You are looking at 11 - 20 of 66 items for
- Author or Editor: Dermot P. Coyne x
In growth chambers at 26°±2°C (day) and 21°±2° (night), a 15 hour photoperiod delayed flowering on ‘Great Northern (GN) Nebraska #1 sel. 27’ by 47 days and in Plant Introduction (PI) 207262 by 48 days over a 10 hour photoperiod. The cultivars ‘GN 1140’ and ‘GN Nebraska #1’ and a near-isogenic determinate ‘GN Nebraska #1’ flowered at the same time under both photoperiods. Both near-isogenic lines, determinate and the early flowering ‘GN Nebraska #1 sel. 27’ flowered earlier than ‘GN Nebraska #1 sel. 27’ in all field experiments. The near-isogenic determinate ‘GN Nebraska #1’ flowered earlier than the ‘GN Nebraska #1 cultivar in 2 out of 3 field experiments. The delay in flowering of ‘GN Nebraska #1 sel. 27’ was much greater at higher night temperatures at Lincoln than under lower temperatures at Scottsbluff when the photoperiod was the same. Delayed flowering of PI 207262 under long photoperiod was controlled by a single recessive gene.
Transplanting is an ancient horticultural practice, which is a good thing because our profession is in need of a transplant—an attitude transplant! I was both encouraged and discouraged as I read Dermot P. Coyne's Presidential Address in the Oct. 1985 issue of HortScience 20:805–808. Encouraged, because he raised points that we need to address; discouraged, because he missed the starting point. Allow me to paraphrase an old saying: “Big grad students from little undergrads grow“. Let me lay it out in the open: I was shocked that our President finds no role for undergraduate education in tackling world hunger. I disagree!
No sources of resistance to Xanthomonas campestris pv. cucurbitae (X.c.c.) in the Cucurbita species have been reported. Cultivars, breeding lines, landraces, and PI lines of 5 Cucurbita species were screened for resistance to X.c.c. in 3 greenhouse tests (GH). A `florist`s frog' was used to inoculate the first fully expanded leaves using a X.c.c. suspension (107 CFU/ml). The disease reaction was recorded as the percentage of inoculated leaf area with necrotic lesions and/or chlorosis. Butternut (b n) breeding lines were also evaluated for reaction to X.c.c. under uniform natural in feetion in 2 field (F) trials. A randomized complete block design was used in all GH and F experiments. C. moschata Nebr. BN PM1-88-8 and C. martinezii had high resistance to X.c.c. All other entries in all tests were susceptible. BN PM-88-8 is an early maturing small stable (no crookneck fruit) near-round BN type squash. The fruit are resistant to black–rot, but the leaves are susceptible to powdery mildew. BN PM-88-8 is ideal for microwave cooking because of its near-round shape permitting more uniform cooking. Release is expected in 1990.
Common bacterial blight, incited by Xanthomonas campestris pv. phaseoli (Smith) Dye (Xcp), is a serious disease of common beans (Phaseolus vulgaris L.). Three experiments were conducted twice in growth chambers at 26 ± 1C under short (10 hours light/14 hours dark) and long (16 hours light/8 hours dark) photoperiods to determine the influence of these photoperiods, flower bud removal, pod development, and pre- and post-inoculation photoperiods on the reaction of common beans to Xcp. In one test, `PC-50' (susceptible; S) flowered earlier and was more susceptible to Xcp under the short photoperiod than under the long photoperiod. BAC-6 (resistant; R) flowered at the same time under both photoperiods but developed rapid leaf chlorosis (RLC) (hypersensitive reaction) under long photoperiods. Flowering and disease reactions to Xcp by XAN-159 (R) were similar under both photoperiods. In a second test, daily removal of flower buds of `PC-50' decreased its susceptibility to Xcp under the short photoperiod. RLC of inoculated leaves of BAC-6 occurred during flowering and pod development under both photoperiods. XAN-159 expressed a high level of resistance to Xcp but showed RLC at later pod development stages. In a third test, the disease reaction of `PC-50' was affected by the particular photoperiod applied post-inoculation but was not influenced by the photoperiod applied before inoculation with Xcp. The implications of these results in breeding beans for resistance to Xcp are discussed.
Factors influencing Agrobacterium tumefaciens-mediated transformation of common beans (Phaseolus vulgaris L.) were examined using an intron-containing β-glucuronidase (GUS) gene as a reporter system to develop a repeatable transformation protocol. Tissue culture procedures used were based on direct shoot organogenesis. Two A. tumefaciens strains—A2760 and EHA105—were used, with emphasis on the former due to its overall higher infection rate. Eleven common-bean genotypes were compared for susceptibility to strain A2760 or EHA105. The pinto bean `Othello' was used extensively in testing different transformation conditions. Factors significantly affecting transformation rate were Agrobacterium × host interactions, explant maturity, preculture and cocultivation conditions, and selection schemes, based on transient GUS gene expression. The best transformation conditions were the use of susceptible genotypes and explants derived from mature seeds, preconditioning of explants in a medium containing 20 μmol of benzyladenine (BA) in darkness or on a filter paper, dipping explants in high concentrations of Agrobacterium cell suspension (OD650 = 0.8-1.0) followed by a long-term (6-day) cocultivation period on a semisolid agar medium in the presence of cytokinin or 3-day cocultivation on a moistened filter paper, and the use of lethal levels of selective agents. About 4% of explants, or 14% of regenerated shoots or buds, were putatively transgenic, as indicated by GUS blue staining throughout the entire shoot or bud, after explants were transformed with Agrobacterium strain A2760 using an optimized protocol.
A need exists for the introduction of a high quality, large fruited butternut squash (Cucurbita moschata Duch ex Poir) stable for fruit shape.
Bacterial pathogens cause destructive diseases on many important vegetable crops throughout the world. Satisfactory chemical control measures for bacterial pathogens have not been achieved. Recommended control measures are: use of disease-free seed and transplants; hot water treatment of seed if feasible; suitable rotations; deep plowing of plant debris; and use of resistant cultivars if available (13, 50, 51, 53, 73, 75, 76, 77).
The inheritance of response to trifluralin (Treflan) at 1.12 kg/ha was studied in the field, using transplants of parents, F1, F2, and BC1 generations of the Cucurbita moschata crosses ‘La Primera’ with ‘Butternut Ponca’ and ‘Waltham’. Parents and F1s were susceptible. Based on segregation data in the F2 and BC1 generations it is hypothesized that a dominant gene T determines resistance but is inhibited by a dominant I-T gene. Proposed genotypes for ‘La Primera’ and the 2 ‘Butternut’ cultivars are I-TI-T T T and i-t i-t t t, respectively.
Differences in potato leafhopper (Empoasca fubae Harris) injury symptoms were noted in 22 cultivars or lines of dry beans (Phaseolus vulgaris L.) in a 1991 field trial at North Platte, Neb. Seed yield, biomass, and plant injury symptoms were recorded. The same 22 dry bean cultivars or lines were planted in a split-plot design, with main plots protected (sprayed with insecticide) vs. unprotected (not sprayed) and cultivars or lines as subplots in 1992 and 1993. Significant differences were observed between cultivars/lines for leafhopper injury and yield in all 3 years. `Tacaragua' (black-seeded) and pinto `Sierra' were highly resistant to leafhoppers, with no visual leafhopper injury symptoms in all 3 years. Significant negative correlation coefficients between leafhopper injury symptoms and yield were recorded in the protected (4.50) and unprotected (-0.33) plots in 1993 but only in the unprotected (-0.46) plots in 1992. A cultivar x spray interaction response to leafhoppers occurred in 1992 but not in 1993. The degree of leafhopper injury symptoms varied between years.
Sixteen Alubia lines (15 with long, straight hairs and one with short, hooked hairs on trifoliolate leaves) derived from single-plant selections made in an Alubia landrace (Argentine) were used to evaluate the relation of abaxial leaf pubescence to reaction to rust in a greenhouse experiment. The pinto cultivar UI-114 (short, hooked hairs) was used as a susceptible check. One plant per pot, replicated six times, in a randomized complete-block design was used. The primary leaves and the sixth trifoliolates of all plants from 12- and 50-day-old plants, respectively, were inoculated with a water suspension of urediniospores (105 cells/ml) of rust isolate US-NP85-10-1. Pustule size and rust intensity were assessed 14 days later. No rust pustules were observed on the sixth trifoliolate leaves of the pubescent (long, straight hairs) Alubia lines, but large pustules were observed on the primary leaves (short, hooked hairs) of all Alubia lines and pinto `UI-114'. as well as on the sixth trifoliolate leaf of A-07-2 and pinto `UI-144' (the latter two with short, hooked hairs).