Fine mapping quantitative resistances to downy mildew in lettuce revealed multiple sub-QTLs with plant stage dependent effects reducing or even promoting the infection
Boer, E. den; Zhang, N. ; Pelgrom, K.T.B. ; Visser, R.G.F. ; Niks, R.E. ; Jeuken, M.J.W. - \ 2013
Theoretical and Applied Genetics 126 (2013)12. - ISSN 0040-5752 - p. 2995 - 3007.
backcross inbred lines - trait locus qtl - bremia-lactucae - leaf rust - durable resistance - stripe rust - genetic dissection - disease resistance - nonhost resistance - wild lettuce
Previous studies on the genetic dissection of the complete resistance of wild lettuce, Lactuca saligna, to downy mildew revealed 15 introgression regions that conferred plant stage dependent quantitative resistances (QTLs). Three backcross inbred lines (BILs), carrying an individual 30–50 cM long introgression segment from L. saligna in a cultivated lettuce, L. sativa, background, reduced infection by 60–70 % at young plant stage and by 30–50 % at adult plant stage in field situations. We studied these three quantitative resistances in order to narrow down their mapping interval and determine their number of loci, either single or multiple. We performed recombinant screenings and developed near isogenic lines (NILs) with smaller overlapping L. saligna introgressions (substitution mapping). In segregating introgression line populations, recombination was suppressed up to 17-fold compared to the original L. saligna × L. sativaF2 population. Recombination suppression depended on the chromosome region and was stronger suppressed at the smallest introgression lengths. Disease evaluation of the NILs revealed that the resistance of all three BILs was not explained by a single locus but by multiple sub-QTLs. The 17 L. saligna-derived sub-QTLs had a smaller and plant stage dependent resistance effect, some segments reducing; others even promoting downy mildew infection. Implications for lettuce breeding are outlined.
Identification of markers associated with bacterial blight resistance loci in cowpea (Vigna unguiculata (L.) Walp.)
Agbicodo, A.C.M.E. ; Fatokun, C.A. ; Bandyopadhyay, R. ; Wydra, K. ; Diop, N.N. ; Muchero, W. ; Ehlers, J.D. ; Roberts, P.A. ; Close, T.J. ; Visser, R.G.F. ; Linden, C.G. van der - \ 2010
Euphytica 175 (2010)2. - ISSN 0014-2336 - p. 215 - 226.
quantitative trait loci - yield-related traits - seed-filling period - grain-yield - growth-rate - developmental behavior - genotypic variation - genetic dissection - agronomic traits - tiller number
Cowpea bacterial blight (CoBB), caused by Xanthomonas axonopodis pv. vignicola (Xav), is a worldwide major disease of cowpea [Vigna unguiculata (L.) Walp.]. Among different strategies to control the disease including cultural practices, intercropping, application of chemicals, and sowing pathogen-free seeds, planting of cowpea genotypes with resistance to the pathogen would be the most attractive option to the resource poor cowpea farmers in sub-Saharan Africa. Breeding resistance cultivars would be facilitated by marker-assisted selection (MAS). In order to identify loci with effects on resistance to this pathogen and map QTLs controlling resistance to CoBB, eleven cowpea genotypes were screened for resistance to bacterial blight using 2 virulent Xav18 and Xav19 strains isolated from Kano (Nigeria). Two cowpea genotypes Danila and Tvu7778 were identified to contrast in their responses to foliar disease expression following leaf infection with pathogen. A set of recombinant inbred lines (RILs) comprising 113 individuals derived from Danila (resistant parent) and Tvu7778 (susceptible parent) were infected with CoBB using leaf inoculation method. The experiments were conducted under greenhouse conditions (2007 and 2008) and disease severity was visually assessed using a scale where 0 = no disease and 4 = maximum susceptibility with leaf drop. A single nucleotide polymorphism (SNP) genetic map with 282 SNP markers constructed from the same RIL population was used to perform QTL analysis. Using Kruskall-Wallis and Multiple-QTL model of MapQTL 5, three QTLs, CoBB-1, CoBB-2 and CoBB-3 were identified on linkage group LG3, LG5 and LG9 respectively showing that potential resistance candidate genes cosegregated with CoBB resistance phenotypes. Two of the QTLs CoBB-1, CoBB-2 were consistently confirmed in the two experiments accounting for up to 22.1 and to 17.4% respectively for the first and second experiments. Whereas CoBB-3 was only discovered for the first experiment (2007) with less phenotypic variation explained of about 10%. Our results represent a resource for molecular marker development that can be used for marker assisted selection of bacterial blight resistance in cowpea
Identification of QTLs influencing agronomic traits in Miscanthus sinensis Anderss. I. Total height, flag-leaf height and stem diameter
Atienza, S.G. ; Satovic, Z. ; Petersen, K.K. ; Dolstra, O. ; Martin, A. - \ 2003
Theoretical and Applied Genetics 107 (2003)1. - ISSN 0040-5752 - p. 123 - 129.
pinus-taeda l. - intergeneric bc1 progeny - wood property traits - loblolly-pine - quantitative traits - nonsaline environments - interspecific hybrid - genetic dissection - arbitrary primers - loci
We have developed the first quantitative trait locus (QTL) analyses for agronomic traits in a cross between F1.1 (P1) and F1.7 (P7) entries of Miscanthus sinensis Anderss. Both lines are offspring of the cross between MS-90-2 and MS-88-110. A map based on random amplified polymorphic DNA markers previously constructed was used to perform the QTL analyses. This map was developed using a new mapping strategy that has been designated offspring cross. Eleven QTLs were detected for height, panicle height and diameter using the programme mapqtl 4.0 and the multiple QTL method. QTL significance was determined using several analyses, including Kruskal-Wallis analyses, empirical determination of LOD critical values using permutation tests, QTLs validation with field data over 2 years and co-localization of QTLs for correlated traits. The results obtained could be the first step in developing a marker-assisted selection programming in this species for biomass production
|Detection of QTL for immune response to Sheep Red Blood Cells in laying hens
Siwek-Gapinska, M.Z. ; Cornelissen, S.J.B. ; Nieuwland, M.G.B. ; Buitenhuis, A.J. ; Bovenhuis, H. ; Crooijmans, R.P.M.A. ; Groenen, M.A.M. ; Vries Reilingh, G. de; Parmentier, H.K. ; Poel, J.J. van der - \ 2003
Animal Genetics 34 (2003)6. - ISSN 0268-9146 - p. 442 - 428.
quantitative trait loci - antibody-response - divergent selection - genetic dissection - biozzi mice - chickens - responsiveness - pigs - populations - resistance
The aim of this study is to detect quantitative trait loci (QTL) involved in the regulation of the primary and the secondary immune response to sheep red blood cells (SRBC) in a resource population using microsatellite DNA markers. The F2 resource population originates from a cross of two divergently selected lines for either high (H line) or low (L line) primary antibody response to SRBC. The F2 population consisted of six half-sib families, three families per each of reciprocal crosses. Total antibody titres to SRBC were determined by agglutination in serum from all birds. F2, F1 and F0 generations were genotyped for 170 microsatellite markers, using a whole-genome scan approach. The half-sib and the line-cross analyses were performed to determine QTL regions associated with regulation of the immune response. In the half-sib analysis, four QTL for SRBC primary response have been identified: on GGA3, GGA5, GGA16 and GGA23. No QTL was identified for SRBC secondary response under the half-sib model. In the line-cross analysis, three QTL were identified on GGA10, GGA16 and GGA27 for SRBC primary response and five QTL were identified on GGA6, GGA9, GGA15, GGA16 and GGA27 for SRBC secondary response. Subsequently, the family contribution of individual families to the QTL was analysed. The family with the largest contribution was genotyped with additional microsatellite markers in the QTL region on GGA5. The extended half-sib analysis with additional genotype information results in narrowing down the QTL region on GGA5.