Components of resistance of cassava to african cassava mosaic virus

Components of resistance of cassava (#Manihot esculenta) to African cassava mosaic virus (ACMV) and their interrelationships were confirmed and quantified in a series of experiments at Adiopodoumé (Ivory Coast, West Africa). The response to virus infection and to #Bemisia tabaci infestation of a large collection of cassava, including local cultivars and others derived from inter-specific #M. glaziovii hybrids was assessed. A consistent correlation was found between virus titre, symptom intensity, disease incidence and non-systemicity (recovery) which suggests that they are different expressions of the same genetic resistance. By contrast, there was no correlation between whitefly infestation and incidence of ACMV, suggesting that resistance to virus and vector are determined by two distinct genetic mechanisms. Several improved cultivars derived from inter-crossing cassava with #M. glaziovii as well as some local cultivars were highly resistant and combined low susceptibility, low symptom intensity, low virus content and high level of recovery. Although yield losses ranged from 10% to 30% in such resistant cultivars, the combined effect of high field resistance and high rate of recovery lead to low disease incidence and limited yield losses, even in areas of high infection pressure such as Adiopodoumé. (Résumé d'auteur

Investeringsimpuls riet

Riet is een gewas met veel nuttige functies zoals biomassaproductie voor energiewinning en de absorptie van nutriënten en zware metalen bij afvalwaterzuivering. Het doel van deze literatuurstudie is om a) riet als productief gewas te waarderen op agronomische kenmerken en te zoeken naar genetische variatie van die kenmerken die de teelt economisch en maatschappelijk verhogen en b) om om de genoemde kenmerken te kwantificeren voor Nederlandse of West-Europese omstandighede

GGO-vrije diervoederketens : kennisscan 2004

De Expertisegroep 'GGO-vrije ketens' van Wageningen UR komt tot deze conclusie dat de realisatie van diervoederketens zonder genetisch gemodificeerde organismen (GGO) steeds lastiger wordt. Binnen de huidige wettelijke kaders is bepaald dat hetpercentage GGO-bestanddelen dat onbedoeld in een partij GGO-vrije diervoeders terechtkomt maximaal 0,9%mag zijn. De biologische sector wil helemaal geen vermenging en streeft naar een percentage van 0%. Het produceren van GGO-vrije diervoeders isproblematisch omdat in belangrijke bestanddelen van diervoeders, met name soja en mais, in veel gevallen al sporen van GGO-variëteiten voorkomen. Dit zal nog verder bemoeilijkt worden als er GGO-varianten van meer gewassen hun intrede doen op de Europeseen wereldmarkt. Vermenging is dus zeer moeilijk te voorkomen en geheel GGO-vrije productie zal in de nabije toekomst alleen gerealiseerd kunnen worden met kostbare ketensystemen die ggo- en ggo-vrije productie gescheiden kunnen houden. Uit het onderzoekblijkt verder dat de mogelijkheden om GGO-vrij te produceren in de praktijk bepaald zal worden door het type veevoederproductieketens. Wanneer in bepaalde veevoeders meer gewassen verwerkt worden waarvan er wereldwijd al GGO-partijen op commerciële basisin productie zijn, zal het lastiger zijn om GGO-vrijeproductiesystemen te handhaven. Het ziet er naar uit dat de kosten voor GGO-vrije productie, moeten worden opgebracht door de sector die GGO-vrij wil leveren. Aangezien aansprakelijkheidskwesties bijonbedoelde vermenging voorlopig niet internationaal of EU-breed geregeld zullen worden, ligt het in de lijn der verwachting dat conflicten op dit terrein niet zullen uitblijven

Genetic linkage of QTLs for late blight resistance and foliage maturity type in six related potato progenies

A set of test crosses of diploid potatoes was used to identify QTLs for foliage resistance against Phytophthora infestans and QTLs for foliage maturity type, and to assess their genetic relationship. The most important locus for both traits was found on chromosome 5 near marker GP21: the allele of marker GP21 that is associated with resistance to late blight is also associated with late foliage maturity. An additional QTL with a small effect on foliage maturity type was identified on chromosome 3, and additional QTLs for late blight resistance were found on chromosomes 3 and 10. Another QTL was detected on chromosome 7 when resistance was adjusted for the effect of foliage maturity type. The additional QTLs for resistance against P. infestans on chromosomes 3 and 10 seem to be independent of foliage maturity type and are not affected by epistatic effects of the locus on chromosome 5. The effects of the additional QTLs for resistance are small, but early maturing genotypes that necessarily have the allele for susceptibility for late blight on chromosome 5 may benefit from the resistance that is provided by these QTLs on chromosomes 3 and 1

Partial resistance to late blight (Phytophthora infestans) in hybrid progenies of four South American Solanum species crossed with diploid S. Tuberosum

Resistant genotypes of the diploid tuber-bearing South American species Solanum arnezii × hondelmannii, S. berthaultii, S. leptophyes and S. microdontum were crossed with three diploid genotypes of S. tuberosum that varied in resistance and maturity type. The progenies were field tested for 2 years for resistance to a complex race of Phytophthora infestans. A wealth of genetic variation for resistance was found in most of the progenies. At least two susceptibility groups could be distinguished in some progenies of S. microdontum. This could be explained by the presence of several major resistance genes in the wild parent and, unexpectedly, in the susceptible parent SH 82-44-111. In most of the wild parents and in the Susceptible parent SH 77-114-2988 there appeared to be minor resistance genes. General combining ability effects were predominant; small specific combining ability effects were detected in some crosses of S. microdontum. Gene action appeared dominant in some crosses.