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- Author or Editor: Dermot P. Coyne x
Abstract
A germination test of seven Cucurbita entries in a dark growth chamber indicated no effects of trifluralin on germination. Increasing the plant population/pot of butternut type squash (C. moschata Poir, cv. Ponca) did not improve trifluralin tolerance. A factorial arrangement of three treatments (six Cucurbita entries × five trifluralin doses × three herbicide incorporation zone placements in pots) with a randomized complete block design was used in two greenhouse experiments. The incorporation zone treatments included surface layering (above seed), subsurface layering (below seed), and full-pot incorporation of the herbicide dose. The layering treatments increased concentration (ppm) of the herbicide due to the concentrated dose in a small volume of sand medium (200 vs. 500 g quartz sand). Total plant dry weight differences were detected between zoning treatments. After an initial stimulating effect, plant dry weight decreased over the dose range. The C. maxima Duch, PI 182202, and C. pepo L., PI 234252, showed the highest tolerance. Adventitious roots developed and senescence of the primary root occurred above the subsurface treated layer that had been treated at high trifluralin concentrations. The root zone was the primary site of herbicide action. C. moschata, C. pepo, and C. maxima spp. (21 entries) were screened in two tests for tolerance to trifluralin over a range of 0 to 0.4 ppm incorporated in quartz sand. Entry, herbicide dose, and entry × dose interaction effects were significant. C. maxima PI lines 368567 and 179264 exhibited the highest tolerance regardless of dose. Chemical name used: α,α,α-trifluoro-2,6-dinitro-N, N-dipropyl-p-toluidine (trifluralin).
Abstract
Increasing the amount of artificial support with wire fencing placed under the canopy of furrow-irrigated ‘Great Northern Valley’ dry beans (Phaseolus vulgaris L.) significantly decreased severity of white mold [Sclerotinia sclerotiorum (Lib.) deBary] and increased seed yield.
Abstract
Dry bean (Phaseolus vulgaris L.) cultivars/lines differed in their iron-deficiency leaf chlorosis response when grown in field trials on a calcareous soil in western Nebraska. The genetic basis of this response was determined. Crosses were made between three susceptible (PI 165078, Navy ‘Tuscola’, and Light Red Kidney ‘Redkloud’) and seven resistant parents (G.N. ‘Valley’, G.N. 1140, G.N. ‘UI 59’, G.N. ‘Emerson’, Pinto EP-1, Pinto ‘Olathe’, and Black Neb-WM1-83-10). The parents, F2, and several F3 progenies were evaluated visually in replicated field trials for leaf iron-deficiency chlorosis. Based on F2 and F3 segregation patterns, it was hypothesized that resistance was controlled by two major complementary dominant genes. The environment also influenced considerably the range in expression of the leaf chlorosis, particularly in the susceptible parents and progenies.
Abstract
Plants of the ‘Crookneck 67-1-7’ rogue, derived from ‘Butternut’ squash, developed straight fruits when grown on a fence; those grown on the ground produced crookneck fruit. Length of neck and bulb circumference were greater in ground-grown crookneck fruit. The outer-curved part of crookneck fruit on the ground had the lowest width of hypodermal zone cells and this was due to an elongation of the cells in the direction of fruit length, while in fence-grown straight fruit, the cells were near-isodiametric. Cell number of the hypodermal zone was the same in all fruits. ‘Crookneck 67-1-7’ ground-grown fruit, oriented horizontally and level with the soil surface, and also vertically, blossom-end up or down, did not show any crooking. Crooking of fruit is due to the interaction of genotype and an impediment causing differential pressure on the cells on each side of the squash. Straightneck fruit, including ‘Butternut’ type, occurred in the F2 and BC generation of the cross of 2 crookneck types, ‘Crookneck 67-1-7’ × ‘Golden Cushaw’, indicating that different genes controlled the crookneck fruit trait in the parents.
Abstract
The leaf and pod reactions of greenhouse-grown plants of reportedly tolerant lines of P. vulgaris L.: Plant Introduction (PI) 169727, PI 197687, PI 163117, PI 207262, PI 325684, PI 325691, ‘Great Northern Nebr. #1 sel. 27’; P. coccineus: PI 165421 and P. acutifolius: Tepary (Nebr. Acc. 10) to Xanthomonas phaseoli (E. F. Smith) Dowson isolates [Xp-S and Xp 816 (Nebr.), Xp-15 (Michigan), Xp-Br (Brazil)], and X.p. fuscans (Burkh.) Starr & Burk. [Xpf-UI (Uganda)], were studied. The multiple needle method was used to inoculate leaves and a dissecting needle was used to inoculate pods of these plants. A differential reaction of lines to isolates was observed for each of the reactions on leaves and pods. All P. vulgaris lines were susceptible or moderately susceptible to the new virulent Xp-Br strain. Leaves and pods of P. acutifolius were highly tolerant to all isolates while P. coccineus PI-165421 showed a differential reaction to all isolates: leaves were highly tolerant and pods highly susceptible. The internal reaction for pods was more severe than the external reaction. P. vulgaris PI 207262 showed a uniform tolerance of leaf and pod to the USA isolates, while ‘GN Nebr. #1 sel. 27’ had a tolerant leaf and susceptible pod. These results suggested differential genetic control of pod and leaf reactions. Transgressive segregation for a high level of leaf tolerance to the virulent Xp-Br strain (water soaking method of inoculation) was observed in field-grown P. vulgaris F2 plants from the crosses ‘GN Nebr. #1 sel. 27’ × PI 163117 and ‘GN Nebr. #1 sel. 27’ × ‘Guali’. Transgressive segregation was confirmed in greenhouse-grown selected F3 families. High leaf tolerance was not associated with pod tolerance. Linkage was detected among the major genes controlling late maturity and indeterminate plant habit, and the polygenes controlling common blight tolerance.
Abstract
Eight known resistant lines of Phaseolus vulgaris L., one resistant line of P. acutifolius A. Gray, and the susceptible ‘Dark Red Kidney’ were evaluated in the greenhouse for their leaf and pod reactions to 7 isolates of Xanthomonas phaseoli (E.F. Sm.) Dows. [= Xanthomonas campestris pv. phaseoli (E.F. Sm. Dye)] from the Dominican Republic (DR) and Nebraska isolate EK-11. P. acutifolius had the highest leaf and pod resistance, followed by Great Northern (GN) Nebr. #1 sel. 27 and Pinto Nebr. EP-1, while the leaves of PI 207262 were highly susceptible to isolates, DR-7 and DR-12. A significant host entry × isolate interaction occurred both for leaf and pod reactions but in some lines the reaction of these plant parts to the isolates was different. Plants of BAT 93 (CIAT) has resistant leaves but susceptible pods to all isolates except Nebr. EK-11, while leaves of BBSR-130 were susceptible to the DR-12 isolate, but its pods were moderately resistant to all isolates.
Abstract
Variations occurred in the rate of water uptake of seeds of different dry bean cultivars (Phaseolus vulgaris L). ‘Pinto UI11’ had a higher water uptake by 24 hours than the other 6 cultivars. The micropyle was the main site for water entry in white-seeded ‘Great Northern’ and it is inferred that the raphe and or hilum areas were mainly involved in water uptake in ‘Pinto UI11’. No water uptake through the seed coat of seeds of 7 cultivars occurred by 2, 4, or 8 hours and only a small amount by 24 hours, except ‘GN Star’ where no water uptake was noted indicating that it had an impermeable seed coat during that period.
Common bacterial blight, incited by Xanthomonas campestris pv. phaseoli (Xcp) is a serious disease of common bean (Phaseolus vulgaris L.). Randomly amplified polymorphic DNA (RAPD) markers and flower color (V gene) previously were reported to be associated with six quantitative trait loci (QTL) affecting leaf and pod resistance to Xcp. However, the markers for the QTL were not confirmed in different populations and environments to indicate their merit in breeding. The objective was to determine if the associations of RAPD markers and the V gene with QTL for leaf and pod resistance to Xcp in a recombinant inbred (RI) backcross population from the cross BC2F6 `PC-50' × XAN-159 and for leaf resistance to Xcp in an F2 population from a different cross pinto `Chase' × XAN-159 could be confirmed. One or two genes from XAN-159 controlled leaf and pod resistance to Xcp. Among six QTL previously detected, five in the RI backcross population and three in the F2 population were confirmed to be associated with resistance to Xcp. The V gene and RAPD marker BC437.1050 on linkage group 5 were most consistently associated with leaf and pod resistance to two to five Xcp strains in the RI backcross population and with leaf resistance to two Xcp strains in the F2 population. One to three QTL affecting leaf and pod resistance to Xcp accounted for 22% to 61% of the phenotypic variation. Gene number (one to two) estimations and number of QTL (one to three) detected for leaf and pod resistance to Xcp in the RI backcross population were generally in agreement. The marker BC437.1050 and V gene, along with other resistance genes from other germplasm, could be utilized to pyramid the different genes into a susceptible or partially resistant bean line or cultivar to enhance the level of resistance to Xcp.
Abstract
Two field experiments were conducted to explore possible causes of inefficient selection for architectural avoidance of white mold disease reported in dry beans (Phaseolus vulgaris L.). Near-isogenic breeding lines for maturity and plant growth habit were blended in 4 paired combinations (with 5 mixture levels/blend) to investigate their intrarow competitive influence on disease severity. Results from regressing the disease severity for each blend component on the mixture level showed the disease severity of an individual plant to be dependent upon its own maturity, as well as on the maturity of its neighbors. An increase in the proportion of late plants in the blend led to a significant and linear increase in their disease severity. A comparable decrease in disease severity was observed as the proportion of early plants in the blend was increased. Disease severity was not influenced by the proportion of indeterminate or determinate plants in the blend, regardless of maturity. The determinate growth habit, however, as well as early maturity, resulted in greater disease avoidance than the indeterminate growth habit or late maturity when grown in pure stands. In a 2nd experiment, 4 dry bean cultivars possessing different architectures were used to study the interrow influence of plant architecture on disease severity, incidence, and seed yield. Significant differences in disease severity and incidence observed between plots bordered by an upright genotype or a dense, prostrate genotype indicated that the level of disease in the test row was determined to a large extent by the architecture of adjacent rows. The failure to obtain an accurate assessment of a genotype's performance may account partially for the difficulty in selecting for architectural avoidance.
Our objective was to identify QTL for seed weight (SW), length, and height segregating in a recombinant inbred line (RIL) population from the cross `PC-50' (Larger SW) × XAN-159 (Smaller SW). The parents and RILs were grown in two separate greenhouse experiments in Nebraska, and in field plots in the Dominican Republic and Wisconsin. Data analysis was done for individual environments separately and on the mean over all environments. A simple linear regression analysis of all data indicated that most QTL appeared to be detected in the mean environment. Composite interval mapping (CIM) analysis was then applied to the means over environments. Eight QTL for SW were detected on common bean linkage groups (LGs) 3, 4, 5, 6, 7, and 8. All eight markers associated with these QTL were significant in a multiple regression analysis (MRA), where the full model explained 63% of the variation among SW means. Six QTL for seed length were detected on LGs 2, 3, 4, 8, and 11 using CIM. The markers associated with the three seed length QTL on LGs 2, 8, and 11 were significant in a MRA with the full model explaining 48% of the variation among seed length means. Three QTL for seed height on LGs 4, 6, and 11 explained 36% of the phenotypic variation for trait means. Four of the six QTL for seed length and two of three QTL for seed height also appeared to correspond to QTL for SW.