A high-density, high-resolution genetic map was constructed for bitter gourd (Momordica charantia L.). A total of 2013 high quality SNP markers binned to 20 linkage groups (LG) spanning a cumulative distance of 2329.2 cM were developed. Each LG ranging from 185.2 cM (LG-12) to 46.2 cM (LG-17) and average LG span of 116.46 cM. The number of SNP markers mapped in each LG varied from 23 markers in LG-20 to 146 markers in LG-1 with an average of 100.65 SNPs per LG. The average distance between markers was 1.16 cM across 20 LGs and average distance between the markers ranged from 0.70 (LG-4) to 2.92 (LG-20). A total of 22 QTLs for four traits (gynoecy, sex ratio, node and days at first female flower appearance) were identified and mapped on 20 LGs. The gynoecious (gy-1) locus is flanked by markers TP_54865 and TP_54890 on LG 12 at a distance of 3.04 cM to TP_54890 and the major QTLs identified for the earliness traits will be extremely useful in marker development and MAS for rapid development of various gynoecious lines with different genetic background of best combiner for development of early and high yielding hybrids in bitter gourd.

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 F2:3 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 (R2%) 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.

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The development of fruits without fertilization is known as parthenocarpy. Parthenocarpy improves the fruit quality, processing attributes, production and productivity of vegetable crops like tomato, cucumber, watermelon etc. Absence of seeds can enhances the shelf life of the fruits, allowing a better conservation, fruit set in adverse climatic conditions, early and offseason production of vegetable crops. Therefore, it is important to ensure yield stability regardless of environmental conditions. Breeding of new cultivars with the ability to develop fruits without pollination or any artificial stimuli is a promising approach. Parthenocarpic vegetables can be natural or can be induced artificially by various methods like, use of plant growth regulators, distant hybridization, mutation, use of irradiated pollen, alternation in chromosome number, gene silencing, gene modifications and genome editing tools. Therefore, present review is focused on genetics, nature of gene action, mapping of QTLs and various breeding methods to induce parthenocarpy in vegetable crops.

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