Introduction
Brinjal (Solanum melongena), also known as eggplant, is grown for its edible fruits. The world production is 497.82 MT lakh and productivity 26.7 MT/ha. India is the second-largest producer of brinjal next to China and produces 135.58 lakh tonnes from a 7.11 lakh ha area with 19.06 MT/ha productivity. Cultivation of brinjal is distributed in almost all states of the country, with the highest in West Bengal, followed by Odisha, Gujarat, and Bihar. The production share of brinjal is 8.3% of the total vegetable production of the country.
Based on plant spread and fruit shape, four botanical varieties are reported under S. melongena, viz. S.melongena var. melongena (Syn: S. melongena var. esculenta) (round and egg-shaped fruits), S. melongena var serpentinum (long and slender fruits), S.melongena var. depressum (early and dwarf cultivars), S.melongena var. incanum (wild and prickly plants with small fruits). Botanically, the fruit of brinjal is a berry, which can be purple, green, white, or striped with wide variations in size and shape.
Climate and soil
Brinjal can be grown under a wide range of temperature conditions, however, a long and warm growing season with a mean temperature of 21-27°C is most favorable for growth, development, and fruit set. Ideal seed germination occurs at 25°C. Cool nights and short summers are unfavorable for its growth. Slow growth at low temperature results in poor fruit quality in terms of size and color. It impedes flowering and develops an abnormal ovary (split) in flower buds. The fruit set is mainly affected by average temperature rather than light intensity and humidity. However, low light intensity shortens the stem, reduces its diameter, increases leaf area, decreases chlorophyll, prolongs flowering, and lowers the yield. At high temperatures, the biological yield potential of brinjal is less due to flower drop. The genotypic differences also persist for tolerance to a higher range of temperature. In India, it is adapted to a diverse climatic condition from north-to-south and east-to-west. In hilly regions, it is grown only as a summer crop. Under northern plains, plant growth and development are adversely affected by low night temperatures during winter. It is a day-neutral warm-season crop and is susceptible to severe frost.
Brinjal can grow on all types of soil ranging from light sand to heavy clay. Sandy soils are good for an early crop, while silt-loam or clay loam increases productivity. Well-drained, leveled and fertile sandy-loam soils with 5.5-6.6 pH are most suited for better growth and development. Increased salinity hinders adsorption of K, Ca, and Mg and increases intake of Na, as a result, leaf size, fruit size, the number of fruits, and yield are reduced. Several cultivars are grown successfully under high pH levels with high use of farmyard manure and or the practice of green manuring before transplanting.
Varieties
The genetic improvement of brinjal is possible both through conventional and biotechnological approaches. Introduction, selection, and hybridization approaches have been commonly used in India. Higher yield has mostly been a major objective of crop improvement, but consumer preference for shape, size, color, and resistance to insect pests and diseases are also given importance. Purple and dark purple fruits are preferred in northwest India; green and variegated are popular in the south, and white is liked in east India. Similarly, round and big fruits are used for bhartha, small round for stuffing, and long in mixed vegetables. Therefore, a large number of cultivars differing in size, shape, and color of fruits are grown in the country.
The varieties and hybrids developed through the conventional breeding approach categorized by distinct features of brinjal are discussed here.
Long fruited: Anamalai, Arka Keshav, Arka Kusumkar, Arka Nidhi, Arka Sheetal, Arka Shirish, ARU 1, ARU 2C, Green Long, Gujrat Brinjal 6, Gulabi, Hisar Pragati, Junagarh Long, KS-331, Nurki Long, Pant Samrat, Punjab Chamkila, Sel 4, Punjab Barsati, Punjab Sadabahar, Punjab Haryana Brinjal 4, Pusa Kranti, Pusa Purple Cluster, Pusa Purple Long, Rajindra Baingan, Swetha, Swarna, Pratibha, Utkal Jyoti, Utkal Keshri, Utkal Madhuri, Azad B 3, Azad Kranti, CO 1, NDB 25, Mysore Green, NHB 2, NDBH 1, Pant Brinjal Hybrid
1, Pusa Bhairav, Pusa Hybrid 5, Pusa Shyamla, DBHL 20, DBL 02, Kashi Taro, Kashi Komal, Arka Anand, H. 4, Pusa Anupum, JC 1, Gulabi, BB 64, Kashi Ganesh, ARBH 786, Swarna Abhilamb, Narendra Brinjal 2, JB. 15, Green Long, Swetha, Utkal Jyoti, GBL 1, KS 331, PBHL 51, PBHL 52.
Round fruited: Azad B 1, Azad B 2, Azad B 4, KS 224, Baramashi, CHBR 1, H 8, Nurki Round, Hisar Shyamal, BR 112, NDBH 6, NDBH 1, P8, Punjab Bahar, Punjab Neelam, Jamuni Gola, Pusa Purple Round, Pusa Hybrid 6, Pusa Hybrid 9, Pusa Upkar, K 2029, Manjri Gota, BR 112, Kalyanpur T 3, Pant Rituraj, NHB 3, Swarna Mani, Swarna Shyamali, Swarna Shree, Kashi Sandesh, GBH 2.
Oval and oblong fruited:ABH 1, ABH 2, Phule Arjun, GJB, Vaisali, White Cluster, Pusa Uttam, MDU 1, TANU Brinjal VRM1, PLR-2; Azad Kranti, Annamalai, Bhagymati, JC 2, Oblong Brinjal 1, PPL1, PKM 1, CO 2, COBH 1, COBH 2, Arka Navneeth, Hisar Jamuni, Junagarh Oblong, JB 15, Pusa Uttam, Surya, Swarna Ajay, Suphal, Swarna Syamali, Uttkal Tarini, Ram Nagar Giant, Gujarat Oblong Brinjal 1, Black Beauty, BH 1, BH 2, Narendra brinjal 1, JC 2, Kashi Prakash.
Small-round fruited:Punjab Nagina, Punjab Moti, Pusa Ankur, Anand Brinjal Small Round 2, Pusa Bindu, Aruna, CO 1, DBSR 44, DBSR 91, Kalpataru, Krishna, Jawahar Brinjal 64, ABSR 2, PBH 3, and White Cluster.
Resistant/tolerant to insect-pest and diseases: Some disease-resistant varieties are
Bacterial wilt: Arka Keshav, Arka Neelkanth, Arka Nidhi, Arka Anand, Pant Brinjal Hybrid 1, Pant Samrat, Uttkal Tarini, Utkal Keshari, JC 2, BB-64, Swarna Abhilamb, Swarna Pratibha, Swarna Shyamali, Swetha, Utkal Jyoti, ARU 2C, NHB 2, Swarna Ajay, PPL 1.
Phomopsis blight: Pant Brinjal Hybrid 1, Pusa Bhairav, Pant Samrat, JC 1, JC 2, Swarna Ajay.
Fusarium wilt: Utkal Madhuri, Utkal Keshari, JC 1, JC 2, Pusa Anupam, Phule Harit, Junagarh Oblong. Little leaf JC 1, JC 2, Hisar Pragati, Phule Harit, Junagarh Oblong, Azad Kranti.
Shoot and fruit borer:Punjab Barsati, Punjab Sadabahar, ABH 1, BH 1, BH 2, JC 1, JC 2, Shyamal, PPL 1.
Root Knot Nematodes: CO 1.
Aphid: Anamalai.
Drought and high temperature:Hisar Pragati, HLB 12, Utkal Madhuri, PKM 1, Azad Kranti, Punjab Moti.
Genetic transformation:The cryptic nature of shoot and fruit borer causes heavy losses and leads to develop transgenic brinjal. The transformation of Bacillus thuringiensis (or Bf) gene using Agrobacterium tumefaciens made it possible to develop transgenic resistance to brinjal shoot and fruit borer (BSFB). Bt-gene is a Gram-positive, soil-dwelling bacterium, commonly used as a biological pesticide. During sporulation, Bt strains produce crystal proteins (proteinaceous inclusions), called 6-endotoxins, that have insecticidal action. This has led to their use as insecticides, and more recently to genetically modified crops. In brinjal, besides transgenic resistance to BSFB, the genetic transformation has also been done to transfer CrylIIB gene against Colorado Potato Beetle, mtlD (bacterial mannitol-1-phosphodehydrogenase) gene for abiotic stress, Mi-1 gene for root-knot nematode resistance, and taaM gene to induce parthenocarpy. In India, transgenic brinjal has been developed and tested under field conditions (awaiting Government approval for commercial release). Bangladesh has become the first country to release BSFB transgenic brinjal for commercial cultivation.
Cultivation
Sowing and transplanting
Brinjal can be grown throughout the year all over the country. However, sowing and transplanting vary in different regions. In Northern India, autumn-winter and spring-summer crops are sown during June-July and November, respectively. Depending upon the crop season, the nursery becomes ready for transplanting in 4 weeks (June July) and 6-8 weeks (November). The young nursery is protected from low-temperature injury during the cold nights of December and January. The seedlings are transplanted in February when the danger of frost is over. In other parts of the country, it is sown from June September and again from January-March. Brinjal can be grown throughout the year under the mild climate of south India; however, it is grown as a summer crop in hills between March and July.
To raise a one-hectare crop, a 62 m² area is required for the nursery raising. A sufficient amount of fine and fully decomposed farmyard manure/compost is properly mixed in the nursery area and irrigated at least 10 days before sowing for germination of the seeds. After fine tilth, 1.5 m wide and 20 cm raised nursery beds are prepared. Beds are well drenched with 1.5% solution of Formalin and covered with a plastic sheet for 24 hours. Thereafter, the soil in beds is turned 4-5 times to escape the harmful fumes of formaldehyde. Generally, 200-250 g seed with good seed germination is sufficient for 1 ha. To avoid the occurrence of seed and soil-borne diseases, the seed is treated with Captan/Thiram @ 3g/kg of seed. Seeds are sown 1.0 to 1.5 cm deep and 5 to 7 cm apart in lines. After sowing the beds are kept moist till germination and for further growth. The germinated seedlings are also drenched with 0.4% suspension of Captan or Thiram to check the post-emergence damping-off of the seedlings. The seedlings are hardened by withholding irrigation before transplanting. Brinjal seed can also be sown in plug/pro-trays having a mixture of coco-peat, vermiculite, and perlite in a 3:1:1 ratio. Water-soluble fertilizers like NPK (19:19:19) @ 2-5g/liter are used to supplement the nutritional requirement of the seedlings.
Healthy and stocky seedlings having 3-4 leaves at the age of 4-6 weeks, which are free from disease, and shoot and fruit borer infestation are transplanted in the field, preferably during evening hours. Depending upon the cultivar and soil, about 30,000-40,000 seedlings of brinjal are required for one hectare. As per the size and spread of the plant, spacing can be adjusted at 60 cm x 45 cm, 60 cm x 60 cm, 75 cm x 60 cm, or 75 cm x 75 cm between rows and plants. More vigorous and late-bearing varieties are planted at wider spacing than a dwarf, upright and early types. Before transplanting, the soil should be thoroughly prepared to the fine tilth with 4-5 deep ploughings.
Manuring and fertilization
Brinjal being long duration crop is a good feeder of nutrients. Higher soil fertility, better soil conditions, and fertilization have a significant effect on its yield. Application of organic and green manures have a positive response on the yield. About 25-30 MT/ha well-rotten organic manure is incorporated into the soil well before the final preparation. The combined application of organic manures and NPK fertilizers gives an added advantage. Generally, 100-120 kg N, 75-85 kg P, and 45-50 kg K are applied. Half N, P, and K are applied before transplanting and the remaining N in two split doses at one-month intervals. Application of starter solution of N alone or NPK in combination at transplanting time has a good effect on yield. Foliar application of 1% urea increased the growth and fruit set. Increased nitrogen increases productivity, but stress conditions increase the number of short-styled flowers and decrease the yield. A high dose of nitrogen (200-400 kg/ha) and potash (>150 kg/ha) increases the incidence of insect pests and diseases. Application of Neem cake @50 q/ ha of poultry manure @15 q/ha also has beneficial effects on brinjal productivity.
However, the problem of micronutrient deficiency in brinjal has not been noticed in the field, but foliar sprays of B, Mn, Cu, and Zn stimulate photosynthesis and increase sugar, dry matter, and vitamin C contents of the fruits. Yield enhancement is observed with the spray of Cu and Mn. Foliar application of potassium nitrate (2,000 ppm), boron and zinc sulphate (500 ppm). The use of biofertilizers like Azospirillium along with inorganic fertilizers is beneficial for increasing the yield of brinjal also.
Weed control
Brinjal being a slow-growing crop is a poor competitor of fast-growing weeds, particularly at the initial phase of plant growth. About 3-4 hand weedings are required for effective control of weeds, proper aeration, and growth of the plant. Mechanical power weeders can be used for intercultural operations in widely spaced rows. Earthing up of the plants prevents lodging and water stagnation, particularly in heavy soils. Pre-emergence application of 0.9-1.5 kg Treflan (trifluralin), or 6 liter Lasso or 4-liter Toke E-25 for one hectare is recommended as chemical weed control. However, Gramaxone (1.25 l/ha) is also effective for postemergence and directed spray weed control. Integrated weed management is effective for better weed control, proper aeration, and growth of the plants. Application of Fluchloralin @2.0 kg/ha or Pendimethalin 1.5 kg or [email protected] 2.0 kg before planting and one hand weeding 30 days after transplanting gives better results with maximum benefit: cost ratio in the brinjal. Besides, pre-planting irrigation, crop rotation, intercropping between the rows, mulch with black LDPE sheets of 25-micron thickness, and drip irrigation reduces the density of weeds to a significant level.
Irrigation
High yields of brinjal are obtained under optimum moisture conditions. First irrigation should be given immediately after transplanting the crop. Fruit set and development are very crucial stages for water requirements. Approximately, 100-110 cm irrigation is required for normal growth of brinjal. Generally, irrigation is required at 4-5 days intervals in summers and 10-15 days in winters. During the rainy season, irrigation depends upon the weather conditions, but water should not be allowed to stagnate in the field. The flooding and aerobiosis cause epinasty and stem hypertrophy due to the increased content of ethylene in the plants. Drought conditions favor downward roots. growth, but affects the yield adversely. Drip irrigation increases water use efficiency, reduces weed occurrence, and increases yield. Drip irrigation and polythene mulching reduces the irrigation requirement by 29% and increases the yield by 18%. Following this approach water use efficiency is increased by 66% and nitrogen fertilizer by 50% than that of flood irrigation.
Cropping systems
Brinjal being a day-neutral plant can be grown successfully throughout the year and can fit well in different short and long period crop rotations. Various cropping sequences under northern Indian conditions can be; brinjal (Jul-Dec)-turnip/radish (Dec-Feb)-cowpea (Mar-Jul); brinjal (Jul-Dec)-onion green (Dec -Feb)- cucurbits (Feb-Jun); cabbage (Oct Jan)-brinjal (Feb-Jun)-radish (Jul-Sept); cauliflower (Nov-Feb)-brinjal (Mar-Jun)-cowpea (Jul-Oct); pea (Oct-Jan)-brinjal (Feb-Jun)-okra (Jul-Oct); brinjal (Jul Oct)-potato (Nov-Jan)-cucurbits (Feb-Jun); seed potato (Oct-Jan)-brinjal (Feb-Sep); wheat (Nov-Apr)-brinjal (Apr-Oct); rice (Jun-Oct)-potato (Nov-Jan)-brinjal (Feb-Ma). Leafy vegetables like coriander, spinach, amaranth, fenugreek, mint, and root crops like carrot, turnip, and radish can be sown as an intercrop with brinjal. Intercropping of brinjal with cabbage and cauliflower from October to November protects it from frost and gives early crop in March. In the rice-vegetable sequential cropping system, rice- brinjal system is more profitable with higher productivity and net returns in low-lying areas. Crop rotation with French bean reduces bacterial wilt incidence. Crop rotation/intercropping with a non-host crop like sorghum, wheat, toria, marigold, onion, and garlic gave good results in checking the root-knot nematode. Brinjal is found as a suitable intercrop in coconut fields also.
Plant growth regulators
Brinjal gives a high response to plant growth regulators for enhancing the yield and quality of the fruits. The response to different growth regulators is summarized as under:
- 2,4-D – Dose – 2 ppm, Stage of application – Flowering, Response – Parthenocarpy, earliness, increased fruit set in short and pseudo style flowers, yield enhancement
- IAA/NAA – Dose – 20 ppm, Stage of application – Flowering, Response – Yield enhancement
- NAA – Dose – 40 ppm, Stage of application – First flowering then two times at 14 days interval, Response – Maximum long-styled flower percent, number of fruits/plant, high fruit yield
- NAA + BA – Dose – 60 + 30 ppm, Stage of application – Flowering, Response – Increased fruit and yield enhancement
- n-metatolyphthalamic – Dose – 250-500 ppm, Stage of application – Flowering, Response – Earliness
- GA3+Ascorbic acid – Dose – 250 + 250 ppm, Stage of application – Seedling roots, Response – Yield enhancement
- Mbxtallol – Dose – 4 ppm, , Stage of application – 4 weeks after transplanting, Response – Yield enhancement
- 4-CPA+Iprodione – – Dose – 20 + 500 ppm, Stage of application – Flowering, Response – Increases fruit size and controls fruit rot
- 24-DNP (dinitriphenol) +5NG (p-nitro-o methaxyphenol) – Dose – 2.5+3.0 ppm, Stage of application – Vegetative, Response – Balances egetative and reproductive growth and controls flower drop
- GA3+NAA +2,4-D – Dose – 10 ppm + 20 ppm + 1 ppm, Stage of application – 30, 60 and 90 days after transplanting, Response – Plant growth, flowering, quality and yield potential.
- NAA and ascorbic acid – Dose – 0.2 mg/l +250mg/l, Stage of application – Soaking of seedling roots, Response – Yield enhancement
Protected cultivation
The protected cultivation of brinjal under low tunnels, net-house, and naturally ventilated poly-houses provides good quality and high yield. In North Indian conditions, the brinjal crop transplanted from October to November can be protected from the frost during winter (December to January) under low plastic tunnels (50 µ) for getting early and high yield. Mulching with a black polythene sheet (25 µ) gave an added advantage by raising the soil temperature during the cool season. Cultivation of brinjal in net and poly net-house pesticide use is lowered, as the entry of shoot and fruit borer is restricted. Due to heterostyled flowers and lack of pollinators, the fruit set is affected under the net and poly net-houses. This problem can be solved with supplementary pollination by tapping the main stem with a stick at the time of pollen shedding (noon hours). This practice increased the yield by 93% of net-house grown brinjal under the Punjab conditions. Training of brinjal plants by retaining two main stems helps in the utilization of the vertical space of protected structures, prevents overshadowing of plants, and facilitates supplementary pollination.
Grafting
The first record of brinjal grafting is available on scarlet eggplant (Solanum integrifolium) in the 1950s. The grafting technique had been successfully adopted on a commercial scale in the 1990s by many Southeast Asian counties like Japan and Korea. In Japan grafted brinjal covered 43% area of open and tunnel cultivation and 94% area of greenhouses. Mainly, the grafted plants provide disease tolerance from the soil-borne pathogens and pests such as Verticillum, Fusarium, and Meloidogyne spp., which causes heavy losses to the yield. In Asia and Europe, eggplant is grafted on Solanum torvum, S. melongena and S. aethiopicum, and various rootstocks are available commercially. The wild relative
Solanum torvum was found resistant to a wide range of soil-borne pathogens like Ralstonia solanacearum, Verticillium dahliae, Fusarium oxysporum, and Meloidogyne spp., and is frequently used in grafting. In general, side grafting and patch budding are found successful. Grafted plants are placed immediately in a healing chamber with 100% relative humidity and 80-84°F temperature for three days without any light. On the fourth day, plants are placed under florescent lights and gradually acclimatized to the full sunlight.
Harvesting and post-harvest management
The fruits are harvested at the immature and tender stage for the market when they have developed to normal size with good color and culinary qualities. Consumers prefer attractive, bright, and glossy fruits of optimum size having freshness and good firmness. The fruits are harvested with stalks up to joints avoiding injury to the branches. Some brinjal cultivars like BR 112 and NDB 25 easily detach at soft joints, while others need a sharp knife or clippers. Brinjal has a great variation in size. Smaller fruits are harvested more frequently than bigger ones. Fruits should be harvested in the evening in order to avoid sun-scald and accumulation of field heat. To maintain the freshness, fruits are pre-cooled by sprinkling water after picking and packed in baskets or cartons for local or distant markets. Ambient storage of brinjal fruits is not possible for longer durations. High respiration and water loss during storage give shrunk appearance and lower cooking quality. Fruits packed in polymeric films (cling or shrink type) stored at room temperature retain freshness and quality for 7-10 days. Storage at 6°C or lower temperature leads to chilling injury. Fruits can be stored successfully for 2-3 weeks at a temperature of 10-11°C and 92% relative humidity.
Yield varies according to the region, cultivar, and duration of the crop. Early crops normally yield low (25-30 MT/ha), while long duration crops yield heavy (35-50 MT/ha). Many F, hybrids give a yield of 45-90 MT/ha under high fertility level.
