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PubMed1991

Stress responses in alfalfa (Medicago sativa L.). 8. Cis-elements and trans-acting factors for the quantitative expression of a bean chalcone synthase gene promoter in electroporated alfalfa protoplasts.

A chimeric gene consisting of a bean (Phaseolus vulgaris L.) chalcone synthase (CHS) promoter fused to a bacterial chloramphenicol acetyltransferase (CAT) reporter gene was strongly expressed, and further induced by fungal elicitor, when electroporated into alfalfa (Medicago sativa L.) suspension cell protoplasts. Functional analysis of 5' deletions of the CHS promoter-CAT construct in these protoplasts indicated that the region between -326 and -130 contained both activator and silencer elements. Co-electroporation experiments confirmed that these cis-acting elements were binding sites for functionally active trans factors. In vitro DNase I footprinting revealed four potential binding sites for alfalfa suspension cell nuclear proteins between positions -326 and -130 of the CHS promoter. These sites mapped to regions shown to contain functional cis-acting elements on the basis of the deletion analysis. Three of these sites mapped to previously identified binding sites for bean nuclear proteins. Competition gel retardation analysis using oligonucleotide probes containing binding site sequences revealed sequence-specific binding of alfalfa nuclear proteins to an AT-rich element and a putative GT-1 factor consensus binding sequence. Our results define cis elements and their cognate trans factors functionally active in determining the quantitative expression of a defense response gene in a heterologous transient expression system.

Acyltransferases↗

PubMedDate not supplied

Pathological and molecular characterizations of alfalfa interactions with compatible and incompatible bacteria, Xanthomonas campestris pv. alfalfae and Pseudomonas syringae pv. pisi.

We report on the interactions of alfalfa with Xanthomonas campestris pv. alfalfae and Pseudomonas syringae pv. pisi. A hypersensitive response was observed when leaves were infiltrated with P. s. pv. pisi, which remained strictly limited to the injected zone. The compatible interaction with X. c. pv. alfalfae was characterized by water-soaking symptoms and the spreading of the bacterium into the leaf blade. Analyses of transcript accumulation were conducted with cDNAs encoding enzymes involved in phytoalexin synthesis: chalcone synthase (CHS), chalcone isomerase (CHI), and isoflavone reductase (IFR). In incompatible interactions the maximum accumulation of the CHS, CHI, and IFR transcripts was observed 6 hr postinfection. In the compatible interaction, the induction of these transcripts was delayed until 25-30 hr postinfection, and the level of their accumulation was considerably lower. Extending this molecular analysis to the root system showed that the reaction of roots during an incompatible interaction was quite comparable to that of leaves. To complete these analyses, expression of genes encoding pathogenesis-related (PR) proteins in leaves was also analyzed by polymerase chain reaction. High-level accumulation of a 0.8-kb transcript encoding a PR protein was observed 6 to 30 hr postinfection in the incompatible interaction.

Acyltransferases↗

PubMed2006

Yield and forage quality of glandular-haired alfalfa under alfalfa weevil (Coleoptera: Curculionidae) and potato leafhopper (Hemiptera: Cicadellidae) pest pressure in Virginia.

Cultivars of glandular-haired alfalfa, Medicago sativa L., such as '54H69', are currently available and marketed as being resistant to potato leafhopper, Empoasca fabae (Harris) (Hemiptera: Cicadellidae). 54H69 and a standard, nonglandular-haired alfalfa 'Choice' were evaluated at two locations in Virginia over a 3-yr period. Dry matter yields and concentrations of crude protein and acid detergent fiber were compared at the first, second, and third harvests. Overall, the two cultivars produced similar dry matter yields of comparable forage quality in the absence of insecticides at both locations in each year. Untreated 54H69 did not produce greater dry matter yields than untreated Choice under either light or heavier potato leafhopper pest pressure. Concentrations of crude protein did not vary between the two cultivars at any harvest. Some differences in concentrations of acid detergent fiber were detected between cultivars, but these differences were not consistent among years, harvests, or between locations. Further comparisons between untreated 54H69 and treated Choice were made, but few significant differences were detected in dry matter yields or forage quality. An economic analysis for the study indicated that a grower planting 54H69 would realize less net revenue than a grower planting Choice, largely because of the seed premium for the glandular-haired cultivar and the evident need to treat 54H69 with insecticide for control of alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera: Curculionidae), and potato leafhopper.

Animals↗

PubMedDate not supplied

Bioavailable phosphorus in runoff from alfalfa, smooth bromegrass, and alfalfa-smooth bromegrass.

Runoff from sloping landscapes cropped with established alfalfa (Medicago sativa L.) may contain bioavailable P (BAP) which accelerates eutrophication of surface water bodies. Such BAP exists as either dissolved reactive P (DRP) or bioavailable reactive particulate P (BPP). We hypothesized that before and after harvest, sod-forming smooth bromegrass (Bromus inermis Leyss.) or alfalfa-smooth bromegrass mixtures would have less BAP, DRP, and BPP runoff losses than taprooted alfalfa. Swards established in 1992 near Lancaster, WI were subjected to a 72 mm simulated rainfall applied for 1 h in 1993 and 1994 to forage regrowth at 4 and 6 wk after first harvest and immediately (0 wk) after second harvest. Hourly BAP losses for all sward types were 82% less when 1.5 Mg ha(-1) of forage dry matter was present. High DRP losses (>0.050 kg ha(-1)) were associated with high DRP concentrations (>7.1 micromol L(-1)) and high surface soil P concentrations (>59 mg kg(-1)) resulting from broadcast maintenance P fertilizer. High BPP losses (>0.035 kg ha(-1)) were associated with high runoff volumes (>24 mm) and sediment concentrations (>2 g L(-1)). Summed over all 6 rainfall simulations, total BAP loss was only 0.07 kg ha(-1) at the 6 wk stage of regrowth compared with 0.35 at 4 wk, and 0.41 at 0 wk. Moreover, there was no significant difference between sward types for DRP concentration, DRP loss, or BAP loss. We conclude that avoiding excessive defoliation was more effective at reducing BAP losses than specific forage species selection.

Agriculture↗

PubMed1995

In vitro evidence that the coat protein of alfalfa mosaic virus plays a direct role in the regulation of plus and minus RNA synthesis: implications for the life cycle of alfalfa mosaic virus.

The coat protein of alfalfa mosaic virus has both structural and regulating functions. The latter is evident from the fact that the genomic RNAs of the virus, although they are of messenger polarity, cannot start an infection cycle in the absence of cost protein. The reason could be that the coat protein is needed for viral RNA synthesis. Indeed, the coat protein has been found in tight association with the viral RNA polymerase (R. Quadt et al., 1991, Virology 182, 309-315). To investigate the role of the coat protein, if any, in viral RNA synthesis, we have isolated that viral RNA polymerase (RNA-dependent RNA polymerase, RdRp) from mock-inoculated tobacco plants transformed with cDNAs 1 and 2, known as P12 plants (P. E. M. Taschner et al., 1991, Virology 181, 687-693), which express the nonstructural proteins P1 and P2. Such an enzyme (called M-RdRp) will contain the viral subunits P1 and P2 but not the coat protein. As a comparison we also isolated the RdRp from virion-inoculated P12 plants (C-RdRp). This enzyme will contain the coat protein. We found that both M-RdRp and C-RdRp could synthesize minus RNA, showing that coat protein is not needed for minus-strand synthesis. In contrast, minus-strand synthesis by both enzymes was inhibited by coat protein. Plus-strand synthesis was unaffected by coat protein in the case of C-RdRp, but strongly stimulated by coat protein in the case of M-RdRp. These data might explain why infected cells, which do not produce coat protein, display a very low accumulation of viral plus-strand RNA. They also give a possible explanation for the noninfectious character of the genomes of alfalfa mosaic virus and ilarviruses in the absence of coat protein. The fact that an active enzyme could be isolated from the same membrane fraction in infected and noninfected P12 plants shows that coat protein is not needed for assembly and targeting of the viral RNA polymerase.

Alfalfa mosaic virus↗

PubMed1985

Residues of five pesticides in field-treated alfalfa seeds and alfalfa sprouts.

Residues of five different pesticides applied to alfalfa seed crops were determined in the harvested seeds and in sprouts grown from these seeds. Although seeds are usually used for future production of alfalfa plants, some of these seeds may be sprouted for human food consumption. The pesticides studied--aldicarb (Temik), chlorothalonil (Bravo), chlorpyrifos (Lorsban), methamidophos (Monitor) and propargite (Comite)--were applied at a normal usage rate and at two to three times that rate. Residues on the seeds and sprouts, if any, were insignificant at rates of application.

Aldicarb↗

PubMed1985

Erwinia herbicola isolates from alfalfa plants may play a role in nodulation of alfalfa by Rhizobium meliloti.

Erwinia herbicola was isolated from roots of plants derived from surface-sterilized seeds of all alfalfa varieties that were tested. Some of these E. herbicola strains affected nodulation by certain strains of Rhizobium meliloti. In previously published work we presented the isolation of slow-and fast-nodulating variants from a single culture of R. meliloti 102F51. In the absence of E. herbicola, the slow-nodulating variant induced the formation of nodules on alfalfa as rapidly as the faster-nodulating strain. The rates of nodulation by the faster-nodulating variant were the same in the presence and absence of E. herbicola. All of the previously reported slower-nodulating strains derived from R. meliloti 102F51 nodulated more rapidly on sterilized plants than in the presence of certain E. herbicola isolates.

Erwinia↗

PubMed2000

Grazing methods and stocking rates for direct-seeded alfalfa pastures: III. Economics of alternative stocking rates for alfalfa pastures.

A framework that permits estimation of economically optimal stocking rates for alternative economic parameters and alfalfa forage allowance was developed and applied to a controlled grazing experiment conducted with Holstein steers (243 kg) placed on direct-seeded alfalfa pastures in central Michigan. Responses of ADG to alternative levels of forage allowance (FA) were summarized by a quadratic function and the associated gains/hectare were calculated. The standard stocking rate (SSR; standard livestock units/ha) that maximized gain/hectare increased with FA and was greater than that which maximized ADG. Net returns to fixed resources(NRFR)/hectare were calculated for alternative SSR and economically optimal SSR were identified under various levels of herbage mass (kg/d). The SSR that maximized NRFR were between the SSR that maximized ADG and gain/hectare. Magnitude of the sale price discount for heavier calves, the slide, influenced the optimal SSR and the sensitivity of net return to SSR. The economically optimal SSR increased as the slide increased because animals stocked under higher SSR weighed less off pasture and therefore received a lower price discount.

Animal Husbandry↗

PubMed1995

Performance of lactating dairy cows fed either alfalfa silage or alfalfa hay as the sole forage.

Alfalfa was harvested from alternate windrows as 40% DM silage or hay in small rectangular bales and fed in two 12-wk 4 x 4 Latin square trials, each with 20 multiparous lactating cows (4 with ruminal cannulas). Diets contained (DM basis) 69 (trial 1) or 66% (trial 2) alfalfa, 26 to 33% high moisture corn, 1.3% minerals and vitamins, and about 1.6 Mcal of NEL/kg of DM. In trial 1, second-cutting silage (21.2% CP) and hay (19.7% CP) containing 35% NDF were fed in diets: 1) silage (17.3% CP), 2) hay (16.3% CP), 3) silage with 3% fish meal (19.1% CP), and 4) hay with 3% fish meal (18.1% CP). Cows had lower DMI and lost BW on diet 1. Yields of milk and milk components were similar on diets 1 and 2 and greater on diet 3 than on the other three diets, except that fat yield was greater on diets 1 and 3 than on diets 2 and 4. In trial 2, first-cutting silage and hay containing 19.9 and 16.5% CP and 40 and 41% NDF were fed in diets: 1) silage (16.8% CP), 2) hay (14.6% CP), 3) silage with 3% fish meal (18.2% CP), and 4) hay with 3% fish meal (16.0% CP). Cows had lower DMI and lost BW on diets 1 and 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1975

Quantitative determination of coumestrol in dried alfalfa and alfalfa leaf protein concentrates containing chlorophyll.

An improved analytical method for the determination of coumestrol in dried alfalfa and leaf protein concentrates is described. In this method, chlorophyll is removed from an alcohol extract prior to the paper chromatographic-fluorometric measurement of coumestrol. Ninety-eight per cent of the coumestrol added to alfalfa leaf protein concentrates is recovered by this method. This improved method gives replicate values with lower standard deviations and coefficients of variation than the literature method.

Animal Feed↗

PubMed1988

Transgenic tobacco expressing tobacco streak virus or mutated alfalfa mosaic virus coat protein does not cross-protect against alfalfa mosaic virus infection.

Transgenic tobacco plants expressing the coat protein (CP) genes of tobacco streak virus (TSV) and alfalfa mosaic virus (AIMV) were used in studies on cross-protection and genome activation. Plants expressing the TSV CP gene were highly resistant to infection with TSV nucleoproteins but were susceptible to infection with AIMV nucleoproteins. Moreover, these plants could be infected with a mixture of AIMV RNAs 1, 2, and 3 in contrast to the nontransformed control plants. This demonstrates that the endogenously produced TSV CP is able to activate the AIMV genome but does not cross-protect against this virus. Conversely, it was shown that plants expressing the AIMV CP gene did not resist TSV infection. Transgenic tobacco plants transformed with an AIMV CP gene with a frame-shift mutation in the reading frame were found to accumulate viral transcripts to a level similar to that obtained in plants expressing a wild-type AIMV CP gene. However, these plants did not produce detectable amounts of viral protein and showed no resistance to infection with AIMV nucleoproteins in contrast to transgenic plants accumulating wild-type AIMV CP. This demonstrates that it is the CP that is responsible for cross-protection in transgenic plants and not the chimeric CP mRNA.

Capsid↗

PubMed1954