Nancy Jo J Ehlke

Mechanism of Inheritance of Diclofop Resistance in Italian Ryegrass (Lolium multiflorum)l

A diclofop-methyl-resistant biotype of Italian ryegrass was characterized to determine the expression and inheritance of herbicide resistance and whether this trait was due to the presence of a diclofop-insensitive form of acetyl-coenzyme A carboxylase (ACCase). At the whole plant level, the resistant biotype was > 93-fold more resistant to diclofop-methyl than the susceptible biotype. Crosses of diclofop-resistant and -susceptible plants were performed to produce Fl plants. No maternal effects were evident in responses of reciprocal Fl plants to diclofop. GRSO diclofop rates determined for resistant, Fl, and susceptible plants were 15, 6.3, and 0.16 kg ha-1, respectively. F2 populations treated with a 7.5 kg ha-1 rate of diclofop exhibited three injury response pheno- types 3 wk after treatment: a susceptible (S) phenotype which was killed, an intermediate resistance (I) phenotype with severe injury, and a resistant (R) phenotype with little or no injury. Testcross progeny exhibited only I and S phenotypes. Observed segregation of phenotypes in F2 and testcross populations conformed to segregation ratios predicted for a trait with inheritance controlled by a single partially dominant nuclear gene. ACCase activity determined in crude cell-free extracts of resistant, Fl, and susceptible biotypes exhibited ISO values of 50, 20, and 0.7 FiM diclofop, respectively. A positive relationship between

Mechanism of diclofop resistance in an Italian ryegrass (Lolium multiflorum Lam.) biotype

Abstract The biochemical basis for diclofop resistance in an Italian ryegrass ( Lolium multiflorum Lam.) biotype discovered in Oregon was examined. Herbicide rates that inhibited shoot growth by 50% (GR 50 values) were determined for two aryloxyphenoxypropionic acid herbicides (diclofop, haloxyfop) and one cyclohexanedione herbicide (sethoxydim). As compared to a wild type Italian ryegrass biotype, the GR 50 values for diclofop, haloxyfop, and sethoxydim were approximately 130-, 22-, and 2-fold greater, respectively, for the resistant biotype. There were little or no differences in the retention, absorption, translocation, or metabolism of diclofop-methyl in resistant and susceptible biotypes. The susceptibility of acetyl-CoA carboxylase (ACCase) to inhibition by selected graminicide herbicides was evaluated in extracts from etiolated shoots of both resistant and susceptible biotypes. The herbicide concentrations that inhibited ACCase activity by 50% (I 50 vulues) for diclofop, haloxyfop, and quizalofop were approximately 28-, 9-, and 10-fold greater, respectively, for the enzyme from the resistant biotype. For the cyclohexanedione herbicides, sethoxydim and clethodim, the I 50 values for ACCase were similar for both biotypes. It is concluded that resistance to diclofop and other aryloxyphenoxypropionic acid herbicides in the Italian ryegrass biotype from Oregon is due to the presence of a tolerant form of ACCase. This modification confers tolerance to the aryloxyphenoxypropionic acids but little or no tolerance to the cyclohexanediones.

Freezing tolerance of selected perennial ryegrass (Lolium perenne L.) accessions and its association with field winterhardiness and turf traits

Many winter stresses affect the ability of a perennial grass to overwinter in cold, temperate climates. Freezing tolerance is one of the major component traits affecting winterhardiness. Although effective freezing tolerance assessment procedures have long been available for perennial ryegrass (Lolium perenne L.), no work has been done to characterize plant collections in the United States that may possess novel variation for freezing tolerance and winterhardiness. In this study, 21 accessions sampled from a larger set of 300 accessions with known winterhardiness and 3 check varieties were subjected to environmentally-controlled, low temperature acclimation, followed by controlled freezing using a programmable laboratory freezer. Eight freezing treatments from −2 to −16°C were used to determine survival across the known spectrum of freezing tolerance in perennial ryegrass. LT50 values were estimated based on whole plant survival, as well as tiller survival at each of the temperature treatments in the evaluation. LT50 values for the accessions and checks ranged from −10.31 to −13.95°C, with 3 accessions possessing significantly greater freezing tolerance than the most freeze-tolerant check, ‘NK200’. LT50 values were well correlated with winterhardiness in St. Paul during the winters of 2004–2005 and 2005–2006. Lower LT50 values in this experiment were associated with greater spring growth following the stressful winter of 2004–2005 and upright growth habit. The lack of negative biological association between freezing tolerance and turf quality components indicates that freezing tolerance testing could be a useful tool in breeding and selection with landrace germplasm.

Condensed tannins in birdsfoot trefoil: Genetic relationships with forage yield and quality in NC-83 germplasm

SummaryGenetic relationships of condensed tannins (CT) with other forage quality parameters have not been adequately studied in birdsfoot trefoil (Lotus corniculatus L.). The objectives were to bidirectionally select for CT concentration in birdsfoot trefoil to determine selection response and to create populations for examination of genetic relationships of CT with forage quality parameters, principally lignin. High-and low-tannin parental clones were selected from NC-83 birdsfoot trefoil germplasm and intercrossed to produce Syn1 populations. Herbage samples, harvested for two years at two locations, were analyzed from high-tannin, low-tannin, and parental populations for CT concentration, herbage yield, and forage quality parameters. The mean condensed tannin concentrations in the high-and low-tannin populations were 69.3±0.8 and 21.1±0.8 g catechin equivalent (CE) kg-1 dry matter (DM) compared with 36.4±0.8 g CE kg-1 DM in the parental population. The selection response exhibited a quadratic relationship, with selection for increased CT concentration more effective than for reduced CT concentration. Compared with the parental population, acid detergent lignin (ADL) was higher, and crude protein (CP) and in vitro digestible dry matter (IVDDM) concentrations were lower for the high-tannin population and the converse was true for the low-tannin population. Lignin concentration was positively correlated with CT concentration (rg=0.66 P≤0.01).

Genetic diversity of rhizobia nodulating Trifolium ambiguum in North America

Kura clover (Trifolium ambiguum M.B.) is a persistent rhizomatous forage legume, whose use in the U.S.A. is limited by establishment difficulties in part attributable to nodulation problems. In this study, soil was collected from established stands of Kura clover growing in 9 diverse North American environments. Rhizobia were plant-trapped using Kura clover cv. Endura as host, then rhizobia from nodules fingerprinted using BOX-PCR. The diversity of isolates from North America was then contrasted to that of rhizobia from a single Caucasian environment (Russia), the center of origin for this species. Populations were characterized using clustering methods, and genetic diversity estimated using the Shannon-Weaver diversity index. The genetic diversity of the North American populations was extremely limited, all isolates being closely related to two of the strains found in a locally available commercial inoculant. In contrast, Russian isolates formed a distinct cluster with significant internal genetic diversity. Genetic diversity indices for the North American and Russian populations were 3.5 and 10.76, respectively. The implication of this and other studies is that Kura clover is highly specific in Rhizobium requirement. If the performance of this legume in the U.S.A. is to be improved, either by modifying current establishment practices or plant breeding, it is essential that these studies be paralleled by more collections and evaluation of rhizobia from its center of origin, given the extremely limited diversity of rhizobia found in North America.

Palatability and nutritive value of native legumes

Native perennial legumes have potential for use as components of grazing systems. Palatability affects forage utilization by grazing livestock, but relative palatability of native legumes is unknown. We determined the palatability of these native legumes of the Fabaceae family based on relative leaf consumption: false indigo (Amorpha fruticosa L.), Illinois bundleflower (Desmanthus illinoensis (Michx.) MacMill. ex B.L. Rob. & Fernald), blue wild indigo (Baptisia australis (L.) R. Br.), wild senna (Senna hebecarpa (Fernald) Irwin & Barneby), and purple prairie clover (Dalea purpurea Vent.); compared with temperate forage legumes (Fabaceae): alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.). Purple prairie clover and Illinois bundleflower were among the most palatable native legumes each year and were readily consumed by grazing sheep (Ovis aries L. [Bovidae]). False indigo, a shrub, was the least palatable native legume. The leafiness, plant maturity, and nutritive value of leaves varied among legumes but were not associated with palatability.Sheaffer CC, Wyse DL, Ehlke NJ. 2009. Palatability and nutritive value of native legumes. Native Plants Journal 10(3): 224–231.

Inheritance of condensed tannins in birdsfoot trefoil

Neither the inheritance of condensed tannins (CT) in tannin-positive birdsfoot trefoil (Lotus corniculatus L.), nor the quantitative genetic analysis of CT concentration in a forage legume have been previously reported. The objective of this study was to determine the inheritance of CT concentration in tannin-positive birdsfoot trefoil. High-, medium-, and low-tannin parents were selected from NC-83 birdsfoot trefoil germplasm and intercrossed in two independent six-parent diallel sets to generate progenies for quantitative genetic analyses. Maturity, herbage yield, leaf fraction (LF) and CT concentration were analyzed for 1067 individual F1 plants from 30 progenies in both diallel sets. Mean CT concentrations of the 30 progenies ranged from 6.1 to 93.4 g catechin equivalent (CE) kg−1 DM. General combining ability (GCA):specific combining ability (SCA) ratios of 0.93 and 1.0 were observed for CT concentration in both diallel sets, at or near the theoretical maximum of unity, indicating a predominance of a...

Seeding rate affects establishment of native perennial legumes in the upper midwestern US

In Minnesota, perennial native legumes (Fabaceae) differed in population and yield response to seeding rates of 14, 67, 135, 275, and 538 pure live seeds (PLS)/m2 (1.3, 6.3, 12.5, 25, and 50 PLS/ft2) when seeded in cultivated seedbeds with little bluestem (Schizachryium scoparium (Michx.) Nash [Poaceae]). Average seeding-year populations were greatest for Illinois bundleflower (Desmanthus illinoensis (Michx.) MacM. ex B.L. Robins. & Fern.) (131 plants/m2); intermediate and similar for false indigo (Amorpha fruticosa L.), wild blue indigo (Baptisia australis (L.) R. Br), and wild senna (Senna hebecarpa (Fern.) H.S. Irwin & Barneby) (average of 72 plants/m2); and least for purple prairie clover (Dalea purpurea Vent) (27 plants/m2). Seeding-year populations of all legumes increased linearly as seeding rate increased. Second-year biomass yield of legumes in mixture with little bluestem ranged from 1.1 Mg/ha(0.5 tons/ac) for purple prairie clover to 5.6 Mg/ha (2.5 tons/ac) for Illinois bundleflower.

Kura clover and birdsfoot trefoil response to soil pH

Use of the rhizomatous perennial forage legume kura clover (Trifolium ambiguum M. Bieb.) has been limited by slow establishment. Mature kura clover responds to liming on some acid soils, but the soil pH required for vigorous growth of young plants is unknown. A factorial greenhouse experiment was conducted with two kura clover cultivars (Rhizo and Endura) and one cultivar of birdsfoot trefoil (Lotus corniculatus L., Norcen) planted in three soil types (Sartell loamy fine sand, Hubbard loamy sand, and Sanborg clay loam) amended with Ca(OH)2 to obtain six soil pH levels. The experiment was performed twice, once using soil taken directly from the field and once using steamed soil. Response of kura clover and birdsfoot trefoil to soil pH differed. Maximum yield increases in kura clover obtained by adjusting soil pH from 4.9 to 6.5 were about 50% on nonsteamed soil and more than 150% on steamed soil. Birdsfoot trefoil did not respond to liming on nonsteamed soil. On steamed soil birdsfoot trefoil response to liming was inconsistent. Optimal soil pH for growth of kura clover and birdsfoot trefoil was generally between pH 6 and 7. Biomass yield was correlated with nodulation in both kura clover and birdsfoot trefoil, but nodulation was correlated with nitrogen uptake only in kura clover. Increased biomass yield of young kura clover plants in response to liming was best explained by alleviation of aluminum (Al), zinc (Zn), and manganese (Mn) toxicities and increased availability of phosphorus (P) and molybdenum (Mo) at higher soil pH levels. Joint contribution of the Minnesota Agricultural Experiment Station and USDA-ARS.

Rotating alfalfa with dry bean as an alternative to corn-soybean rotations in organic systems in the Upper Midwest

Dry bean (Phaseolus vulgaris) can be grown as a local food source and as an alternative to soybean (Glycine max) to diversify organic crop rotations. To understand the benefits of diversification of organic cropping systems, the effects of preceding alfalfa (Medicago sativa) and corn (Zea mays) crops on yields of five dry bean types and one soybean type, and the effect of bean type on following spring wheat (Triticum aestivum) yields, were tested at four Minnesota locations. Dry bean and soybean yields following alfalfa were 25% greater than yields following corn at two of four locations, though bean yields following corn were greater at one location. A preceding alfalfa crop benefited bean yields at locations where hog manure or no manure was applied to corn, whereas bean yields following corn fertilized with cow manure were similar to or greater than bean yields following alfalfa. Among dry bean types, black bean yielded similarly to soybean at three of four locations, but dark red kidney bean consistently yielded 25–65% lower than soybean. Navy, pinto and heirloom dry bean types yielded similarly to soybean at two of four locations. Across locations, weed biomass was 3–15 times greater in dry bean than in soybean and dry bean yield response to weed competition varied among bean types. However, dry bean, regardless of the preceding crop, demonstrated the potential to produce yields comparable with soybean in organic systems and the substitution of dry bean for soybean did not affect subsequent wheat yields. More studies are needed to identify nitrogen fertility dynamics in organic systems as they relate to dry bean yield.