Abstract
Potato growers suffer losses due to potato soft rot and blackleg caused by pectinolytic bacteria of different species. These bacteria cause yield loss during cultivation and storage, and can be transmitted to the next generations through seed tubers. The prevalence of Pectobacterium atrosepticum has decreased over the last 20 years in Europe in favour of Dickeya solani and P. carotovorum subsp. brasiliense. Twenty-six diploid interspecific Solanum hybrids, previously selected for tuber resistance to P. atrosepticum, were screened for resistance to a highly aggressive D. solani strain in terms of tuber and blackleg reaction. The bacterial strain used for inoculation was characterised by a relatively high optimal growth temperature in vitro, ranging from 33 to 35 °C. Twenty-four diploid clones did not differ in terms of tuber reaction to inoculation with this strain of bacteria in comparison with the clone USA 249, which is the somatic hybrid of S. brevidens (+) S. tuberosum with proven resistance to Pectobacterium. Seventeen clones performed significantly better in terms of blackleg resistance than the resistant potato cultivar Glada. Eleven of the selected diploids produced unreduced gametes, which allows their use in improving the resistance of tetraploid potatoes to diseases caused by bacteria of both Pectobacterium and Dickeya.
Highlights
Two diseases of potato (Solanum tuberosum), namely, blackleg of the foliage and soft rot of the tubers, are caused by soft rot Enterobacteriaceae (SRE), which belong to the genera Pectobacterium and Dickeya
§ Mean values that were obtained in three independent experiments, 30 tubers per genotype, from two growing seasons; SR—soft rot parameter, mean weight of rotten tissue of all tested tubers; DS—disease severity, mean weight of rotten tissue of tubers with symptoms; DI—disease incidence, proportion of tubers with rot symptoms, in columns SR or DS numbers followed by the same letter are not significantly different at P ≤ 0.05 according to Duncan’s test; # number of tested plants (N) and the mean percentage of plants (%) with symptoms of blackleg after inoculation with the isolate of D. solani that were assayed in two independent experiments; *, ** and *** are the significance of differences between tested clone/cultivar and the standard potato cv
The greatest differences in rotting of tubers among potato cultivars were observed at higher temperatures (26–30 °C), while differences in the number of successfully infected tubers between medium-resistant and susceptible cultivars were observed at lower temperatures (20–24 °C)
Summary
Two diseases of potato (Solanum tuberosum), namely, blackleg of the foliage and soft rot of the tubers, are caused by soft rot Enterobacteriaceae (SRE), which belong to the genera Pectobacterium and Dickeya. Lebecka and Czarniak (2019) tested the resistance of tubers of ten potato cultivars, namely, Brooke, Glada, Hermes, Irys, Lady Claire, Lady Rosetta, Omega, Smith Comet, Verdi and VR 808, using for inoculation two aggressive isolates of D. solani and P. brasiliense sp. IPO2276)—was determined as differences in optimal growth temperature among SRE species/genera are known, and because some of the bacteria causing potato blackleg, from genus Dickeya, have been found as ‘cold strains’ (Pérombelon 2002)
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