Adult Plant Slow Rusting Genes Confer High Levels of Resistance to Rusts in Bread Wheat Cultivars From Mexico

Abstract

Rust diseases continuously threaten global wheat production: stem rust, leaf rust, and yellow rust caused by Puccinia graminis f. sp. tritici, Puccinia triticina, and Puccinia striiformis f. sp. tritici, respectively. Recent studies indicated that the average losses from all these three rusts reached up to 15.04 million tons per year, which is equivalent to an annual average loss of around US $2.9 billion per year. The major focus of Mexican and worldwide breeding programs is the release of rust resistant cultivars, as this is considered the best option for controlling rust diseases. In Mexico, the emphasis has been placed on genes that confer partial resistance in the adult plant stage and against a broad spectrum of rust races since the 1970s. In this study, a set of the first-generation tall varieties developed and released in the 1940s and 1950s, the first semi-dwarfs, and other releases in Mexico, all of which showed different levels of rust resistance have been phenotyped for the three rust diseases and genotyped. Results of the molecular marker detection indicated that Lr34, Lr46, Lr67, and Lr68 alone or in different gene combinations were present among the wheat cultivars. Flag leaf tip necrosis was present in all cultivars and most were positive for brown necrosis or Pseudo Black Chaff associated with the Sr2 stem rust resistance complex. The phenotypic responses to the different rust infections indicate the presence of additional slow rusting and race-specific resistance genes. The study reveals the association of the slow rusting genes with durable resistance to the three rusts including Ug99 in cultivars bred before the green revolution such as Frontera,

Resistance Evaluation of Dominant Varieties against Southern Rice Black-Streaked Dwarf Virus in Southern China

“…However, crop resistance should include characteristics that slow down a disease epidemic. The concept of slow rusting for wheat rust resistance was put forward by Caldwell [ 20 ] and applied successfully to breeding wheat-rust-resistant varieties [ 21 , 22 , 23 ].…”

Adult resistance genes to barley powdery mildew confer basal penetration resistance associated with broad‐spectrum resistance

“…In cereals, APR is effective against a range of pathogens, such as wheat powdery mildew (Vikas et al, 2020;Wang et al, 2005), wheat rust (Huerta-Espino et al, 2020), barley leaf rust (Rothwell et al, 2019), and spot and net forms of barley net blotch (reviewed in Clare et al, 2020). Adult plant resistance to barley powdery mildew has been documented previously (Heitefuss et al, 1997;Hwang & Heitefuss, 1982), with Gupta et al (2018) being the first to report an APR quantitative trait locus (QTL) in the accessions 'CLE210' from Uruguay and 'Denar' from the Czech Republic.…”

The Strategy for Marker-Assisted Breeding of Anthocyanin-Rich Spring Bread Wheat (Triticum aestivum L.) Cultivars in Western Siberia

“…The resistance could be associated with the slow rusting Sr2 gene complex, Sr2+Yr30+Lr27+Pbc (pseudo-black chaff), located on chromosome 3BS [59,60]. The Sr2-complex originating from the cv Hope could be identified by the pseudo-black chaff or brown necrosis phenotype on the glumes and below the nodes [61], that were observed on the glumes of the purple-grained lines developed in the background of BW49880 during their ripening ( Figure A5). This complex reduced epidemic development and provided durable and adult plant resistance to a broad spectrum of rusts including Ug99 in the CIMMYT-derived spring wheat germplasm [62].…”