Cultural, Morphological and Pathogenic Variability among Isolates of Fusarium oxysporum f. sp. capsici Causing Wilt of Hot Pepper in Central Rift Valley, Ethiopia

Fusarium wilt, caused by Fusarium oxysporum f. sp. capsici (FOC) is one of the major pathogens that constrained productivity of hot pepper in Ethiopia. The present study was conducted to characterize FOC isolates and evaluate the pathogenic variability of FOC isolates from Central Rift Valley of Ethiopia. Collection of diseased Fusarium wilt samples were carried out in Alaba, Adama, Adami Tullu Jiddo Kombolcha, Dugda, Mareko and Meskan districts, during the 2018 main cropping season. FOC isolates were characterized based on morphological features and pathogenicity test under greenhouse conditions. Regarding the characterization of FOC isolates, from the collected 70 root and stem samples, 49 were identified as F. oxysporum based on macroscopic (colony color, shape and margin) as well as microscopic characteristics (production of microconidia, macroconidia and chlamydospores). Of these, except 4AA2 (isolated from Alaba district), all were found pathogenic to the susceptible Mareko Fana variety, confirming the identity of the 48 isolates as FOC. However, Isolate 4DGK was identified as the most virulent isolate with 100% wilt incidence and 4.89 vascular discoloration index. Therefore 4DGk were identified as the master isolate for further study. The macroscopic and microscopic features of 4DGK isolate on potato dextrose agar are pink (color), filamentous (shape and margin), flat (elevation) and produce macroconidia with 1, 3 and 5 cell, microconidia and chlamydospore. However, 4AA2 was white (color), round (shape), raised (elevation) and entire (margin) macroscopically and produce macroconidia with single cell, microconidia and chlamydospore. Therefore, for the effective development of pepper variety resistant to Fusarium wilt should using virulent isolates like 4DKG together with other mixed isolates, in order to test a disease interaction and select for durable resistant genotypes.