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Wheat Information Service
Number 89: 23-29 (1999)
Research article
Further evidences on the usefulness of
Lr34/Yr18 gene in developing adult plant rust resistant wheat
genotypes
J. Kumar, R.P. Singh, S. Nagarajan* and A.K. Sharma
Directorate of Wheat Research, Karnal, Post Box-158,
Haryana-132001, India
Summary
During 1995-97 twenty one aestivum wheat genotypes were
evaluated for AUDPC (area under disease progress curve) for
Puccinia striiformis tritici. The genotypes fell in three
categories representing strong vertical resistance (AUDPC below 1% of
susceptible check), higher (AUDPC below 20% of susceptible check) and
lower levels (AUDPC between 21- 50% of susceptible check) of slow
rusting. Parental lineage of these genotypes was examined by using a
software package GRIPI developed by CIMMYT, Mexico. It revealed that
slow rusting of higher level occurred in those genotypes which
essentially involved Yaktana 54 in their parentage. Yaktana 54 could
not be traced in the pedigree of those genotypes which had lower
level of slow rusting. The slow rusting of higher level may be
attributed to the presence of adult plant resistance (APR) gene
Yr18. This APR gene against yellow rust seems to have
descended into Yaktana 64 from one of its parent cultivar Frontana,
which is a designated source of Lr34 (an APR gene for brown
rust) having tight linkage with Yr18.
Key words: Wheat, Yellow rust, Adult plant resistance,
Yr18
Introduction
Yellow rust of wheat caused by Puccinia striiformis West.
inflicts heavy yield losses in northern parts of India, if cool and
humid weather persists between December to March. Use of genetic host
resistance is the most effective, economic and ecofriendly approach
for disease control. A number of genes are known to confer resistance
to yellow rust (McIntosh et al. 1995). In general, major seedling
genes such as Yr2 (Sonalika), Yr2 (Kalyansona) and
Yr9 have been widely used by Indian breeders for developing
yellow rust resistant cultivars (Nayar et al. 1994). But,
effectiveness of these race specific genes have reduced since
matching pathotypes emerged from time to time (Kumar et al. 1989,
1990, 1991, 1994; Prashar et al. 1997). The introduction of
resistance from proven durable resistance sources carrying genes
other than major genes, may provide durable resistance (APR) to
yellow rust. Several workers have demonstrated that adult plant
resistance remains durable and appears to involve slow rusting
mechanism (Allan et al. 1966; Johnson 1980; Krupinsky and Sharp 1979;
Milus and Line 1986a,b; Pope 1968; Qayoum and Line 1985; Sharp 1968;
Sharp et al. 1976; Singh and Rajaram 1994). Durability of field
resistance in cultivars can be achieved by using partial adult plant
resistance expressed as slow rusting as they are known to sustain
longer in the field (ParlevIiet 1988).
*Corresponding author: E mail: rpsingh@ nde.vsnl.in, FAX:
0184-251390
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