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- Author or Editor: Dermot P. Coyne x
The leaf reaction of the Phaseolus vulgaris L. germplasm—UNECA (M6 mutant derived from the cultivar Chimbolito, Costa Rica), `Chimbolito', BAC-6 (Brazil), XAN-159 (Centro Internacional de Agricultura Tropical, Cali, Colombia), and `PC-50' (Domican Republic)—to Xanthomonas campestris pv. phaseoli strain V4S1 (Dominican Republic) were determined in two replicated trials conducted in a greenhouse in Lincoln, Neb. (Feb.–Mar. and July–Aug. 1993). `PC-50' and `Chimbolito' were susceptible to Xcp strain V4S1 in both tests. UNECA, BAC-6, and XAN-159 had similar levels of resistance to Xcp in the July to August trial. However, in the February to March trial, the resistance of UNECA was greater than that of BAC-6 but less than that of XAN-159.
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.
Few studies on embryogenesis in common bean (Phaseolus vulgaris L.) have been reported and only the early stages of somatic embryogenesis were observed. Dry seeds from two common bean lines were germinated in darkness on L-6 medium containing 4% sucrose, 0.2 g casein hydrolysate /liter and 2.0 g phytagel /liter. The medium for seed germination was supplemented with 0, 2, 4 or 6μM forchlorfenuron (CPPU). Explants from cotyledonary leaves, petioles, hypocotyls and shoot apices were prepared from 14 day-old seedlings. Callus was derived from explant cultures incubated in darkness at 26C on the medium containing 4 μM 2,4-D and 1 μM Kinetin. The callus was transferred after 4 weeks into 125 ml Erlenmeyer flasks containing 50 ml liquid medium and placed on a gyrotary shaker (120 rpm) under cool-white light (12 μmol.m-2 .s-1 ). The liquid medium was used with 2, 4 or 6 μM of 2,4-D alone or with zeatin supplements at relative concentrations of 0.25 and 0.5. Up to 200 somatic embryos from 40 to 50 mg callus inoculations were induced after 4 to 5 weeks. Callus derived from seedlings grown on CPPU-containing medium gave more repetitive somatic embryos. Cotyledonary stage embryos with clear bipolar structure were observed only from callus derived from seedlings grown on CPPU when transferred to suspension cultures containing 2,4-D and zeatin. All somatic embryos differentiated strong roots and some developed leaf-like structures on conversion medium.
Plant regeneration has been achieved in two common bean lines from pedicel-derived callus that was separated from the explant and maintained through successive subcultures. Callus was induced either on B5 or MS medium containing 2% sucrose and enriched with 0.5 or 1.0 mg thidiaznron/liter alone or plus various concentrations of indoleacetic acid. The presence of 0.07 or 0.14 g ascorbic acid/liter in the maintenance media prolonged the maintenance time. Up to 40 shoot primordia were observed in 4-week-old cultures obtained from 40 to 50 mg callus tissues on shoot-induction medium containing 1-mg benzyladenine/liter. These shoot primordia developed two to five excisable shoots (>0.5 cm) on medium with 0.1-mg BA/liter. A histological study confirmed the organogenic nature of regeneration from the callus tissues. The R2 line from a selected variant plant showed stable expression of increased plant height and earlier maturity. Chemical names used: ascorbic acid, N- (phenylmethyl)-1H-pnrin-6-amine [benzyl-adenine, BA], 1H-indole-3-acetic acid (IAA), N- phenyl-N'-1,2,3-thiadiazol-5-ylurea [thidiazuron, TDZ].
Field reaction of 25 red mottled bean (Phaseolus vulgaris L.) genotypes to common bacterial blight [Xanthomonas campestris pv. phaseoli (Smith) Dye] was evaluated in Puerto Rico over 2 years. The average disease severity (percent leaf area with symptoms) was similar over years. The determinate red mottled genotypes had almost twice as much disease as indeterminate genotypes. Eight of the indeterminate genotypes had significantly less disease than the mean of the field experiments. These genotypes may serve as useful sources of resistance to common bacterial blight. The size of the chlorotic zone around necrotic lesions varied between growing seasons, showing that environment can influence the expression of common bacterial blight symptoms.
Eight species and 57 selections/cultivars of Penstemon were compared for genetic variability using Random Amplified Polymorphic DNAs (RAPDs). The RAPD technique was used to help understand the genetic relationships in species and cultivars in the genus Penstemon. Ten RAPD primers (from Operon) were screened to identify polymorphisms among these eight species and 57 selections. More than 100 RAPD polymorphic bands were obtained. A principle component analysis was used to study genetic relationships. Variation among species was greater than variation among selections/cultivars within species. RAPD markers distinguished differences between most cultivars tested. DNA fingerprints generated by RAPDs should be useful to distinguish cultivars of Penstemon, as well as to assist in determining genetic relationships between species.
Bean rust, caused by Uromyces appendiculatus, is an important disease of common bean (Phaseolus vulgaris L.). The objective was to identify RAPD markers linked to the gene (Ur-6) for specific resistance to rust race 51 using bulked segregant analysis in an F2 segregating population from the common bean cross pinto `Olathe' (resistant to rust) × great northern Nebraska #1 selection 27 (susceptible to rust). A single dominant gene controlling specific resistance to race 51 was hypothesized based on F2 segregation, and then was confirmed in the F3 generation. A good fit to a 3:1 ratio for band presence to band absence for each of three markers was observed in 100 F2 plants. Three RAPD markers were detected in a coupling phase linkage with the Ur-6 gene. Coupling-phase RAPD marker OAB14.600 was the most closely linked to the Ur-6 gene at a distance of 3.5 cM among these markers. No RAPD markers were identified in a repulsion phase linkage with the Ur-6 gene. The RAPD markers linked to the gene for specific rust resistance of Middle American origin detected here, along with other independent rust resistance genes from other germplasm, could be utilized to pyramid multiple genes into a bean cultivar for more durable rust resistance.
Bean rust, caused by Uromyces appendiculatus, is a major disease of common bean (Phaseolus vulgaris). The objective was to identify RAPD markers linked to the gene (Ur-7) for specific resistance to rust race 59 using bulked segregant analysis in an F2 segregating population from the common bean cross GN1140 (resistant to rust) × Nebraska #1 (susceptible to rust). A single dominant gene controlling specific resistance to race 59 was found in the F2 and was confirmed in the F3. Seven RAPD markers were detected in a coupling-phase linkage with the Ur-7 gene. Coupling-phase RAPD markers OAA11.500, OAD12.550, and OAF17.900 with no recombination to the Ur-7 gene were found. Three RAPD markers were identified in a repulsion-phase linkage with the Ur-7 gene among the three markers at a distance of 8.2 cM. This is the first report on RAPD markers linked to the Ur-7 gene in common bean. The RAPD markers linked to the gene for specific rust resistance of Middle American origin detected here, along with other independent rust resistance genes from other germplasm, could be used to pyramid multiple genes into a bean cultivar for more-durable rust resistance.
Dry seeds from two lines of common bean (Phaseolus vulgaris L.) and one cultivar of faba bean (Vicia faba L.) were germinated on Murashige and Skoog (MS) medium containing B vitamins, 30 g sucrose/liter, and either 2.5, 5.0, or 7.5 μm benzyladenine (BA). Axenic seed cultures were grown at 22 to 24C in darkness and under continuous light from cool-white fluorescent tubes (40 μmol·m-2·s-1). Explant tissues were prepared from cotyledonary nodes (CN) and primary nodes (PN) of 14-day-old seedlings. Explants were cultured on corresponding seedling growth medium and maintained under continuous cool-white light (40 μmol·m-2·s-1). The percentages of CN and PN (in one line of common bean) explants that regenerated shoots and the number of shoots per explant (in all germplasm) were highest when nodal tissues were prepared from seedlings germinated in darkness. These responses were optimal on medium containing 5 μm BA during seedling growth and subsequent culture of explants. The number of shoots per explant was two to five times higher on explants cultured on medium with 0.25 to 1.0 μm forchlorfenuron (CPPU) or thidiazuron (TDZ) than on medium with 5 μm BA. Higher (2.5 and 5 μm) CPPU and TDZ concentrations inhibited shoot elongation and stimulated callus production. Histological analyses indicated that adventitious meristems formed 6 to 8 days after explant culture. Progenies from regenerated plants appeared similar to plants raised from the original seed stocks. Chemical names used: N- (phenylmethyl) -1 H- purin-6-amine (benzyladenine, BA); N- (2-chloro-4-pyridyl)-N'- phenylurea (forchlorfenuron, CPPU); N- phenyl -N' -1,2,3-thiadiazol-5-ylurea (thidiazuron, TDZ).
Abstract
Common blight in beans (Phaseolus vulgaris L.) incited by Xanthomonas campestris pv. phaseoli (Smith) Dye (X c p) reduces crop yield and seed quality. The objective of this experiment was to study heritability and phenotypic correlations of the disease reaction to various strains of X c p at several plant developmental stages in specific bean crosses using diverse methods of inoculation. Leaf and pod disease reactions to strains of X c p were inherited quantitatively and narrow-sense heritability estimates were low in the following crosses between Phaseolus vulgaris cultivars/lines: Bac-6 (moderately resistant = MR) × NE-EP1 (MR); Bat-862 (MR) × ‘Pompadour Checa’ (susceptible = S); ‘Pompadour Checa’ (S) × Bac-6 (MR); ‘Venezuela 44’ (S) × Bat-862 (MR). Pod disease reaction was not correlated with leaf disease reaction at any growth stage. Low or nonsignificant phenotypic correlations were detected between disease reactions of leaves at the seedling and flowering stages with the several methods of inoculation. Intermediate phenotypic correlations were found for disease reactions with three methods of inoculation at the seedling stage, but only with two methods in the flowering stage. Negative or nonsignificant phenotypic correlations were observed between leaf disease reaction and number of days to first flower. Different duplicate recessive genes were found to control two foliar abnormality traits: crippled growth and variegated leaves. No plants with a combination of both traits were observed. An association was found between crippled growth and a high level of resistance to strain V3S8 of X c p in the cross Bat-862 × ‘Pompadour Checa’.