Heat tolerance

Cauliflower is heat susceptible, but not to the same extreme degree as broccoli. Some of the Indian cauliflowers such as 'Pusa Katki' have the greatest heat tolerance, but these are early and have relatively poor quality curds. If the temperature is high, then the curd may develop bracts (green bracts corresponding to auxilary leaves are usually present in the curd, Fig. 2.6) which make it unmarketable. Bracting is recessive, and heritability was reported at 73%. The curd may also produce true green leaves in the head.

The curd may also turn purple if exposed to the sun; this may be due to development of small purple buds, which are similar to the small white velvety buds which develop in some curds and is called 'ricey'.

Growing the plants under hotter than ideal conditions will allow for selection for heat tolerance. Solidity of the curd is also desirable, and continued selection for this trait is required as soft curded plants will bolt more readily and have a selective advantage. Solid tends to be recessive, although it is a quantitative factor, and there may be more than one genetic route to solidity, so that crosses of two solid curds does not necessarily mean the hybrid will be solid.

Brocoli Bracting
Fig. 2.6. Illustration of leaf bracting in cauliflower (Brassica oleracea var. botrytis) (M.H. Dickson).
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