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Lih-Yuh Yueh and David L. Hensley

The influence of 12 pesticides on C2H4 reduction and modulation of soybean (Glycine max L. Merr.) and lima bean (Phaseolus lunatus L.) was evaluated. All except diazinon were innocuous at 3× the label rate. Diazinon decreased C2H4 reduction of soybean 2 days after application, but not after 7 days or at normal label rates. Nitrogen fixation of excised nodules imbibed with diazinon indicated that it may have directly affected nitrogenase function. Soybean nodule numbers were decreased by application of 3× rates of methomyl and trifluralin, but lima bean nodule numbers were decreased only by trifluralin. Trifluralin also depressed soybean but not lima bean modulation at label rates. Methomyl did not affect soybean modulation at label rate. Both chemicals were non-toxic to Rhizobium sp. in a disc inhibition study.

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Jelka Šustar-Vozlič, Marko Maras, Branka Javornik, and Vladimir Meglič

There is a long tradition of common bean cultivation in Slovenia, which has resulted in the development of numerous landraces in addition to newly established cultivars. The genetic diversity of 100 accessions from the Genebank of the Agricultural Institute of Slovenia (AIS) were evaluated with amplified fragment length polymorphism (AFLP) markers and phaseolin seed protein. Twenty-seven standard accessions of known Mesoamerican and Andean origin, 10 wild Phaseolus vulgaris accessions and two related species, P. coccineus L. and P. lunatus L., were also included. Ten AFLP primer combinations produced 303 polymorphic bands, indicating a relatively high level of genetic diversity. Based on the marker data, unweighted pair group method with arithmethic mean (UPGMA) analysis and principal coordinate analysis (PCoA) all P. vulgaris accessions were separated into three well-defined groups. Two groups consisted of accessions of Mesoamerican and Andean origin, while the third was comprised of only four wild P. vulgaris accessions. A set of Slovene accessions formed a well-defined sub-group within the Andean cluster, showing their unique genetic structure. These data were supported by phaseolin analysis, which also revealed additional variants of “C” and “T” phaseolin types. The results are in agreement with previous findings concerning diversification of common bean germplasm introduced in Europe.

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Stuart R. Reitz and John T. Trumble

We examined two aspects of treating plants with a cytokinin-containing seaweed extract (SWE). In the first series of experiments, we tested the hypothesis that immature lima bean (Phaseolus lunatus L.) and tomato (Lycopersicon esculentum Mill.) plants provided with exogenous cytokinins could recover from defoliation by a generalist insect herbivore, Spodoptera exigua (Hübner), more rapidly than plants without cytokinin supplements. However, the SWE inhibited growth of lima beans at all levels of herbivore damage. The SWE neither inhibited nor stimulated growth of tomatoes following defoliation. Because SWE effects largely were neutral for tomato growth, we conducted a second series of experiments to test the hypothesis that SWE treatments alter the attractiveness of tomato foliage to S. exigua larvae. In these experiments, we determined consumption of, and preference for, SWE-treated tomato foliage by S. exigua larvae. Repeated root applications of SWE led to increased consumption and preference by S. exigua. Repeated foliar applications did not alter consumption or preference compared with controls. Spodoptera exigua larvae gained significantly more mass when feeding on SWE-treated foliage compared with controls. While these data indicate that plant responses to exogenous cytokinin-containing materials depend on taxa and application method, the practical uses of SWE appear limited given the negative effects on plant growth and increased attractiveness of treated foliage to herbivores.

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Sujatha Sankula, Mark J. VanGessel, Walter E. Kee, and J.L. Glancey

Field studies were conducted in 1997 and 1998 to evaluate labeled (1×) or reduced (0.5×) rates of metolachlor plus imazethapyr preemergence either broadcast or band applications to lima bean (Phaseolus lunatus L.) planted in 30-inch (76-cm) or 15-inch (38-cm) rows for weed control, yield, harvestability, and harvest recovery. Lima bean was planted in large plots simulating a commercial production system. All 30-inch rows were cultivated once 40 days after planting in 1997 and 21 days after planting in 1998. No differences were noted in weed densities between treatments both years. Marketable lima bean yield was greater from plots thatwere spaced 15 inches apart in 1997 only. However, total hand-harvested yield in both years, machine-harvested yield in 1998, and marketable yield in 1998 were not different between treatments. Measurements on harvest recovery revealed that a greater number of unstripped pods were left on plants after harvest in 15-inch row plots that were sprayed broadcast with 1× herbicide rate in 1997 only. Weight of beans lost per unit area and trash weight from 7-oz (200-g) bean sample was similar among treatments both years. Overall, weed control, yield, and harvest efficacy of lima bean was not impacted by row spacing, herbicide rate, or method of herbicide application in a commercial production system.

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Lih-Yuh Yueh and David L. Hensley

The influence of 12 pesticides on acetylene reduction (N2 fixation) and modulation of soybean (Glycine max L. Merrill cv. Williams 82) and lima bean (Phaseolus lunatus L. cv. Geneva) was evaluated. All pesticides except diazinon were found to be harmless to nitrogen fixation at 3× the manufacturer's recommended rate, Diazinon significantly decreased C2H2 reduction of soybean 2 days after application, but not after 7 days or at normal label rates, Acetylene reduction of excised nodules imbibed with diazinon indicated that the chemical may have affected nitrogenase function directly. Soybean nodule counts were significantly decreased by application of 3× rates of methomyl and trifluralin, whereas lima bean nodule counts were decreased only by trifluralin. Tritluralin also depressed soybean modulation at label rates, but had no effect on lima bean modulation. Methomyl was innocuous to soybean modulation at the recommended label rate. Both chemicals were nontoxic to Bradyrhizobium/Rhizobium sp. based on a disc inhibition study. Chemical names used: O,O -diethyl O -(2isopropyl-4-methyl-6-pyrimidinyl phosphorothiote (diazinon); S-Methul- N -((methylcarbamoyl)oxy)-thioacetimidate (methomyl); a,a,a -Trifluoro-2-6dinitro-N-N -dipropyl-p-toluidine (triflnralin).

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Ed Kee, Tracy Wootten, and James Glancey

Average yields of baby lima beans ( Phaseolus lunatus L.) are consistently lower in Delaware than California and the Pacific Northwest. Comparison of production practices revealed differences in plant populations, soil type, irrigation, relative

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Sujatha Sankula, Mark J. VanGessel, Walter E. Kee Jr., C. Edward Beste, and Kathryne L. Everts

Potential increases in the yield of agronomic crops through enhanced light interception have led many growers to consider using narrow rows in lima bean (Phaseolus lunatus L.). However, no information is available on how narrow row spacing affects weed management or fits into an integrated pest management strategy. To address this, field studies were conducted in Delaware and Maryland in 1996 and 1997 to evaluate the effects of row spacing (38 vs. 76 cm) on weed control, and on yield and quality of lima bean. Weed management inputs were also evaluated with labeled or reduced pre-emergence rates of metolachlor plus imazethapyr applied broadcast or banded. Only 76-cm rows were cultivated according to the standard practice for this production system. In general, row spacing, herbicide rate, and herbicide application method had no effect on lima bean biomass or yield, on weed density, control, or biomass production, or on economic return. However, weed control consistency was improved when wide rows were used, even with reduced herbicide rates, possibly because of cultivation. Using reduced herbicide rates and band applications resulted in 84% less herbicide applied without affecting weed control. Chemical names used: 3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide (bentazon); 2-[4,5-dihydro-4-methyl-4-(1-methylethyl-4-(1-methylethyl)-5-oxo-1Himidazol-2-yl]-5-ethyl-3-pyridinecarboxylic acid (imazethapyr); 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide (metolachlor); 2-[1-(ethoxyimino)butyl]-5-[2-ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one (sethoxydim).

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Timothy G. Porch, Matthew W. Blair, Patricia Lariguet, Carlos Galeano, Clive E. Pankhurst, and William J. Broughton

closely related to other cultivated Phaseolus species, including P. acutifolius (tepary bean), P. coccineus (scarlet runner bean), and P. lunatus (lima bean) as well as to legumes in the Phaseoleae tribe, including Cajanus cajan (pigeonpea

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Ping Li, Dong Liu, Min Guo, Yuemin Pan, Fangxin Chen, Huajian Zhang, and Zhimou Gao

bean ( Phaseolus lunatus L.), snap bean ( Phaseolus vulgaris L.), fraser fir [ Abies fraseri (Pursh) Poir.], and certain weeds ( Davidson et al., 2002 ; Gevens et al., 2008 ; Quesada-Ocampo et al., 2009 ). As a heterothallic species, P. capsici

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Rakesh Kumar, Mahendra Dia, and Todd C. Wehner

and seed set: Evidence from an experimental population of Cucumis sativus Evolution 38 1350 1357 Harding, J. Tucker, C.L. 1964 Quantitative studies on mating systems. I. Evidence for nonrandomness of outcrossing in Phaseolus lunatus Heredity 19 369