Evaluating susceptibility of almonds to anthracnose disease caused by Collectotrichum gloeosporioides.

Susceptibility of almond fruit (Prunus dulcis (Mill.) Webb.) to anthracnose caused by Colletotrichum gloeosporioides Penz. (=Gloeosporium amygdalinum Brizi) was investigated. Fruits were punctured, and a drop of spore suspension of the desired size and density was placed on the wound. Fruits were placed in a humid chamber for one week at 22°C. The diameter of the lesion of the infected fruits was used as an indicator of susceptibility. Disease development was found to be negatively correlated with the age of the fruit. The inoculation concentrations used in this research have no effect on the disease development, although the volume of the drop affected the size of the lesion to some extent. With constant, high relative humidity (saturation), the diameter of the anthracnose lesion increased by 1 mm per day, while under dry room conditions the increase was less than 0.5 mm per day. At 22°C lesions developed faster than at either 15° or 27°C. A detailed procedure for assessing sensitivity of fruit to anthracnose is described. This should enable improved comparison of susceptibility between genotypes and in different environments. [ABSTRACT FROM AUTHOR]