Onion is the most important vegetable crop among various
Alliums grown in India. It is used in every household every day in vegetables, soups and curries. Onion possesses rich medicinal values and used for preparation of various homeopathic, unani and ayurvedic medicines. It shows strong anti-platelet and blood thinning activities in human blood, protect against arteriosclerosis, cardiovascular disease, stroke, diabetes, osteoporosis and heart attack
(Augusti, 1990). China and India are the primary onion growing countries, followed by the USA, Egypt, Iran, Turkey, Pakistan, Brazil, the Russian Federation and the Republic of Korea
(FAO, 2012). In India, onion is predominantly cultivated during
rabi about 60% followed by 20% each in
kharif and late
kharif season
(Tripathy et al., 2014). In India area under onion cultivation is 12, 93,000 ha with a total production of 2, 17, 18, 000MT and an average yield of 16.8 MT/ha
(NHB, 2019). Maharashtra is leading state whereas productivity is highest in Gujarat. There has been a steady increase in area and production of onions in the last few decades.
Kharif crop is grown on almost one lakh hectare area in India. Main
kharif onion producing states are Karnataka, Andhra Pradesh, Rajasthan, Tamil Nadu and Maharashtra.
In India main onion produce comes from
rabi season crop, some of which is exported and rest is stored for domestic consumption. The stored onion gets exhausted by August- September and people of India face onion crises every year from October to March till fresh produce comes to the market
(Sharma and Dogra, 2017). However some states like Maharashtra, Karnataka and Madhya Pradesh are producing
kharif onion. The kharif produce from these states calms down the consumers’ needs to some extent but is not sufficient to be supplied in whole country and we have to import onion from other countries due to which prices goes very high. Apart from this late monsoon, heavy rainfall during crop growth season in these states results in heavy crop losses in
kharif onion
(Sharma, 2009;
Mohanta et al., 2017). In addition to these problems, unavailability of seeds of high yielding varieties in
kharif season also leads to non-acceptance of
kharif onion production by the farmers
(Hiraveet et al., 2015). However by using scientific techniques like use of high yielding varieties, planting on raised beds, sets planting, making channels to drain irrigation water, using weedicides to control weeds, taking proper plant protection measures farmers can successfully raise
kharif onion
(Yoo et al., 2019; Tripathi and Lawande, 2015;
Kandil et al., 2013 and
Lawande et al., 2011). Kharif onion production is important in stabilizing onion prices as well as it ensures round the year supply to the consumers
(Abd EI-All et al., 2012;
Sharma and Jarial, 2017).
Kharif onion prices are high as compared to
rabi crop and hence farmers can earn more benefits by its cultivation
(Tripathy et al., 2014). Most of the farmers are ignorant about the
kharif onion production and therefore this technique should be deliberately popularized among the farming community. More emphasis is needed towards varietal development and seed production. Salient research work done by many institutes and researchers in this direction is being reviewed here in this article.
Potential
Kharif crop (rainy season) is now being adopted by many farmers in the north and eastern parts of the country which has revolutionized the onion production and marketing in the country.
Kharif season produce can bridge the gap between demand and supply of onion during lean period (October-March) in our country. Besides price stabilization onion production in
kharif season
(Pandita, 1994) offers a good alternative to the farmers for obtaining higher returns. It can help in foreign exchange earnings by increasing the export of onion from main crop (
rabi) most of which is generally utilized for domestic consumption. Maharashtra, Karnataka and Madhya Pradesh are major
kharif onion producing states in India. In India, Maharashtra is main kharif onion producer and three crops are taken here in a year
i.
e., in
kharif season 10-15 per cent, in late
Kharif 20-40 per cent and in
Rabi season 50-60 per cent. Maharashtra leads in
kharif onion cultivation due to availability of extreme short-day cultivars (
viz., N-53, B-780, Phule Samarth, Agri Found Dark Red and local strains) and favorable climatic conditions. To make onion available throughout the year in India
kharif onion production by farmers need to be prioritized
(Sharma and Jarial, 2017). For this main focus should be given on development of new varieties with high yield, diseases and pest resistance, low splitting and bolting and having long shelf life. Nursery production of
kharif onion crop is also a major problem due to scorching sun in May-June. Therefore, improved techniques for nursery production and use of sets for crop planting should be adopted.
Kharif onion production possesses a huge potential in terms of increased profits to the farmers as well as uplifting of society. Therefore, it should be popularized among farmers of every state so that area and production under
kharif onion can be increased.
Challenges and bottlenecks
Kharif crop of onion is often affected severely by cloudy atmosphere, late rains and incidence of various pests and diseases. Therefore, at present its cultivation is restricted to certain area with low yield potential and poor keeping quality. Successful nursery production during summer season is the main problem for growing of
kharif season crop. However, to avoid these problems,
kharif onion crop can be raised successfully through onion sets. Sets are small onion bulblets which are harvested before scorching summer prevails and then stored for replanting in
kharif season. Seed rate, set planting time and sets size
(Mohanta et al., 2017) are the most important factors which may influence the growth and yield of onion bulbs. It is important to increase the yields for enhancing the export level, so that it helps in foreign exchange earning to the country. The present review article is therefore written to provide information about the current status of research and development on
kharif onion. The production of
kharif onion is very low due to erratic monsoon, cloudy weather, constant drizzling during crop growth period. These climatic conditions aggravate many foliar as well as soil born diseases. The occurrence of weeds during rainy season is also very high. All these factors leads to yield losses and productivity of
kharif onion is not more than 10 t/ha. In India various research institutes like DOGR, Rajgurunagar, Pune, NHRDF, Nasik, IIHR, Bangluru, IARI, New Delhi and many State Agricultural Universities (SAU’s) are working on these constrains and developing technologies to enhance
kharif onion production. National Research Centre for Onion and Garlic demonstrated that
kharif onion productivity can be enhanced from 10 to 25 t/ha
(Tripathi and Lawande, 2015).
Problems faced in kharif onion production are
►Lack of standardized/ recommended varieties for specific agro-ecological situations.
►Lack or unavailability of planting material (seed or sets) in time.
►Water stress/high temperature during the time of seedling /nursery production.
►High disease incidence during monsoon.
►Problems in curing and drying of onions after harvest.
►Low shelf life due to sprouting in storage.
►Severe weed problem in rainy season.
►Lack of fertilization/ fertigation schedule.
►Lack of awareness among farmer.
For getting benefit of high prices farmers need to enhance their productivity. Poor yield, more disease and pest incidence, weeds and poor storage life due to more moisture content in bulbs are major problems in
kharif onion production. Due to these lacunas farmers prefer to grow
rabi crop and avoid
kharif onion production. Efforts have been made to solve these problems by various research organizations in the past. Therefore, standardization of
kharif onion cultivars, raising healthy nursery or sets, plant protection, growth regulation and curing, chemical treatments for prevention of post-harvest losses are some important aspects towards the successful cultivation of
kharif onion.
Advances in production technology
Standardization of suitable variety
The productivity of
kharif onion is far behind as compared to
rabi crop. The higher productivity could be achieved by selection of suitable varieties, balanced nutrition, optimum water management as well as need based plant protection measures. Among all these factors, selection of suitable varieties plays an important role in enhancing the yield as well as productivity. To have continuous supply of onion round adoption of
kharif and late
kharif onion production is of utmost importance. While going for kharif onion production selection of appropriate variety is a basic step towards its success. Keeping this in view, many researchers from India are working on standardization of some improved varieties and advanced lines of common onion (
Allium cepa L.) for cultivation in
kharif season. For
kharif onion production cultivars having early maturity, free from early bolting, longer storage life and high yields are desirable. In addition, ideal
kharif variety should have early bulbing, high photosynthetic efficiency, thin neck and resistance to diseases and tolerant to water stagnation. It was found that N-53, Baswant–780, Agrifound Dark Red, Arka Kalyan perform good for
kharif season
(Tripathiand Lawande, 2015).
Twelve varieties of onion were evaluated by
Mohanty et al., (2000) during the
kharif season and they reported highest bulb yield of 315.2 q/ha from variety Agrifound Dark Red which was statistically
at par with N-53 (302.5 q/ha). Agrifound Light Red and Arka Niketan had shown better keeping quality among the tested varieties.
Mohantyand Prusti (2001) evaluated twelve varieties of onion during kharif season and recorded highest yield in variety Arka Kalyan (21.06 t/ha) which was at par with Arka Niketan (19.64 t/ha) and Pusa Madhavi (18.96 t/ha). Arka Niketan and Pusa Madhavi produced medium bulb with better storage quality. Onion varieties Agri found Light Red and N-53 had performed best during kharif season
(Mohanty, 2002) with highest bulb yield. On the basis of performance of five onion cultivars during kharif season
Sarkar and Jain (2002) observed highest bulb yield in variety Agrifound Dark Red (174.39 q/ha) whereas, maximum plant heightand number of leaves per plant, bulb diameterand TSS was found in variety Arka Niketan. Agrifound Dark Red and Arka Niketan with better keeping quality, medium bulb and moderately high yield was suggested
(Mohanty et al., 2003) as a substitute to N-53 and Arka Kalyan for commercial cultivation in the rainy season. The cultivar Bhima Red and Bhima Raj performed well for the Akola region in
kharif season as reported by
Hirave et al., (2015). Sharma (2009) tested onion varieties bred by different institutes for their performance in the low hills of Himachal Pradesh and revealed that Baswant-780 was the top yielder with a mean bulb production of 230.50 q/ha. As reported by
Sharma and Jarial (2017) Agrifound Dark Red was found to be the best suited cultivar for kharif onion production in lower hills of Himachal Pradesh.
Sharma and Dogra (2017) evaluated four varieties of onion in
kharif season which were planted on five dates separated at 10 days intervals starting from 15
th July to 25
th August and they observed highest bulb yield in variety Agrifound Dark Red transplanted on 15
th August.
Another important point to be considered while selecting a good variety is ratio of bolting and doubling in a variety. Bolting and doubling may be due to higher temperature prevalence throughout the crop period, smallest bulb size, varietal character and late transplanting. Both of these are considered as negative parameter with respect to onion bulb production as they reduce the marketable yield.
Hirave et al., (2015) observed zero bolting percentage and minimum splitting percentage in variety Bhima Red. Bhima Red had shown 0.33% splitting of bulb which was found to be at par with variety Bhima Raj (0.67%), Agrifound Dark Red (1.00%), Bhima Super (1.33%) and Baswant-780 (1.67%). Whereas, maximum splitting percentage (2.67%) of bulbs was reported from variety Phule Samarth. Similar observations were also recorded by
Jadhav et al., (1990). Khar et al., (2007) evaluated ten promising lines of onion and reported that variety Baswant 780 performed well with less bolters and this variety found stable for this trait. The variations in the bulb yields of different varieties of onion have also been reported from several places
(Patil et al., 1991;
Bhonde et al., 1992; Khan, 1997;
Mohanty and Prusty, 2002).
Lawande et al., (2011); Lawande et al., (2011a) had reported superiority of Bhima Super and Bhima Red for
kharif onion production. Recently Directorate of Onion and Garlic Research (DOGR) had recommended release of two varieties
i.
e. Bhima Super (red coloured bulbs) and Bhima Shubhra (white bulbs) for
kharif season at national level.
Standardization of transplanting time and set size
The nursery for
kharif onion is generally sown in April-May. At this time, it is very difficult to raise healthy seedlings due to scorching heat and lack of irrigation water in summer. Seedling transplanting coincides with onset of monsoon, heavy showers and water stagnation which leads to high seedling mortality. For obtaining healthy seedlings, seeds of selected varieties should be treated with captan or thiram or bavistin prior to sowing. The treated seeds should be sown in lines at 10-15 cm spacing on broad based furrow during first week of May. Drip or sprinkler irrigation saves upto 40-50% water and ensures 90 to 100 per cent seed germination with good seedling stand. Shading over nursery beds using 50% agri shade net or hessian cloth protects young seedlings from scorching sunlight and ensures rapid and higher seed germination. Shade net should be removed after 30-35 days after which seedlings get established properly to avoid etiolation and lanky growth
(Tripathy and Lawande, 2015). Use of sets or bulblets is another method to avoid nursery production during harsh summer months. Planting
kharif onion using sets is also helpful in getting early crop so as to meet the demand of green onion for salad in early winter. Sets of
kharif onion using varieties like Agrifound Dark Red, Baswant 780, N-53 and Arka Kalyan can be raised from mid February to mid March. Raised beds of 3.0×1.0×0.15 m size are prepared. To cover one square meter area of the bed 15 g of seeds are sufficient. The plants are kept in the nursery bed itself up to April-May till they develop small bulblets called sets of 1.5-2.0 cm diameter. Harvesting is done along with the tops and sets are stored till July-August in a well-ventilated house. Such well stored sets are used for replanting in the
kharif season. Medium sets of 1.5-2.0 cm diameter are ideal for
kharif onion production as they do not bolt much and the proportion of splitted bulbs and doubles was also found minimum in this category
(Madisa, 1994;
Ansari et al., 2009). Khokhar et al., (2002) observed highest percentage of bolting (31.1%), doubles (69.4%) and higher un-marketable bulb yield in kharif onion raised using large set sized sets. The tendency to develop double bulbs in large sized sets affects their consumable appeal as reported by
Rabinowithch (1979);
Khokhar et al., (2001). The planting time of
kharif onion varies from place to place and it generally starts from first week of June to second week of August. Onion is photo-thermo sensitive crop and bulb production occurs in long photoperiods, but early cultivars react faster to a long photoperiod and leads to early bulbing with short bulbs without completing vegetative period. The interaction between temperature and photoperiod strongly affects bulb production as well as bolting in plants. The bulbing ratio increases with increasing temperature and photoperiod. It has been reported by
Tarakanov and Alemzadeh (1997) that increase in photoperiod promoted bulbing, while under very short photoperiods (8 hours per day) no cultivars bulbed, even after 60 days of growth. Bulb maturity found to decrease linearly with increasing temperature and lengthening photoperiod. Low temperature and increased photoperiod (8–14 h d
-1) shortened the time to floral initiation as reported by
Khokhar (2008). Set size used for replanting also affects the bulb production and bolting. In kharif onion production using sets the sets diameter is also a primary factor that affects bulb or flower stalk production. A large onion set produces flowering stalks more rapidly than a small one as reported by
Heath and Mathur (1944).
Yamaguchi (1980) had also reported that the ideal size of a set should be 1.5-2.0 cm in diameter and bulbs greater than 2.5 cm in diameter are prone to vernalization and bolting at low temperature.
Time of planting
kharif onion varies in different parts of the country. In Maharashtra planting is done July to August and in northern plains from mid or end of August whereas in West Bengal and Orissa late transplanting is done
i.e. from August to September
(Pandey, 1993). In Himachal Pradesh best time for
kharif onion cultivation is from 25
th July to 15
th August as advocated by
Sharma and Jarial (2017);
Sharma and Dogra (2017);
Sharma et al., (2009). Further delay in transplanting leads to a continuous decrease in plant height. Highest plant height (55.06 cm) was observed on 5
th July transplanting, whereas the minimum plant height (47.64 cm) with transplanting on 25
th August. This might be attributed to longer growth period of early planted crop before the initiation of bulb development
(Sharma and Jarial, 2017). Significant effect of transplanting dates on plant height in kharif onion was also reported by
Dev et al., (2005). Good production is often associated with good growth and development of any crop. The growth and yield of cultivated crops are influenced by genotype, growing environment and agronomic practices. Planting time is one of the important factors that greatly influence the growth, yield and quality of onion
(Abd EI-All et al., 2012;
Kandil et al., 2013). Most of onion cultivars are sensitive to photoperiod and their range of adaption is limited. Kharif onion is an off-season cultivation of the crop for which standardization of varieties is of immense utility
(Hirave et al., 2015). Thus, it is imperative to assess the stability inperformance of recommended varieties of onion for aspecific location, especially for kharif onion
(Haldar et al., 2009). The conventional method of planting which farmers usually follow is to plant on flat bed or in ridges and furrows with surface irrigation. These methods do not provide efficient nutrient management and drainage which results more small size bulbs and higher disease incidence. Therefore crop should be planted on raised beds with drip or sprinkler irrigation resulted in higher yield of bigger bulbs than other methods
(Tripathi and Lawande, 2015).
Irrigation and fertigation schedule
The nutrient management in kharif onion production is very important because the leaching and runoff losses of nutrient are high due to frequent rains. The recommended dose of fertilizers for
kharif onion is 100 kg nitrogen, 50 kg phosphorus and 50 kg potassium per hectare. In addition to NPK fertilizers regular dose of 50 kg sulfur per hectare should also be applied. The half of nitrogen and full doses of phosphorus, potassium and sulfur should be applied before planting while the remaining 50% of nitrogen should be applied as topdressing during the growth period of the crop. If fertigation facility is available it should be given in ten split doses after every five days. The foliar application of nutrients containing water-soluble fertilizer and micronutrient mixture is also helpful. These should be applied between 45 to 75 days after transplanting. This helps in bulbs enlargement.
Weed management
Weed is a severe problem in growing
kharif onion. Due to high temperature and humidity in rainy season rapid weed growth takes place and frequent removal is needed to save the crop. To control weeds in nursery use of stomp (Pendimethalin) @ 2 ml/litre of water after seed sowing checks weeds up to 30 days. It can also be used for direct seed sown crop. In case transplanted crop spray of weedicides like Goal @ 1.6 ml per litre or stomp @ 3.5ml per litre of water after trans planting of seedlings or just before transplanting of onion followed by immediate irrigation is effective. These effectively control weeds up to 30 to 35 days but after that hand weeding should be done. Two hand weedings effectively controlled the weed population in onion nursery of variety Agrifound Dark Red during
kharif season, followed by combined application of pendimethalin @ 1.5 ml + quizalofop ethyl @ 0.75 ml/L before seed sowing and at 15 days after seed sowing (NHRDF, 2017-18).
Plant protection
In onion, purple blotch caused by fungus
Alternaria porii is a major problem in almost all parts of the country
(Kareem et al., 2011). It is more severe during
kharif and late
kharif season. Among the pests, thrips are most damaging insect affecting growth and yield of onion. The fungus required moderate temperature (around 25°C) and high relative humidity (90% or higher) for sporulation. Symptoms include small white sunken spots on the leaves which enlarge, become eye shaped under moist conditions. Finally, these spots turn to purple coloured lesions surrounded by a broad chlorotic margin. Ultimately leaves dry up and drop after 2-3 weeks. Sprays of mancozeb or chlorothalonil @ 2.5 gm/l at 10 days intervals have been found effective in reducing the disease. Cultivars
i.
e. Bhima Kiran, Bhima Super, NRCRO-2 and Col-652 showed tolerance to both purple blotch as well as thrips
(Kareem et al., 2011) infestation under kharif season. Anthracnose caused by
Colletotrichum gloeosporiodes (Glomerellacingulata) is another serious disease occurring in
kharif onion. During rainy season conidial movement with water is high which spread the disease to large area in short time. The symptoms appear as pale yellow water soaked spots on the leaf, which increase lengthwise covering the whole leaf. The affected leaves shrivel, droop down and finally wither. Since the pathogen survive on crop residue, sanitation and destruction of infected plant debris helps in reducing the disease. Proper drainage is essential for control of disease. Application of benomyl @ 0.2% as soil treatment, spray of mancozeb @ 0.25% carbendazim @ 0.1% and captafol (0.2%) gave good control of the disease. Thrips is most injurious insect pest of onion. The insect is very minute and yellow to dark brown in colour which sucks the sap of the leaves. The thrips infested leaves develop spotted appearance which turn pale white blotches.Incase of severe infestation leaves coiling and twisting occur and plant shows stunted growth. The yield loss may be upto 50-60%. The regular application of insecticides such as malathion @ 0.1% or metasystox @ 0.1% and cypermethrin @ 0.01% or deltamethrin 2.8% @ 20 ml a.i./ha control the insect. Since the control of thrips is difficult, thus an integrated approach is necessary for the effective control of this insect. Biological control using natural enemies, including predaceous mites, minute pirate bugs and lacewings feeding on thrips considerably lower their population. Avoid planting onions near cereal fields if possible, because thrips often increase in those fields in the spring and migrate to onion fields when the grain senesces, or when the alfalfa is cut. Overhead irrigation and rainfall also suppress the thrips numbers.
Harvesting and post-harvest management
The excessive vegetative growth is a big problem in
kharif onion. The plant height sometime goes up to one meter and neck of plant becomes thick while the bulbs size remains small. This happens because of poor translocation of assimilates from leaves to bulbs. Storage is one of the most important aspects for post-harvest handling of onion. It is also very difficult to store kharif onion for a longer period due to its higher moisture content. Rotting, sprouting, physiological loss in weight and moisture evaporation results in serious losses up to 50-90 per cent depending upon genotype and storage conditions.
Pre-harvest sprays had been widely applied without impairing the keeping quality of onion. Application of growth substances and fungicides like ethrel, cycocel, carbendazim and aureofungin as pre-harvest foliar application have gained prominence. These compounds greatly enhance storage through inhibition of sprouting, rooting andreduction in the physiological loss in weight. Pre harvest sprays of 100 ppm salicylic acid or cycocel at the rate of 2,500 ppm in
kharif onion considerably enhance the crop growth, yield and reduced various post harvest losses such as weight loss, loss in diameter, sprouting and rotting during storage
(Sharma and Chauhan, 2021).
Dwivedi et al., 2019 reported that pre harvest spray of GA3 at the rate of 100ppm reduce neck thickness and improves yield in
kharif onion. Many researchers had used different chemicals to enhance the shelf life of onions and a few among them are abscisicacid (ABA), gibberellin (GA3), auxin and cytokinin (CK)
(Abdel-Rahman and Isenberg, 1974), maleichydrazide (MH), cycocel (CCC) and ethrel
(Misra and Pande, 1979), trakepho and ethrel
(Pospisilova and Janyska, 1978), paraquat
(Bubl et al., 1979) and wondalhid, ethrel, fruitone,offshoot and antack
(Iordachescu and Mihailescu, 1981). Decreasing rotting percentage as compared to control was observed when onion crop sprayed with cycocel (lihocin) @ 2500 ppm on 75 and 90 days after transplanting
(Anonymous, 2004). Application of micronutrients has been also found effective in enhancing storage life of onion. It was noticed that application of CaCl2 (0.5%) at 60, 75 and 90 DAT performed better than all the treatments in terms of lowest total loss. Foliar application of boric acid (0.25%) at 30, 45 and 60 DAT performed better in terms of lowest physiological weight loss whereas foliar application of boric acid (0.25%), zinc sulphate (0.5%) and CaCl
2 (0.5%) at 60, 75 and 90 DAT showed lowest decay loss (NHRDF, 2017-18).Application of these synthetic growth regulators can alter the levels of the naturally occurring hormones, resulting in modification of growth and development in the desired direction and to the desired extent. Techniques like proper curing, neck cut and exposure of bulbs to gamma irradiation before storage are proved to be useful techniques in delaying sprouting and their subsequent deterioration resulting in improved shelf life
(Anbukkarasi et al., 2013).
The
kharif season crop matures in 90-105 days but neck fall do not occur and plant remains in active growth stage. The bending of neck of plants by rolling of empty barrel two or three days before harvesting found useful for increasing shelf life. The curing of
kharif onion is important for better shelf life but high humidity and cloudy weather do not facilitate proper curing which results in more losses. Use of both end open plastic tunnels helps in increasing shelf life of kharif onion. Many workers has studied the effect of curing methods on storage behavior of onions and found that both field and artificial curing methods were effective in reducing physiological weight loss and rotting percentage than the non-cured bulbs. Field curing by windrow method for three to five days, shade curing with tops for 10 to 12 days and 2.5 cm neck length had shown minimum storage losses in onion, more number of scales and colour retention for longer period as reported by
Singhal (2000).
Satish and Rangann (2002) reported that artificial curing of onion bulbs for 10 to 14 hours at 45°C with air flow rate of 222 m3 per minute had shown good results as compared to 8 to 10 days of sun curing. Some workers suggested bulb harvesting with leaf intact method to enhance storage life of onion
(Nega et al., 2015). Kukanoor et al., (2006) suggested maximum physiological loss in bulb weight was noticed when bulbs were stored without leaves. This may be due to absence of foliage resulting in full exposure of the bulbs to the temperature leading to increased surface temperature and moisture reduction. However
Yoo et al., (2019) linked the presence of leaves after harvesting with increased pungency in onion bulbs. This may be due to translocationof flavor (sulfur) compounds from the leaves to the bulbs duringthe drying period after onion plants are pulled from the soil indicating that leaf cutting immediately after harvesting prevents increase in bulb pungency.
Another important technique to control losses due to sprouting in onion storage is use of gamma irradiation. Many researchers had done considerable work in this direction and they confirmed the sprout-inhibiting effect of gamma irradiation.
Sawyer and Dallyn (1959) reported complete onion sprout suppression with 8000 r gamma irradiation treatment. The sprouting of onion bulbs was completely inhibited at 3000 r
(Ogata et al., 1959). They also noticed that the Inner buds of onion bulbs which were compelled to inhibit the sprouting by the irradiation were browned and dead, but the injured parts did not extend to the outside of the buds.
Furata et al., (1978) reported that gamma irradiation of onions at 5-200 Gy was more effective in sprout inhibition both at the high irradiation doses and at the high dose rates.
Studies focusing on evaluating the effect of ionizing radiation on onion sprout inhibition have been carried out since the fifties.
Sawyer and Dallyn (1959) have reported the ability of low doses of gamma irradiation to inhibit sprout development during storage of onion.
Thomas et al., (1975) reported for getting a complete inhibition of sprouting by irradiation at 6 to 9 krad during storage only if the bulbs were irradiated within a fortnight of harvest when they were in the dormant state.
Future potential
For the last few years, we are continuously observing shortage of onion from October to March months due to which price gets increased. To combat this issue our Government has to import onion from other countries during lean period which also adds to the increased cost.
Kharif onion production in India is done in very small area. Though it is a very important option and needs to be popularized among farmers for wide adoption. This will help in price stabilization as well as fulfilling consumers demand throughout the year. Apart from this kharif onion production can provide chances to export more quantity of
rabi produce in the international market.
