When it comes to blotchy ripening in tomato, be familiar with how to recognize it, factors that contribute to its development and steps that can be taken to limit its occurrence. Blotchy ripening is characterized by one or more conditions specific to the external and/or internal color of individual tomato fruit. Idealized versions of individual mature tomato fruit are uniformly red over their entire surface and nearly so throughout their interior flesh. Fruit exhibiting blotchy ripening, however, are not. Instead, defected fruit are mostly red on the outside but marked with areas that remain green, yellow, gray or a much paler red than the remainder of the fruit. Blemished areas may be restricted primarily to the half of the fruit nearest the stem. Internally, the flesh, especially vasculature, of fruit exhibiting ‘blotchy ripening’ may be brown in color or broken down.
Symptoms associated with blotchy ripening are not unique to it. These symptoms can be traced to physiological, disease or insect feeding causes. The symptoms can also vary in intensity and frequency; i.e., with regard to the proportions of individual fruit and entire crops or pickings that are affected and to what extent (e.g., of discoloration). Regardless, it is important to note that fruit are said to exhibit blotchy ripening only when they are also in the mid-late stages of ripening as determined by changes in firmness and other variables and when insect (e.g., whitefly) and disease (e.g., TMV) are ruled out as causal agents. These two criteria separate truly ‘blotchy’ ripened fruit from firm, immature fruit in the early stages of ripening (which can be mottled in color inside and out) and fruit damaged by the action of pathogens and/or insects. Blotchy ripening is a physiological ripening disorder.
Blotchy ripening has been discussed as a potentially significant marketable yield issue in research and extension publications for at least 76 years. Many agree that blotchy ripening occurs more often in greenhouse- and high tunnel-grown crops but open field plantings can also be affected.
What’s behind the disorder? Why do certain fruit ripen unevenly? What can tomato growers do to limit the disorder in their crops?
Immature tomato fruit are green and photosynthetic. In fact, early in their development, tomato fruit can produce a significant portion of the sugars found in them through photosynthesis. Later however, the set of pigments found in fruit of most hybrids shifts and red becomes the dominant color.
This shift is pre-programmed but influenced by conditions surrounding the fruit and within the plant and soil. The first and one of the most reliable steps in minimizing blotchy ripening is selecting varieties known to display it very infrequently – i.e., among few crops year to year and among few fruit within a season.
A variety’s genes may predispose it to physiological disorders like blotchy ripening but this weakness can be minimized or masked with luck and proper management. The causes of physiological disorders can be difficult or take a long time to determine because blotchy ripening and other disorders are difficult to induce experimentally. That said, many years of research and experience have revealed that blotchy ripening is most prevalent when air temperatures during mid-late stages of fruit ripening are extreme (e.g., below 60 deg F and/or above 90 deg F) or highly variable, when humidity levels remain high, and/or when these conditions prevail and light levels are low. Unfortunately, these are exactly the types of conditions common on some farms in the region recently, especially those containing high tunnels. In general, skies have been intermittently cloudy and sunny, temperatures have risen and fallen sharply over short time periods (often reaching below 60 deg F in unheated areas), and rain has been abundant, leading to prolonged periods of high humidity, especially in minimally ventilated high tunnels. These conditions, in combination with varieties susceptible to blotchy ripening, are causing some marketable yield losses.
Nothing can be done to change the weather. Going forward, in addition to careful variety selection, growers are encouraged to minimize temperature extremes and fluctuations as much as possible. As conditions allow, high tunnels should be ventilated so that the interior humidity levels are no higher than ambient, outdoor conditions. Field or high tunnel, though, growers are particularly encouraged to examine their soil fertility and moisture management plans carefully since plant nutrient and water status also influence the occurrence of blotchy ripening.
Severe cases of blotchy ripening are most often associated with factors that limit the supply of potassium to maturing fruit. These factors include: waterlogged and/or compacted soils, below-optimal potassium application rates, above-optimal nitrogen application rates, excessive application of potassium competitors, excessively large or dense canopies, and the environmental conditions mentioned previously. Potassium supplies may be restricted for different reasons; so, in evaluating and modifying your irrigation and nutrient management plans, do not over-compensate.
Supplying too much water on dark days when transpiration is minimal is by far the most common error. Some speculate that an excessive fruit load may also raise the probability that blotchy ripening will be a problem in some pickings.
Immature tomato fruit are green and photosynthetic. In fact, early in their development, tomato fruit can produce a significant portion of the sugars found in them through photosynthesis. Later however, the set of pigments found in fruit of most hybrids shifts and red becomes the dominant color.
This shift is pre-programmed but influenced by conditions surrounding the fruit and within the plant and soil. The first and one of the most reliable steps in minimizing blotchy ripening is selecting varieties known to display it very infrequently – i.e., among few crops year to year and among few fruit within a season.
A variety’s genes may predispose it to physiological disorders like blotchy ripening but this weakness can be minimized or masked with luck and proper management. The causes of physiological disorders can be difficult or take a long time to determine because blotchy ripening and other disorders are difficult to induce experimentally. That said, many years of research and experience have revealed that blotchy ripening is most prevalent when air temperatures during mid-late stages of fruit ripening are extreme (e.g., below 60 deg F and/or above 90 deg F) or highly variable, when humidity levels remain high, and/or when these conditions prevail and light levels are low. Unfortunately, these are exactly the types of conditions common on some farms in the region recently, especially those containing high tunnels. In general, skies have been intermittently cloudy and sunny, temperatures have risen and fallen sharply over short time periods (often reaching below 60 deg F in unheated areas), and rain has been abundant, leading to prolonged periods of high humidity, especially in minimally ventilated high tunnels. These conditions, in combination with varieties susceptible to blotchy ripening, are causing some marketable yield losses.
Nothing can be done to change the weather. Going forward, in addition to careful variety selection, growers are encouraged to minimize temperature extremes and fluctuations as much as possible. As conditions allow, high tunnels should be ventilated so that the interior humidity levels are no higher than ambient, outdoor conditions. Field or high tunnel, though, growers are particularly encouraged to examine their soil fertility and moisture management plans carefully since plant nutrient and water status also influence the occurrence of blotchy ripening.
Supplying too much water on dark days when transpiration is minimal is by far the most common error. Some speculate that an excessive fruit load may also raise the probability that blotchy ripening will be a problem in some pickings.
Tidak ada komentar:
Posting Komentar