Alternaria brassicae interactions with the model Brassicaceae member Arabidopsis thaliana closely resembles those with Mustard (Brassica juncea)

Abstract

Alternaria leaf blight, a disease of oilseed Brassicas is caused by a necrotrophic phytopathogenic fungus . The details of its pathogenesis and defence responses elicited in the host upon infection have not been thoroughly investigated. Here, accession Gre-0 was identified to be highly susceptible to . A comparative histopathological analysis for disease progression and plant responses to in and revealed significant similarities between the two compatible pathosystems. Interestingly, in both the compatible hosts, ROS accumulation, cell death and callose deposition correlated with the development of the disease. Based on our results we propose that - can be an apt model pathosystem since it emulates the dynamics of the pathogen interaction with its natural host- Brassicas. The existing genetic diversity in can be a starting point to screen for variation in responses to Alternaria leaf blight. Furthermore, several tools available for can facilitate the dissection of genetic and molecular basis of resistance.

ROS accumulation and associated cell death mediates susceptibility to Alternaria brassicae in Arabidopsis accessions

“…Following germination, A. brassicae invades the host tissue by developing Appressoria Like swollen, globular Structures (ALS) at the hyphal apices. Similar Appressoria like structures were also observed when the fungus invaded its natural host B. juncea (Mandal et al, 2018). Fungal penetration attempts could be observed in all accessions ( Supplementary Table S2).…”

“…Also, it is well established that ABA induces closure of stomata. Stomata have been shown to be the major penetration site of A. brassicae in our previous study (Mandal et al, 2018). Therefore, ABA might have an important role in defence against A. brassicae.…”

“…The interaction and disease responses in the model pathosystem appear to be closely resembling the natural host Brassica juncea-A. brassicae interaction (Mandal et al, 2018). Variation in the response of a set of natural Arabidopsis accessions to A. brassicae was observed.…”

“…This is in concordance with the recent study by Ranjan et al, 2017, which showed that the pathogenic invasion of S. sclerotiorum requires the host RBOHs and the silencing of a specific RBOH in soybean led to enhanced resistance against the pathogen. In addition to host generated ROS, A. brassicae is also known to produce ROS at the penetrating hyphal tips (Mandal et al, 2018). The role of pathogenproduced ROS in the Arabidopsis-A.…”

Genome‐wide association mapping in Arabidopsis identifies novel genes underlying quantitative disease resistance to Alternaria brassicae

“…The GORK mutant has been reported to show limited stomatal closure in response to abscisic acid (ABA) and jasmonic acid (JA) (Becker et al, 2003). A previous study in Brassica juncea (Giri et al, 2013) and studies from our laboratory (Mandal et al, 2017) have shown that A. brassicae preferentially penetrates through stomatal openings. The culture filtrate of A. brassicae caused infection-like symptoms on both resistant and susceptible accessions and mimicked the spore inoculation symptoms very closely.…”