Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

Yellow rust of wheat in Nepal: an
overview
C.B. Karki, 1 S. Sharma 2 and E. Duveiller 3
1. Plant Pathology Division, Nepal Agricultural Research Council, Khumaltar,
Lalitpur, Nepal
2. Plant Pathology Division, Nepal Agricultural Research Council, Khumaltar,
Lalitpur, Nepal
3. CIMMYT, South Asia, Kathmandu, Nepal
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Introduction
Yellow rust caused by Puccinia striiformis West. f.sp. tritici Eriks. and Henn. has
been known to occur since 1964 (Khadka and Shah, 1967), and is the most
damaging wheat disease in Nepal, where wheat is sown on 650 000 ha, with an
average yield of 2 t/ha. Most wheat is spring bread wheat, although facultative
or winter types are grown in some high hill areas. Since modern genotypes
were introduced, 26 cultivars have been recommended: 12 of them for the hills
and the others for the terai (plains). This paper summarizes the yellow rust
situation in Nepal and presents highlights on epidemiology, pathotype, grain
yield loss and host resistance.
Distribution, incidence and severity
Yellow rust is uniformly distributed in the mid-hills belt. In annual surveys, it
is principally observed on local varieties at 600–1500 masl, particularly in the
central and far western hills. Improved wheat varieties, especially RR 21,
started showing susceptibility in the central and eastern regions after the mid-
1980s. Cv. Annapurna 1 showed susceptibility in Kabre and in Kathmandu
valley during the same period (Karki and Sharma, 1990). Epidemics were
observed in parts of western hills in the mid-1990s (Karki, 1998). Severity
increased in river basin areas of the central region during the late 1990s, and
greater yellow rust severity was recorded even in the mid-western inner terai
(Dang) below 300 masl.
In resistance screening trials conducted in the field at disease hot-spot
locations or in growth chambers, many improved varieties and advanced lines
appear resistant, in contrast to local susceptible genotypes (Karki, 1980). In
1986–1988, infection was observed in improved wheat varieties such as RR 21,
Annapurna 1, Annapurna 2, BL 1022, Lerma Rojo 64, Kalyansona and