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Genetic distance was estimated among 65 Phaseolus lunarus genotypes, which included 4 large seeded and 8 small seeded cultivars, and 53 landraces from the the Caribbean, North, Central and South America. Based on 130 polymorphic RAPD bands two major clusters were observed among the landraces, which generally corresponded with small and large seed size (Fig. 1). The four `Forkhook' type cultivars and a landrace from the USA formed a separate cluster, which was most closely related the the large seeded landraces.
Legume plants capable of fixing N2 in the presence of abundant N in the soil are desirable to better integrate legumes into crop rotations including high N-demanding cereals. It has been suggested that the exotic bean line 'Puebla 152' may be insensitive to nitrate levels that normally inhibit bean nodulation and/or rate of fixation. Four levels (0, 30, 60, 120 Kg N/ha) of N as 15N-depleted ammonium nitrate were partialized into five weekly applications and imposed on Puebla 152, snap bean `Eagle', and non-nodulating soybean `Clay', in field experiments conducted in 1991 and 1992 on a very low N soil. CIAT's non-nod bean line Nod 125 was included in 1992. Each increment of added N increased the total N accumulated by the plants, in all genotypes. No significant genotype × N fertilizer interactions were detected. In average, Puebla 152 accumulated 25 and 46% more N than Eagle and Clay, respectively, in 1991, and 53, 119 and 119% more N than Eagle, Clay and Nod 125, respectively, in 1992. The analysis of 15N to estimate the proportion of N derived from the atmosphere is underway and will be presented at the meeting.
Abstract
Seeds from three cycles of recurrent selection in a heterogeneous cucumber (Cucumis sativus L.) population for improved percentage of germination at 15°C were subjected to five treatments and evaluated for percentage of emergence and average number of days to emergence at 15°, 20°, and 25° under controlled conditions. Treatments included dry seed, imbibed seed, and pregerminated seed in combination with a supporting gel at sowing. Results indicate that the mechanism for improved low temperature germination is not due to enhanced imbibition. Data also suggest that the percentage of emergence of imbibed seed with or without gel is complemented by the genetic potential to germinate at low temperatures and that no such complementation exists for pregerminated seed. Percentage of emergence of dry and imbibed seed with or without gel at 15° was improved while selecting only for improved germination at 15°, indicating a correlated response to selection.
The magnitude of genetic differences among and the heterogeneity within cultivated and wild American ginseng populations is unknown. Variation among individual plants from 16 geographically separated, cultivated populations and 21 geographically separated, wild populations were evaluated using RAPD markers. Cultivated populations from the midwestern U.S., the southern U.S., and Canada were examined. Wild populations from the midwestern U.S., the southern U.S., and the eastern U.S. were examined. Polymorphic bands were observed for 15 RAPD primers, which resulted in 100 scored bands. Variation was found within and among populations, indicating that the selected populations are heterogeneous with respect to RAPD markers. The genetic relationships among individual genotypes were estimated using the ratio of discordant bands to total bands scored. Multidimensional scaling of the relationship matrix showed independent clusters corresponding to the geographical and cultural origins of the populations. The integrity of the clusters were confirmed using pooled chi-squares for fragment homogeneity. Average gene diversity (Hs) was calculated for each population sample, and a one-way analysis of variance showed significant differences among populations. Overall, the results demonstrate the usefulness of the RAPD procedure for evaluating genetic relationships and comparing levels of genetic diversity among populations of American ginseng genotypes.
Lima beans are an important vegetable crop to the processing industry in Delaware, but yields in Delaware are below other areas due to heat. The objective was to correlate RAPD markers from heat-tolerant and intolerant cultivars with phenotypic data. Twenty-five primers were used, 10 of which generated 25 polymorphic bands among 11 cultivars. MDS analysis of genetic distance among the cultivars shows segregation into two major clusters, with Kingston as a distant outlier. Kingston's position can be correlated to published data reporting its consistently good yields even when temperatures are high. The results of this study indicate RAPD markers may be used to screen for cultivars that have high yield potentials despite high temperatures. Further studies to screen F, and inbreeds will determine the usefulness of these markers in breeding programs.
To measure the effect of added Ca fertilizer on the Ca concentration of snap bean pods, four snap bean cultivars were grown during Summer 1996 and 1997 at Hancock, Wis. Fertilizer treatments consisted of 80 kg of Ca per hectare applied as Ca sulfate (CaSO4·2H2O) or Ca nitrate [Ca(NO3)2], and the control (no Ca applied. The experimental design was a randomized complete block with a factorial set of treatments (4 × 3). Calcium sulfate was applied at planting, whereas Ca nitrate was split applied four times at weekly intervals starting 1 week before flowering. Yield and Ca concentration in pods were determined. The statistical analysis showed no significant effect of Ca fertilizers on pod Ca concentration or yield. A strong cultivar effect was detected for both parameters measured. `Evergreen' (5.47 mg Ca per gram dry weight) had the highest pod Ca concentration and `Labrador' (4.10 mg Ca per gram dry weight) the lowest. No significant fertilizer × cultivar interactions were observed. Results for pod Ca concentration remained consistent, even when significant year effects were found for both parameters.
This study was designed to compare snap and dry beans (Phaseolus vulgaris L.) for pod Ca concentration, and to identify genetic resources that might be useful in breeding programs directed to increase Ca concentration in bean pods. Pods from eight snap bean and eight dry bean cultivars were evaluated for Ca concentration during 1995 and 1996 at Hancock, Wis. A randomized complete-block design was utilized with three replications in 1995 and six in 1996. Beans were planted in June and hand-harvested in August for both experiments. Soil Ca at planting time was 580 mg·kg–1 in 1995 and 500 mg·kg–1 in 1996. No additional Ca was added. Plots consisted of 10 plants each. At harvest, a pooled sample of 10 to 15 size no. 4 pods was collected from each plot. Atomic absorption spectrophotometry was used to determine Ca content. Significant differences (P ≤ 0.01) were detected among and within bean types (dry and snap). Although bean type × year interaction was nonsignificant, a strong year effect was observed (P ≤ 0.01). Snap beans (4.6 ± 0.7 mg·g–1 dry weight) had significantly higher pod Ca concentration than did dry beans (4.2 ± 0.6 mg·g–1 dry weight). Within snap beans, `Checkmate' had the highest pod Ca concentration (5.5 ± 0.3 mg·g–1 dry weight) and `Nelson' the lowest (3.8 ± 0.3 mg·g–1 dry weight). Within dry beans, `GO122' had the highest (5.1 ± 0.4 mg·g–1 dry weight) and `Porrillo 70' the lowest pod Ca concentration (3.6 ± 0.3 mg·g–1 dry weight). Six cultivars had pod Ca concentrations significantly (P ≤ 0.01) higher than the overall mean (4.4 ± 0.3 mg·g–1 dry weight).
Abstract
Two gynoecious pickling cucumber inbred lines, GY 14-2 and GY 2, and 4 hybrids derived from crosses of these gynoecious lines by a monoecious determinate (M 20-2), and a monoecious indeterminate line (M 11) were grown at densities of 1, 2, and 4 plants per hill, all at populations of 84,000 plants/ha. Increasing numbers of plants/hill reduced the percentage of pistillate nodes/plant in all hybrids, the number of flowering nodes in both gynoecious inbred lines and their hybrids, and the percentage of gynoecious plants in both gynoecious inbred lines, and in their hybrids with the determinate M 20-2 line.
Sugars, including glucose, fructose, and sucrose, contribute significantly to the flavor and consumer acceptance of snap beans (Phaseolus vulgaris L.). Sugar accumulation and changes in sugar profiles during snap bean development contribute to overall assessments of quality for breeding lines and cultivars. Developing fruit from a diverse group of four snap bean cultivars containing Andean germplasm and one Mesoamerican dry bean cultivar were sampled at 5-day intervals from 10 to 30 days after flowering over 2 years. Glucose, fructose, and sucrose in pod and seed tissue was quantified using high-performance liquid chromatography. Percent seed mass relative to pod mass increased with days after flowering, but the rate of increase was heterogeneous among cultivars. Significant differences in sugar accumulation patterns of mono- and disaccharides were observed with time of development and between pods and seeds. Glucose and fructose decreased rapidly in pods and seeds with time after flowering. In contrast, sucrose concentration increased in pod tissue but remained constant in seeds of the snap bean cultivars with time after flowering. The patterns of changes in pod and seed sugar concentrations with time after flowering were similar among all snap bean cultivars. In contrast to the snap beans, seed sucrose increased with time after flowering in the Mesoamerican dry bean cultivar Puebla 152. No year by day after flowering interactions were observed for sugar accumulation patterns or sugar concentrations. Younger snap beans had the highest sweetness index based on observed sugar concentrations, percent seed mass, and perception of relative sweetness by the human palate. Although mean sweetness varied between cultivars, the rate of decrease in sweetness with time was the same for all five cultivars. These findings indicate that variation for sweetness exists in snap beans and can be exploited by breeding to develop cultivars with a potentially more desirable, sweet flavor.
Bacterial brown spot (BBS), incited by the bacterial pathogen Pseodomonas syringae pv. syringae is important disease of common bean. Phenotypic visual readings of infected areas and a leaf freezing assay estimating the population size of Pss on leaf surface were used for disease assessment for 2 years using 78 RI lines derived from Belneb RR-1 x A55 population grown in Wisconsin. The objectives of this research were to determine the genomic regions of QTL affecting the genetic variation of bacterial brown spot resistance in both assays over 2 years (1996 and 1998) and to determine the size of their genetic effects. In addition, we examined the consistency of detected QTL over environments. Three chromosomal regions associated with QTL for BBS resistance were identified in both assays in 1996 and one chromosomal region was consistently detected over 2 years.