Morpho-physiological characterization of bread wheat genotypes and their molecular validation for rust resistance genes Sr2, Sr31 and Lr24

AbstractPhysiology-based differentiation of SH genes and Hemileia vastatrix races is the principal method employed for the characterization of coffee leaf rust resistance. Based on the gene-for-gene theory, nine major rust resistance genes (SH1-9) have been proposed. However, these genes have not been characterized at the molecular level. Consequently, the lack of molecular data regarding rust resistance genes or candidates is a major bottleneck in coffee breeding. To address this issue, we screened a BAC library with resistance gene analogs (RGAs), identified RGAs, characterized and explored for any SH related candidate genes. Herein, we report the identification and characterization of a gene (gene 11), which shares conserved sequences with other SH genes and displays a characteristic polymorphic allele conferring different resistance phenotypes. Furthermore, comparative analysis of the two RGAs belonging to CC-NBS-LRR revealed more intense diversifying selection in tomato and grape genomes than in coffee. For the first time, the present study has unveiled novel insights into the molecular nature of the SH genes, thereby opening new avenues for coffee rust resistance molecular breeding. The characterized candidate RGA is of particular importance for further biological function analysis in coffee.

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Molecular marker aided characterization of race specific and non-race specific rust resistance genes in elite wheat (Triticum spp.) germplasm

Australasian Plant Pathology ◽

10.1007/s13313-022-00850-3 ◽

2022 ◽

Author(s):

Dharam Pal ◽

Subodh Kumar ◽

S. C. Bhardwaj ◽

Harikrishna ◽

Narayana Bhat Devate ◽

...

Keyword(s):

Molecular Marker ◽

Resistance Genes ◽

Rust Resistance ◽

Triticum Spp ◽

Rust Resistance Genes

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Identification of Winter Habit Bread Wheat Landraces in the National Small Grains Collection with Resistance to Emerging Stem Rust Pathogen Variants

Plant Disease ◽

10.1094/pdis-04-21-0743-re ◽

2021 ◽

Author(s):

Tyler Gordon ◽

Yue Jin ◽

Samuel Gale ◽

Matthew Rouse ◽

Samuel Stoxen ◽

...

Keyword(s):

Bread Wheat ◽

Resistance Genes ◽

Stem Rust ◽

Rust Resistance ◽

Stem Rust Resistance ◽

Field Nursery ◽

Small Grains ◽

Stem Rust Resistance Genes ◽

Landrace Accessions ◽

Rust Resistance Genes

Wheat stem rust caused by Puccinia graminis f. sp. tritici (Pgt) is a widespread and recurring threat to wheat production. Emerging Pgt variants are rapidly overcoming major gene resistance deployed in wheat cultivars and new sources of race-nonspecific resistance are urgently needed. The National Small Grains Collection (NSGC) contains thousands of wheat landrace accessions that may harbor unique and broadly effective sources of resistance to emerging Pgt variants. All NSGC available facultative and winter-habit bread wheat landraces were tested in a field nursery in St. Paul, MN against a bulk collection of six common U.S. Pgt races. Infection response and severity data were collected on 9,192 landrace accessions at the soft-dough stage and resistant accessions were derived from single spikes. Derived accessions were tested in St. Paul a second time to confirm resistance and in a field nursery in Njoro, Kenya against emerging races of Pgt with virulence to many known resistance genes including Sr24, Sr31, Sr38, and SrTmp. Accessions resistant in the St. Paul field were also tested at the seedling stage with up to 13 Pgt races, including TTKSK and TKTTF, and with 19 molecular markers linked with known stem rust resistance genes or genes associated with modern breeding practices. Forty-five accessions were resistant in both U.S. and Kenya field nurseries and lacked alleles linked with known stem rust resistance genes. Accessions with either moderate or strong resistance in the U.S. and Kenya field nurseries and with novel seedling resistance will be prioritized for further study.

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