ABSTRACT
KEY MESSAGE: Identification of novel resistance QTL against wheat aphids. First QTL-resistance report for R. padi in wheat and chromosome 2DL for S. graminum . These sources have potential use in wheat breeding. The aphids Rhopalosiphum padi and Schizaphis graminum are important pests of common wheat (Triticum aestivum L.). Characterization of the genetic bases of resistance sources is crucial to facilitate the development of resistant wheat cultivars to these insects. We examined 140 recombinant inbred lines (RILs) from the cross of Seri M82 wheat (susceptible) with the synthetic hexaploid wheat CWI76364 (resistant). RILs were phenotyped for R. padi antibiosis and tolerance traits. Phenotyping of S. graminum resistance was based on leaf chlorosis in a greenhouse screening and the number of S. graminum/tiller in the field. RILs were also scored for pubescence. Using a sequence-based genotyping method, we located genomic regions associated with these resistance traits. A quantitative trait locus (QTL) for R. padi antibiosis (QRp.slu.4BL) that explained 10.2 % of phenotypic variation was found in chromosome 4BL and located 14.6 cM apart from the pubescence locus. We found no association between plant pubescence and the resistance traits. We found two QTLs for R. padi tolerance (QRp.slu.5AL and QRp.slu.5BL) in chromosomes 5AL and 5BL, with an epistatic interaction between a locus in chromosome 3AL (EnQRp.slu.5AL) and QRp.slu.5AL. These genomic regions explained about 35 % of the phenotypic variation. We re-mapped a previously reported gene for S. graminum resistance (putatively Gba) in 7DL and found a novel QTL associated with the number of aphids/tiller (QGb.slu-2DL) in chromosome 2DL. This is the first report on the genetic mapping of R. padi resistance in wheat and the first report where chromosome 2DL is shown to be associated with S. graminum resistance.
Subject(s)
Aphids , Breeding , Quantitative Trait Loci , Triticum/genetics , Animals , Antibiosis/genetics , Chromosome Mapping , Chromosomes, Plant , Epistasis, Genetic , Genotype , Genotyping Techniques , Phenotype , Polymorphism, Single NucleotideABSTRACT
The genus Salix (willow) contains a number of species of great value as biomass crops. Efforts to breed varieties with improved biomass yields and resistances to pests and diseases are limited by the lack of knowledge on the genetic basis of the traits. We have used AFLP and microsatellite markers to construct a genetic map of willow from a full-sib cross of the diploid species Salix viminalis (2n = 38). In accordance with a double pseudo-testcross approach, separate parental maps were constructed and merged to produce a consensus map comprising 291 AFLP and 39 willow microsatellite markers. Nineteen poplar microsatellites were also tested in willow. Five of these amplified loci, of which two were mapped. Linkage groups of the consensus map that could be identified in the parental maps are presented here and spanned 1,256.5 cM with an average interval between markers of 4.4 cM.
ABSTRACT
The genus Salix (willow) contains a number of species which have great potential value as biomass crops in short rotation coppice (SRC). Efforts to improve biomass willows by breeding are currently hampered by the limited information available on genetic diversity and on genetic relationships within and among species, clones, and hybrids in the gene pool. Hybridisation occurs commonly in nature and the relatedness of many clones is unclear. Molecular markers were used to assess genetic diversity in a reference set of willows maintained within the U.K. National Collection and 16 elite clones currently being evaluated in field trials at several European sites. The two marker systems tested, RAPDs and AFLPs, were equally informative for revealing relationships within the reference set of clones. No differences were observed when alternative similarity coefficients were compared or when analysis was restricted to the use of polymorphic bands only. Good agreement with available knowledge of the clonal origins was obtained and one instance of duplicate clones was identified. AFLPs revealed more genetic diversity and discriminated between closely related clones. A difference in the relationships revealed was observed with one AFLP primer combination. RAPDs were more problematic, both in terms of reproducibility and scorability.
Subject(s)
Genetic Variation , Polymorphism, Restriction Fragment Length , Random Amplified Polymorphic DNA Technique , Trees/genetics , DNA, Plant/analysis , Trees/classificationABSTRACT
The toxicities of selected host secondary plant substances to eggs of theBrassica specialistDasineura brassicae were estimated in a laboratory test. Isothiocyanates (ITCs) and 1-cyano-2-phenylethane, autolysis products of glucosinolates, were more toxic than a "green leaf alcohol,"cis-3-hexen-1-ol, found in numerous plant families. The most toxic compound, 2-phenylethyl ITC, occurs in all investigatedBrassica hosts ofD. brassicae. However, the less suitableBrassica hosts additionally release comparatively large amounts of allyl ITC. This suggests that even a crucifer specialist may be restricted in its use of particular hosts due to their compositions and concentrations of glucosinolate compounds.
