Bulb onion (Allium cepa L.) is an ancient crop that is thought to have originated in Central Asia and has been cultivated for over 5000 years. Classical genetic and plant breeding approaches have been used to improve onion yield, quality, and resistance against biotic and abiotic stresses. However, its biennial life cycle, cross-pollinated nature and high inbreeding depression have proved challenging for the characterization and breeding of improved traits. New technologies, notably next-generation sequencing, are providing researchers with the genomic resources and approaches to overcome these challenges. Using these genomic technologies, molecular markers are being rapidly developed and utilized for germplasm analysis and mapping in onion. These new tools and knowledge are allowing the integration of molecular and conventional breeding to speed up onion improvement programmes. In this review, we outline recent progress in onion genomics and molecular genetics and prospects for enhancing onion yield and quality in the future.

Seventy nine genotypes of tomato (15 lines, four testers and their 60 F 1 hybrids produced in line · tester fashion) were evaluated under normal (E 1 ) and late planting (E 2 ) conditions in the Department of Vegetable Crops, Punjab Agricultural University, Ludhiana, India, to determine the nature of gene action controlling yield, quality and shelf life characteristics and to identify a few good combiner genotypes which may be used in further breeding programmes to extend the fruit availability period of tomato in North Indian plains. The lines were significantly different from testers for most of the characters thereby justifying the choice of testers. Additive gene action was predominant for days to ripening, total yield per plant, marketable yield per plant, number of fruits per plant, average fruit weight, fruit shape index and lycopene in both the environments, whereas non-additive genetic variance predominated in controlling firmness index, number of locules, pericarp thickness, alcohol insoluble solids (AIS), dry matter, total soluble solids (TSS), titratable acidity, TSS:Acid ratio, pH, ascorbic acid and shelf life, under both normal and late planting conditions. The best general combining ability (gca) effects, among females, in respect of yield per plant were shown by Spectrum in E 1 and by LT-42 in E 2 . Among the testers, the best gca values in both the environments were possessed by nor-RM-1 for total yield per plant, marketable yield per plant, number of fruits per plant, dry matter and TSS; by rin-RM-2 for firmness index, pericarp thickness and alcohol insoluble solids; by alc-IIHR-2050 for average fruit weight, number of locules and shelf life and by alc-IIHR-2052 for lycopene. The gca of ripening mutants had a nice consonance with their per se performance for most of the characters indicating that additive gene action was operative in these mutants for majority of the traits.

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Parthenocarpy is the growth of ovary into seedless fruit in the absence of pollination and fertilization. It may occur naturally or can be induced artificially by exogenous application of hormones or their enhanced endogenous level. Parthenocarpy improves the yield, quality and processing attributes of vegetable crops like cucumber, eggplant and watermelon, where seed is a limiting factor during consumption. This trait proved highly useful to develop fruits under environmental conditions that are unfavorable for successful pollination and fertilization, particularly in green house cultivation and especially in cross-pollinated crops. It is an established fact that phytohormones play important role in fruit setting and their genetic manipulation can lead to seedlessness. Apical shoot is considered as source of inhibitors preventing fruit growth in the absence of stimulus like pollination or application of phytohormones. The exploitation of biotechnological tools can further enhance its utility for the benefit of mankind. Therefore, present review is focused on factors and potential of parthenocarpy in vegetable crops.

This study investigated the impact of sprouting in four Indian onion varieties (Punjab White, Punjab Naroya, PRO-6 and Commercial). Results showed significant (P < 0.05) increase in protein, crude fibre, ascorbic acid content, total phenol content, total flavonoid content, antioxidant activity, anthocyanin content and significant (P < 0.05) decrease in total carbohydrate, energy value and hardness due to sprouting in all the four varieties. HPLC analysis revealed irregular pattern of increase and decrease in flavonoid components. There was no particular trend observed within analysed flavonols due to sprouting in all the four varieties except with the maximum increase in quercetin (219.3-287.4 mg kg À1 ), kaempferol (13.8-17 mg kg À1 ), myricetin (34.6-40.9 mg kg À1 ), quercetin-3ꞌ-glucoside (2.9-4.1 mg kg À1 ) and quercetin-4ꞌ-glucoside (83-87.1 mg kg À1 ) in case of PRO-6 variety only. The present research work implied sprouting to be beneficial in onion as nutritional and functional potential of all the four onion varieties was improved by sprouting.

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Six systemic fungicides viz., Kitazin 48 EC (iprobenfos), Tilt 25 EC (propiconazole), Folicur 25 EC (tebuconazole), Score 25 EC (difenoconazole), Amistar Top 325 SC (azoxystrobin 18.2% + difenoconazole 11.4%) and Nativo 75 WG (trifloxystrobin 25% + tebuconazole 50%), and two non-systemic fungicides viz., Indofil M-45 75 WP (mancozeb) and Kocide 77 WP (copper hydroxide), were evaluated under in vitro and field conditions for their efficacy to manage purple blotch complex of onion caused by Alternaria porri and Stemphylium vesicarium. Field efficacy of the fungicides at different concentrations were determined in controlling the purple blotch complex of onion under artificial epiphytotic conditions on bulb and seed crop (cultivar PRO-6) during the Rabi season 2014-2015 and 2015-2016, respectively. The triazole fungicides, tebuconazole and difenoconazole proved superior in inhibiting growth of A. porri and S. vesicarium under in vitro conditions, respectively. Further, foliar sprays (3 for bulb crop and 4 for seed crop) of tebuconazole 25 EC (Folicur) @ 0.1 per cent at fortnightly interval most effectively managed purple blotch complex of onion under field conditions with highest Benefit: Cost ratio (8.75:1 and 88.7:1) in bulb and seed crop, respectively. Seed-to-seed method of onion seed production recorded significantly lower disease severity and higher seed yield than that of bulb-to-seed method under natural epiphytotic conditions. The present findings can be instrumental in devising strategy for the integrated management of A. porri, S. vesicarium singly as well as in complex, serious limiting biotic factors in onion production.

Onion powder has an extensive demand and wide application worldwide as flavour additive in convenience foods and medicinal products. Conventionally onion powder is prepared by hot air drying of onion slices followed by grinding. Convective air drying when used alone demands longer drying time and thus has a high expense of energy. As bulk of onion is water (82-87 %), removal of moisture prior to drying can reduce moisture loading on dryer and hence the energy consumption. Keeping this in view, onions were partially dewatered using centrifugal force before convective drying. The effect of partial mechanical dewatering and drying air temperature was studied on drying time, specific energy consumption and onion powder quality (colour and flavour). The combination process was also optimized to achieve increased drying rate and product quality comparable to products obtained using convective drying alone. Onions subjected to 60 % partial mechanical dewatering and hot air drying at 70°C exhibited significantly (p≤0.5) shortened drying time, decreased energy consumption and maintained colour and flavour of the dried product.