Critical temperature thresholds-tomato case study

Posted by : Gordon Rogers | Category : Vegetables | Comments : 0 Comments


In Australia, fresh tomatoes are produced in Queensland (Bowen, Bundaberg, Lockyer Valley), NSW (Narromine, MIA, Sydney Basin), Vic (Goulburn Valley – including processing), SA (Murray Bridge, Adelaide Plains) and WA. Queensland accounts for around 70% of fresh market tomato production. Processing tomatoes are grown as an irrigated summer crop in Victoria and New South Wales.

In Queensland, tomatoes are grown all the year round with the main production in Bowen, Bundaberg and south-east Queensland. Bowen production is predominantly an autumn to spring crop.  Bundaberg grows all year round with production peaking in autumn and late spring to summer. In South East Queensland, the crop is produced through summer and autumn as winter is too cold for production.Tomatoes are cold and frost sensitive, and production times in each region are regulated by both low and high temperatures.

For tomato, the 8 to 13 day period prior to anthesis is the most critical developmental phase. The critical temperature varies according to cultivar tolerance to elevated temperatures. The critical temperature for heat sensitive cultivars is 29°C whilst more heat tolerant cultivars are not impacted until the maximum temperature exceeds 32°C. Temperatures which exceed the maximum influence pollination and fruit set. Under marginal conditions fruit may set without adequate pollination but the internal fruit segments will contain few seeds and the tomato will be flat sided and puffy. Irregular pollination can also cause the fruit disorder known as catface.

Even moderate increases in mean daily temperature (from 28/22°C to 32/26°C day/night) have been shown to result in a significant decrease in the number of fruit set. This occurs because temperatures slightly above the optimal range disrupt sugar metabolism and proline translocation during the narrow window of male reproductive development.

As maximum temperatures continue to rise through to 2030, due to further climate change, the temperature threshold of 29°C  will impact on all production districts in Queensland, except the Granite Belt. The impact will be in the form of reduced yields,if more adaptable cultivars are not available. As temperatures continue to rise, then the adverse effects of high temperature on tomato yields will demand more heat tolerant cultivars which will allow growers to maintain production. Without these more tolerant cultivars, the production season in all regions in Queensland will contract to the cooler months.

Summer production will be very difficult in all regions except in SE Queensland. At beginning and end of the summer season in SE Queensland, growers may be able to take advantage of earlier planting in the spring, and later planting in the autumn. These future early and late plantings are currently constrained by low minimum temperatures. The availability of a profitable market at these times of the year will also have a significant influence over the capacity of growers to take advantage of these earlier plantings, which will extend future planting and harvest times in this summer tomato growing district.

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