Mechanisms Involved in Soybean Rust‐Induced Yield Reduction

Abstract

Soybean rust (SBR; caused by Phakopsora pachyrhizi Syd. and P. Syd.) leads to premature leaf loss and yield reduction. The objectives of this study were to assess effects of SBR infection on soybean [Glycine max (L.) Merrill] yield and to identify causes for the yield reduction. Experiments were conducted in the 2005–2006 and 2006–2007 growing seasons at Londrina, Brazil. The five treatments were SBR infection beginning at either (i) the R2 or (ii) R5 growth stages; nondiseased defoliation treatments to mimic the leaf loss when SBR started at either (iii) the R2 or (iv) R5 growth stages; and (v) a disease‐free, nondefoliated control. The control and defoliation treatments were protected against SBR by fungicide applications. Disease severity, lesion area, and leaf area were monitored from R2 to R7. Biomass and seed yield were measured at maturity. Mean SBR‐induced yield reductions were 67% when infection started at R2 and 37% when infection started at R5. Leaf loss alone reduced yield significantly in only one year and only when defoliation treatments were begun at R2 (31% in 2005–2006). Soybean rust–induced yield loss was attributable to (i) premature leaf loss, (ii) reduction in canopy green leaf area due to SBR lesions, (iii) reduction in dry matter accumulation per unit absorbed radiation by the nonlesion green leaf area, and (iv) reduction in harvest index. The response of harvest index was attributable to reduced seed set and seed mass resulting likely from SBR‐induced reductions in rate of dry matter accumulation.

Advances on molecular studies of the interaction soybean - Asian rust

“…A recent study depicted a two-year field trial in Brazil where soybean rust was responsible for 37-67 % of soybean seed yield losses (Kumudini et al 2008). This study coincided with yield losses observed in Asia up to 80 % (Miles et al 2003).…”

Biphasic Gene Expression Changes Elicited byPhakopsora pachyrhiziin Soybean Correlate with Fungal Penetration and Haustoria Formation

“…Long-term decreases in the expression of photosynthesis-related genes in compatible interactions would be consistent with observations of actual photosynthesis in P. pachyrhiziinfected soybean leaves. As P. pachyrhizi infection progresses, reduced photosynthesis and assimilation of CO 2 occur, due in part to defoliation and reduction of the green leaf area index as lesions form (Kumudini et al, 2008a). In addition, P. pachyrhizi also reduces the efficiency of photosynthesis in the remaining green tissues that visually appear to be healthy (Kumudini et al, 2008b).…”

Fontes de fosfito e acibenzolar-S-metílico associados a fungicidas para o controle de doenças foliares na cultura da soja

“…A ferrugem asiática é uma das mais agressivas doenças da soja, com dano entre 10% a 90% (Kumudini et al, 2008), e no Brasil vem provocando prejuízos desde 2001/02 pela falta de resistência genética e ampla área de semeadura (Yorinori et al, 2005;Godoy et al, 2009). Esta doença pode infectar a cultura a partir dos estádios iniciais de desenvolvimento e as condições ambientais são fundamentais no desenvolvimento das epidemias.…”