Physiological disorders in solanaceous vegetable crops and their management
Author: Amish Kumar Sureja
Disorders occur in solanaceous vegetable crops where there is no involvement of pathogen and they are more or less due to the unfavourable environmental conditions like nutrition, water, light, soil etc. The major disorders in solanaceous vegetable crops and their management are discussed below.
1. Blossom-end rot (BER)
It is caused by a localized Ca deficiency in the developing fruit. It begins with light tan, water-soaked areas which enlarge and turn black and leathery in appearance. Mostly the problem occurs at the blossom end of the fruit. Many factors can increase BER viz. low soil Ca, high N rates, using ammoniacal sources of N, high concentrations of soluble K and Mg in the soil, high salinity, low humidity, inadequate soil moisture, excess soil moisture, damage to root system by nematodes, disease, mechanical means or heavy pruning.
Correction measures: Prevent with proper fertilization and good water management. Foliar applications of Ca materials have not proven to reduce BER, since very little Ca is taken up by the fruit and that taken up by the leaves cannot be translocated to the fruit.
2. Blotchy Ripening or Gray Wall
Internally graywall is characterized by dark necrotic areas usually in the vascular tissue of the outer walls. Outward symptoms occur as grayish appearance caused by partial collapse of the wall tissue. It mostly develops on green fruit prior to harvest but can develop later. Cause is not completely understood. There are variety differences in susceptibility. Graywall is more of a problem during cool and short days. High N may increase the problem and adequate K may reduce the problem.
Affected tomato fruit has a gross deformity, usually located on the blossom end of the fruit and is generally not marketable. Cool or cold temperatures if occur about 3 weeks before bloom can increase the catfacing. In general, jointless varieties are more prone to catfacing than jointed varieties. Heavy pruning in indeterminate varieties has been shown to increase catfacing. In indeterminate varieties, catfacing is thought to be related to reduction in auxins in the plant from removing the growing points. Heavy thrips feeding on young fruit can cause a type of catfacing.
Correction measures: Select proper varieties. Prevent soils from becoming waterlogged.
4. Fruit Cracking
Two different forms of cracking occur in tomato fruit. Radial cracking originates from the stem end and progresses toward the blossom end. Concentric cracking occurs in a ring or rings around the stem scar. Both types can occur on the same fruit. Cracking occurs when the internal expansion is faster than the expansion of the epidermis and the epidermis splits. Varieties differ greatly in their susceptibility to cracking. Mature fruits become more susceptible.
Correction measures: Select tolerant varieties, reduce fluctuations in soil moisture, and maintain good foliage cover. Exposed fruits are more susceptible to cracking. Wide fluctuation in air temperature can also increase cracking.
Severe puffy fruit appears light, flat-sided or angular in nature. When fruit are cut, open cavities are observed between the seed gel area and the outer wall. This is caused by any factor that affects fruit set viz. inadequate pollination, fertilization, or seed development.
6. Sunscald or Solar Injury
Sunscald can be of 2 types, sub lethal and lethal. In sub lethal sunscald, yellow, hard area appear usually on the shoulder of fruit. This occurs when tissue temperature rises above about 86°F. The high tissue temperature will not allow the red pigment to develop nor the flesh to soften, but allows the yellow pigments to develop. In lethal sunscald, the tissue turns white and dies. It occurs when tissue temperatures rise above 104°F. Damage usually occurs when fruits are suddenly exposed to sunlight. Over pruning increases sunscald problems. Correction measures: Ensure good foliage cover and use a sun screen material to reduce sunscald.
1. Fruit Splitting or Skin Cracking
The cracking around the shoulder of fruits is often associated with fluctuations in temperature and humidity.
2. Blossom end rot
Lesions appear at blossom end of the fruit while it is green. Water soaked spots appear at the point of attachment of the senescent petals. This occurs due to sudden change in the rate of transpiration, especially in reduced moisture.
Correction measures: Supply light irrigation regularly, avoid heavy application of nitrogen fertilizers and adding lime to the soil or spray anhydrous calcium chloride.
3. Flower and Fruit Drop (Unfruitfulness)
Due to high temperature and low humidity, low light intensity, short day and high temperature. Give light and frequent irrigation at flowering and fruit set stages.
Correction measures: Spray the crop either NAA @ 50 ppm or Tricontanol @ 2 ppm at full bloom stage.
4. Sun Scald
Exposed fruits shows blistered water soaked appearance. Rapid desiccation lead to sunken area usually had white or grey colour in green fruits.
Correction measures: Transplant seedling at closer spacing and grow abundant foliage varieties and control defoliating insects.
1. Black heart
This occurs due to internal breakdown of tissues in tubers and become black. Lack of oxygen is the probable cause. It is also probable that at high storage temperature (35-40oC) accumulation of CO2 at the centre of the tuber might contribute to damage and the subsequent decrease in respiration and development of black heart.
Correction measures: Avoid storage temperature above 35oC and poor ventilation.
2. Hollow heart
Hollow heart consists of an irregular cavity in the centre of tubers. In tissue surrounding the cavity, there is no decay or discoloration. Hollow heart condition appears often in varieties which bulk rapidly and produce large sized tubers.
Correction measures: Adopt closer spacing of plants and avoid excessive use of fertilizers.
When tubers are exposed to sun, they develop green colour due to formation of chlorophyll and thus proper earthing up is required in potato.
About Author / Additional Info:
Working as a Senior Scientist at ICAR-Indian Agricultural Research Institute, Pusa, New Delhi