Description of Wheat Rusts and Their Virulence Variations Determined through Annual Pathotype Surveys and Controlled Multi-Pathotype Tests

Abstract

Wheat production started in Australia around 1788 using early maturing varieties adapted to Australian conditions that were able to escape diseases as well as moisture stress conditions. Wheat production is concentrated on mainland Australia in a narrow crescent land considered as the wheat belt occupying an area of about 13.9 million hectares. Rusts are the most important production constraints to wheat production in the world and Australia causing significant yield losses and decreased the qualities of grains. Wheat is affected by three different types of rust diseases: leaf rust, stripe rust or yellow rust, and stem rust. Each species of the rust pathogen has many races or pathotypes that parasitize only on certain varieties of host species, which can only be traced and identified by differential cultivars. Pathotype surveillance is the basis for information on the virulence or pathogenic variations existing in a particular country or wheat growing region of the world. Studies in pathotype variation are conducted in controlled environments using multi-pathotype tests. The currently cultivated commercial wheat varieties of Australia possess leaf rust resistant genes: Lr1, Lr3a, Lr13, Lr13+, Lr14a, Lr17a, Lr17b, Lr20, Lr23, Lr24, Lr26, Lr27, Lr31, Lr34, Lr37, and Lr46; stem rust resistance genes: Sr2, Sr5, Sr8a, Sr8b, Sr9b, Sr9g, Sr11, Sr12, Sr13, Sr15, Sr17, Sr22, Sr24, Sr26, Sr30, Sr36, Sr38, and Sr57; and stripe rust resistance genes: Yr4, Yr9, Yr17, Yr18, Yr27, and Yr33. This paper discusses the historical and current significance of rusts to wheat production in the world with particular reference to Australia viz-a-viz detail description of each of the three rusts and their respective virulence variations through the resistance genes deployed in the commercial cultivars.

Mining of Leaf Rust Resistance Genes Content in Egyptian Bread Wheat Collection

“…Remarkably, few studies have been released during the last decades describing the wheat germplasm that carries Lr genes, especially in Egypt. This apparent lack of knowledge might be attributed to the giant genome of wheat and the existence of various pathotypes (races) that attack only certain varieties of wheat [ 58 ].…”

Occurrence of two races of Puccinia kuehnii causing orange rust of sugarcane in Florida

“…Virulence of rust fungi may vary greatly and many pathotypes or races have been reported for wheat rusts, for example (Gessese, 2019 (Brown & Hovmøller, 2002;Purdy et al, 1985). This hypothesis is supported by the recent reports of occurrence of P. kuehnii in African countries such as Cameroon and Ivory Coast (Saumtally et al, 2011).…”

Impact of Stripe Rust Resistance Alleles on Wheat Grain Yield Using Landraces and Improved Accessions

“…That causality effect between yield reduction and stripe rust resistance was highly pronounced by the negative and highly significant correlation between both traits, as expected. The negative impact of stripe rust on grain yield production was reported by several authors [1,[7][8][9]12,13,33,36,37]. That negative impact could be attributed to the photosynthesis impairment and assimilates reduction due to stripe rust infection, which reduces flower development, fertilization, and the development of ovules and consequently seed setting [38,39].…”

“…In total, 81 stripe rust resistant genes were identified on various wheat chromosomes [1], designated Yr1 to Yr67, Yr73, and Yr74 [12,13]. Out of the 81 stripe rust-resistant genes, 18 are adult-plant resistance genes; Yr11-Yr14, Yr16, Yr18, Yr29, Yr30, Yr34, Yr36, Yr39, Yr46, Yr48, Yr49, Yr52, Yr54, Yr59, and Yr62, whereas 54 are seedling resistance genes [14].…”

“…Wheat rusts (Puccinia spp.) are among the most devastating pathogens that attack wheat, causing significant yield losses [1]. The most common types of wheat rust are leaf rust caused by Puccinia triticina f.sp.…”