A disease of French beans (Phaseolus vulgaris L.) caused by subterranean clover stunt virus

Abstract

A disease causing serious crop losses in early-sown French beans in the East Gippsland area of Victoria has been shown to be caused by subterranean clover stunt virus.

The virus infected a wide range of leguminous plants and persisted through a moult of its principal vector, Aphis craccivora Koch. It was not seed-borne, nor was it mechanically transmissible.

The field symptoms of the disease on French beans consisted of chlorosis and epinasty of leaves, the whole plant being markedly stunted with a reduction in the length of the internodes. These symptoms were reproduced in the glasshouse by aphid inoculation of the virus to French beans. However, the virus was recovered from both naturally infected and artificially inoculated beans with difficulty.

In field tests, no cultivar of French bean tested was immune to the virus, although a high degree of tolerance was observed in the cultivars Red Mexican U.I.3, U.I.34, and U.I.37, and Pinto U.I.72 and U.I.78.