TITLE:
Characterization of Congolese Strains of Xanthomonas axonopodis pv. manihotis Associated with Cassava Bacterial Blight
AUTHORS:
G. Mamba-Mbayi, P. Tshilenge-Djim, K. K. Nkongolo, A. Kalonji-Mbuyi
KEYWORDS:
Cassava Bacterial Blight (CBB); Xanthomonas axonopodis pv. manihotis; Morphological and Physiological Characters; CBB Incidence; Strains Aggressiveness; DR-Congo
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.5 No.9,
April
4,
2014
ABSTRACT: Cassava bacterial
blight (CBB) caused by Xanthomonas
axonopodis pv. manihotis has
been reported in several African countries since 1970. Knowledge of the virulence and diversity of Xanthomonas axonopodis pv. manihotis strains
is important for an integrated control of CBB. The main objective of the
present study was to characterize strains of Xanthomonas axonopodis collected
from various regions in the DR-Congo. There was variability
among strains for shape (form), contour (margin) and elevation. Bacterial cell
size for the strains analyzed varied from 24.1 μm × 11.3 μm to 11.4 μm × 4.2 μm. All the Xanthomonas axonopodis pv. manihotis strains
but one was motile. Two distinctive
groups were identified based on radial growth of their colonies. The first
group grows faster (7.8-10.5 mm/d) compared to the second group (4.8-6.9
mm/d). Five strains (Gandajika, Inera/Stat, Kansasa, Mulumba and
Musakatshi) were classified as virulent with a damage rating ≤ 1 and four were
aggressive (Luputa, M'vuazi, Boketa and Kiyaka) with a damage rating > 1.
Significant differences were also observed among strains for disease onset,
incidence and plant mortality. The highest incidence (33%) of bacterial blight
21 days after infestation (DAI) resulted from the Boketa strain inoculation and
the lowest (0 % disease incidence) from INERA/STAT and Musakatshi strains.
There was no clear association between geographic origin of the strains and
their aggressiveness.