Evaluation of five fluorescent pseudomonads for the prevention of tomato crown root rot and tomato wilt disease caused by Fusarium oxysporum f. sp. Radicis lycopersici and Fusarium oxysporum f. sp. lycopersici

Phytophthora infestans causes late blight on a range of solanaceous plant species. The most frequently used management strategy against this disease relies on repeated fungicide applications and use of partially resistant cultivars. Eighteen new Italian breeding clones of potato were evaluated for their resistance to late blight under controlled and field conditions in absence of chemical treatments. Foliage resistance tests were conducted inoculating 60-day-old potato plants with a P. infestans isolate phenotipically characterized for mating type (A1) and avirulence genes (R1, R2, R3, R4, R6, R7, R8, R10, R11). The pathogen isolate was also used to inoculate tubers of the same clones following the shallow wounds method. One clone showed high resistance to foliage late blight while other two clones showed very high resistance on tuber assay. Field trials were carried out in 2006 and 2007 under natural inoculum pressure in Sicily. In 2006, pathogen pressure was very low, preventing the detection of significant differences among the clones. On the contrary in 2007, under high pathogen inoculum pressure, one clone that had shown good resistance levels in greenhouse tests was found very tolerant. Our results did not show significant correlation between tuber and foliage resistance of the same genotype as reported in the literature. Moreover, these results suggest that preliminary greenhouse screenings could partially predict field resistance levels helping breeder's work.