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Poster: Biology & Disease Mgmt: Genetics of Resistance


Lack of interaction between Fusarium oxysporum f. sp. niveum and Meloidogyne incognita on cucurbit rootstocks resistant to Fusarium wilt of watermelon
A. KEINATH (1), P. Agudelo (1) (1) Clemson University, U.S.A.; (2) Clemson University, U.S.A.

Interspecific hybrid squash (Cucurbita maxima × C. moschata ‘Strong Tosa’) and bottle gourd (Lagenaria siceraria ‘Macis’) rootstocks are resistant to Fusarium oxysporum f. sp. niveum (FON) but susceptible to Meloidogyne incognita, Southern root-knot nematode. Co-infection with root-knot nematode has rendered Fusarium resistance ineffective in other hosts. The objectives of this study were to determine if such an interaction occurred between M. incognita and FON races 1 and 2 on ‘Strong Tosa,’ ‘Macis,’ and watermelon ‘Fascination’ (resistant to race 1) and ‘Tri-X 313’ (susceptible to both races). The four hosts were inoculated in a greenhouse with one of four pathogen treatments: FON applied as 2 x 107 microconidia per pot, M. incognita applied as 2000 J2 per pot, both pathogens, or neither pathogen. Each race was tested twice with 10 replicate plants per host and inoculation treatment. Plants not inoculated with FON did not wilt. After 4 weeks, severity of Fusarium wilt and recovery of F. oxysporum did not differ when hosts were inoculated with FON alone or with FON and M. incognita together (host-by-treatment interactions not significant, P≥0.08 and P≥0.17 for races 1 and 2, respectively). Galling was present on ≥10% of the root system of 90% of the plants inoculated with M. incognita, and no non-inoculated plants had galls. In conclusion, resistance to FON in cucurbit rootstocks is not compromised when M. incognita infects the roots.