Genetic diversity within a range of cultivars and landraces of flax (Linum usitatissimum L.) as revealed by RAPDs

Analysis of the extent and distribution of genetic diversity incrop plants is essential for optimizing sampling and breedingstrategies. We used random amplified polymorphic DNA (RAPD)markers to assess genetic diversity and relationships in 22 Canadiancultivars, 29 selected world cultivars and 10 landraces of flax(Linum usitatissimum L.). RAPDvariation was generally low and more variation was detected among,than within, the investigated flax accessions. Based on 53 variableRAPD loci observed for the 61 accessions, the landraces had a lowerproportion of fixed recessive RAPD loci (0.427) (i.e.,more genetic variation) than all of the flax cultivars examined(0.492). The linseed cultivars had a lower proportion ofrecessive loci (0.469) than the fiber flax cultivars(0.529). Canadian linseed cultivars had a lower proportionof recessive loci (0.465) than the selected world flaxcultivars (0.512). A trend was also observed that the rateof loss in genetic variation in Canadian flax breeding programs overthe last fifty years was approximately two variable loci per 100 lociper 10 years. Clustering analyses based on similarity estimatesshowed that the fiber cultivars were more related (or similar toeach other) and were classified as a homogeneous group. All ofthe linseed cultivars were clustered in diverse groups with the ninelandrace accessions. Implications of these findings for flax breedingand germplasm management are discussed.     

Sorghums of the Sudan: analysis of regional diversity and distribution

Sorghum [Sorghum bicolor (L.) Moench] is a very important crop in the Sudan serving as a primary source of food, beverage, and total livelihood for millions of people in the country. The crop originated in the Northeast quadrant of Africa, and the Sudan is widely recognized as a major center of diversity. Although Sudanese sorghum germplasm has been assembled and stored over the last 50 years, careful analysis of this valuable germplasm has not been made. The objectives of this study were to assess phenotypic diversity and compare pattern of distribution among Sudanese sorghum landraces collected from different geographical regions. Phenotypic diversity among landraces was high, as expressed by the large range of variation for mean quantitative traits and the high (0.81) Shannon-Weaver diversity index. Landraces from Gezira-Gedarif tended to be shorter in stature, earlier in maturity and less sensitive to changes in photoperiod. They also had long, narrow and compact panicles that may result from adaptation to low rainfall and early adoption of mechanized farming practices. In contrast, taller and later maturing plant types characterized sorghums from Equatoria, most of which delayed their flowering in response to increased day-length. These sorghums included many genotypes with small and light kernels. Collections from Kassala showed a higher frequency of landraces with kernels that were more difficult to thresh. Landraces from Blue Nile tended to have greater agronomic eliteness with higher proportion of landraces with white kernels, poorly covered and that were easy to thresh. Sorghums from the Upper Nile tended to have loose panicles with poorly covered kernels that may result from adaptation to high rainfall of the Southern region. Although distinct distributions of types were represented by geographical origin, a high level of within-region diversity was present among all Sudanese sorghums.     

On the potential of documenting decadal-scale avifaunal change from before-and-after comparisons of museum and observational data across North America

Studies of biodiversity dynamics have been cast on either long(systematics)or short(ecology)time scales,leaving a gap in coverage for moderate time scales of de...     

Jefferson's yeoman farmer as frontier hero a self defeating mythic structure

American agrarianism, as informed by the frontier myth, has provided fundamental inventional resources for agricultural rhetoric. These myths have deflected farmers from positive adaptation, reinforcing instead the self-image of a hero victimized by circumstances. Critical examination of these independent myths reveals their literalized status as well as inconsistencies with fundamental agricultural goals.     

Triiodothyronine (T3) suppression test. An aid in the diagnosis of mild hyperthyroidism in cats

The purpose of this study was to develop a T3 suppression test to help in the diagnosis of mild hyperthyroidism in cats. We evaluated the response in circulating T4 concentrations to exogenous T3 (liothyronine) administration in 44 clinically normal cats, 77 cats with hyperthyroidism, and 22 cats with nonthyroidal disease. The test was performed by first collecting blood samples for basal serum T4 and T3 determinations, administering liothyronine at an oral dosage of 25 micrograms three times daily for seven doses, and, on the morning of the third day, again collecting serum samples for T4 and T3 determinations 2 to 4 hours after the seventh dose of liothyronine. The mean basal serum concentrations of T4 (53.1 nmol/L) and T3 (1.8 nmol/L) were significantly higher in the cats with hyperthyroidism than in the normal cats (T4 = 25.3 nmol/L, T3 = 1.3 nmol/L) and the cats with nonthyroidal disease (T4 = 29.5 nmol/L, T3 = 1.4 nmol/L); however, there was a great deal of overlap of basal values between the three groups of cats. Of the 77 cats with mild hyperthyroidism, 41 (53%) had serum T4 values and 55 (71%) had T3 values that were within the established normal ranges. After administration of liothyronine, mean serum T4 concentrations fell much more markedly in the normal cats and the cats with nonthyroidal disease than in the hyperthyroid cats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of Two Reagent Strips and Three Reflectance Meters For Rapid Determination of Blood Glucose Concentrations

We evaluated three reflectance meters (Accu-Chek II, Glucometer II, and Glucoscan 2000) and two reagent strips (Chemstrip bG and Glucostix) for accuracy and precision in determining blood glucose concentrations in the dog. To evaluate accuracy, we compared results of blood glucose determinations performed on 95 samples using the various strips and meters vs. the glucose concentrations obtained using the glucose-oxidase method on a Beckman Glucose Analyzer. Accuracy was evaluated statistically using least squares regression analysis. To evaluate precision, samples in various ranges of blood glucose concentration were tested repeatedly (20 times within a 1-hour period) on the same reflectance meter. Coefficient of variation (CV) was determined to evaluate reproducibility of results. Overall, there were significant correlations (P less than 0.001) between the laboratory glucose values and the blood glucose concentrations obtained with Chemstrip bG (r = 0.976), Glucostix (r = 0.904), Accu-Chek II (r = 0.986), Glucometer II (r = 0.911) and Glucoscan 2000 (r = 0.944). In the precision study, all three meters had excellent CVs in the normal range (3.6% to 4.9%). However, Accu-Chek II was found to be more precise in the hypoglycemic and hyperglycemic ranges (3.6% and 2.6%, respectively) than either Glucometer II (8.8% and 5.4%) or Glucoscan 2000 (7.8% and 8.2%). The results of this study indicate that all of the meters and reagent strips tested are highly accurate in determining blood glucose concentrations in the dog. However, both in terms of accuracy and reproducibility of results, Accu-Chek II and Chemstrip bG, gave the highest correlation coefficients and, as such, are probably of the greatest clinical value.     

Acute sterile hemorrhagic cystitis after a single intravenous administration of cyclophosphamide in three dogs.

Three dogs receiving cyclophosphamide IV as part of a combination chemotherapeutic regimen developed macrohematuria, stranguria, and pollakiuria within 24 hours of administration of the first dose of this drug. An 11-year-old spayed mixed-breed dog with an oral squamous cell carcinoma was administered 250 mg of cyclophosphamide/m2 of body surface, whereas a 4-year-old castrated male Gordon Setter was treated with 100 mg of cyclophosphamide/m2 and a 6-year-old male German Shepherd Dog with a cutaneous hemangiosarcoma was administered 140 mg of cyclophosphamide/m2. Aerobic bacterial culture, antimicrobial susceptibility testing, and urinalysis were performed on urine obtained by cystocentesis from all 3 dogs after hematuria was observed. Sterile hemorrhagic cystitis was diagnosed on the basis of large numbers of RBC in the urine, lack of pathogens on bacterial culturing of urine, and clinical signs. Although cyclophosphamide-induced cystitis in dogs has been reported in the literature numerous times, acute episodes developing within 24 hours of administration of the first dose have not been reported in this species with the use of therapeutic doses. Therefore, appropriate precautionary steps should be taken, even when the drug is being administered intermittently.     

Evaluation of a stented laryngoplasty for correction of cranial glottic stenosis in four dogs

After laryngeal surgery, cranial glottic stenosis secondary to laryngeal web formation was diagnosed as the cause of upper airway obstruction in 4 dogs. Initial treatment of 3 dogs by peroral laryngeal web excision resulted in rapid recurrence of clinical signs. Subsequently, these 3 and the fourth dog were treated by scar excision, mucosal flap coverage, and placement of a silicone intraluminal laryngeal stent for 14 days. By 5 months (average) after surgery, on the basis of clinical evaluation of exercise intolerance, respiratory distress, and stridor, all dogs had alleviation of upper airway obstruction.     

Lack of circulating thyroid stimulating immunoglobulins in cats with hyperthyroidism

Although feline hyperthyroidism has become a commonly diagnosed disorder of older cats, the underlying etiology remains unknown. Pathological findings of adenomatous hyperplasia involving both thyroid lobes in most hyperthyroid cats suggests the possibility that feline hyperthyroidism may be similar to human Graves' disease, which results from high circulating levels of thyroid stimulating immunoglobulins (TSIs). To exclude high circulating levels of TSIs as the cause of feline hyperthyroidism, we measured intracellular concentrations of cyclic adenosine monophosphate (cAMP) in functioning rat thyroid cells (FRTL-5) incubated with IgG extracted from hyperthyroid cat serum. Since TSIs stimulate thyroid hormone secretion through activation of cAMP, their presence can be evidenced in vitro by generation of high cAMP concentrations in cultured thyroid cells. No significant difference was found in intracellular cAMP concentrations in FRTL-5 cells incubated with IgG from normal versus hyperthyroid cats. In contrast, IgG from a human patient with Graves' disease caused substantially more cAMP generation than either normal human IgG or IgG from the cats of this study. These results indicate that feline hyperthyroidism does not result from high circulating concentrations of TSI and, in that respect, is not analogous to Graves' disease.