Virusinfections in faba beans (Vicia faba L.) : Combined effects of sowing date and straw mulch on aphid infestation and virus infection

Fababohnen (Vicia faba L.) nehmen in der Ökologischen Landwirtschaft als Protein- und N-Quelle eine wichtige Stellung in der Fruchtfolge ein (Lampkin 1994; Müller & von Fragstein und Niemsdorff 2006). Als ertragslimitierende Faktoren spielen neben Wasserknappheit auch Schaderreger wie Insekten, Pilze und verschiedene Viruserkrankungen (Cockbain 1983) eine wichtige Rolle. Virusbedingte Ertragseinbußen wurden von Schmidt (1984) in konventionellen Fababohnen Ostdeutschlands auf jährlich ca. 8% geschätzt. Unter den nicht-chemischen Verfahren zur Minderung von vektorvermittelten Viruserkrankungen in Ackerkulturen, mit zugleich potentieller Eignung für ökologische Anbauverhältnisse, gehört neben der Frühsaat (Heathcote & Gibbs 1962) auch die Anwendung von Strohmulch. Mulchen erzielte insbesondere bei nicht-persistenterÜbertragung durch Blattläuse virusreduzierende Effekte in Lupinen. (Jones 1994), Kartoffeln (Heimbach & al. 1998; Saucke & Döring 2004) und Raps (& al. 2002). Ziele der vorliegenden Arbeit bildeten die Anwendung von Strohmulch in Kombination mit Früh- und Spätsaat in einem faktoriellen Parzellenversuch im Ökologischen Anbau von Fababohnen hinsichtlich der Auswirkungen auf Blattlausbesiedelung, Virusinfektionen, Pflanzenentwicklung und Ertrag.We investigated the combined effects of straw mulch and sowing date on aphid infestation and virus incidence in faba beans in organically managed small scale field experiments. Straw mulch was applied in early and late sown treatments shortly before commencing vector activity in May. Aphids were monitored by yellow water traps. In addition, crop colonisation over time was assessed for the main vectors Acyrthosiphon pisum and Megoura viciae. PEMV (pea enation mosaic virus) and BYMV (bean yellow mosaic virus) were most abundant in three consecutive years, constituting 22-54% and 9-69% of the detected virus total, respectively. However, relationships between Acyrthosiphon pisum activity and virus loads were less consistent within years. Significantly decreased A. pisum colonisation over time by mulching was prevalent but restricted to one or few dates within the entire colonisation period. Factorial analysis of resulting virus loads revealed significant reduction by early sowing but not by mulching and interaction within these factors was not significant or poor. It is suggested that relatively weak mulching effects towards visually guided aphids were assigned to rapid canopy closure in combination with the tall crop stature. In late sowings however, the ratio of soil background to vegetative cover was more permissive to interfere with vector alighting. Irrespective from mulch application, exposure of young plants lead to significantly enhanced virus loads. Straw mulching in late spring had a neutral effect on yield and did therefore not compensate for yield depression in late sown treatments. Thus, the perspectives of a mulching approach to control virus diseases in faba beans are apparently lower than anticipated

Virusinfections in faba beans (Vicia faba L.) : Combined effects of sowing date and straw mulch on aphid infestation and virus infection

Fababohnen (Vicia faba L.) nehmen in der Ökologischen Landwirtschaft als Protein- und N-Quelle eine wichtige Stellung in der Fruchtfolge ein (Lampkin 1994; Müller & von Fragstein und Niemsdorff 2006). Als ertragslimitierende Faktoren spielen neben Wasserknappheit auch Schaderreger wie Insekten, Pilze und verschiedene Viruserkrankungen (Cockbain 1983) eine wichtige Rolle. Virusbedingte Ertragseinbußen wurden von Schmidt (1984) in konventionellen Fababohnen Ostdeutschlands auf jährlich ca. 8% geschätzt. Unter den nicht-chemischen Verfahren zur Minderung von vektorvermittelten Viruserkrankungen in Ackerkulturen, mit zugleich potentieller Eignung für ökologische Anbauverhältnisse, gehört neben der Frühsaat (Heathcote & Gibbs 1962) auch die Anwendung von Strohmulch. Mulchen erzielte insbesondere bei nicht-persistenterÜbertragung durch Blattläuse virusreduzierende Effekte in Lupinen. (Jones 1994), Kartoffeln (Heimbach & al. 1998; Saucke & Döring 2004) und Raps (& al. 2002). Ziele der vorliegenden Arbeit bildeten die Anwendung von Strohmulch in Kombination mit Früh- und Spätsaat in einem faktoriellen Parzellenversuch im Ökologischen Anbau von Fababohnen hinsichtlich der Auswirkungen auf Blattlausbesiedelung, Virusinfektionen, Pflanzenentwicklung und Ertrag.We investigated the combined effects of straw mulch and sowing date on aphid infestation and virus incidence in faba beans in organically managed small scale field experiments. Straw mulch was applied in early and late sown treatments shortly before commencing vector activity in May. Aphids were monitored by yellow water traps. In addition, crop colonisation over time was assessed for the main vectors Acyrthosiphon pisum and Megoura viciae. PEMV (pea enation mosaic virus) and BYMV (bean yellow mosaic virus) were most abundant in three consecutive years, constituting 22-54% and 9-69% of the detected virus total, respectively. However, relationships between Acyrthosiphon pisum activity and virus loads were less consistent within years. Significantly decreased A. pisum colonisation over time by mulching was prevalent but restricted to one or few dates within the entire colonisation period. Factorial analysis of resulting virus loads revealed significant reduction by early sowing but not by mulching and interaction within these factors was not significant or poor. It is suggested that relatively weak mulching effects towards visually guided aphids were assigned to rapid canopy closure in combination with the tall crop stature. In late sowings however, the ratio of soil background to vegetative cover was more permissive to interfere with vector alighting. Irrespective from mulch application, exposure of young plants lead to significantly enhanced virus loads. Straw mulching in late spring had a neutral effect on yield and did therefore not compensate for yield depression in late sown treatments. Thus, the perspectives of a mulching approach to control virus diseases in faba beans are apparently lower than anticipated

Turnip mosaic potyvirus probably first spread to Eurasian brassica crops from wild orchids about 1000 years ago

Turnip mosaic potyvirus (TuMV) is probably the most widespread and damaging virus that infects cultivated brassicas worldwide. Previous work has indicated that the virus originated in western Eurasia, with all of its closest relatives being viruses of monocotyledonous plants. Here we report that we have identified a sister lineage of TuMV-like potyviruses (TuMV-OM) from European orchids. The isolates of TuMV-OM form a monophyletic sister lineage to the brassica-infecting TuMVs (TuMV-BIs), and are nested within a clade of monocotyledon-infecting viruses. Extensive host-range tests showed that all of the TuMV-OMs are biologically similar to, but distinct from, TuMV-BIs and do not readily infect brassicas. We conclude that it is more likely that TuMV evolved from a TuMV-OM-like ancestor than the reverse. We did Bayesian coalescent analyses using a combination of novel and published sequence data from four TuMV genes [helper component-proteinase protein (HC-Pro), protein 3(P3), nuclear inclusion b protein (NIb), and coat protein (CP)]. Three genes (HC-Pro, P3, and NIb), but not the CP gene, gave results indicating that the TuMV-BI viruses diverged from TuMV-OMs around 1000 years ago. Only 150 years later, the four lineages of the present global population of TuMV-BIs diverged from one another. These dates are congruent with historical records of the spread of agriculture in Western Europe. From about 1200 years ago, there was a warming of the climate, and agriculture and the human population of the region greatly increased. Farming replaced woodlands, fostering viruses and aphid vectors that could invade the crops, which included several brassica cultivars and weeds. Later, starting 500 years ago, inter-continental maritime trade probably spread the TuMV-BIs to the remainder of the world

Details of the data sets used for estimation of nucleotide substitution rate and time to the most recent common ancestor.

a<p>HC-Pro; Helper component-proteinase protein. P3; Protein 3. NIb; Nuclear inclusion b protein. cCP; Coherently-evolving coat protein. cCP+16; Sequences that include the 16 codons (48 nucleotides) at 5′-terminus immediately adjacent to cCP.</p

Maximum-likelihood tree of the complete polyprotein sequences of 37 non-recombinant <i>Turnip mosaic virus</i> isolates.

<p>Nodes are labelled with bootstrap support percentages.</p

Host reactions of some isolates of <i>Turnip mosaic virus</i> from <i>Orchis</i> spp. and other hosts.

a<p>Reaction of inoculated leaves/uninoculated upper leaves. At least three plants were inoculated. BSS; Black stem streak, CS; Chlorotic spot, D; Dead, LD; Leaf deformation, LI; Latent infection, M; Mosaic, Mo; Mottle, ND: Not detected, NLL; Necrotic local lesion, NS; Necrotic spot, NR; Necrotic ringspot, PSF; Pod set failure, St; Stunting, VC; Vein clearing, -; No infection, (); Occasionally. All the leaves were examined for <i>Turnip mosaic virus</i> (TuMV) infection by DAS-ELISA. All the absorbance values at 405 nm of DAS-ELISA were greater than 1.0 2.5 hrs after adding substrate.</p>b<p>OS and ORM isolates are aphid transmissible but OM-N isolate is not.</p>c<p>Typical symptom for most of TuMV brassica isolates.</p>d<p>Viruses were detected only in upper two leaves, and not in the third.</p