Dumaguete long purple: A waterlogging-tolerant eggplant

Eggplant is a popular vegetable that is cultivated for its immature fruits, which may be fried, pickled, processed, roasted, or stuffed. Young fruits are also eaten raw.

Eggplant can be grown from low- to mid-elevation areas throughout the year. Highest production can be achieved during the cool, dry months. It thrives best in sandy loam soil with pH 5.5-6.5.

The Dumaguete Long Purple is an old variety that is waterlogging-tolerant eggplant that matures in 100 days and yields 20-25 tons per hectare (t/ha). Its fruits are large, slightly tapering, shiny, and greenish purple.

Fig. 1. Fruits of DLP eggplant variety (CSC, UPLB-IPB n.d.).

Waterlogging-tolerant eggplants with resistance against bacterial wilt and other major diseases can be used as stock plants with high-yielding tomato cultivars as scions. Grafted plants can be grown as alternative crops during the rainy months or offseason production of tomatoes.

Cultural management 

Land Prepation
Prepare land by plowing and harrowing twice. Make furrows 1 meter (m) apart. Spread fully decomposed chicken manure along rows at 1 kilogram (kg)/m or 500 grams (g)/hill. Apply complete fertilizer (14-14-14) at 10-35 g/hill and lightly cover with soil. Establish furrows 0.75 m or 1 m apart.

Seedling Production
Prepare five seedbeds measuring 1 m x 10 m each. Incorporate 1 kg fully decomposed chicken manure and 300 g carbonized rice hull per square meter.

Wet the seedbeds and make shallow lines 5 inches (in) apart. Sow thinly 200-250 g of seeds and cover lightly with soil. Mulch with rice hull or chopped rice straw. Provide rain shelter during the wet season and water regularly. (Better still, sow seeds in plastic seedling trays using processed seedling media like Biomedia from Novatech, or a mixture of carbonized rice hull, cocopeat, and sand.- editor)

Transplanting and Maintenance Harden seedlings one week before transplanting by decreasing the frequency of watering and by fully exposing the seedling to sunlight to minimize transplant shock.

Transplant 4-5 week-old seedlings that are 3-4 inches tall with 7-8 true leaves. Leave a distance of 40-50 cm between plants. Maintain 0.75 m-1 m distance between rows. If planted with other eggplant varieties, maintain an isolation distance of at least 200 m to avoid cross-pollination.

Water the plants weekly.

Fertilizer management

Apply 12 bags of complete fertilizer (14-14-14) mixed with one bag muriate of potash (0-0-60) per hectare or equivalent to 20 g (2 tbsp) of fertilizer per plant before transplanting. Apply fertilizer at least 10 cm away from the seedlings. Use fully-dried chicken or animal manure through basal application to improve soil condition and to supply the plants with micronutrients not found in commercial fertilizers.

Use fermented plant juice from market refuse as foliar organic fertilizer. Mix chopped fruits with equal parts of molasses and ferment for one week, then extract the juice. Apply weekly during the fruiting stage at a rate of 1 tablespoon (tbsp)/4 liters (L) water.

Water management

Water is essential during the long growing period. The amount of water needed depends on soil type and growing conditions. Water or irrigate by furrows as needed. Raised beds and furrows are still recommended even when the DLP variety can withstand prolonged flooding and waterlogged conditions.

Pest diseases management

Major pests include aphids, green leafhopper, thrips, and tip borer. Uproot and burn virus-infected plants to minimize spread of disease. Maintain a weed-free field by weeding regularly or mulching with rice straw to prevent build-up of army worm, cotton leafhopper, mites, fruit and shoot borer, and thrips. Plant early to control thrips.

Remove and burn fruits and shoots damaged by borers. Gather and destroy egg masses of fruit and shoot borers found on the underside of the leaves. To control green leafhopper, grow sacrificial plants such as okra around the area or use recommended pesticides.

Instead of practicing monocropping, intercrop eggplant with other vegetables, as well as cereals and legumes to minimize pest incidence. Plant aromatic crops such as alliums, basil, ginger, lemon grass, and marigold to repel insects. Grow flowering plants such as cosmos, sunflower, and zinnia as border rows to attract beneficial insects.

To control Phomopsis rot, mulch and prune infected basal leaves and fruits. Spray chemical only for serious disease and insect infestations.

Harvest and postharvest handling

Harvest the fruits two weeks after fruit setting when these have reached full
luster and are firm enough.

Harvest twice a week to prevent fruits from becoming too mature or ripe and to reduce damage from fruit borers. Exclude damaged or deformed fruits during harvest to prevent spread of pests and diseases.

Line crates with banana leaves before packing fruits. Do not expose fruits to high temperatures.

Seed production

Soften fruits intended for seed production by rolling them gently on a flat surface or by beating gently with a wooden bat or stick. Apply just enough pressure without cracking the fruit.

Cut a small portion at the end of the fruit peduncle, and open the whole fruit by hand to expose the seeds. Submerge the fruits in a pail of water, and press out the seeds from the fibrous tissues. Good seeds will settle at the bottom while the immature seeds will float. Discard the immature seeds and tissues, and refill the pail with water. Repeat the process until no seeds float.

Place the clean seeds in net bags and airdry for 2-3 days, then sun-dry for 4-5 days while turning the seeds from time to time. When oven-drying, initially dry the seeds to no more than 30 degrees Celsius (OC), and increase the temperature to 40OC as the seeds dry.

Store dry seeds in moisture-resistant packaging materials such as aluminum-lined packets, thick polyethylene plastic bags, tin cans, or glass jars. Place desiccants such as calcium chloride (CaCl2), charcoal, quick lime, silica gel, or wood ash at the bottom of containers. Cover the containers tightly and seal well. Store the containers in a cool, dry place to prolong the shelf life of seeds.

This appeared in Agriculture Monthly’s August 2018 issue.