Red leaf blotch (Dactuliochaeta glycines) of soybeans (Glycine max) and its relationship to yield

Abstract

Red leaf blotch of soybeans, caused by Dactuliochaeta glycines, was evaluated on soybean plants in field plots located in Zambia. Two experiments were conducted in each of two seasons. Experiment 1 had four cultivars that were either fungicide-sprayed or not sprayed. Disease severity was greatest on leaves at the lowest nodes from early vegetative through the reproductive growth stages. Area under the disease progress curve (AUDPC) values and percentage of nodes defoliated at growth stage R5 were significantly (P 0 . 05) greater in unsprayed plots for all cultivars in both seasons. Yield losses ranged from 8 to 37% while reduced seed size ranged from 21 to 29% for the four cultivars. Number of pods per plant in fungicide-sprayed plots did not differ from those in unsprayed plots. However, the number of seeds per plant and seeds per pod were significantly (P 0 . 05) greater in sprayed than unsprayed plots for some cultivars. In experiment 2, cultivar Tunia was either fungicide-sprayed at different times or not sprayed. The lowest attached leaf had the most variation in the amount of disease while ratings of the most median leaf in the canopy were generally less variable. The AUDPC values calculated from the lowest attached leaf, the mean of all attached leaves, and the median attached leaf differed significantly (P 0 . 05) the number of times plants were sprayed with fungicide. Defoliation and vertical incidence of red leaf blotch from lower to higher nodes were significantly (P 0 . 05) reduced in fungicide-sprayed plots in one season, but not the other. One thousand-seed weight and yield differed significantly (P 0 . 05) with treatment as one application of triphenyltin acetate increased yields by 18% over unsprayed plots in season 1. One thousand-seed weight and yield, regressed on the AUDPC for the median leaf in the canopy, explained 92 and 72% of the variation, respectively.

Annotation and analysis of the mitochondrial genome of Coniothyrium glycines, causal agent of red leaf blotch of soybean, reveals an abundance of homing endonucleases

“…The disease red leaf blotch (RLB) occurs predominantly in central and southern Africa [ 2 ] and the incidence of the disease has increased concomitantly with increased soybean production in regions where the pathogen is found. Yield losses of up to 50% have been reported in Zambia and Zimbabwe [ 3 ][ 4 ]. While it does not currently occur within the United States, the ability of sclerotia to survive high temperatures and dry conditions suggest it could survive in soybean growing regions of the southern United States [ 5 ].…”

Métodos De Preservação De Fungos Em Laboratório

“…2).Os fungicidas afetam a fotossíntese em plantas cultivadas, e a AACPD e a porcentagem de nós desfolhados no estádio R5 apresentaram diferenças significativas entre parcelas tratadas e não tratadas com fungicidas SINCLAIR, 1996).…”

EFICÁCIA DE COMBINAÇÕES DE ESTROBIRULINAS E TRIAZÓIS SOBRE COMPLEXOS DE DOENÇAS E PRODUTIVIDADE DA SOJA (Glycine max)

“…2).Os fungicidas afetam a fotossíntese em plantas cultivadas, e a AACPD e a porcentagem de nós desfolhados no estádio R5 apresentaram diferenças significativas entre parcelas tratadas e não tratadas com fungicidas SINCLAIR, 1996).…”