Development of diseases in cultivated crops depends on the complex interrelationship among host, pathogen and prevailing environmental conditions. In nature, plants are rarely, if ever, subject to the influence of only one potential pathogen and this is especially true of soil-borne pathogens like fusarium wilt (Fusarium oxysporum). In the present study, the co-occurrence of root-knot nematode (Meloidogyne species) and Fusarium oxysporum f.sp. lycopersici was surveyed in the main tomato growing areas of the central rift valley of Ethiopia. Mineral and organic samples were collected from 59 farmlands representing five districts and two commercial farms during the main cropping season of 2017. Cultural, morphological and virulence analysis of these pathogens revealed their coexistence. Out of 59 samples, 39% were found infected with the disease complex [Meloilodogyne species.* Fusarium oxysporum f.sp. lycopesici (FOL)]. Off which, 16.9% and 6.8% resulted from concomitant infection of Meloidogyne incognita* FOL and Meloidogyne javanica* FOL, respectively. The percent prevalence of the disease complex ranged between 27.3% and 60%. The co-occurrence of these pathogens within a single host plant within the same ecological niche will indicate the probability of any type of interaction between each other. Therefore, subsequent research studies on their nature of interaction should be done in the future.

Development of diseases in cultivated crops depends on the complex interrelationship between host, pathogen and prevailing environmental conditions. The significant role of nematodes in the development of nematode-fungus interaction is demonstrated in many crops throughout the world. However, there is scanty research information in Ethiopia. Therefore, the main objectives of this study were to: (i) investigate the effect of Meloidogyne incognita (MI)-Fusarium oxysporum f.sp. lycopersici (FOL) interaction on selected tomato genotypes based on their order of inoculation and (ii) evaluate the reaction of selected tomato genotypes against the MI-FOL interaction. The greenhouse experiment was laid out in a completely randomized design (CRD) factorial with four replications. Three-week-old tomato seedlings were inoculated with MI suspension at a rate of 3000 second-stage juveniles (J 2) and 10 ml FOL suspension (3x10 6 conidia/ml/pot) around the root rhizosphere. Tomato growth, biomass and pathogen related data were recorded starting first week after inoculation to eight weeks of post inoculation. The result revealed that simultaneous inoculation of MI and FOL (NF) and FOL 10 days after MI (N1F2) was found significantly (p ≤ 0.05) reducing tomato growth, biomass and pathogen related parameters compared to single pathogen or un-inoculated control. Among the three tomato genotypes tested, Assila was moderately resistant as measured by the lower number of root gall and egg mass per plant, that it could be of a good choice to manage this disease complex or interaction. Performance evaluation study at MI-FOL hot spot farmers' field should be investigated in the near future.