Black spot partial resistance in diploid roses: 
QTL discovery and linkage map creation

2019 ◽  
pp. 135-142 ◽  
Author(s):  
M. Yan ◽  
D.H. Byrne ◽  
P.E. Klein ◽  
W.E. van de Weg ◽  
J. Yang ◽  
...  
Keyword(s):  
Linkage Map ◽  
Partial Resistance ◽  
Black Spot ◽  
Qtl Discovery

High density SNP and SSR linkage map and QTL analysis for resistance to black spot in segregating rose population

2020 ◽  
pp. 191-198 ◽  
Author(s):  
D.C. Lopez Arias ◽  
A. Chastellier ◽  
T. Thouroude ◽  
M. Leduc ◽  
F. Foucher ◽  
...  
Keyword(s):  
Linkage Map ◽  
Qtl Analysis ◽  
Black Spot ◽  
High Density

scholarly journals Components of Partial Resistance to Black Spot Disease (Diplocarpon rosae Wolf) in Garden Roses

HortScience ◽  
1998 ◽  
Vol 33 (1) ◽  
pp. 96-99 ◽  
Author(s):  
A.G. Xue ◽  
C.G. Davidson
Keyword(s):  
Partial Resistance ◽  
Black Spot ◽  
Lesion Length ◽  
Diplocarpon Rosae ◽  
Large Numbers ◽  
On Line ◽  
Rose Breeding ◽  
Sporulation Capacity ◽  
Cultivar Responses ◽  
High Level

Eleven rose (Rosa spp.) cultivars and advanced lines from the Morden rose breeding program were tested in controlled conditions for five components of partial resistance to two isolates of Diplocarpon rosae Wolf, the causal agent of black spot. The isolates were collected from diseased rose leaves in 1995 at Morden, Man., and in Ottawa, Ont. The components examined include incubation period (IP), leaf area with symptoms (LAS), number of lesions (NL), lesion length (LL), and sporulation capacity (SC). Differences in cultivar responses were found for all components. Of the 11 rose genotypes, no visible symptoms developed on line 91V8T201 even at 14 days after inoculation. This line was considered completely resistant to the two isolates tested. X6, T5, and `Prairie Joy' had a high level of partial resistance. N3 and `Cuthbert Grant' were intermediate. The remaining five cultivars or lines exhibited a low level of partial resistance. Linear correlations among LAS, IP, NL, and LL were high. Correlations between SC with IP, NL, or LL were nonsignificant. Although each of the five components can be used in selection for partial resistance, any one component may not represent the complete potential for a particular rose genotype. Results of this study suggest that LAS and SC are preferable as criteria for resistance to minimize the labor requirement when evaluating large numbers of rose genotypes in the greenhouse.

scholarly journals Characterization of Partial Resistance to Black Spot Disease of Rosa sp.

HortScience ◽  
2017 ◽  
Vol 52 (1) ◽  
pp. 49-53 ◽  
Author(s):  
Qianni Dong ◽  
Xinwang Wang ◽  
David H. Byrne ◽  
Kevin Ong
Keyword(s):  
Partial Resistance ◽  
Black Spot ◽  
Lesion Length ◽  
Horizontal Resistance ◽  
Narrow Sense Heritability ◽  
Spot Disease ◽  
Diplocarpon Rosae ◽  
Whole Plant ◽  
Black Spot Disease

Black spot disease, caused by the fungus Diplocarpon rosae Wolf, is one of the most serious diseases of garden roses. Both complete (vertical) resistance conditioned by dominant Rdr genes and partial (horizontal) resistance conditioned by multiple genes have been described. The use of resistant rose cultivars would reduce the demand of agrochemical applications. The characterization of 16 genotypes for resistance to black spot using two laboratory assays, the detached leaf assay (DLA) and the whole plant inoculation (WPI) approach, indicated that these techniques were well correlated. Thus, either method could be used to assess the resistance of the plants to black spot. Fifteen diploid hybrid populations from 10 parents segregating for partial (horizontal) resistance to black spot derived from Rosa wichuraiana ‘Basye’s Thornless’ (RW) were assessed for black spot resistance by quantifying the percentage of the leaf area with symptoms (LAS) and lesion length (LL) measured by the diameter of the largest lesion per leaf in DLAs. The narrow-sense heritability of partial resistance to black spot as measured by LAS and LL data of DLA was estimated to be from 0.28 to 0.43 when calculated with a genetic variance analysis and from 0.74 to 0.86 when generated from offspring–midparent regression. This suggests that the development of rose cultivars with high levels of stable partial resistance to black spot is a feasible approach for the rose industry.

scholarly journals Partial Resistance Against Erysiphe pisi and E. trifolii Under Different Genetic Control in Lathyrus cicera: Outcomes from a Linkage Mapping Approach

Plant Disease ◽  
2020 ◽  
Vol 104 (11) ◽  
pp. 2875-2884 ◽  
Author(s):  
Carmen Santos ◽  
Davide Martins ◽  
Diego Rubiales ◽  
Maria Carlota Vaz Patto
Keyword(s):  
Powdery Mildew ◽  
Linkage Map ◽  
Genetic Control ◽  
Recombinant Inbred Line Population ◽  
Recombinant Inbred ◽  
Partial Resistance ◽  
Resistance Mechanisms ◽  
Erysiphe Pisi ◽  
Powdery Mildews ◽  
Lathyrus Cicera

Powdery mildew infections are among the most severe foliar biotrophic fungal diseases in grain legumes. Several accessions of Lathyrus cicera (chickling pea) show levels of partial resistance to Erysiphe pisi, the causal agent of pea powdery mildew, and to E. trifolii, a powdery mildew pathogen recently confirmed to infect pea and Lathyrus spp. Nevertheless, the underlying L. cicera resistance mechanisms against powdery mildews are poorly understood. To unveil the genetic control of resistance against powdery mildews in L. cicera, a recombinant inbred line population segregating for response to both species was used in resistance linkage analysis. An improved L. cicera genetic linkage map was used in this analysis. The new higher-density linkage map contains 1,468 polymorphic loci mapped on seven major and two minor linkage groups, covering a total of 712.4 cM. The percentage of the leaf area affected by either E. pisi or E. trifolii was recorded in independent screenings of the recombinant inbred line population, identifying a continuous range of resistance-susceptibility responses. Distinct quantitative trait loci (QTLs) for partial resistance against each pathogen were identified, suggesting different genetic bases are involved in the response to E. pisi and E. trifolii in L. cicera. Moreover, through comparative mapping of L. cicera QTL regions with the pea reference genome, candidate genes and pathways involved in resistance against powdery mildews were identified. This study extended the previously available genetic and genomic tools in Lathyrus species, providing clues about diverse powdery mildew resistance mechanisms useful for future resistance breeding of L. cicera and related species.

A Method for Setting the Clearance Angle

1972 ◽  
Vol 30 ◽  
pp. 388-389
Author(s):  
Michael T. Bucek ◽  
Howard J. Arnott
Keyword(s):  
Experimental Evidence ◽  
Light Source ◽  
Black Spot ◽  
Critical Factor ◽  
Clearance Angle ◽  
Crude Approximation ◽  
Ultrathin Sections

It is believed by the authors, with supporting experimental evidence, that as little as 0.5°, or less, knife clearance angle may be a critical factor in obtaining optimum quality ultrathin sections. The degree increments located on the knife holder provides the investigator with only a crude approximation of the angle at which the holder is set. With the increments displayed on the holder one cannot set the clearance angle precisely and reproducibly. The ability to routinely set this angle precisely and without difficulty would obviously be of great assistance to the operator. A device has been contrived to aid the investigator in precisely setting the clearance angle. This device is relatively simple and is easily constructed. It consists of a light source and an optically flat, front surfaced mirror with a minute black spot in the center. The mirror is affixed to the knife by placing it permanently on top of the knife holder.

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