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- Author or Editor: J. Nienhuis x
- Journal of the American Society for Horticultural Science x
Abstract
A “gynoecious synthetic” (GS) population, developed by random mating of 50 adapted Cucumis sativus L. cultivars and breeding lines, and a “hardwickii semi-exotic” (HSE) population, developed by open-pollinating an F2 population derived from a cross between a Cucumis sativus var. hardwickii (R.) Alef. accession LJ 90430 and a gynoecious inbred line GY 14, were subjected simultaneously to S1 line (S1 and reciprocal full-sib (RFS) recurrent selection. S1 selection resulted in increased fruit number per plant in the GS and HSE populations, and in the GS × HSE population hybrid. In contrast, RFS selection did not result in increased fruit number per plant in the GS and HSE populations or their hybrid. The contrasting responses to S1 compared to RFS selection suggests that additive gene effects were more important than nonadditive effects in the expression of fruit number per plant. Correlated responses to selection resulted in increased number of days to harvest in the GS population, and in reduced percentages of gynoecious plants and pistillate flowers in the HSE population. No change in fruit firmness, and a reduction in length : diameter ratio of fruit only in the GS × HSE population hybrid developed through S1 selection, suggests that selection for increased fruit number per plant should not adversely affect these fruit quality characteristics in either the GS or HSE populations.
Abstract
Recurrent half-sib selection within a heterogeneous population of cucumber (Cucumis sativus L.) was effective in improving germination at 15°C from 34.4% in cycle 0 to 92.4% in cycle 3. The linear regression coefficient indicated an average increase of 19.8% units per cycle of selection. Correlated responses to selection resulted in increased percentage of germination at 20° and 25° and decreased days to germination at 15°, 20°, and 25°.
The development of a complete linkage map, including both classical (visible) and molecular markers, is important to understand the genetic relationships among different traits in common bean (Phaseolus vulgaris L.). The objective of this study was to integrate classical marker genes into previously constructed molecular linkage maps in common bean. Bulked segregant analysis was used to identify 10 random amplified polymorphic DNA (RAPD) markers linked to genes for five classical marker traits: dark green savoy leaf (dgs), blue flower (blu), silvery [Latin: argentum] green pod (arg), yellow wax pod (y) and flat pod (a spontaneous mutation from round to flat pod in `Hialeah' snap bean). The genes for dark green savoy leaf (dgs) and blue flower (blu) were located in a previously constructed molecular linkage map. These results indicate that classical marker genes and molecular markers can be integrated to form a more complete and informative genetic linkage map. Most of the RAPD markers were not polymorphic in the two mapping populations used, and molecular markers from those mapping populations were not polymorphic in the F2 populations used to develop the RAPD markers. Alternative genetic hypotheses for the pod shape mutation in `Hialeah' are discussed, and the experimental difficulties of pod shape classification are described.
Genetic differences among eleven cultivated and eight wild-type populations of North American ginseng (Panax quinquefolium L.) and four cultivated populations of South Korean ginseng (P. ginseng C.A. Meyer) were estimated using RAPD markers. Cultivated P. ginseng population samples were collected from four regions of S. Korea. Cultivated P. quinquefolium population samples were collected from three regions in North America: Wisconsin, the Southeastern Appalachian region of the United States, and Canada. Wild-type P. quinquefolium was collected from three states in the United States: Pennsylvania, Tennessee, and Wisconsin. Evaluation of germplasm with 10 decamer primers resulted in 100 polymorphic bands. Genetic differences among populations indicate heterogeneity. The genetic distance among individuals was estimated using the ratio of discordant bands to total bands scored. Multidimensional scaling of the relationship matrix showed independent clusters corresponding to the distinction of species, geographical region, and wild versus cultivated types. The integrity of the clusters was confirmed using pooled chi-square tests for fragment homogeneity.
To understand the genetics that control pod Ca concentration in snap beans, two snap bean (Phaseolus vulgaris L.) populations consisting of 60 genotypes, plus 4 commercial cultivars used as checks, were evaluated during Summers 1995 and 1996 at Hancock, Wis. These populations were CA2 (`Evergreen' × `Top Crop') and CA3 (`Evergreen' × `Slimgreen'). The experimental design was an 8×8 double lattice repeated each year. No Ca was added to the plants grown in a sandy loam soil with 1% organic matter and an average of 540 ppm Ca. To ensure proper comparison for pod Ca concentration among cultivars, only commercial sieve size no. 4 pods (a premium grade, 8.3 to 9.5 mm in diameter) were sampled and used for Ca extractions. After Ca was extracted, readings for Ca concentration were done via atomic absorption spectrophotometry. In both populations, genotypes and years differed for pod Ca concentration (P = 0.001). Several snap bean genotypes showed pod Ca concentrations higher than the best of the checks. Overall mean pod Ca concentration ranged from a low of 3.82 to a high of 6.80 mg·g-1 dry weight. No differences were detected between the populations. Significant year×genotype interaction was observed in CA2 (P = 0.1), but was not present in CA3. Population variances proved to be homogeneous. Heritability for pod Ca concentration ranged from 0.48 (CA2) to 0.50 (CA3). Evidently enhancement of pod Ca concentration in beans can successfully be accomplished through plant breeding.
Two commercial snap bean (Phaseolus vulgaris L.) cultivars (Hystyle and Labrador) that differ in pod Ca concentration were grown aeroponically to assess physiological factors associated with these differences. Xylem flow rate, Ca absorbed, and Ca concentration in sieve sap and pods (all and commercial size no. 4) were measured. Flow rate, Ca absorption and pod Ca concentration, but not sap Ca concentration, differed between cultivars, and this suggests that genetic variability in pod Ca concentration is caused mainly by differences in flow rate, rather than differences in sap Ca concentration. `Hystyle' showed 1.6 times greater flow rate, 1.5 times greater pod Ca concentration, and 1.7 times greater Ca absorbed than `Labrador'. Flow rate correlated positively with Ca absorbed (R = 0.90), Ca concentration in pods of size no. 4 (R = 0.55), and total pods (R = 0.65). Plant maturity influenced sap Ca concentration and Ca translocated increased as plant matured. These results provide evidence that flow rate differences may cause variability for pod Ca concentration in snap beans.
Stomatal density of pods and leaves were determined for six commercial snap bean cultivars (Phaseolus vulgaris L. `Evergreen', `Hystyle', Labrador', `Tenderlake', `Top Crop', and `Venture') grown at three planting dates, in an attempt to find morphological traits that could be related to cultivar differences in pod Ca concentration. Snap beans were planted three times at ≈1-week intervals beginning 15 June 1995, and harvested 59 to 62 days after planting. Stomatal counts were performed using a microscope linked to a video camera, and Ca concentration determinations were made using atomic absorption spectrophotometry. Calcium concentration and stomatal density of leaf tissue was higher than that of pods. Cultivar differences for pod Ca concentration (P = 0.001) and stomatal density (P = 0.001) were observed although cultivars with higher pod stomatal density did not necessarily result in higher pod Ca concentration. Calcium concentration and stomatal density for leaves did not differ among cultivars. Stomatal density and Ca concentration of pods were positively correlated (R 2 = 0.37), while pod maturity was negatively associated to both pod Ca concentration (R 2 = 0.93), and pod stomatal density (R 2 = 0.99). The effect of planting dates was absent in pod Ca concentration and significant in pod stomatal density.
Randomly amplified polymorphic DNA (RAPD) molecular markers were used to construct a partial genetic linkage map in a recombinant inbred population derived from the common bean (Phaseolus vulgaris L.) cross PC-50 × XAN-159 for studying the genetics of bacterial disease resistance in common bean. The linkage map spanned 426 cM and included 168 RAPD markers and 2 classical markers with 11 unassigned markers. The seventy recombinant inbred lines were evaluated for resistance to two strains of common bacterial blight [Xanthomonas campestris pv. phaseoli (Smith) Dye] (Xcp). Common bacterial blight (CBB) resistance was evaluated for Xcp strain EK-11 in later-developed trifoliolate leaves and for Xcp strains, DR-7 and EK-11, in first trifoliolate leaves, seeds, and pods. One to four quantitative trait loci (QTLs) accounted for 18% to 53% of the phenotypic variation for traits. Most significant effects for CBB resistance were associated with one chromosomal region on linkage group 5 and with two regions on linkage group 1, of the partial linkage map. The chromosomal region (a 13-cM interval) in linkage group 5 was significantly associated with resistance to Xcp strains DR-7 and EK-11 in leaves, pods, and seeds. The regions in linkage group 1 were also significantly associated with resistance to both Xcp strains in more than one plant organ. In addition, a seedcoat pattern gene (C) and a flower color gene (vlae ) were mapped in linkage groups 1 and 5, respectively, of the partial linkage map. The V locus was found to be linked to a QTL with a major effect on CBB resistance.