Influence of plant stage and organ age on the receptivity of Pisum sativum to Mycosphaerella pinodes

Abstract

International audienceOn spring pea, ascochyta blight (Mycosphaerellapinodes) frequently appears at the plant base on yellowing stipules and disease scores are higher on basal parts of the plants than on the uppermost parts. In order to investigate the relationship between pea plant growth stage and/ororgan age, and ascochyta blight on whole plants and detached stipules and pods, two experiments were conducted in 2009 and 2010 under controlled conditions. This study showed that plant stage does not influence receptivity to ascochyta blight before the appearance of the first visual signs of senescence (beginning of yellowing). When stipules were green, regardless of the plant stage, no differences of receptivity was observed (except for the youngest stipule(s) at the top of the plant). Plant stageonly had an effect on receptivity by the way of the importance of the visual senescence of the organs and visual senescence has a more predominant effect on plant receptivity than the plant stage considered alone. An effect of the nodal position, linked with the stipule age, was observed on whole plant inoculation, with a decreasing disease severitygradient from the base to the top of the plant which was explained by a greater receptivity for the basal/ older stipules which had begun yellowing. On detached stipules, a higher receptivity was observed as soon as visual senescence had been observed. On pods, during their filling, few symptoms appeared and severity was important as soon as they began to yellow. The effect of ascochyta blight on induced senescence of the infected stipules was also observed

Pathogenicity Traits Correlate With the Susceptible Vitis vinifera Leaf Physiology Transition in the Biotroph Fungus Erysiphe necator: An Adaptation to Plant Ontogenic Resistance

“…This age-related resistance, commonly called ontogenic resistance (when young tissues are susceptible) or receptivity (when old tissues are susceptible), could be defined as the dynamic modification of tissue receptivity during organ development, triggering resistance/tolerance to pathogenic micro-organisms. Ontogenic resistance has been described for many plant-pathogen systems [e.g., strawberry-powdery mildew (Carisse and Bouchard, 2010), cucurbit fruit— Phytophthora capsici (Ando et al, 2009), tobacco— Phytophthora parasitica (Hugot et al, 1999), apple-apple scab (Li and Xu, 2002), cocoa— Phytophthora megakarya (Takam Soh et al, 2012), pea-powdery mildew (Fondevilla et al, 2006), pea-aschochyta blight (Richard et al, 2012)]. They are therefore common traits but remain underexploited in disease management, principally because of a lack of understanding of the underlying mechanisms and of the potential variability linked to the physiological responses of the host to environmental factors.…”

A Generic Model to Simulate Air-Borne Diseases as a Function of Crop Architecture

“…Equation 5 presents an example of decreasing ontogenic resistance with the unit aging and showing an increase in the rate of infection on the onset of leaf senescence (). Ontogenic resistance was modeled as a pathosystem-specific function [30] as tissues could get less resistant to infection with aging (pisum-aschochyta [31], potato late blight [32]) or, conversely, could become nearly immune in older organs (vitis-powdery mildew [33]). Biotrophic or necrotrophic behaviours were partly reproduced by this function.…”

“…a varying disease score upon the canopy height, caused by the development of ascochyta blight on pea fields [20]. This observed behaviour is assumed to be a consequence of two processes: a frequent disease initiation on lower leaves (older and more receptive) and a local dispersion to upper nodes [31]. The bell shape of the disease profiles is interpreted as a gradient of age-based (ontogenic) resistance, as upper and younger leaves are more resistant to infection and lower leaves could become senescent before being fully infected.…”

“…Refining the model prediction at this scale will require additional experiments on controlled conditions (e.g. on leaf receptivity, [31]). …”

Plant age and timing of epidemic initiation affect mycosphaerella blight in field pea

“…Means followed within the same cultivar by the same letter do not differ based on a protected LSD test at P ≤ 0.05. progress in the crop (Chongo & Gossen 2001). However, Richard et al (2011) observed that receptivity to M. pinodes, as measured by degree of whole-plant infection, changed very little until senescence was visible.…”