Molecular diversity and pathogenicity of ralstonia solanacearum species complex associated with bacterial wilt of potato in Rwanda

Publication Type

Journal Article

Publication Date (Issue Year)

2021

Journal Name

American Phytopathological Society

Abstract

Bacterial wilt (BW), caused by Ralstonia solanacearum species complex
(RSSC), leads to substantial potato yield losses in Rwanda. Studies were
conducted to (i) determine the molecular diversity of RSSC strains asso-
ciated with BW of potato, (ii) generate an RSSC distribution map for ep-
idemiological inferences, and (iii) test the pathogenicity of predominant
RSSC phylotypes on six commercial potato cultivars. In surveys con-
ducted in 2018 and 2019, tubers from wilting potato plants were collected
for pathogen isolation. DNA was extracted from 95 presumptive RSSC
strain colonies. The pathogen was phylotyped by multiplex PCR and
typed at sequevar level. Phylotype II sequevar 1 strains were then haplo-
typed using multilocus tandem repeat sequence typing (TRST) schemes.
Pathogenicity of one phylotype II strain and two phylotype III strains
were tested on cultivars Kinigi, Kirundo, Victoria, Kazeneza, Twi-
haze, and Cruza. Two RSSC phylotypes were identified, phylotype II
(95.79%, n = 91) and phylotype III (4.21%, n = 4). This is the first report
of phylotype III strains from Rwanda. Phylotype II strains were identified
as sequevar 1 and distributed across potato growing regions in the coun-
try. The TRST scheme identified 14 TRST haplotypes within the phylo-
type II sequevar 1 strains with moderate diversity index (HGDI = 0.55).
Mapping of TRST haplotypes revealed that a single TRST ‘8-5-12-7-5’
haplotype plays an important epidemiological role in BW of potato in
Rwanda. None of the cultivars had complete resistance to the tested phy-
lotypes; the level of susceptibility varied among cultivars. Cultivar
Cruza, which is less susceptible to phylotype II and III strains, is recom-
mended when planting potatoes in the fields with history of BW

Keywords

molecular epidemiology, multilocus tandem repeat sequence typing, RSSC, potato cultivars

Rsif Scholar Name

Nduwayezu Anastase

Rsif Scholar Nationality

Rwanda

Cohort

Cohort 2

Thematic Area

Climate Change

Africa Host University (AHU)

University Felix Houphouët-Boigny (U-FHB), Côte d'Ivoire

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