scholarly journals Identification of Quantitative Trait Loci for Resistance Against Verticillium longisporum in Oilseed Rape (Brassica napus)

2008 ◽  
Vol 98 (2) ◽  
pp. 215-221 ◽  
Author(s):  
W. Rygulla ◽  
R. J. Snowdon ◽  
W. Friedt ◽  
I. Happstadius ◽  
W. Y. Cheung ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Quantitative Trait Loci ◽  
Oilseed Rape ◽  
Length Polymorphism ◽  
Fragment Length ◽  
Quantitative Trait ◽  
Fragment Length Polymorphism ◽  
Linkage Groups ◽  
Verticillium Longisporum ◽  
Dh Lines

Verticillium longisporum is one of the major pathogens of oilseed rape (Brassica napus; genome AACC, 2n = 38) in Europe. Current European cultivars possess only a low level of resistance against V. longisporum, meaning that heavy infection can cause major yield losses. The aim of this study was to identify quantitative trait loci (QTL) for resistance against V. longisporum as a starting point for marker-assisted breeding of resistant cultivars. Resistance QTL were localized in a segregating oilseed rape population of 163 doubled haploid (DH) lines derived by microspore culture from the F1 of a cross between two B. napus breeding lines, one of which exhibited V. longisporum resistance derived by pedigree selection from a resynthesized B. napus genotype. A genetic map was constructed comprising 165 restriction fragment length polymorphism, 94 amplified fragment length polymorphism and 45 simple sequence repeats (SSR) markers covering a total of 1,739 cM on 19 linkage groups. Seedlings of the DH lines and parents were inoculated with V. longisporum isolates in four greenhouse experiments performed in Sweden during autumn 1999. In three of the experiments the DH lines were inoculated with a mixture of five isolates, while in the fourth experiment only one of the isolates was used. The intention was to simulate four different environments with variable disease pressure, while still maintaining uniform conditions in each environment to enable reliable disease scoring. The disease index (DI) was calculated by scoring symptoms on a total of 21 inoculated plants per line in comparison to 21 noninoculated plants per line. Using the composite interval mapping procedure a total of four different chromosome regions could be identified that showed significant QTL for resistance in more than one environment. Two major QTL regions were identified on the C-genome linkage groups N14 and N15, respectively; each of these QTL consistently exhibited significant effects on resistance in multiple environments. The presence of flanking markers for the respective QTL was associated with a significant reduction in DI in the inoculated DH lines.

Mapping quantitative trait loci for bean traits and ovule number in Theobroma cacao L.

Genome ◽  
2003 ◽  
Vol 46 (1) ◽  
pp. 103-111 ◽  
Author(s):  
D Clement ◽  
A M Risterucci ◽  
J C Motamayor ◽  
J N'Goran ◽  
C Lanaud
Keyword(s):  
Quantitative Trait Loci ◽  
Length Polymorphism ◽  
Fragment Length ◽  
Quantitative Trait ◽  
Theobroma Cacao ◽  
Fragment Length Polymorphism ◽  
Shape Index ◽  
Interval Mapping ◽  
Trait Loci ◽  
Theobroma Cacao L

Quantitative trait loci (QTL) mapping for bean traits and the number of ovules per ovary was carried out in cocoa (Theobroma cacao L.) using three test-cross progenies derived from crosses between a lower Amazon Forastero male parent (Catongo) and three female parents: one upper Amazon Forastero (IMC78) and two Trinitario (DR1 and S52). RFLP (restriction fragment length polymorphism), microsatellite, and AFLP (amplified fragment length polymorphism) markers were used for mapping. Between one and six QTL for bean traits (length, weight, and shape index) and one and four QTL for the number of ovules per ovary were detected using composite interval mapping (CIM). Individual QTL explained between 5 and 24% of the phenotypic variation. QTL clusters were identified on several chromosomes, but particularly on chromosome 4. QTL related to bean traits were detected in the same region in both Trinitario parents and in a close region in the upper Amazon Forastero parent. In reference to a previous diversity study where alleles specific to Criollo and Forastero genotypes were identified, it was possible to speculate on the putative origin (Criollo or Forastero) of favorable QTL alleles segregating in both Trinitario studied.Key words: Theobroma cacao, bean traits, quantitative trait loci (QTL).

Mapping quantitative powdery mildew resistance of barley using a restriction fragment length polymorphism map

Genome ◽  
1992 ◽  
Vol 35 (6) ◽  
pp. 1019-1025 ◽  
Author(s):  
M. Heun
Keyword(s):  
Quantitative Trait Loci ◽  
Powdery Mildew ◽  
Restriction Fragment Length Polymorphism ◽  
Restriction Fragment ◽  
Length Polymorphism ◽  
Fragment Length ◽  
Quantitative Trait ◽  
Fragment Length Polymorphism ◽  
Trait Loci ◽  
Restriction Fragment Length

To map the genes underlying the quantitative resistance (QR) of the spring barley cultivars Proctor and Nudinka to powdery mildew, the relative pustule number of F1-derived doubled haploids (DHs) was determined and combined with the restriction fragment length polymorphism (RFLP) mapping data of these DHs via MAPMAKER/QTL. Applying a log-likelihood (LOD) threshold of 2.50, two putative quantitative trait loci (QTLs) were found in two different genome areas that accounted for 19.8% of the observed variance. One of the QR-related RFLPs (Xcnl.CDO36) is located on chromosome 1S, the other one (Xcnl.CDO749) is tightly linked with the nucleolus organizer region on chromosome 7. By comparing the means of subpopulations of DHs carrying alternative parental marker alleles, it was found that both RFLPs were also linked with some genes causing thousand kernel weight differences in this population. For the QR trait measured, LOD scores < 1.00 were found for the Mla12 region on chromosome 5S indicating that the Mla12 virulent isolate used neutralized this major resistance gene and that no residual effect of that locus occurred.Key words: barley, powdery mildew, restriction fragment length polymorphism, quantitative trait loci.

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