Abstract
Leaf rust caused by Puccinia triticina is an economically-important disease in wheat worldwide. A combination of different types of resistance genes may significantly enhance rust resistance under rust-favorable conditions. To investigate the interactions between the rust resistance gene Lr34 and the lesion mimic gene lm on 1BL in Ning 7840, a segregating F8-10 population of 180 recombinant inbred lines was developed from Ning 7840/Chokwang and evaluated for both lesion mimic expression and leaf rust response at the adult plant stage in a greenhouse. A major quantitative trait locus (QTL), derived from Sumai 3, was co-localized with Lr34 on chromosome 7D and explained 41.5% of phenotypic variations for rust severity and 22.1% for leaf tip necrosis (LTN). The presence of Lr34 was confirmed by Lr34-specific markers cssfr1 and cssfr2 in Ning 7840 and Sumai 3. Unlike Lr34, lm conditioned a spontaneous lesion mimic phenotype and had a significant effect on reducing uredinial size, and a smaller effect on severity. Additive effects were observed between lm and Lr34 for severity and LTN, and an epistatic effect was observed for infection type. Single marker analysis also identified several other QTL with minor effects on severity, infection type, or LTN.
Highlights
Leaf rust, caused by Puccinia triticina Erikss., is an economically-important wheat disease worldwide
Ning 7840 produced an Infection type (IT) of 22+, Chokwang 3+4, and the recombinant inbred line (RIL) had IT values ranging from 22+ to 4 with a majority with 3 in both experiments
The effect of the rust resistance quantitative trait loci (QTL) at the Lr34 locus was consistent with previous reports [4,34]
Summary
Leaf rust, caused by Puccinia triticina Erikss., is an economically-important wheat disease worldwide. Lr34 confers a non-hypersensitive reaction (HR) type of resistance [6] and was recently cloned as an ABC transporter [8] This gene remains durable, and virulence towards plants carrying Lr34 has not been observed to date [8]. In Arabidopsis, LM mutants lsd and acd showed enhanced resistance to the bacterial pathogen Pseudomonas syringae and oomycete Peronospora parasitica [15–17] In wheat, both naturally-occurring [18] and chemical- or transgenic-induced LM have been reported [19–22]. Both naturally-occurring [18] and chemical- or transgenic-induced LM have been reported [19–22] These mutants express HR-like phenotypes in pathogen-free environments and exhibit enhanced resistance to biotrophic pathogens, including P. triticina. The main objectives in this study were to elucidate the effects of HR-like lm and non-HR Lr34 on adult plant response to leaf rust and to reveal additional chromosomal loci involved in rust resistance
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