Abstract

Nabavi Mostafa, Mohammad Ardakani and Hasan Heidar Arfaa

Diseased stem and root samples from 20 olive nurseries of Golestan province, northern Iran, Fifty six Macrophomina phaseolina isolates were recovered from different nurseries. The recovered M. phaseolina isolates were characterized for pathogenicity and colony phenotype on PDA and chlorate selective media. Inoculum density for all nurseies varied between 4 and 9 propagules per gram of air-dried soil with average 7.61±0.73. All the recovered isolates were pathogenic to the tested cultivars, Mary, Rooghany and Zard, as incited stem lesions ranged between 6.01 cm and 9.02 cm and plant death percent ranged between 56.7 and 78.6 in the pathogenicity test. One color phenotypes (brown colony color) on PDA and three growth patterns were recognized on chlorate media. Chlorate sensitive isolates divided into two classes. Isolates of the first class grew sparse with a feathery like pattern, being the most frequent (94%), and the secondary had a completely restricted radial growth. All the recovered M. phaseolina isolates tested were pathogenic to the tested olive cultivars (Mary, Rooghany, and Zard). Analysis of variance of the interaction between olive cultivars and isolates of M. phaseolina showed significant (p=0.05) effects of cultivar (Table 1) but nonsignificant effects (p=0.05) for isolate, and cultivar × isolate interactions for the tested parameters. Cultivar × isolate interactions were not important factor in determining the variation in root damage.