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- Author or Editor: Geunhwa Jung x
The development of a complete linkage map including both morphological and molecular markers is important to understand the genetic relationships among quantitatively and qualitatively inherited traits in common bean. The objective of this study was to identify RAPD markers linked to genes for four morphological traits using bulked segregant analysis and to map the markers to a molecular linkage map previously constructed in common bean. Three segregating populations were evaluated. Two BC2F2 populations with dgs (dark green savoy leaf) and blu (blue flower) induced mutant was developed with a Florida breeding line 7-1404 and 5-593 as the recurrent parent. In addition, a BC3F2 population with the y (yellow wax pod) and the arg (silvery green pod) mutants was developed from the Lamprecht line PI 527858 and 5-593 as the recurrent parent. RAPD markers linked in coupling to the morphological traits were detected to be 4.1 cM, 4.3 cM, 7.3 cM, and 12.3 cM distant from the dgs, blu, y, and arg genes, respectively. The linked RAPD markers were mapped in the molecular linkage map previously constructed using recombinant inbred population of the cross PC-50 × XAN-159. In this linkage map, we observed a linkage between the C locus and blu gene whose location was not previously known. In addition, a linkage between an abaxial leaf pubescent gene and dgs gene was observed. These results indicate that integrating morphological markers and molecular markers can result in a more complete genetic linkage map in common bean.
One of the highest levels of common bacterial blight (CBB) resistance identified in Phaseolus vulgaris is found in XAN-159, which was developed for leaf resistance to CBB through six generations of pedigree selection of progenies derived from the interspecific cross [(`Pinto UI 114' × PI 319441) × P. acutifolius PI 319443] × `Masterpiece'. A RAPD genetic linkage map was previously constructed in a recombinant inbred population derived from the common bean cross PC-50 × XAN-159 for identification of genomic regions associated with bacterial disease resistance in XAN-159. To confirm that chromosomal regions associated with CBB resistance in XAN-159 were introgressed from tepary bean, we investigated the parentage of each genomic interval in XAN-159 by studying the genomic constitutions of the four different parents involved in the pedigree. The results indicate that all genomic regions associated with CBB resistance contain intervals derived exclusively from tepary bean. The uniqueness of marker polymorphisms associated with resistance to CBB in XAN-159 will allow the application of marker assisted selection for these resistance genes in most populations of common bean.
Knowledge of genetic relationships and genetic diversity among accessions is essential for the efficient construction, maintainance and utilization of large ex-situ germplasm collections. Furthermore, streamlining of large collections into care collections necessitates validation of germplasm sampling techniques. DNA molecular markers provide potentially unbiased estimators of genome diversity end may facilitate organization, maintainance, and sampling of plant genetic resources. Our data suggests that RAPD markers will be o good tool for testing tore collection concepts and organizing genetic diversity in common bean. However, the genomic distribution of markers is unknown. Currently we are using recombinant inbred (RI) populations to place RAPD markers in the context of the bean genetic map. We hove evaluated the the distribution of RAPD markers in three RI populations: Bat93 × Jalo EEP558, PC50 × Xan159, and BAC6 × HT7719. Cultivated P.vulgaris has two primary renters of diversity Mesoamerican and Andean, the RI populations used for mapping RAPD markers ore Meso × Andean, Andean × Andean, and Meso × Meso crosses respectively. In the Bat93 × Jalo EEP558 population 383 markers have been mapped for a map length of 735 cM. However, approximately 150 of these markers ore members of 9 dusters which span only 90 cM. This inter gone pool mop is being integrated with linkage mops constructed in the other two populations to compare within and between gene pool marker distributions and to evaluate clustering of markers on the different mops. Implications for the application of RAPD markers will be discussed.
Halo blight (HB), brown spot (BS), and rust incited by the bacterial pathogens Pseudomonas syringae pv. phaseolicola (Psp), Pseudomonas syringae pv. syringae (Pss) and the fungal pathogen Uromyces appendiculatus, respectively, are important diseases of common beans. The objectives were to construct a RAPD linkage map, and to locate HB and BS resistance genes and genes for some other traits. One-hundred-seventy RAPD markers were mapped in 78 RI lines of the cross BelNeb 1 and A 55. Eleven main and nine minor linkage groups were identified. MAPMAKER/QTL, interval mapping, was used to identify genomic regions involved in the genetic control of the traits. One region was found to control HB leaf reactions to strain HB16 while three regions controlled reactions to strain HB 83. These regions accounted for 22% and 18%, 17%, and 17% of phenotypic variation of resistance, respectively. Four putative QTLs were identified for resistance to BS, and accounted for 37%, 26%, 23%, and 19% of the phenotypic variation. Rust resistance was determined by a single major gene to both rust strains US85NP 5-1 and D82vc74fh. However, linked markers were not identified. The V gene controlling flower and stem color was tightly linked with the Operon marker O10.620.
A significant pest affecting commonly planted Betula spp. is the birch leafminer (Fenusa pusilla Lepeletier), an insect that can be present in large populations in the landscape and can greatly reduce the vigor and ornamental value of these trees. Twenty-two interspecific crosses were performed between leafminer resistant and susceptible Betula species in an attempt to create the novel combination of ornamental white bark and significant leafminer resistance. Of the nine successful crosses, two produced resistant offspring. Progeny of the diploid × hexaploid cross B. turkestanica Litvin (2x) × B. alleghaniensis Britt. (6x) displayed a broad range of resistance levels, likely the result of segregating alleles contributed by the hexaploid parent. All crosses involving highly resistant individuals of B. costata Trautv. (2x) yielded leafminer susceptible progeny. These results suggest that the larval antibiosis demonstrated by B. alleghaniensis and B. costata is inherited as a recessive trait, and exhibits a gene dosage effect as evidenced by the B. turkestanica × B. alleghaniensis offspring. While most progeny of the B. populifolia Marsh (2x) × B. maximowicziana Regal (2x) cross were susceptible, a single resistant offspring, which was found to be triploid (3x), displayed a mechanism of resistance similar to that of a hypersensitive response. No strong intersectional barriers to hybridization were observed and all interploidy crosses were successful. The chromosome numbers of B. costata (2n = 2x = 28) and B. turkestanica (2n = 2x = 28) are reported here for the first time. The results of this study indicate that the potential exists for the development of insect resistant, ornamental white-barked birch clones through the implementation of a planned, systematic breeding program.
Common bacterial blight (CBB), incited by Xanthomonas campestris pv. phaseoli (Xcp), is an important seed-transmitted disease of common bean (Phaseolus vulgaris L.). Tepary bean (Phaseolus acutifolius A. Gray) has high resistance to Xcp. The objective of this study was to identify RAPD markers linked to genes controlling resistance to three isolates of Xcp using bulked segregant analysis in an F2 population from the tepary bean cross CIAT-G40005 (resistant to Xcp) × Nebr.#4B (susceptible to Xcp). Twelve RAPD markers were mapped in a coupling-phase linkage with three genes for resistance to Xcp. The linkage group spanned a distance of 19.2 cM. A marker L7750 was linked to the genes for resistance to Xcp strains EK-11 and LB-2 at 8.4 cM and 2.4 cM, respectively. Markers U10400 and Y14600 were detected as flanking markers for the resistance gene to Xcp strain SC-4A at 2.4 cM and 7.2 cM, respectively. The symbols Xcp-1, Xcp-2, and Xcp-3 were assigned for the genes for resistance to Xcp strains EK-11, LB-2, and SC-4A, respectively. RAPD markers linked to the genes for resistance to Xcp could be used for transferring all of the resistance genes from P. acutifolius to a susceptible P. vulgaris cultivar.
Common bacterial blight (CBB) incited by the bacterial pathogen Xanthomonas campestris pv. phaseoli (Smith) Dye is an important disease of common bean. In a previous study, QTL associated with CBB resistance were described based on RAPD marker analysis of a recombinant inbred population derived from the common bean cross BAC-6 (R) × HT-7719 (S) (resistant × susceptible). The objective of this research is to confirm these previously described candidate marker locus-QTL associations using an inbred backcross PC-50 (S) × BAC-6 (R) and a recombinant inbred Venezuela 44 (S) × BAC-6 (R) population. Two markers previously found to be associated with QTL for CBB resistance in the BAC-6 × HT-7719 population were found to account for 30% of the phenotypic variation for CBB resistance in the PC-50 × BAC-6 inbred backcross population. The three most resistant BC2F3 lines based on marker locus genotypes were ranked 1, 3, and 7 (out of 64) based on phenotypic evaluation. These results provide important confirmation of marker locus-QTL associations and indicate that RAPD markers linked to loci controlling the expression of CBB resistance in common bean may be used to transfer resistance genes into susceptible breeding material.
Common bacterial blight, incited by Xanthomonas campestris pv. phaseoli (Xcp), is a serious disease of common bean (Phaseolus vulgaris). RAPD markers and flower color (V gene) previously had been reported to be associated with six QTL affecting leaf and pod resistance to Xcp. However, the markers for the QTL were not confirmed in different populations and environments to indicate their merit in breeding. Our objective was to determine if the associations of RAPD markers and the V gene with QTL for leaf and pod resistance to Xcp in a RI backcross population from the cross BC2F6 `PC-50' × XAN-159 and for leaf resistance to Xcp in a F2 population from a different cross Pinto `Chase' × XAN-159 could be confirmed. Among six QTL previously detected, five in the RI backcross population and three in the F2 population were confirmed to be associated with resistance to Xcp. The V gene and RAPD marker BC437.1050 on linkage group 5 were most consistently associated with leaf and pod resistance to two to five XCP strains in the RI backcross population and with leaf resistance to two Xcp strains in the F2 population. The confirmed marker BC437.1050 and V gene on linkage group 5, along with other resistance genes from other germplasm, could be used to pyramid the different genes into a bean cultivar to enhance the resistance to Xcp.
White mold, incited by Sclerotinia sclerotiorum (Ss), is an important disease of common bean (Phaseolus vulgaris). Our objective was to identify RAPD markers and seedcoat pattern associated with QTL affecting resistance to Ss isolates 152 and 279 in a molecular marker-based linkage map previously constructed using a recombinant inbred (RI) population from the common bean cross `PC-50' (resistant to Ss) x XAN-159 (susceptible to Ss). White mold reactions were derived from a greenhouse straw test. Continuous distributions for the reactions to Ss isolates 152 and 279 were observed for RI lines, indicating quantitative inheritance. An intermediate (+0.67) Pearson correlation was observed between the reactions to Ss isolates 152 and 279. Low (0.24 and 0.23) narrow-sense heritabilities were found for the reactions to Ss isolates 152 and 279. Three QTL affecting resistance to Ss isolate 152 explained 33% of the phenotypic variation. Four QTL affecting resistance to Ss isolate 279 explained 54% of the phenotypic variation. The seedcoat pattern marker (C) on linkage group I was most consistently associated with resistance to Ss isolates 152 and 279, and explained 10% and 24% of the phenotypic variation for the traits, respectively. This is the first report on detection of QTL for white mold resistance in common bean. The RAPD markers and seedcoat pattern could be useful in breeding for white mold resistance.