Epidemiological and histological components of crown rust resistance in oat genotypes

Abstract

Crown rust, caused by Puccinia coronata f. sp. avenae, can cause significant damage in all regions where oats (Avena sativa L.) are cultivated. The primary means of controlling crown rust has been through genetic resistance, although in most cases resistance has been quickly overcome by the pathogen. More durable partial or non-specific resistance may possess different mechanisms from those underlying genes with specific effects. We studied the epidemiological and histological components of crown rust resistance with potential use in plant protection. Among the components evaluated, pustule density showed the clearest effect on resistance, while the latent period was not an important component. Cell death associated with the accumulation of autofluorescent and phenolic compounds was common in the resistant genotypes, but temporally distinct for the genotypes studied. Genotype Pc68/5*Starter, which has race-specific resistance, showed rapid cell death that prevented the development of pathogen colonies. Conversely, with cultivar URS 21 and genotypes 04B7113-1 and 04B7119-2, cell death and associated accumulation of autofluorescent and phenolic compounds was delayed until pathogen colonies were already established. Pathogen colonies developed normally in susceptible plants genotypes, and had usually produced sporogenic tissue by 5 days after inoculation. The data suggest that the resistance mechanisms, especially hypersensitivity and phenolic compound production, active in resistant plants are similar but may be differently expressed over time. The temporal variation in the expression of hypersensitivity and phenolic compound production reflects the level of field resistance in these genotypes.

URS Altiva - a new oat cultivar with high agronomic performance

“…Partial resistance was characterized by abundant chlorosis and necrosis around small pustules on the leaf laminae, and early telia formation on green leaf tissue of the plants. Similar symptoms have been identified in the cultivar URS 21 and other oat genotypes that presented partial resistance to crow rust (Graichen et al 2011, Zambonato et al 2012, and more recently, in the cultivar URS Brava . The resistance mechanism in the oat-crown rust system is not yet fully understood, even though reactive oxygen species seem not to be important in this pathosystem.…”

“…The resistance mechanism in the oat-crown rust system is not yet fully understood, even though reactive oxygen species seem not to be important in this pathosystem. It seems that in the partial resistance mechanism, observed in URS 21, the death of the fungus occurs first than the death of the cells, differing from the hypersensitive response, in which the cell is killed first (Graichen et al 2011). Another particularity observed in URS 21 is that the production of phenolic compounds was more pronounced than in a cultivar that presented hypersensitive response (Figueiró et al 2015).…”

URS Brava - a new oat cultivar with partial resistance to crown rust

“…In addition, the presence of early telia on green leaf tissue was also observed. These signs had been previously observed in association with partial resistance to crown rust and were later confirmed in a study with the cultivar URS 21 and other oat genotypes showing partial resistance to crown rust (Graichen et al 2011). Thus, the expectation was that the population under selection could have high levels of partial resistance to crown rust, the most destructive oat crop disease.…”

“…Therefore, the Oat Breeding Program of the Federal University of Rio Grande do Sul (Universidade Federal do Rio Grande do Sul -UFRGS) aims to develop cultivars with wide adaptability, high grain yield, high milling yield, excellent agronomical traits such as the vegetative cycle , plant height, lodging tolerance, frost tolerance, and toxic aluminum tolerance (Nava et al 2006), as well as with an adequate level of genetic resistance to the main crop diseases (Graichen et al 2011, Zambonato et al 2012.…”

Discriminating Important Agronomic and Industrial Parameters of White Oat Cultivars Treated with Fungicide Based on SIMCA Algorithm

“…In addition, crown rust can reduce the grain quality, which negatively affects the industrialization and commercialization of oat grain [12]. The primary means of controlling crown rust have been through genetic resistance, although in most cases, resistance has been quickly overcome by the pathogen [13]. Triazole fungicides are one of the top 10 classes of current-use pesticides and have higher consumption as compared to other fungicides available worldwide [14].…”