Resistance in potato to two haplotypes of ‘Candidatus Liberibacter solanacearum’

Abstract

The disease zebra chip (ZC) caused by the bacterium ‘Candidatus Liberibacter solanacearum’ causes important economic losses in potato in New Zealand, the United States, Mexico and Central America; in Mexico, haplotypes LsoA and LsoB of the bacterium have been found in chili and potato. The pathogen is transmitted by the psyllid Bactericera cockerelli, and the presence of internal marking in the form of necrotic striation in the medulla of the tubers is considered a typical diagnostic symptom. The potato cultivars currently grown in Mexico are susceptible to this bacterium. The present study evaluates the responses of potato cultivars Atlantic (highly susceptible control), Milagros, one new entry, Real 14, and the experimental clones Bajio 143 and T05–20-11 to inoculation with two haplotypes of the bacterium over two production cycles. The plants inoculated with the mixture of LsoA and LsoB haplotypes, compared with inoculation with only LsoB, showed greater severity of foliar damage and area below the curve of progress of the disease, but not of necrosis in tubers (with exception of cv. Milagros). The cv. Real 14 showed a lower percentage of tuber discolouration than three other tested cultivars after inoculation with the mixture of haplotypes, and less than cvs Atlantic and Bajio 143, after inoculation with LsoB. The same cultivar expressed significantly less severe plant symptoms than cv. Atlantic. The clone T05–20-11 showed significantly less severe tuber symptoms than cv. Atlantic, after inoculation with mixed haplotypes and less severe symptoms than cvs Atlantic and Bajio 143 after, inoculation with LsoB.