under refrigerated condition did not decrease as rapidly as it was under room temperature condition with the duration of pollen storage. Maximum stigma receptivity was noticed at anthesis time and pollination during this interval recorded maximum fruit set. Gynoecious lines were earlier in flowering and fruiting than monoecious varieties.

Mean performance of gynoecious cucumber hybrids in sub-tropical climate of eastern India

A field study was conducted in zaid season of 2019 to investigate the mean performance of 27 diverse genotypes (5 parents, 20 F1 crosses and 2 standard checks) of cucumber for earliness, growth and yield attributing traits following full diallel mating design by utilizing two gynoecious lines, two monoecious lines and one parthenocarpic gynoecious line. Analysis of variance in randomized block design suggested that there were significant differences among the genotypes for 10 quantitative traits out of 13 traits used in the study. Results showed that gynoecious hybrids (involving both gynoecious parents) expressed earliness for flowering and fruiting, i.e., took minimum days to first female flower anthesis, node to first female flower, and days to first fruit harvest. The result of the present study showed that hybrid BRPCU-8 × BRGCU-4 was found to be better for earliness related traits viz., days to first flowering, first fruit harvest, and node to first female flower. Hybrid BRCU-10 × BRCU-1 was the better performer for fruit morphological traits viz., fruit length, fruits per plant, average fruit weight and yield-related traits; hybrid BRCU-1 × BRPCU-8 was superior for vegetative growth traits, namely crop duration and vine length. Monoecious cucumber hybrids involving both monoecious parents such as Punjab Naveen × BRCU-1 outperformed gynoecious hybrids involving gynoecious parents for growth characteristics such as vine length and crop duration. Overall, hybrid BRGCU-10 × BRCU-1 was observed as the best genotype.

Mapping and linkage analysis of epistatic QTLs for gynoecious trait (F) in cucumber (Cucumis sativus L.)

ABSTRACT The QTL mapping for gynoecy in cucmber (Cucumis sativus L.)was carried out by using backcross populations (BC1F2 & BC1F3) of a cross using two inbred lines; one monoecious with multiple (≥ 5) lateral branching habit cv. Pusa Uday (Indian slicing type) and gynoecious exotic line Gy14 (American pickling type) with few lateral branches (1–2). QTL detection was performed by employing QTL Ici mapping software (version 4.1) of the two mapping populations. We detected seven gynoecious QTLs in two genomic regions (chromosome 5 and 6), on which three significant QTLs (qGyn 5.1, qGyn 6.5 and qGyn 6.6) had higher LOD score (10.5, 26.2, and 24.5) and phenotypic variance (5.9, 14.5 and 14.5%) in BC1F2 population. However, two significant QTLs (qGyn 5.1 and qGyn 6.1) accounted for gynoecism which could explain 22.90 and 12.88% of the phenotypic variation with the LOD score of 15.86 and 11.82 in linkage group 5 and 6, respectively in BC1F3 population. Out of 82 simple sequence repeats (SSR) markers, three (SSR00233, SSR15516 and SSR13251) was found tightly linked and flanked to gynoecious trait QTLs (qGyn6.5 and qGyn6.6) in BC1F2 population at <1.5 cM, which could be used for marker-assisted selection (MAS) in cucumber improvement programmes. In order to increase the productivity of Indian cucumber, the introgressed Indian gynoecious cucumber lines derived from an exotic genetic background using MAS may be directly used as a variety or parent of hybrid.

Gynoecy instability in cucumber (Cucumis sativus L.) is due to unequal crossover at the copy number variation-dependent Femaleness (F) locus

Cucumber, Cucumis sativus is an important vegetable crop, and gynoecy has played a critical role in yield increase of hybrid cucumber production. Cucumber has a unique genetic system for gynoecious sex expression, which is determined by the copy number variation (CNV)-based, dominant, and dosage-dependent femaleness (F) locus. However, this gynoecy expression system seems unstable since monecious plants could often be found in F-dependent gynoecious cucumber inbreds. We hypothesized that gynoecy instability (gynoecy loss) may be due to unequal crossing over (UCO) during meiosis among repeat units of the CNV. In this study, using high throughput genome resequencing, fiber-FISH and genomic qPCR analyses, we first confirmed and refined the structure of the F locus, which was a CNV of a 30.2-kb tandem repeat. Gynoecious plants contained three genes: CsACS1, CsACS1G, and CsMYB, of which CsACS1G is a duplication of CsACS1 but with a recombinant distal promoter that may contribute to gynoecy sex expression. In two large populations from self-pollinated gynoecious inbred lines, ‘gynoecy loss’ mutants were identified with similar mutation rates (~0.12%). We show that these monecious mutants have lost CsACS1G. In addition, we identified gynoecious lines in natural populations that carry two copies of CSACS1G. We proposed a model to explain gynoecy instability in F-dependent cucumbers, which is caused by UCO among CSACS1/G units during meiosis. The findings present a convincing case that the phenotypic variation of an economically important trait is associated with the dynamic changes of copy numbers at the F locus. This work also has important implications in cucumber breeding.

Ứng dụng chỉ thị phân tử SSR13251 và SSR18956 trong nhận diện giới tính hoa dưa leo

In the cucumber hybrid breeding process, the use of gynoecious lines as a maternal line has many advantages such as decreasing the breed confusion caused by self-pollination, requiring lesss labor for removing male or covering female flowers, making use of insects for pollinating, and ensuring high yield. Molecular marker is a useful tool to early and accurately identify cucumber gynoecious lines. This study investigated the correlation between the two molecular markers e.g. SSR13251 and SSR18956 with the sex of flowers of 50 pure cucumber samples (19 gynoecious lines, 31 monoecious lines). PCR reactions were performed to amplify the target sequences. The results showed that SSR13251 marker did not distinguish the different cucumber lines. Meanwhile, the PCR product size of SSR18956 marker differed among cucumber lines that helped to exactly identify the gynoecious lines. After screening 50 pure cucumber samples with SSR18956 marker, the compatibility between this marker and the sexual phenotype of cucumber flowers was 84%. Therefore, the SSR18956 marker could be a potential marker to identify the gynoecious lines in cucumber.

Exploitation of heterosis in cucumber for earliness, yield and yield contributing traits under protected structure

The research was conducted at Vegetable Research Centre, Gobind Ballav Pant University of Agriculture and Technology, Pantnagar, Uttarakhand during 2015-16. Fourteen parental lines including eight parthenocarpic lines, three gynoecious lines and three testers of monoecious lines were used to develop 33 F1 hybrids of cucumber by Line × Tester mating design to determine the magnitude of heterosis for earliness, yield and yield related traits during March-June and August –December in protected structures. The mean sum of squares were highly significant for all the characters indicated a wide genetic variation for the characters studied and the Parthenocarpic parental lines (PCUCP-2, PCUCP-3 and PCUCP-8) and monoecious parent (Pant Khira-1, PCUC-8, and PCUC-25) were observed to be the three top performing parents for yield per plant. Appreciable heterosis was observed over better parent and standard parent for most of the characters studied. The best F1 hybrid PCUCP-4 × PCUC-8, promising in both E1 and E2 showing 835% and 453% heterosis, respectively for yield per plant followed by PCUCP-3 x PCUC-8 (769%, 559%) for average fruit weight and PCUCP-1 × PCUC-8 (-98.77%, -95.53%) for node number to first female flower over standard check Pant Khira-1. So, PCUCP-4 × PCUC-8 can be tested as most stable genotype across the spring –summer and kharif-winter environments under polyhouse condition in northern plains and three hybrids viz., PCUCP-4 × PCUC-8, PCUCP-3 × PCUC-8 and PCUCP-1 × PCUC-8 may be exploited for commercial cultivation.

Gene action and combining ability analysis for horticultural traits in bitter gourd

All traits exhibited higher variance due to sca than their respective gca variance indicating the predominanceof non-additive genes effects in the expression of all the traits. Among parents, gynoecious line PDMGy-201 wasgood general combiner for earliness, sex ratio and flesh thickness, S-2 for fruit length, S-54 for fruit diameter,Pusa Do Mausami (PDM) for average fruit weight and Pusa Aushadhi (PA) for number of fruits and total yieldper plant. The hybrids which showed best sca effects were PDMGy201 × S-2 for earliness and sex ratio, S-54× S-57 for fruit weight and flesh thickness and PDMGy201 × Pusa Vishesh (PV) for number of fruits and totalyield per plant. The role of cumulative effect of additive and additive × additive gene effects were found in thecrosses PDMGy-201 × S-54 for number of days to first female flower and S-2 × PDM for yield per plant which hadhigh per se performance with significant sca effects and both the parents of these crosses were good generalcombiners. The role of dominant gene action denoted in high performed crosses resulted from a combinationbetween one good and one poor general combiner parent such as PDMGy-201 × S-2 for sex ratio, S-32 × PA forfruit length, S-54 × S-57 for fruit diameter, S-54 × S-57 for flesh thickness, S-2 × PA for number of fruits per plant,PDMGy-201 × PDM for average fruit weight and PDMGy-201 × PV for yield per plant. Almost all hybrids withhigher sca effects have at least one of the most outstanding parental lines, PDMGy-201, PDM, S-2, PV and PA.