ISHS Acta Horticulturae 193: XIII International Symposium on Fruit Tree Virus Diseases
THE INFLUENCE OF TEMPERATURE ON THE EXPRESSION OF GREEN CRINKLE IN GRANNY SMITH APPLE FRUIT |
| Authors: | G.R. Johnstone, P.J. Sampson |
| Abstract:
The occurrence of crinkled fruit in a group of Granny Smith trees infected with apple green crinkle (AGC) growing at Grove, Tasmania varied greatly between seasons. Symptoms of infection were more common and severe in those seasons when the spring temperatures were cooler. The critical period when temperature influenced symptom expression most was from 28 October (the calyx stage) for a period of 19 days each year. The relationship between temperature and symptom expression was defined by a linear regression equation. Symptoms were never expressed when the mean daily temperature over the critical period exceeded 12.6°C. Environments having mean daily temperatures below 10°C during the critical period are needed to reliably index for AGC. Important AGC disease problems are also liable to occur in sensitive cultivars in those environments. Symptom expression of AGC appeared to be enhanced when infected trees were propagated on precocious rather than seedling rootstocks, especially when they bore heavy fruit loads. | |
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