Genetics and molecular mapping of leaf rust resistance in T. dicoccum accession Khapli-72
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Date
2019
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DIVISION OF GENETICS AND PLANT BREEDING ICAR-INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI
Abstract
Wheat is the most important food crop in India. At least 30% of the Indian population is
solely dependent on wheat for its consumption in a direct or indirect way. Wheat production
is affected by several biotic and abiotic stresses, among which leaf rust caused by Puccinia
triticina is widespread in India and is capable of causing a yield loss of about 65 per cent
under intense epidemic conditions. Breeding for genetic resistance is economically feasible
and environmentally viable method. Till now about 79 Lr genes have been documented but
with the evolution of new virulent pathotypes many native as well as alien genes became
ineffective to provide resistance. So, breeders have to search for new and broad-spectrum leaf
rust resistance genes.
The tetraploid T.dicoccum accession Khapli-72(2n=4X=28, AABB) having resistance
to leaf rust is maintained at Division of Genetics, IARI, New Delhi, selected for present
investigation. Multipathotype testing of two parents (Khapli-72 and A9-30-1) at seedling
stage with 18 leaf rust races indicated that Khapli-72 is having broad-spectrum resistance to
all the leaf rust pathotypes while A-9-30-1 is found to be susceptible to all the races.
Inheritance study was conducted with the most virulent and prevalent leaf rust pathotype of
India, 77-5. Genetic analysis in F2 suggested that leaf rust resistance in Khapli-72 is governed
by two genes, one dominant and one recessive by segregating in 13R:3S ratio. Screening of
F2:3 families and BC1F1 generation (Khapli-72/A-9-30-1//A-9-30-1) with leaf rust race 77-5
confirmed the presence of one dominant and one recessive gene in Khapli-72 by segregating
in 7HR: 8SEG: 1HS and 1R:1S ratios respectively. As there are two genes, one dominant and
one recessive, there mapping cannot be done using F2 population. Mapping of dominant and
recessive gene require large segregating F2:3 populations of F2 resistance (AaBB) and F2
susceptible (aaBb) (AA: Dominat gene; bb: Recessive gene) plants respectively. Moreover
the F2 resistant plants with genotypes AaBB and AaBb both will segregate in F3 generation.
So one need to differentiate the F3 population segregating in 3:1 from13:3 ratio to map the
dominant gene. In the current study only BSA was performed to identify the putatively linked
molecular markers. Three SSR markers, Xcfd79 and Xwmc559 located on 3AS and Xwmc786
located on 6BL were identified to be putatively linked. The markers of two leaf rust resistance
genes, Lr53/Yr35 and Lr64 reported to be transferred from T. dicoccoides were validated in
parents as well as bulks showed monomorphic banding pattern suggesting that the leaf rust
resistance gene present in Khapli-72 is new and can be used in future breeding programmes.
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Description
T-10237