Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2000
Publication Date: N/A
Interpretive Summary: Increasing the calcium content of fruits and vegetables has been shown to reduce decay caused by Botrytis cinerea, an important postharvest pathogen. However, there may be significant genetic variability between isolates within this pathogen species. The goal of this study was to determine whether calcium had an inhibitory effect on B. cinerea isolates from different sources and therefore would be successful in reducing decay caused by this fungus in general. Three different isolates of Botrytis cinerea which differed in various virulence factors and their resulting ability to decay fruit were studied. Even though these isolates were genetically different, calcium treatment of apple fruit significantly reduced decay caused by all three isolates. Increasing the calcium content of apples could help the grower maintain fruit quality and reduce his dependency on fungicides.
Technical Abstract: Botrytis cinerea Pers.: Fr is an economically important pathogen with a broad host range. Because of the genetic variability within this species, epidemiological studies are difficult. Calcium infiltration of fruit has been shown to reduce decay caused by this fungus. The goals of this work were to study this variability and also to compare the inhibitory effects of calcium on three isolates of B. cinerea from decayed apple (B) and grape (C and C77:4). Isolate B had the least radial growth and a sporulation rate twice that of isolates C77:4 and C when cultured on PDA. The dry weight of B was higher than C and C77:4 in a modified Richard's solution for 10 days, but this isolate also had the greatest variation. When the pathogenicity of the 3 isolates was tested in situ on fruit from 4 apple cultivars, isolate C produced the largest area of decay on 3 of the apple cultivars. In vitro, this isolate also had the highest polygalacturonase activity after 7 days growth in Richard's solution. Calcium did not significantly affect protein secretion but inhibited polygalacturonase activity at 1 g/liter Calcium Chloride for isolate C and C77:4 and at 16 g/liter Calcium Chloride for isolate B. The pathogenicity of each isolate was greatly reduced when apple fruit were infiltrated with Calcium Chloride solutions. These results support the fact that the biological and statistical variability in a research project can be affected by the B. cinerea isolate selected. Despite this variation, calcium treatment of apples reduced decay caused by all 3 isolates.