Effect of temperature and photoperiod on the in vitro germination of conidia of Botrytis squamosa, the causal agent of Botrytis leaf blight of onion

Abstract

ABSTRACT Temperature and photoperiod have a direct effect on spore germination and, for Botrytis squamosa, there is scare information on this subject. Learning the biology of the causal agent has a great importance to understand the development of the disease in the field, as well to take control measures. With the aim of evaluating the influence of temperature and photoperiod on B. squamosa conidial germination, an experiment was conducted in a completely randomized design with four replicates. A 0.1-ml suspension of 1.65x105 conidia per ml was added and spread on Petri dishes containing 1% water-agar. The Petri dishes were placed in BOD incubators adjusted to 10, 15, 20, 25 and 30°C without light, and the percentage of germination of 100 conidia was evaluated under an optical microscope by measuring the germ tube after 24 hours of incubation. In a second moment, this experiment was repeated by incubating the spores at 23°C and photoperiods of 0, 6, 12, 18 and 24 hours, and by evaluating the percentage of germination after 24 hours. Results showed that the highest germination percentages can be obtained in the temperature range between 10 (79.75%) and 30°C (92.5%), and the optimum temperature for germination is 23°C. In relation to photoperiod, the highest germination percentage (94%) was obtained without light, which indicates that B. squamosa germination is favored by shorter periods of light. Thus, the information obtained on the biology of the causal agent of botrytis leaf blight allows better understand the epidemiology of this disease, and such results can be used to help develop a disease forecasting system.