Introduction
A number of minor gourds, viz. sweet gourd (Momordica cochinchinensis), teasel gourd (M. subangulata subsp. renigera), and spine gourd (M. dioica) are grown in certain parts of the country. These are rich in minerals and vitamins. Being bitterless and traditionally ascribed. with many medicinal properties, they are high-value vegetables mostly wild gathered or cultivated to a small extent in selected pockets as in the case of teasel gourd. All three being perennials overwintering through underground tubers, they have the potential as ratoon crops adapted to home gardens. Being dioecious in nature, maintaining an optimal sex ratio, and managing pollination is important for good fruit set in these crops. All three species are native to India.
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Teasel gourd is cultivated to a small extent in Asom, Tripura, West Bengal, Odisha, North Eastern States, and the Andaman Islands. The sweet gourd is a rare wild gathered or semi-domesticated home garden vegetable in Tripura, Jharkhand, Odisha, West Bengal, Asom, and the Andaman Islands. Spine gourd is mostly a wild gathered vegetable naturally distributed in almost all Indian states except Andaman & Nicobar Islands, Lakshadweep, and North Eastern states with a higher frequency in Maharashtra, Odisha, Madhya Pradesh, Jharkhand, Odisha, Chhattisgarh, Rajasthan, Andhra Pradesh, Telengana and Tamil Nadu.
Climate and soil
All the three species grow well in hot and humid climates but spine gourd can adapt equally well to arid and semi-arid tracts also. All are cultivated to a small extent during spring, summer, and more often during the rainy season, but not during winter. Well-drained and humus-rich soils are good for their cultivation. Well worked-out laterites and river alluvium are equally good; but, flooded and water-logged soils should be avoided. The ideal soil pH is 6-7.
Varieties
Only a few varieties are available for large-scale cultivation. Arka Neelachal Gaurav in teasel gourd (CHES, Bhubaneshwar), Arka Neelachal Shree (CHES, Bhubaneshwar) and Indira Kakonda (IGKVV, Raipur) in spine gourd, besides Arka Neelachal Shanti, an interspecific hybrid of teasel gourd and spine gourd (CHES, Bhubaneshwar) are the only released varieties. However, farmer-selections and landraces like Narayan Kakrol, Sundar Kakrol, and Australian hybrid of teasel gourd in Tripura, Phulbani local, Jangli Kakonda, Chottadeshi Kakonda (all in Odisha) DPLMD-7, DPLMD-4, DPLMD 2-1(K KVV, Dapoli) in Maharashtra are also popular among farmers.
Arka Neelachal Shree: Yields 4-5 kg/plant, adaptable to east Indian plains comprising Odisha, West Bengal, and Assam.
Indira Kakonda: Dark green color fruits with an average fruit weight of 14 g; yield levels 0.8-1.0 tonnes/ ha during the first year, 1.0-1.5 tonnes/ha in the second year, and 1.5-2 tonnes/ha in the third year.
Arka Neelachal Gaurav: Dark green and oval fruits; average fruit weight of 50 g; 230-250 fruits per vine (12-15 kg) on assured pollination in a season; extended bearing till (June-October); moderate resistance to pumpkin caterpillar and adapted to eastern plains.
Arka Neelachal Shanthi: The first inter-specific hybrid between teasel gourd and spine gourd, combining the natural insect pollination of spine gourd and high adventitious root propagation efficiency of teasel gourd. Average fruit weight 35 g, dark green fruits, yields on an average 10-15 kg per plant, extended bearing period of six to seven months.
Propagation
Seed propagation is slightly difficult due to high seed dormancy in all three species. Careful decortication (just before sowing) of seeds after ripened (stored after harvest) for at least 4 months enhance germination. Germinated seedlings may be transplanted to polybags or germinated in pro-trays themselves before actual planting in the field for a uniform plant stand. In spine gourd, seedlings may be allowed to remain in polybags for the first year to demarcate sex and sprouting female and male tubers may be transplanted in a 10:1 ratio in the field.
All the three spp. are amenable to rooting of vine cuttings; however, plants developed from such vine cuttings do not persist beyond one season in spine gourd, affecting ratooning. Adventitious root tubers are in plenty in teasel gourd. Dormant tubers in teasel gourd and rooted two-node cuttings in sweet gourd may be used for field planting. Top and mid-level cuttings harvested at the early flowering stage and treated with rooting hormones root well in mist chambers and even outside during monsoon season. An improvised mist effect can be provided by using big transparent polybags of 30 x 15 cm size with the basal portion up to 5 cm filled with sand and 2-node cuttings with a leaf planted thereon. Water should be sprinkled on the walls of the polybag and the mouth of the polybag should be covered with a rubber band during the day. Raising the cuttings in trenches covered with a transparent polythene sheet during monsoon season also serves the purpose. Micro-propagated plants of spine gourd are available from Anand Agricultural University, Gujarat.
Being totipotent, random-cut pieces of tubers can also be used as propagules in teasel gourd; but, only longitudinal cuttings with a portion of intact apical bud give rise to new plants in spine gourd. Cut surface needs to be treated with fungicides and shade dried for wound healing before planting. In sweet gourd, wedge grafting of growing tips on vigorous sprouts gives nearly 100% establishment, compact vine growth, and higher yield. Unproductive male plants can be converted to bearing female plants by this technique.
Cultivation
The field should be well ploughed and harrowed to remove weeds and plant debris. Pits of 30, 45, and 60 cm² are dug for spine gourd, teasel gourd, and sweet gourd, respectively, and filled with the recommended quantity of FYM and topsoil and raised to mounds of 20-30 cm height, with provision for water drainage as none of the three species can tolerate water-logging. Planting density: Planting density varies in all three species depending upon the area covered by each species. About 6,000 plants/ha in spine gourd, 4,500 plants/ ha in teasel gourd and 1,500-2,000 plants/ha in sweet gourd are generally recommended. A few male plants to the extent of 10% on staggered sowing may be retained on field borders as a pollen source. A spacing of 1 m x 1 m in spine gourd, 1.5 m x 1.5 m in teasel gourd, and 3 m x 3 m in sweet gourd may be adopted in the initial years and subsequently increased in the ratoon crop by culling out a few less productive plants. Sowing time varies across the country depending upon the availability of pre-monsoon rains. February-April is the ideal sowing time in southwest coastal plains and the Western Ghats, whereas June is the best sowing time in eastern India, the deciding factor being the onset of pre-monsoon rains. In Kerala and Andaman Islands, two crops of teasel gourd per year, the first during February-August and second during September-January can be grown subject to assured irrigation for the second crop. In sweet gourd and spine gourd, flowering and fruiting are restricted to the rainy season from February to September.
Training and pruning
As all three species are weakly stemmed and need a trellis to support the climbing vines. A bower or single line trellis system using iron or bamboo poles, metallic wires, and nylon nets are ideal. The height of the bower or trellis should be kept at breast height for easy hand-pollination in teasel gourd. Sweet gourd requires a very strong support system as the canopy is very heavy. In-home gardens, teasel gourd, and spine gourd can be trailed to dried branches and bamboo tops and sweet gourds to small trees or thatched sheds. Non-productive side branches should be removed up to the first 10 nodes. Annual pruning after the cessation of the active growth period helps to keep a healthy and compact canopy in the sweet gourd. In the other two species, aerial parts dry up naturally with the end of the southwest monsoon and hence do not need any pruning.
Weed and water management
Application of post-emergence weedicides before planting followed by hand-weeding the mounts/beds and hoe weeding the interspace may be followed. The application of plastic mulch or mulching with crop residues also helps to keep weeds at bay. Off-season protection of underground tubers by mulching the plant basin is essential to protect the tubers from sunburn.
Sweet gourd, spine gourd, and teasel gourd do not require irrigation if regular rainfall is received during active crop season, though sweet gourd requires life-saving irrigation during summer. In uneven rains, light irrigation at 3-5 days intervals will be advantageous. Need-based irrigation may be given, depending on water holding capacity and moisture level of the soil, a period of flowering and fruit set are critical for higher yield. Drip and sprinkler irrigation is ideal, but, flood irrigation should be avoided as none of the three species tolerate waterlogging.
Nutrition management: The fertilizer requirement depends on the amount of nutrients available in the soil, soil type, and crop. In general, FYM @ of 10-12 tonnes/ha in teasel gourd and spine gourd and 20-25 tonnes/ha for sweet gourd applied in planting pits as the basal dose is recommended. In-home gardens, 25 kg FYM and 250 g neem cake as basal dose for teasel gourd, and 5 kg FYM and 100 g neem cake for spine gourd is recommended. Application of 40-45 kg N, 40 kg P₂0, and 40 kg K₂O/ha is the general recommendation for teasel gourd which may be reduced to half for spine gourd and doubled for the sweet gourd. On a per plant basis, 150 g of single super phosphate, 50 g muriate of potash, and 30 g urea as two split doses for spine gourd and 225 g single super phosphate, 90 g muriate of potash and 50 g urea as two split doses for teasel gourd are recommended for eastern India. However, no specific recommendations for sweet gourd is available as its optimum fertilizer requirement is yet to be worked out. In the organic homestead farming system, no chemical fertilizers are given; however, 250 g bone meal and 100 g groundnut oil cake are given to teasel gourd on a per plant basis and double the quantity to the sweet gourd. Pollination management: Insect pollinators are specific to all three species. Spine gourd is pollinated naturally by moths and other nocturnal visitors. The sweet gourd is pollinated by native bees, but hand pollination increases fruit set. However, teasel gourd requires hand pollination for assured fruit set, especially outside its home range ere its natural pollinators are absent. Using a camel hair brush, pollen can be dusted on receptive stigma, preferably in the morning hours.
Diseases and pests
All three crops are susceptible to foliar damage by ladybird beetle (Epilacna septima) and spine gourd, to a lesser extent to red pumpkin beetle (Aulocophora fevicollis) and leaf minor (Liriomyza trifolii). Root-knot nematodes are a severe problem for sweet gourd and teasel gourd in endemic areas; however, spine gourd is resistant to root-knot nematodes. Fruit fly (Bactrocera cucurbitiae) damage to young fruits is a severe problem in teasel gourd and sweet gourd even though spine gourd has a moderate level of tolerance. The pumpkin caterpillar (Diaphania indica) is a serious pest of teasel gourd and spine gourd which damages the leaves, flowers, and fruits. Vector transmitted witches broom disease has acquired epidemic proportion in a sweet gourd and spine gourd in Odisha. Maintaining field cleanliness, uprooting of virus-affected plants, and destruction of fruit fly-damaged fruits are of utmost importance in checking the spread of the pest. A surface spray of Deltamethrin 0.028% is effective to control Epilacna larvae. Application of Bacillus thuringinsis @ 2 ml/1 of water or methomyl, carbaryl, or dimethoate @ 2 ml/1 as surface spray also helps to reduce pumpkin caterpillar population. Cue lure traps and pheromone traps are effective in reducing the fruit fly population. Covering the young fruits with a paper or polybag is an eco-friendly method to protect the fruits from fruit fly. Field sanitation and destruction of tunneled leaves help to control leaf minor damage. Application of Carbaryl 10% WP in soil and spraying of Sevin 50WP (2g/1) is effective in controlling red pumpkin beetle. Burning the planting pits with agro-wastes before planting, application of 250-500 g neem cake as basal dose, and or application of bionematon 10 g/pit first as basal dose and in endemic soils, a second dose of bionematon 10g/pit 40 days after planting may be resorted to for root-knot nematode control.
Harvesting and Post-harvest Management
Fruits of all three species are ideally harvested at a tender stage while the outer skin is still green. Ten twelve days old fruits fetch a premium price in the market and beyond fifteen days, teasel gourd and sweet gourd develop gradual reddening of the outer skin and seeds get hardened in all three species. Teasel gourd and spine gourd are hand-picked, the former with the long stalk intact. Sweet gourd needs to be harvested using a sharp knife with a portion of the fruit stalk. Tender fruits are packed in aerated baskets and sent to market immediately after harvest. Fruits can be kept fresh for 3-4 days under room temperature and up to 10 days under refrigeration when packed in airtight polybags.
Sweet gourd for Gac (as commonly known in Vietnam) products should be harvested at a dead ripe stage (90-110 days) when the rind becomes scarlet red. and soft on pressing. Red ripe gac fruits remain fresh for 2-3 days under room temperature and up to eight days under refrigeration.
Value addition and utilization
Fresh green fruits of all three species are cooked as delicacy vegetables in the same way as bitter gourd. There is a consumer preference for these bitterless bitter gourds as vegetables, though much of the traditional medicinal properties are ascribed to the bitter constituents. Surplus produce can be preserved as sun-dried crisp fry. Gac paste extracted from the aril of red ripe sweet gourd fruits is a high-value product in Vietnam and other southeast Asian countries. It can be processed into candy, jam, dried spray powder, nutraceutical products, and ready-to-serve drinks. Being rich in ß carotene (17-35 mg/100 g of edible part), it is one of the best health supplements to manage vitamin A deficiency, prevalent in South and Southeast Asian countries. When cooked along with sticky rice, it imparts a red color to the produce and is called Xoigac in Vietnam. Tender leaves and clippings of all three species are consumed as a leafy vegetable by indigenous people.
