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In Brassica oleracea, heterosis is the most efficient tool providing impetus to hybrid vegetable industry. In this context, we presented the first report on identifying superior heterotic crosses for yield and commercial traits in cauliflower involving cytoplasmic male sterile (CMS) and doubled haploid (DH) lines as parents. We studied the suitability of genomic-SSRs and EST-SSRs based genetic distance (GD) and agronomic trait based phenotypic distance (PD) for predicting heterosis in F1 hybrids using CMS and DH based parents. 120 F1 hybrids derived from 20Ogura based CMS lines and 6 DH based testers were evaluated for 16 agronomic traits along with the 26 parental lines and 4 commercial standard checks. The genomic-SSRs and EST-SSRs based genetic structure analysis grouped the 26 parental lines into 4 distinct clusters. The CMS lines Ogu118-6A, Ogu33A, Ogu34-1A were good general combiner for developing early maturity hybrids. The SCA effects were significantly associated with heterosis suggesting non-additive gene effects for the heterotic response of hybrids. Less than unity value of σ2A/D coupled with σ2gca/σ2sca indicated the predominance of non-additive gene action in the expression of studied traits. The correlation analysis of genetic distance with heterosis for commercial traits suggested that microsatellites based genetic distance estimates can be helpful in heterosis prediction to some extent.

The present study analysed the molecular and agro-morphological diversity in a set of 92 diverse cauliflower genotypes and two each of cabbage and broccoli. Field evaluation of the genotypes was done in randomized block design (RBD) at two locations ( i . e . IARI, New Delhi and ICAR-RC-NEH Region, Barapani) during Rabi 2019-20. Genotypes showed variation for all the eight observed traits at both locations and, the differences in early and snowball groups were distinct. Pusa Meghna, DC-33-8, Pusa Kartiki and CC-14 were earliest for curd initiation. Genotypes showed higher values for curd traits at Delhi. Molecular diversity was detected with 90 polymorphic simple sequence repeats (SSR). Number of alleles ranged from 1 to 9 with mean value of 2.16 and the highest polymorphic information content (PIC) value was observed for primer BoGMS0742 (0.68) with a mean value of 0.18. Cluster analysis using agro-morphological traits substantiated classification of the genotypes for maturity groups. However, SSR analysis revealed four clusters and with a composite pattern of genotype distribution. STRUCTURE analysis also supported the admixture and four subpopulations. The studyindicates for introgression of genetic fragments across the maturity groups, thereby, potential for use in further genetic improvement and heterosis breeding.

Key message Overview of the current status of GMS and CMS systems available in Brassica vegetables, their molecular mechanism, wild sources of sterile cytoplasm and exploitation of male sterility in hybrid breeding. The predominantly herbaceous family Brassicaceae (crucifers or mustard family) encompasses over 3700 species, and many of them are scientifically and economically important. The genus Brassica is an economically important genus within the tribe Brassicaceae that comprises important vegetable, oilseed and fodder crops. Brassica vegetables display strong hybrid vigor, and heterosis breeding is the integral part in their improvement. Commercial production of F 1 hybrid seeds in Brassica vegetables requires an effective male sterility system. Among the available male sterility systems, cytoplasmic male sterility (CMS) is the most widely exploited in Brassica vegetables. This system is maternally inherited and studied intensively. A limited number of reports about the genic male sterility (GMS) are available in Brassica vegetables. The GMS system is reported to be dominant, recessive and trirecessive in nature in different species. In this review, we discuss the available male sterility systems in Brassica vegetables and their potential use in hybrid breeding. The molecular mechanism of mt-CMS and causal mitochondrial genes of CMS has been discussed in detail. Finally, the exploitation of male sterility system in heterosis breeding of Brassica vegetables, future prospects and need for further understanding of these systems are highlighted.

Cucumber is a highly preferred salad vegetable, but it is highly sensitive to drought due to its high water requirement. Therefore, the identification of genomic regions will be highly effective in understanding drought-tolerance breeding programs. In our study, an association panel of 86 diverse cucumber breeding lines was used to detect significant marker-trait associations (MTAs) through the Genome-wide Association Study (GWAS). Phenotyping was done under two different stress conditions – water-deficit and PEG-stimulated stress in the hydroponic medium by measuring different shoot and root system architecture-related traits such as Seedling survivability percentage (SSP), Shoot length (SL), Total root length (TRL), Root volume (RV), Root surface area (RSA), Average root diameter (ARD), Number of root tips (NRT), forks (NRF) and crossings (NRC). Analysis of variance and descriptive statistics revealed the significant differences among these studied traits, and thus, these data can be processed for further association analysis. Through GWAS, a total of 52 stable SNPs were identified for all the traits except for ARD, and five were linked to more than one trait, i.e. pleiotropic influence. The maximum stable SNPs were detected on Chromosome 3, followed by Chromosome 7 and Chromosome 5. Further, in silico search of these stable SNPs against the C. s. var. sativus reference genome revealed the presence of 12 SNPs at or near (1 kb) the genomic regions encoding for putative candidate genes (e.g. RBPs , ARFs , WDRs , etc.) and transcription factors ( bHLH , ZNF , LRR-RLK ) which are highly relevant for further in-depth functional analysis of cucumber root system. In future, these stable SNPs will be highly useful for marker-assisted transfer of the genes/QTLs to develop climate-smart drought-resilience cultivars.

Bitter gourd ( Momordica charantia L.) is an economically important vegetable crop grown in tropical parts of the world. In this study, a high-density linkage map of M. charantia was constructed through genotyping-by-sequencing (GBS) technology using F 2:3 mapping population generated from the cross DBGy-201 × Pusa Do Mausami. About 2013 high-quality SNPs were assigned on a total of 20 linkage groups (LGs) spanning over 2329.2 CM with an average genetic distance of 1.16 CM. QTL analysis was performed for six major yield-contributing traits such as fruit length, fruit diameter, fruit weight, fruit flesh thickness, number of fruits per plant and yield per plant. These six quantitative traits were mapped with 19 QTLs (9 QTLs with LOD > 3) using composite interval mapping (CIM). Among 19 QTLs, 12 QTLs derived from ‘Pusa Do Mausami’ revealed a negative additive effect when its allele increased trait score whereas 7 QTLs derived from ‘DBGy-201’ revealed a positive additive effect when its allele trait score increased. The phenotypic variation (R 2 %) elucidated by these QTLs ranged from 0.09% (fruit flesh thickness) on LG 14 to 32.65% (fruit diameter) on LG 16 and a total of six major QTLs detected. Most QTLs detected in the present study were located relatively very close, maybe due to the high correlation among the traits. This information will serve as a significant basis for marker-assisted selection and molecular breeding in bitter gourd crop improvement.

Cucumber is one of the important salad vegetables cultivated worldwide and is highly sensitive to water stress. However, till date, no drought-tolerant cucumber genotypes have been identified using a large set of diverse germplasms via high-throughput phenotyping methods. This study involved screening of a large set of Indian-origin cucumber germplasms for drought stress response using water-deficit and polyethylene glycol (PEG)-induced stress conditions in hydroponic solutions. Water-deficit and PEG-induced methods were optimized before screening of an entire set of germplasm for key physiological traits. Pearson’s correlation revealed non-significant difference between these two methods. Hierarchical cluster analysis and drought tolerance matrix score (DTMS) were calculated based on key physiological traits for ranking of the genotypes. Furthermore, the entire set of genotypes was exposed to water stress (< 8% soil moisture) for 15 d under field conditions to record yield-related traits for validation of the hydroponic-based ranking. Finally, eight tolerant genotypes were identified with high seedling survivability percentage, minimum reduction in root–shoot dry weight, fresh weight and water content percentage, highest DTMS and minimum yield reduction under field stress conditions compared with seven identified sensitive genotypes. The optimized rapid phenotyping method and identified drought-tolerant lines will be instrumental in understanding the physiological and molecular basis of drought tolerance and in facilitating the development of climate-resilient improved cucumber genotypes in the future.

Cucumber is an important vegetable crop that suffers from significant yield loss because of sub-optimal temperatures during the growing season. High temperature affects the plant's health and reduces the quality and quantity of the final harvest. Huge diversity in terms of different economically important traits, including wide temperature adaptation, is recorded in indigenous cucumber germplasm because of its Indian origin. It is necessary to identify the key traits and genotypes with the contrasting response from a large set of germplasm associated with heat stress response for understanding the physio-biochemical and molecular network associated with heat tolerance. A set of 123 germplasm was evaluated in a growth chamber with temperature stress treatment (40 °C/35 °C) for two subsequent seasons. Besides, 10 selected genotypes based on their response in the seedling stage were grown under natural field conditions with high temperatures to validate the physio-biochemical response in the seedling stage and yield parameters in the reproductive stage. Among the different parameters, slow degradation of chlorophyll, higher anti-oxidant enzyme activity, higher membrane stability index, and higher canopy temperature depression were identified as key traits explaining the heat stress response in cucumbers. Besides, the photosynthetic activities of the tolerant genotypes at the reproductive stage were also higher under field conditions, resulting in higher economic yield. Heat tolerance index was developed for 123 genotypes for seven physiological traits recorded in the present study. The optimised screening technique in the seedling stage and their validation for yield response under natural field facilitated the evaluation of a large number of genotypes for use in breeding for heat stress tolerance in cucumbers. Besides, the identified germplasm, WBC-13, DGC-103 and DARL-106 with effective heat stress tolerance will be instrumental in understanding the molecular basis of heat tolerance and designing climate-smart cucumber cultivars.

Cucumber is an extremely perishable vegetable; however, under room conditions, the fruits become unfit for consumption 2–3 days after harvesting. One natural variant, DC-48 with an extended shelf-life was identified, fruits of which can be stored up to 10–15 days under room temperature. The genes involved in this economically important trait are regulated by non-coding RNAs. The study aims to identify the long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) by taking two contrasting genotypes, DC-48 and DC-83, at two different fruit developmental stages. The upper epidermis of the fruits was collected at 5 days and 10 days after pollination (DAP) for high throughput RNA sequencing. The differential expression analysis was performed to identify differentially expressed (DE) lncRNAs and circRNAs along with the network analysis of lncRNA, miRNA, circRNA, and mRNA interactions. A total of 97 DElncRNAs were identified where 18 were common under both the developmental stages (8 down regulated and 10 upregulated). Based on the back-spliced reads, 238 circRNAs were found to be distributed uniformly throughout the cucumber genomes with the highest numbers (71) in chromosome 4. The majority of the circRNAs (49%) were exonic in origin followed by inter-genic (47%) and intronic (4%) origin. The genes related to fruit firmness, namely, polygalacturonase, expansin, pectate lyase, and xyloglucan glycosyltransferase were present in the target sites and co-localized networks indicating the role of the lncRNA and circRNAs in their regulation. Genes related to fruit ripening, namely , trehalose-6-phosphate synthase, squamosa promoter binding protein, WRKY domain transcription factors, MADS box proteins, abscisic stress ripening inhibitors, and different classes of heat shock proteins (HSPs) were also found to be regulated by the identified lncRNA and circRNAs. Besides, ethylene biosynthesis and chlorophyll metabolisms were also found to be regulated by DElncRNAs and circRNAs. A total of 17 transcripts were also successfully validated through RT PCR data. These results would help the breeders to identify the complex molecular network and regulatory role of the lncRNAs and circRNAs in determining the shelf-life of cucumbers.

Tomato (Solanum lycopersicum L.) is the most important vegetable crop grown in India after potato. Root-knot nematodes (RKNs) (Meloidogyne spp.) cause yield loss between 11 and 35% in tomato. RKNs are also known to be involved in the tomato wilt disease complex in association with Fusarium oxysporum sp. lycopersici and Ralstonia solanacearum. The nematode resistance gene, Mi1 from Solanum peruvianum, is currently the only source of RKN resistance in modern tomato cultivars. Mi1 mediated resistance is temperature sensitive and ineffective above 28 °C soil temperature. Nematode resistance gene, Mi-9 found in S. arcanum accession LA2157 is heat-stable and is located on the short arm of chromosome 6. In our study, LA2157 was crossed with tomato cultivar Kashi Amrit. The inter-specific hybrid was successfully developed through embryo rescue. The hybridity of embryo rescued plants was confirmed by morphological features and molecular marker assay. LA2157 and F1 hybrid showed immune reaction to M. incognita under the high inoculation pressure of 2000s stage infective juveniles per plant, while cv. Kashi Amrit exhibited a highly susceptible reaction. Among hundred F3 plants from ten F2s, ten F3 plants each of two separate F3 families (43 and 119) have shown resistance and no segregation was observed within the family for resistance during April–May, 2020 (high temperature). All F4 plants derived from 43F3 also gave an immune reaction to M. incognita indicating homozygous nature of 43F2 plant for Mi-9 gene. We believe that this set of resistant plants can be utilized to transfer heat-stable nematode resistance in the background of cultivated tomatoes. Key messageInter-specific tomato hybrid of Kashi Amrit and LA2157 was developed through embryo rescue from fruits of 33–34 days after pollination. The identified F4 family homozygous for Mi-9 can be used to transfer heat-stable nematode resistance to cultivated tomatoes.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.