Further Studies on Leaf-curl of Cotton in the Sudan

Abstract

The reasons for adopting the name “ leaf-curl ” for the virus disease which is manifested by symptoms of “ leaf-crinkle ” on certain varieties of cotton, and by “ mosaic ” on certain others, are discussed.A brief review is given of the very few references in previous literature which are relevant to leaf-curl.Up to the end of February 1931, 168 straightforward attempts had been made to transmit crinkle from Sakel cotton to Sakel by means of white-flies (Bemisia gossypiperda, Misra & Lamba), of which no fewer than 157 were successful. No transmission was obtained with any other insects.A single white-fly can transmit the disease to a healthy plant, though infection is less regularly obtained when one or only a few white-flies are used.There is a large amount of negative evidence which indicates that the virus is not transmitted through the seed of Sakel cotton. There is also no evidence that it can be transmitted through the soil.In nearly 200 controlled experiments, the incubation period of the virus in the plant varied from 8 to 34 days, but over two-thirds of the recorded periods were between 11 and 19 days. Possible causes of the variation in the incubation period are discussed.Little is known with certainty about the factors which influence the severity of the disease.At least one case of complete recovery from the disease appears to have been observed. Partial recovery is not infrequent.