Sugarcane smut

Sugarcane smut is caused by Ustilago scitaminea. In India, Cultivar Co.419 is susceptible while Co.421 is resistant. In Zimbabwe (then Southern Rhodesia), these reactions were reversed, and it was incorrectly assumed that there was a differential interaction, and a vertical subsystem. It later transpired that, on being imported from India, the labels of these two cultivars had been accidentally transposed and, in fact, the resistances were the same as in India.

In Kenya, a similar difference of susceptibilities was found, and this was believed to support the Zimbabwean conclusions. However, it was soon shown that all the smutted plants in crops of Co.421 were rogues of the susceptible Co.419, and that stands of pure Co.421 were resistant. (These data are based on personal recollection and, to the best of my recollection, they have not been previously published).

In any event, sugarcane is derived from a continuous wild plant pathosystem, and no gene-for-gene relationships have been conclusively demonstrated, although they have been incorrectly reported on occasion.

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