Distribution of wheat stem rust disease in the northern zone and southern highlands of Tanzania: Comparative epidemiology and implications for management
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Date
2017
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Publisher
AJOL
Abstract
Surveys were conducted in farmers’ fields in the northern and southern highlands of Tanzania to
determine the distribution of wheat stem rust disease caused by Puccinia graminis f. sp. tritici and
response of farmer selected wheat varieties to the disease under their natural habitat. Regions
surveyed in the northern zone included Manyara, Arusha and Kilimanjaro, while in the southern
highlands; the survey was carried out in Iringa, Njombe and Mbeya. Four quadrants from every
corner of the surveyed field and one from the center, 1 m2 each were used to assess rust disease
incidence (%) by counting the infected plants divided by total plants per quadrant times one
hundred. Rust disease severity was assessed by using a 0-9 scale: 0=healthy plants, 1=1-10%
stem area with rust pustules, 3=11-25% stem area with rust pustules, 5=26-50% stem area with
rust pustules, 7=51-75% stem area with rust pustules, 9=>75% stem area with rust pustules. Both
rust disease incidence and severity was log transformed before analysis of variance. A total of 17
wheat fields were found infected, 10 from the northern zone and 7 from the southern highlands. In
the northern zone, 50% of the fields had disease incidence above 40% (P>0.05). In the southern
highlands, varieties Sifa and Juhudi were tolerant with disease incidence of 10% in Mbeya and
Njombe respectively. However, the disease incidence of 90% was recorded in Mbeya region on
the same Juhudi variety. Generally, the mean disease incidence recorded were 33.5% and 35.7%
from northern and southern highland zones respectively. Njombe with the same variety Juhudi had
10%, rust disease incidence, indicating presence of a variant of Puccinia graminis f. sp. tritici
with higher virulence. The best performing variety in Mbeya was found to be Sifa whose fields
had an incidence of 10%. In the northern zone the disease incidence in Manyara, Kilimanjaro
and Arusha ranged from 20-60 % with the susceptible variety Mbayuwayu being preferred by
most farmers instead of the variety Ngamia grown in Manyara with incidence of 10% (P>0.05).
The most tolerant or resistant varieties were Ngamia and Sifa grown in northern and southern
highlands zones respectively. There was a distinct difference in disease severity between the two
agro-ecological zones with more severity being observed in the northern zone. Disease severity was
mostly proportional to disease incidence. The study revealed wheat stem rust potential hotspots,
resistant varieties and provides background information for future research and development of
management strategies of wheat stem rust disease.
Description
Tanzania Journal of Agricultural Sciences (2017) Vol. 16 No. 1, 17-24
Keywords
Disease incidence, Disease severity, Variety reaction, Pathogen variant