Indian Society of Genetics & Plant Breeding
Two independent DNA segments with two linked genes
each namely, Lr19/Sr25 and Sr36/Pm6 were introgressed
by three cycles of backcrossing into fifteen bread wheat
(Triticum aestivum L.) cultivars, susceptible to leaf rust
(Lr), stem rust (Sr) and powdery mildew (Pm). Evaluation
of the BC
3-F5 along with their recurrent parents and
controls carrying specific Lr and Sr genes under natural
and artificial conditions indicated that conventionally
improved newly constituted lines confer resistance to leaf
rust, stem rust and powdery mildew in adult stage against
the pathotypes prevailing in the Nilgiris. Some of these
lines also displayed resistance to leaf rust pathotype 77-8
(253R 31) in adult stage. However, the improved lines, viz.,
C306*3/Cook*6/C80-1, HD2687*3/Cook*6/C80-1, MACS2496*3/
Cook*6/C80-1, PBW226*3/Cook*6/C80-1, UP2338*3/Cook*6/
C80-1 and UP262*3/Cook*6/C80-1 showed moderate
susceptibility to 77-8. The leaf rust pathotype 77-8 was
found avirulent on Lr26. The resistance in UP262 can be
ascribed to Lr23 and some unknown gene(s) possessed
by it. Since Lr19 is effective to all the pathotypes of leaf
rust in India except 77-8, the differential response exhibited
by BC3-F5 lines against a mixture of prevailing races at
Wellington and against a new pathotype 77-8 at New Delhi
indicated unambiguously the presence of Lr19 in the
introgressed lines. High degree of resistance to stem rust
and powdery mildew in all the BC3-F5 lines evidenced that
these carry the genes Sr36 and Pm6. The conventional
methodology proved successful in phenotype-based
selection of resistance gene combinations in the absence
of molecular markers. To ensure the correct identity of
target genes, the BC3-F5 lines (2 to 9) were tested with
molecular markers SCS265, SCS253 and Gb linked to leaf
rust resistance gene Lr19 and SSR stm773 for stem rust
resistance gene Sr36. The presence of genetically
associated genes was verified by the amplification of
translocated DNA segment in most of the backcross lines.
With the detection and testing with a new Lr19 virulence,
host-pathogen interaction test response against leaf rust
and the molecular test response did not correspond in
HW2004*3/Cook*6/C80-1 because of presence of an
additional segment of Lr24/Sr24. The availability of a
combination of major genetically diverse resistance genes
in adapted wheat cultivars would facilitate the strategic
deployment to achieve enhanced durable resistance. Also
these lines could be used as donor and supplement the
molecular mapping and tagging of genes.
Keywords: Leaf rust, stem rust, powdery mildew, adult plant resistance, seedling test, backcrossing, Triticum aestivum
Year: 2009
Volume: 69
Issue: 1
Article DOI: N/A
Print ISSN: 0019-5200
Online ISSN: 0975-6906
M. Sivasamy info_circle
Vinod, Sushma Tiwari, R. S. Tomar, Bhanwar Singh, J. B. Sharma, S. M. S. Tomar info_circle
Suresh Chand info_circle
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