Detached and AttachedArabidopsisLeaf Assays Reveal Distinctive Defense Responses Against HemibiotrophicColletotrichumspp.

Abstract

The agriculturally important genus Colletotrichum is an emerging model pathogen for studying defense in Arabidopsis. During the process of screening for novel pathogenic Colletotrichum isolates on Arabidopsis, we found significant differences in defense responses between detached and attached leaf assays. A near-adapted isolate Colletotrichum linicola A1 could launch a typical infection only on detached, but not attached, Arabidopsis leaves. Remarkably, resistance gene-like locus RCH1-mediated resistance in intact plants also was compromised in detached leaves during the attacks with the virulent reference isolate C. higginsianum. The differences in symptom development between the detached leaf and intact plant assays were further confirmed on defense-defective mutants following inoculation with C. higginsianum, where the greatest inconsistency occurred on ethylene-insensitive mutants. In intact Arabidopsis plants, both the salicylic acid- and ethylene-dependent pathways were required for resistance to C. higginsianum and were associated with induced expression of pathogenesis-related genes PR1 and PDF1.2. In contrast, disease symptom development in detached leaves appeared to be uncoupled from these defense pathways and more closely associated with senescence: an observation substantiated by coordinated gene expression analysis and disease symptom development, and chemically and genetically mimicking senescence.

Myosins XI modulate host cellular responses and penetration resistance to fungal pathogens

“…For this fungus, abundant conidial germination and appressorial formation were observed on leaf surface, but no visible symptom development and no invasive hyphae were detected in leaf epidermal cells of Col-0 plants (Fig. 4C), consistent with a previous report (41). In contrast, the 4KO mutant was fully susceptible to the Cd infection and displayed necrotic water soaking lesions on inoculated leaves at 5 dpi (Fig.…”

“…All T-DNA insertion lines were confirmed by PCR or sequencing analysis. Previously described adapted and nonadapted fungal pathogens on Arabidopsis were used in pathogenicity studies (41,44). Chemical treatments included myosin inhibitors and inhibitors involved in endocytosis and protein synthesis.…”

Three Inoculation Methods for Evaluating Sclerotinia Blight Resistance in Peanut

“…In another pathosystem, different responses were observed in assays using detached plant parts than in assays using intact plants. The hemibiotrophic pathogens Colletotrichum linicola and C. higginsianum caused more severe symptoms on detached than on attached leaves of Arabidopsis (Liu et al, 2007). The mechanisms responsible for the varying results with Red River Runner in this study using S. minor, a necrotroph, are unknown.…”

Improved Detached Leaf Assay for Rapid Screening against Late Leaf Spot in Groundnut

“…Detached leaves have been used to screen plant material against many diseases like early leaf spot of groundnut (Ricker et al, 1985), anthracnose in white beans (Tu, 1986), Colletotrichum of Arabidopsis (Liu et al, 2007), crown rust of oat (Jackson et al, 2008), late leaf spot of groundnut (Janila et al, 2013), powdery mildew in pea (Azmat et al, 2013), leaf rust of wheat (Boydom et al, 2013) and Net Blotch of Barley (El-Mor et al, 2018) The objective of this study was to examine the feasibility of using improved detached leaf assay for disease reaction assessment of breeding lines. Our approach was to compare results for inoculated detached leaves of different crop growth stages.…”