The effect of powdery mildew (Erysiphe graminis f. sp. hordei) and leaf rust (Puccinia hordei) on spring barley in New Zealand. II. Apical development and yield potential

Abstract

Reduced yields caused by powdery mildew and leaf rust in two seasons were associated with reduced plant growth. Combinations of early, late and full epidemics in one season, and 12 epidemic combinations in the second, were designed to identify crop sensitivity to disease by comparing growth and development with healthy plants. Early epidemics reduced ear number by increasing tiller death, and reduced grain number by effects on spikelet, floret or grain abortion, depending on the type of epidemic. Epidemics later in crop growth increased floret and grain abortion and also reduced grain weight. There was no compensation by later‐determined components for reduced growth and delayed development at earlier growth stages. Plants infected at early growth stages were more sensitive to late infections, seen as effects on the later‐determined components, than plants which were healthy initially. Interactions occurred between epidemics at different times and are likely to occur between diseases and other constraints.

The effect of powdery mildew (Erysiphe graminis f. sp. hordei) and leaf rust (Puccinia hordei) on spring barley in New Zealand. I. Epidemic development, green leaf area and yield

“…Jenkins et af (1972) and Melville et al (1976) attributed similar discrepancies to the same type of error in their leaf rust trials. In our trials there was no representational error, and the discrepancy was associated with effects of powdery mildew and leaf rust on other yield components such as ear and grain number (Lim & Gaunt 1986).…”

“…The trial was harvested on 16 March 1978 at approximately 15"o grain moisture content. Whole plants were sampled from five areas (each 01 m-) in the central rows of each treatment area, bulked, the ears threshed and the total grain number and mean dry weight per grain determined after analysis of yield components (Lim & Gaunt, 1986). The trial was also harvested by machine (Walter and Wintersteiger Universal Seedmaster, Austria) and the total and mean weight per grain recorded.…”

Spring Barley Responses to Row Spacing and Fungicide Triadimefon in Regions with a Short Crop‐growing Season

“…Powdery mildew can cause damage at any growth stage. Early epidemics directly affect plant growth by causing chlorosis and reducing green leaf area (LIM and GAUNT 1986). During the early growth stages, reductions in root development, grain size and number of tillers with infected spikes have been observed in crops infected with powdery mildew (BROOKS 1972).…”

“…During the early growth stages, reductions in root development, grain size and number of tillers with infected spikes have been observed in crops infected with powdery mildew (BROOKS 1972). Late epidemics of powdery mildew have resulted in the increased floret and gram abortion and reduced grain size (BROOKS 1972, LIM andGAUNT 1986).…”

The effect of leaf rust (Puccinia hordei) on yield response in barley (Hordeum vulgare L.) crops with different yield potentials

“…King & Polley, 1976;Melville et al, 1976). The yield response has been related to the disease intensity, the time of onset of the disease relative to host development and the duration of the epidemic (Teng et al, 1979;Lim & Gaunt, 1986b). However, as with other pathosystems, little information is available for leaf rust on response to disease in crops with different healthy crop yield (yield potential).…”