Genetic variation in partial resistance to leaf rust in winter wheat: disease progress, foliage senescence and yield reduction

Abstract

Relations between leaf rust progress, foliage senescence and yield reduction were studied for seven winter wheat genotypes, differing in their partial resistance to leaf rust. Leaf rust accelerated leaf and ear senescence. Photosynthesis measurements showed, however, that the photosynthetic capacity of the remaining green surface was not affected. Differences between genotypes in yield reduction were largely explained by differences in leaf senescence and, therefore, in cumulative light interception (r = 0.83) and crop photosynthesis. Reduction in cumulative light interception was closely related to the area under the disease-progress-curve (r = 0.85), which was also closely associated with yield reduction (r = 0.88). However, the time taken to reach a 501t!o reduction of green leaf area and the pustule density on I July (i.e. halfway through the epidemic) were just as good predictors of yield reduction as cumulative light interception and area under diseaseprogress-curve, suggesting that the former are useful criteria in the selection for partial resistance to leaf rust.

Ratio Between Virtual and Visual Lesion Size as a Measure to Describe Reduction in Leaf Photosynthesis of Rice Due to Leaf Blast

“…The reduction in leaf photosynthetic rate due to leaf rust in wheat was characterized with a f3 value that did not differ significantly from 1. This is in accordance with the conclusion drawn by Spitters et al (19) that after leaf rust infection the photosynthetic capacity of the remaining green surface is not affected. The f3 value for powdery mildew in wheat expressed clearly that the pathogen's effect on leaf photosynthetic rate of the host is much stronger than in the case of leaf blast in rice.…”

“…Independent sets of data used to explore utility of the model with other pathosystems. Two data sets on reduction of leaf photosynthesis in winter wheat due to leaf rust (19) and powdery mildew (18) were used to explore the utility of the model for other pathosystems. Spitters et al (19) measured leaf photosynthesis of the flag leaf on wheat cultivar Cappelle Desprez.…”

“…Two data sets on reduction of leaf photosynthesis in winter wheat due to leaf rust (19) and powdery mildew (18) were used to explore the utility of the model for other pathosystems. Spitters et al (19) measured leaf photosynthesis of the flag leaf on wheat cultivar Cappelle Desprez. The measurements were taken in the field using a portable leaf chamber gas analyzer similar to the one described previously.…”

“…For various pathosystems, an effect of the pathogen on photosynthesis of the remaining green leaf area has been reported (for example, Erysiphe graminis on wheat [18] and Alternaria alternata on cotton [5]). Pathosystems in which the pathogen did not impair photosynthesis of healthy leaf tissue also have been reported (for example, Puccinia recondita on wheat [19] and Phytophthora infestans on potato [22]). Obviously, the effect of a pathogen on host photosynthesis varies according to the pathosystem under consideration.…”

Simulation of yield reduction by leaf rust in winter wheat, applied to the analysis of genetic variation in partial resistance

“…In an earlier paper, differences in yield reduction between winter wheat genotypes due to leaf rust were attributed to differences in disease progress and to differences in acceleration of plant senescence (Spitters et al, 1990). The variation in yield reduction can be analysed further by dividing epidemiology, crop growth and their interaction into various subprocesses.…”