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Wheat Information Service
Number 93: 38-39 (2001)
Research information
Appropriate pathotypes of stem rust and leaf rust
for evaluating resistance in durum wheat and bread wheat
A. N. Mishra, Kamini Kaushal and H. N. Pandey
Indian Agricultural Research Institute, Regional Wheat Research
Station, Indore 452 001, India
Differential response of durum and bread wheats to selected cultures
of leaf rust has been reported from India (Pandey and Rao 1984;
Sharma et al. 1996). Hence, a study was conducted to assess the
suitability of different leaf rust pathotypes for evaluating
resistance in durum and bread wheats, and to find out whether the two
wheat species respond differently to various cultures of stem rust
also. The present, communication reports identification of
appropriate pathotypes of leaf rust and stem rust for evaluating
resistance in durum and bread wheats, based on the above study
involving seedling tests of a number of host genotypes with different
rust cultures.
A total of 52 bread wheat and 50 durum wheat genotypes including
recent and past cultivars released in India, genetic stocks and local
varieties, were tested with 11 and 12 pathotypes of leaf rust and
stem rust, respectively. These wheat genotypes and rust cultures were
selected carefully to represent a cross section of the diversity
existing in the wheat crop and the variability occurring in the rust
populations in India. Seedlings of the test lines were evaluated at
18-27C (temperatures mostly ranging between 20-25C) using standard
glasshouse procedures (Stakman et al. 1962). Bread wheat cultivar
Agra Local, susceptible to all the Indian pathotypes of stem rust and
leaf rust, served as check. Infection types 3, 3+ and 4 produced by a
pathotype on a host line indicated virulence of the respective
pathotype to that host line, whereas infection types 0; 1, 2 and X
indicated avirulence. Percent virulence values were rounded off to
the nearest whole number.
The currently prevalent pathotypes of leaf rust races 77 and 104 were
more virulent to bread wheat lines, compared to durums, while other
leaf rust pathotypes were relatively more virulent to durum wheats
(Table 1). The leaf rust pathotype 77-5 was
highly virulent to bread wheats (Table 1).
In fact, only three bread wheat varieties, HI 1454, HP 1633 and HUW
468, showed resistance to this pathotype, and to all the other leaf
rust pathotypes tested. However, the pathotype 77-5 was avirulent to
most of the durum wheat lines. In contrast, the leaf rust races 106
and 108, presumed to be weak races due to their low levels of
virulence to known leaf rust resistance genes, were more virulent to
durums, compared to bread wheats (Table 1).
These findings confirm the earlier observations on the differences in
leaf rust resistance between durum and bread wheats. While durum
wheats showed high levels of resistance to the leaf rust race
77-pathotypes (Honrao and Rao 1996, Nayar et al. 1996, Sharma et al.
1996, Pandey and Rao, 1984), the bread wheats were generally
susceptible to them, particularly to the pathotype 77-5 (Sharma et
al. 1996, Mishra unpubl). Thus, in addition to leaf rust pathotypes
12-2 and 104-2 which showed considerable virulence to both durum and
bread wheats, the pathotypes 77-1, 77-5 and 77-7 should be used for
evaluating resistance in bread wheat, and the pathotypes 12-4, 106,
108 and 162 need to be included for evaluating leaf rust resistance
in durum wheats, based on the virulence frequencies of these
pathotypes to the tested host lines (Table
1).
E-mail: iariindore@sancharnet.in
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