GENETIC ANALYSIS OF LEAF RUST RESISTANCE GENE “LrSyn55” IN WHEAT
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Date
2019
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DIVISION OF GENETICS ICAR-INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI
Abstract
Wheat productivity is severely impacted by incidence of rust infection across the globe.
Among the wheat rusts, leaf rust is most common and causes economic loss to the wheat crop.
Leaf rust of wheat caused by Puccinia triticina Eriks, is an ‘obligate biotrophic parasite’ that
evolves frequently and develops new pathotypes to overcome major resistance genes being
exploited in wheat breeding.
Therefore, to handle this rapidly evolving rust pathogen, there is a continuous quest for
identifying new resistance genes throughout the world. In this effort, one of the Synthetic
Hexaploid Wheats (SHW), Synthetic 55 [GAN/Ae. squarrosa (180), CIMMYT Synthetic ID:
221, Cross ID: CIGM 90-799] available at Indian Agricultural Research Institute, New Delhi
was investigated for confirmation of inheritance of leaf rust resistance gene “LrSyn55”,
effectiveness of Lr genes located on 1DS and testing the allelic relationship of LrSyn55 with
the other four known genes located on short arm of chromosome 1D.
Leaf rust resistance gene carried by Synthetic55, LrSyn55 was confirmed to be
monogenic dominant in 3 F2 and 3 Test cross populations involving Thatcher, HD2932 and
HD2733 as susceptible parent. As LrSyn55 was reported to be located on chromosome 1DS,
having 4 other Lr genes viz., Lr21, Lr42, Lr60 and LrSyn45. The multipathotype testing against
21 pathotypes suggested the resistance of LrSyn55, LrSyn45 and Lr42 to be effective against
all the pathotypes. The chances of LrSyn55 being Lr21 and Lr60 were ruled out based on
infection types against different pathotypes, although multipathotype testing of Lr60 could not
be performed due to unavailability of true stock. The likelihood of LrSyn55 being Lr42 and
LrSyn45 was ruled out by observing recombinant susceptible seedlings in F2 population
developed by inter crossing the effective Lr genes on chromosome 1DS. The research work
undertaken confirms the uniqueness of LrSyn55 compared to other Lr genes located on
chromosome 1DS. The study also identifies its broad spectrum effectiveness to be exploited
for resistance breeding.
Keywords: Synthetic Hexaploid Wheat, Resistance, LrSyn55, Leaf Rust, Genetic Analysis
Description
T-10267
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