Search Results

Abstract

The accessions, PI 255960 (P₁) (purple flowers, colored seed, curved pod tip, large seed) and G-19007 (P₂) (white flowers, straight pod tip, white seed) of Phaseolus vulgaris L., both late maturing with many ovules and seeds per pod, were crossed with each other and with 2 early maturing, white flowered, white seeded, straight pod tip, low ovule number/pod parents, ‘Great Northern (GN) Emerson’ (P₃) and ‘GN UI#59’ (P₄). P₁ and P₂ appeared to possess the same genes for high ovule number/pod. The continuous distributions of ovule number/pod, seed number/pod, and seed weight in the F₂ generations of the other crosses indicated quantitative inheritance. However, segregation data in their F₃ generations suggested that ovule number/pod may be determined by additive action of the alleles of a single major gene. Moderately high broad sense heritability estimates were obtained for these traits. Purple flower color and seed-coat color were controlled by 2 different complementary dominant genes. Striped pod color and curved pod tip shape (Ct) were each controlled by different single dominant genes. Days to flowering was controlled by a single completely dominant gene; pod maturity was controlled by a single incompletely dominant gene for lateness. Linkage occurred between genes for flower color and pod color pattern, flower color and pod tip shape, and flower color and maturity. High seed number/pod was associated with purple flowers, colored seeds, and late maturity in the F₂ of P₃ × P₁. Late maturity and high seed number/pod were also associated in the F₂ of P₄×P₁, P₃× P₂ and P₄ × P₂. Moderately large negative correlations were found between number of seeds/pod and seed weight in all crosses involving P₁ and P₂. High ovule number/pod was associated with indeterminate growth habit and moderately late flowering in the F₂ progeny from the indeterminate cultivar ‘G.N. Nebr. # 1’, crossed with a determinate isoline. No association between seed weight & seed-coat color was observed in the F₂ of P₃ × P₁, and P₄ × P₁, but there was association between large seed and both late maturity and flower color.

Abstract

The inheritance of resistance in butternut squash (Cucurbita moschata Poir) to powdery mildew (Erysiphe cichoracearum DC) was studied under greenhouse and field conditions using F₁ F₂, and BC₁ generations derived from crosses of ‘La Primera’ (resistant) (calabaza type) with 2 butternut cultivars ‘Ponca’ (susceptible), and ‘Waltham’ (susceptible), and ‘Ponca’ x ‘Seminole Pumpkin’ (intermediate resistance). The breath-blowing method of inoculation was effective in greenhouse tests. Petiole and stem reactions of plants in both field and greenhouse trials and leafblade reactions of plants in the field tests indicated that 3 alleles at a single locus determined resistance reactions in crosses involving ‘Ponca’, ‘Waltham’, and ‘La Primera’. Proposed genotypes for the susceptible ‘Ponca’ and ‘Waltham’ butternut squash are pm – l^p pm – l^p and pm – l^w pm – l^w , respectively, and for the resistant ‘La Primera’, pm – l^L pm – l^L . The partial and complete dominance relations of these alleles for the leaf-blade (field) and petiole/stem reactions (field/greenhouse), respectively, are pm – l^p > pm – l^L > pm – l^w . A different gene, pm – 2^s , controlled the intermediate resistance of ‘Seminole Pumpkin’. However, a quantitative inheritance pattern of disease reactions of leaf blades was observed in the greenhouse trials in all crosses, presumably because of the higher inoculum load and the increased intermediate ratings of the heterozygotes under these conditions. Leaf-blade and stem/petiole resistance was completely associated in segregating progenies in the field but not in the greenhouse because of the intermediate susceptibility of the leaf blades of heterozygotes under those conditions. Scanning electron micrographs of powdery mildew on compatible and incompatible hosts showed that differential compatibility occurred in conidial germination. Resistance in ‘La Primera’ involved delayed conidia germination, retarded hyphal growth, shorter conidiophores, and weak sporulation.

Abstract

A Hunter Color Difference meter and a white-paint color chart were used to determine the degree of whiteness among 8 white-seeded Great Northern (GN) cultivars of Phaseolus vulgaris. A correlation coefficient of +0.84 was found between the 2 methods. The former method provided better separation of cultivars for degrees of whiteness than the latter method. Two genetic studies were conducted, with seed-coat whiteness determined by use of the white-paint color strip. ‘GN Emerson’ had the whitest seed-coat. The inheritance of seed-coat whiteness was investigated in 1978 using parents, F²s of the crosses Plant Introduction (PI) 165078 (bright white) with ‘GN Emerson’ (moderately bright white), ‘GN Valley’ (dull white) and ‘GN UI 59’ (dull white) and in the reciprocal cross ‘Bulgarian White’ (brightest white) × ‘GN UI 59’ (dull white). A quantitative pattern of inheritance was observed. Broad sense heritability estimates for this trait ranged from 46 to 57%. The Gardner and Eberhart model, Analysis II, was used in 1979 to estimate genetic effects for the trait in a 6 parent diallel cross involving ‘GN Emerson’, ‘GN UI 59’, ‘Bulgarian White’, ‘GN Star’ (dull white), ‘GN 1140’ (dull white) and ‘GN D-88’ (dull white). Additive genetic effects were predominant; but heterosis effects were also important, including significant effects for specific combining ability, and reciprocal crosses. ‘Bulgarian White’ showed high combining ability for brighter whiteness. The genetic data indicate that improvement of seed-coat whiteness in dry beans should be relatively easy to accomplish.

A new in vitro protocol was developed for multiple bud induction and plant regeneration from embryonic axis explants of four common bean (Phaseolus vulgaris L.) and two tepary bean (P. acutifolius A. Gray) lines. The explants were prepared from two embryo sizes, 3 to 4 mm and 5 to 7 mm, corresponding to pods collected after 15 and 25 days from flowering, respectively. The embryonic axis was cultured on Gamborg's B₅ basal medium with 0, 5, 10, or 20 μm BA in combinations with 0, 1, or 2 μm NAA. The cultures were maintained at 24 to 25C under continuous light or incubated in darkness for 2 weeks followed by continuous light before transfer to the secondary B₅ medium (0 or 2 μm BA or 2 μm BA plus 4 μm GA₃). Adventitious roots or a single shoot with roots formed on the explants cultured on media without plant growth regulators. Multiple buds were induced on all BA media, but more were produced with 5 or 10 μm for most lines. Dark incubation greatly enhanced multiple bud initiation. Shoot buds were not produced on media containing NAA alone or in combinations with BA. On the secondary medium, six to eight shoots per explant for common bean and up to 20 shoots per explant from tepary bean were observed after 3 weeks. Mature, fertile plants were produced from these shoots. Chemical names used: benzyladenine (BA); 1-naphthaleneacetic acid (NAA); gibberellic acid (GA₃).

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.

Nine bean cultivars/lines were grown in a Tripp sandy-clay loam (high pH), a Sharpsburg silty clay loam (neutral pH), and a potting mix (equal volume of sand, soil [Sharpsburg silty clay loam], vermiculite and moss pest) (low pH) in greenhouse (one experiment), growth chamber (two experiments), and field (two experiments) in Lincoln, NE, in order to evaluate the leaf reaction of the plants to a Nebraska rust (Uromyces appendiculatus var. appendiculatus) isolate US85-NP-10-1. A factorial arrangement of soil media and cultivars/lines in a randomized complete block design was used in the greenhouse and growth chamber experiments, while a split-plot design (soil media as main plots and cultivars/lines as sub-plots) was used in the field experiments. Significant differences were observed for rust pustule size of cultivars/lines grown on the three different soil media. Plants grown on potting mix medium showed significant Increases in rust pustule size compared with Tripp (high pH) or Sharpsburg silty clay loam soils (neutral pH). A significant interaction occurred between soil media and cultivars/lines for the rust reaction. A positive correlation (R= +0.5) was observed between the increased concentration of C1 and Mn,, and a negative correlation for lower K (R+ -0.44) and soil pH in the potting mix and larger rust pustule size of leaves. These results have implications for plant breeders and pathologists involved in evaluating bean progenies and lines for rust resistance.

Nine bean cultivars/lines were grown in a Tripp sandy-clay loam (high pH), a Sharpsburg silty clay loam (neutral pH), and a potting mix (equal volume of sand, soil [Sharpsburg silty clay loam], vermiculite and moss pest) (low pH) in greenhouse (one experiment), growth chamber (two experiments), and field (two experiments) in Lincoln, NE, in order to evaluate the leaf reaction of the plants to a Nebraska rust (Uromyces appendiculatus var. appendiculatus) isolate US85-NP-10-1. A factorial arrangement of soil media and cultivars/lines in a randomized complete block design was used in the greenhouse and growth chamber experiments, while a split-plot design (soil media as main plots and cultivars/lines as sub-plots) was used in the field experiments. Significant differences were observed for rust pustule size of cultivars/lines grown on the three different soil media. Plants grown on potting mix medium showed significant Increases in rust pustule size compared with Tripp (high pH) or Sharpsburg silty clay loam soils (neutral pH). A significant interaction occurred between soil media and cultivars/lines for the rust reaction. A positive correlation (R= +0.5) was observed between the increased concentration of C1 and Mn,, and a negative correlation for lower K (R+ -0.44) and soil pH in the potting mix and larger rust pustule size of leaves. These results have implications for plant breeders and pathologists involved in evaluating bean progenies and lines for rust resistance.

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.

The objective was to detect molecular markers associated with QTL for partial physiological resistance (PPR) to two white mold (WM) isolates, partial field resistance (PFR), plant architecture (PA), and plant height (PH) in a genetic linkage map constructed using recombinant inbred lines (RILs) from the cross `PC-50' (resistant to WM) × XAN-159 (susceptible to WM). Significant correlations (+0.39 and +0.47) were noted between the WM reactions in the greenhouse and field. A significant but negative correlation (–0.33) was observed between the WM reaction and PH in the field. Six QTL affecting PPR to isolate 152 were found on LGs 4, 5, 7, and 8. Six QTL affecting PPR to isolate 279 were found on LGs 2, 3, 4, 7, and 8. Five QTL for PFR were observed on LGs 2, 5, 7, 8, and 11. Two QTL affecting PA were detected on LGs 7 and 8. Two QTL affecting PH were identified on LGs 7 and 8. On one end of LG 8 marker H19.1250 was significant for PPR to both isolates. On the other end of LG 8 the region closely linked to the C locus was significantly associated with PPR to both isolates, PFR, PA and PH. Marker J09.950 on LG 7 was significantly associated with PPR to both isolates, PFR, PH and seed weight. Marker J01.2000 on LG 2 was the most significant locus for both PPR to the isolate 279 and PFR. QTL on LG 5 were found for PPR to the isolate 152 and PFR. Overall, four of the five QTL affecting PFR were also found for PPR to one or both isolates.

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.