Tomatoes: fruit quality

PC 122:

This study clearly demonstrates the delaying ventilation until glasshouse air temperatures reach 25˚C in summer can result in increased fruit softness, blotchy ripening, dark patches and gold spot. These defects result in fruit being downgraded with a loss if income to the grower. The overall appearance of Class I fruit is also reduces, having a negative effect on the image of UK tomatoes with consumers and ultimately an effect on demand for the product. By maintaining lower ventilation set points these potential problems can be avoided.

There are occasions when bright conditions result in high fruit temperatures even with the low ventilation set points and fruit quality defects result. Further research is underway in a Horticulture LINK project to identify the mechanisms responsible for causing these defects both under these conditions and at reduced ventilation to allow more effective use of CO₂.

PC 122a:

The findings of this investigation conclusively demonstrate that key summer fruit quality defects are caused principally by high temperature events during the late maturation phase of ripening (between mature green and colour stage 4/5). Both an increasing magnitude and duration of a heat pulse exacerbated the level of defects. Linear relationships between selected defects and heat pulse temperature have been successfully formulated and can be used to predict the anticipated impact of mean temperature over a 3-day period in the range 20.0-26.0°C, on marketable fruit quality. A critical limit of temperature, above which unacceptable commercial losses will be incurred due to key summer fruit quality defects, has been identified as 23.0°C over 3-days.

PC 122:

Summer fruit quality in UK tomatoes can be reduces by softness, blotchy ripening, netting, gold spot, low acidity and a range of other disorders. The trend of increasing input of CO₂ had led to many growers raising summer ventilation set points in order to conserve CO₂. This has the effect of allowing glasshouse temperatures and humidities to rise with possible implications for fruit quality.

Deficiencies of potassium (K) and calcium (Ca) and believed to play a role in causing a number of defects and through manipulation of the concentration of these elements in feed solutions it may be possible to reduce the incidence and severity of some disorders.

The aim of this project was to determine the importance of K and Ca nutrition in combination with high temperatures in causing fruit softness, blotchy ripening, netting, gold spot, low acidity, and other disorders. This was achieved by imposing two ventilation regimes together with two K and two Ca concentrations in feed solutions.

PC 122a:

Common summer fruit quality defects of tomatoes grown under glasshouse conditions in the UK include uneven ripening, dark patches and fruit softness. However, the precise environmental conditions that caused these defects were unknown. Anecdotal evidence suggested that the most severe incidences of fruit quality defects occurred during periods of high temperature. The overall aim of the project was to quantify the critical limits of key environmental factor(s) that lead to summer fruit quality defects. The project was carried out at HRI Efford and Wellesbourne over a three-year period from 1998 to 2000 and addressed five key hypotheses:

• That temperature has a direct effect on fruit quality
• That temperature can affect quality at various stages of fruit development
• That K and Ca accumulation in the fruit play a key role in the incidence of these defects
• That changes in water relations in the fruit under high temperature have an important role in mediating fruit quality defects
• That the root environment has an important role in regulating fruit nutrient accumulation