Spatiotemporal changes in fungal growth and host responses of six yellow rust resistant near‐isogenic lines of wheat

Abstract

The objective of the present study was to investigate to what extent the macroscopic phenotype of incompatible host–pathogen interactions reflects differences in fungal development and host responses at the histological level. This was done by conventional and advanced microscopic analysis of six wheat near‐isogenic lines differing by individual R genes and inoculated with an avirulent isolate of Puccinia striiformis. Wheat line AvocetYr15 had the lowest macroscopic infection type (IT) 0–1, in which fungal growth was stopped at early stages due to extensive expression of a hypersensitive response (HR) at all time points (4, 8 and 16 days post‐inoculation, dpi) without any sign of haustorial bodies. AvocetYr5 and AvocetYr1 had IT 1, in which most fungal colonies developed secondary hyphae. Many colonies were encased by HR at 16 dpi, more extensively in AvocetYr1 than AvocetYr5. In AvocetYr6 (IT 2), HR was expressed after the formation of secondary hyphae at 4 dpi, after which fungal growth and HR increased simultaneously until most colonies became encased by HR. AvocetYr27 (IT 2–3) and AvocetYr17 (IT 4–5) showed similar fungal growth and HR at 4 dpi, where HR was only weakly expressed in a few host cells. Encasement of secondary and runner hyphae increased significantly in AvocetYr27, but at 16 dpi, HR was often circumvented by large, intermingled fungal colonies in both lines. No resistance responses were observed in Avocet S (susceptible control). The very different histological patterns conferred by the six R genes suggests differences in the timing of the host–pathogen recognition and onset of host defence pathways.

Role of Fungicide Applications on the Integrated Management of Wheat Stripe Rust

“…2019; Liu et al, 2019;Mu et al, 2019;Rahmatov et al, 2019;Saleem et al, 2019;Wamalwa et al, 2019;Xu et al, 2019;Zeng et al, 2019;Zhang et al, 2019;Ramachandran et al, 2020), the development of commercially available resistant cultivars will still need several years and considerable investment in many countries (Solh et al, 2012;Chaves et al, 2013;Ellis et al, 2014;Beddow et al, 2015). Besides, genetic improvement in search of resistant wheat cultivars is not carried out equally in the different wheat producing regions with different climates.…”

Histochemical and Phenotypic Studies Revealed the Diverse Nature of Wheat-Yellow Rust Interaction

“…The wheat stripe rust fungal colonies on the leaves of the genotype RS46 at 10 dpi were 258 µm in size but fungal colony size decreased to 125 µm at 20 dpi. The decrease in fungal colony size might have resulted from the synchronized activation of defense mechanisms (Saleem et al, 2019), like biosynthesis of phytoalexin and the production of Pathogenesis Related Proteins (PRP) (Agrios, 2005). The induced lignification might also have avoided the intercellular spread of wheat stripe rust fungus.…”

Penicillium simplicissimum and Trichoderma asperellum counteract the challenge of Puccinia striiformis f. sp. tritici in wheat plants

“…Rust severity was determined according to the proportion of leaves covered with rust pustules following Cobb's scale (Peterson et al 1948). A calibrated eyepiece micrometre was used to determine rust pustule colony sizes (mm 2 ) (Saleem et al 2019). The number of kernels per 10 spikes, weight of kernels/10 spikes and the weight of 1000 kernels were determined to compute yield components at the harvest stage.…”