Wheat Leaf Rust Uredospore Production on Adult Plants: Influence of Leaf Nitrogen Content and Septoria tritici Blotch

Abstract

Leaf rust uredospore production and lesion size were measured on flag leaves of adult wheat plants in a glasshouse for different lesion densities. We estimated the spore weight produced per square centimeter of infected leaf, per lesion, and per unit of sporulating area. Three levels of fertilization were applied to the plants to obtain different nitrogen content for the inoculated leaves. In a fourth treatment, we evaluated the effect of Septoria tritici blotch on leaf rust uredospore production. The nitrogen and carbon content of the spores was unaffected or marginally affected by lesion density, host leaf nitrogen content, or the presence of Mycosphaerella graminicola on the same leaf. In leaves with a low-nitrogen content, spore production per lesion was reduced, but lesion size was unaffected. A threshold effect of leaf nitrogen content in spore production was however, evident, since production was similar in the medium- and high-fertilizer treatments. In leaves inoculated with M. graminicola and Puccinia triticina, the rust lesions were smaller and produced fewer spores. The relationships among rust lesion density, lesion size, and uredospore production were fitted to a model. We determined that the density effect on spore production resulted mainly from a reduction in lesion size, the spore production per unit of sporulating surface being largely independent of lesion density. These results are consistent with those obtained previously on wheat seedlings. The main difference was that the sporulation period lasted longer in adult leaves.

Wheat leaf photosynthesis loss due to leaf rust, with respect to lesion development and leaf nitrogen status

“…This does not mean, however, that the plant N content did not affect the pathogen. First, in the same experiment, we found (Robert et al, 2004b) that the low fertilisation treatment induced a lower spore production by the lesions. Second, although the plants of the three treatments were inoculated by the same method, the highest lesion density was 33 lesions cm −2 in N0, compared with 59 lesions cm −2 in N1 and 100 lesions cm −2 in N2.…”

“…The pathogen's development is influenced by the plant age (Rapilly, 1991) and the leaf age ( Johnson & Teng, 1990). Moreover, the nutritional state of the leaves shows a large range of values in field situations, which may influence lesion development and damage expression (Snoeijers et al ., 2000;Robert et al ., 2004b).…”

Pathogen and host genotype differently affect pathogen fitness through their effects on different life-history stages

“…Host genotype had little effect on infection efficiency but strongly affected later life-history stages of latent period and sporulation capacity. Latent periods were significantly longer on the Ogle host line while sporulation capacity was significantly greater on the Otana host line, suggesting differences among these hosts in levels of host defense [53] or resource availability [54,55]. …”

Variation in aggressiveness is detected among Puccinia triticina isolates of the same pathotype and clonal lineage in the adult plant stage

“…Lesion density was first analyzed as a response variable to estimate potential differences in infection efficiency and then was introduced as a quantitative co-variable in the analysis of latent period, spore production and lesion size, which are potentially density-dependent variables (Mehta and Zadoks 1970;Shaner 1983;Robert et al 2004). In the lesion size analysis, log-transformation of lesion density was needed to linearize the data.…”