Field evaluation for resistance to the black rot pathogen Xanthomonas campestris pv. campestris in cabbage (Brassica oleracea)
European Journal of Plant Pathology
Department of Plant Biology, Royal Veterinary and Agricultural University, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark; Department of Agricultural Sciences, Royal Veterinary and Agricultural University, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark; Sokoine University of Agriculture, P.O. Box 3005, Morogoro, Tanzania; Tengeru Horticultural Research Institute, P.O. Box 1253, Arusha, Tanzania; Asian Vegetable Research and Development Center, Africa Regional Program, P.O. Box 10, Duluti, Arusha, Tanzania
Black rot, caused by Xanthomonas campestris pv. campestris, (Xcc), is one of the most serious diseases of crucifers world-wide. Forty-nine genotypes were evaluated for resistance under field conditions in Tanzania after artificial inoculation with Xcc race 1. Open pollinated white cabbage cultivars were generally susceptible, while Portuguese and pointed cabbages exhibited partial resistance. Some F1 white cabbage cultivars were highly susceptible, whereas others exhibited a high level of partial resistance. The most promising of the hybrid cultivars were T-689 F1, Gianty F1, No. 9690 F1, N 66 F1, and SWR-02 F1. Breeding line Badger I-16 exhibited the highest level of resistance of all genotypes. The genotypes accounted for 72.9-75.5% of the variation of the disease severity when assessed on the leaves, and 71.4% of the variation when assessed as internal black rot in heads at harvest. High correlations (equal to or above 0.7) were found between disease severities assessed on leaves three times during the growing season and also with the amount of internal black rot in heads. Leaf loss also was correlated with disease severity. The high genetic determination of the trait and the high correlations between disease assessments indicate that selection for resistance to black rot will be efficient when field screenings are carried out. Evaluation of genotypes for disease severity on leaves during the growing season combined with evaluations of head resistance in the most promising genotypes may be a simple method to select resistant cultivars. © Springer 2005.
bacterial disease; disease control; disease resistance; disease severity; genotype; Africa; East Africa; Sub-Saharan Africa; Tanzania; Bacteria (microorganisms); Brassica oleracea; Brassica oleracea var. capitata; Taxidea taxus; Xanthomonas campestris; Xanthomonas campestris pv. campestris