Abstract

Wheat leaf rust, caused by Puccinia triticina Eriks., is a common and destructive disease of wheat worldwide. The durable leaf rust-resistance gene Lr34 is typically described as an adult plant resistance gene, which is not expressed at the seedling stage at normal greenhouse temperatures. However, Lr34 is expressed at the seedling stage when plants with Lr34 are grown at low temperatures, i.e. approximately 8°C. Lines and cultivars with Lr34 demonstrate a range of responses from near immunity to intermediate reactions on the primary leaf. The Thatcher-Lr34 near isogenic lines ‘RL6058ʹ (Thatcher*6/PI58548) and ‘RL6091ʹ (Tc*6/Chinese Spring) were resistant to a number of P. triticina virulence phenotypes at the seedling stage when grown under these cool conditions, but were susceptible at typical greenhouse temperatures. A double haploid population from a cross between ‘Thatcher’ and ‘RL6058ʹ, previously genotyped for Lr34, was grown at 8°C and screened for leaf rust response at the seedling stage. The population is segregated by a seedling resistance gene that corresponds to the presence of a resistance allele of Lr34. After extended incubation at cold temperatures, the seedling progeny lines with Lr34 also developed distinct leaf tip necrosis; this phenotype was absent in susceptible plants, similar to their reaction as adult plants. When uninfected plants from this population were grown to the adult plant stage at 10°C, those with the Lr34 resistance allele had extensive leaf necrosis and shrunken, sometimes sterile, spikes.

摘要

小麦叶锈病，导致的小麦叶锈菌意立，是一种常见的和小麦全世界的破坏性疾病。耐久叶锈病抗性基因Lr34通常被描述为成株抗性基因，在正常温室温度下在苗期不表达。然而，当具有Lr34 的植物在低温（即大约 8°C）下生长时，Lr34在幼苗阶段表达。具有Lr34 的品系和栽培品种表现出从近乎免疫到初级叶上的中间反应的一系列反应。等基因系'RL6058ʹ（Thatcher*6/PI58548）和'RL6091ʹ（Tc*6/Chinese Spring）附近的Thatcher- Lr34对许多P. triticina在幼苗期在这些凉爽条件下生长时的毒力表型，但在典型的温室温度下易感。来自 'Thatcher' 和 'RL6058' 杂交的双单倍体种群，先前已对Lr34进行基因分型，在 8°C 下生长，并在幼苗期筛选叶锈病反应。该群体由幼苗抗性基因分离，该基因对应于Lr34抗性等位基因的存在。在低温下延长孵育后，Lr34的幼苗后代系还出现明显的叶尖坏死；这种表型在易感植物中不存在，类似于它们作为成年植物的反应。当来自该种群的未感染植物在 10°C 下生长到成株阶段时，那些具有Lr34抗性等位基因的植物会出现大面积的叶片坏死和皱缩，有时甚至是不育的穗状花序。