Evaluation of genetic diversity among some Iranian wild asparagus populations using morphological characteristics and RAPD markers

An evaluation of genetic diversity in 39 wild asparagus populations was carried out using morphological and RAPD markers. A combination of morphological traits and random RAPD primers was used to examine the level of genetic variation and polymorphisms among the populations. A factor analysis using Ward's method on mean values of morphological characteristics indicated seven main factors resulting in four groups. Analysis of polymorphic bands using Jaccard's similarity coefficient indicated that genetic similarity ranged between 0.71 and 0.29. At a similarity level of 0.64, the populations were divided in three sub-clusters, containing 34, four and one populations, respectively. Significant regression associations were found between 21 morphological characteristics and 18 RAPD markers, revealing some informative markers associated with some traits. The highest R² was related to 18 RAPD markers associated with gender (53.5%) that among them BA-04₂₀₀₀ had a maximum R². The results showed that Iranian wild asparagus with its high levels of genetic variation could be considered as a valuable gene pool for future asparagus breeding programs. Furthermore, it could be inferred that morphological characteristics and RAPD markers are suitable tools to discriminate asparagus populations for the evaluation of genetic diversity.     

Screening for resistance to clover rot (Sclerotinia spp.) among a diverse collection of red clover populations (Trifolium pratense L.)

Red clover (Trifolium pratense) is an important perennial forage crop that is widely cultivated in Europe. Clover rot remains a major disease in red clover, but resistance breeding is hampered by the lack of available sources of resistance. Moreover, little is known about the factors that influence clover rot resistance. In this paper we evaluated the variation in clover rot susceptibility among a diverse collection of 113 red clover accessions, with the aim of identifying more resistant accessions. Clover rot susceptibility was assessed with a high throughput bio-test on young plants. We found significant variation in clover rot susceptibility, within and among accessions. ‘Tedi’, ‘Maro’ and ‘No 292’ were the most resistant accessions. Fifteen diploid accessions were more susceptible than the average accession with the cultivar ‘Nemaro’ being the most susceptible. Clover rot susceptibility was not correlated with isoflavone levels from Mullaney et al. (Agronomy abstract. ASA, Madison, p 195, 2000). Cultivars were more resistant than landraces and wild accessions and tetraploid cultivars were more resistant than diploid cultivars. Besides the in-depth analysis for clover rot susceptibility, possible correlations with plant architecture and other diseases were investigated. Growth habit, branching, plant yield, flowering date and susceptibility to mildew, virus and rust diseases were investigated in a 3-year field trial. Unlike previously suggested, clover rot susceptibility was not correlated with branching or with plant yield over three years. On the other hand, late flowering accessions and accessions with erect growth habit were less susceptible to clover rot. Clover rot susceptibility was not correlated with susceptibility to rust disease (Uromyces trifolii) or viral diseases, but negatively with susceptibility to mildew (Erysiphe polygoni). Because no completely resistant accessions were found, the best way to improve clover rot resistance would be to select recurrently for resistant genotypes among diverse cultivars and landraces with lower susceptibility. Tetraploidisation of diploid populations with a higher resistance level can provide an additional level of protection.     

The use of the log-linear model to evaluate the effects of three herd factors on Streptococcus agalactiae mastitis occurrence in California, 1977

Epidemiologic relationships among Streptococcus agalactiae infected dairy herds and herd size, location and California Dairy Herd Improvement Association (CDHIA) participation were examined using log-linear methodology. Dairies located in five out of the six California Bureau of Animal Health veterinary districts were studied. Data sources included the Dairy Cattle Data Base, which uniquely identifies each of the 2875 dairies in California, the 1977 statewide CDHIA year-end summary report and microbiological results from a 1977 statewide survey of bulk tank milk samples. These data were merged, fitted and the best model selected using likelihood-ratio statistics. The model included all four “main effects”, the six possible “1st-order effetss” and the “2nd-order effect” due to the interaction of herd size, location and CDHIA participation. Subsequently, a logit model was used to estimate the effect of the independent herd factor variables (size, location and CDHIA participation) on the log odds of the dependent S. agalactiae variable. This model required conditioning on the three-way relationship among the independent variables.medium-sized, non-CDHIA herds in district 2 (northcentral California) showed the highest expected odds (3.37) for S. agalactiae in bulk tank milk, while small, CDHIA herds in district 3 (northcentral coastal California) produced the lowest odds (0.39).     

Efficacy of tulathromycin in the treatment and prevention of natural outbreaks of bovine respiratory disease in European cattle

The efficacy of tulathromycin in the treatment (phase 1) and prevention (phase 2) of bovine respiratory disease (BRD) was evaluated on commercial farms in France, Germany, Italy, and Spain. In phase 1, commingled cattle with clinical BRD were treated with tulathromycin (n = 128) or florfenicol (n = 125) on day 0. Similar percentages of animals showed sustained clinical improvement at day 14 (tulathromycin 83.3% versus florfenicol 81.0%) and had not relapsed by day 60 (tulathromycin 63.3% versus florfenicol 58.4%). In phase 2, healthy in-contact cattle were treated with tulathromycin (n = 492), tilmicosin (n = 494), or saline (n = 265) on day 0. Significantly more (P = .0001) tulathromycin-treated cattle remained healthy to day 14 (92.4%) than tilmicosin-treated (83.7%) or saline-treated (63.7%) cattle, and this was maintained through day 60 (tulathromycin 85.4% versus tilmicosin 75.1% and saline 56.2%). Tulathromycin was highly effective in the treatment and prevention of BRD.     

Evaluation of tulathromycin for the treatment of pneumonia following experimental infection of swine with Mycoplasma hyopneumoniae

Tulathromycin was evaluated in the treatment of pneumonia in weaned pigs inoculated intranasally with Mycoplasma hyopneumoniae. Five days postchallenge, the pigs were randomized to treatment with a single IM administration of saline, a single IM administration of tulathromycin (2.5 mg/kg; day 0), or three IM administrations of enrofloxacin (5.0 mg/kg; days 0, 1, 2). Pigs were necropsied on day 12 or 13. Unchallenged controls remained healthy with no lung pathology. Compared with saline, coughing, mean lung lesion score, and proportional lung weight were significantly reduced and weight gain was significantly greater for tulathromycin-treated pigs (P < .05). Compared with enrofloxacin, there were no significant differences in proportional lung weight or weight gains, but coughing and lung lesion scores were greater for tulathromycin-treated pigs (P < .05). Tulathromycin was effective in the treatment of pneumonia following experimental infection with M. hyopneumoniae.     

Factors Affecting the Spread of Plum pox virus Strain M in Peach Orchards Subjected to Roguing in France

ABSTRACT We evaluated the impact of roguing on the spread and persistence of the aggressive Plum pox virus strain M (PPV-M) in 19 peach orchard blocks in Southern France. During a 7- to 10-year period, orchards were visually inspected for PPV symptoms, and symptomatic trees were removed every year. Disease incidence was low in all orchards at disease discovery and was <1% in 16 of the 19 orchard blocks. The spread of Sharka disease was limited in all 19 blocks, with an annual disease incidence between 2 and 6%. However, new symptomatic trees were continuously detected, even after 7 to 10 years of uninterrupted control measures. An extended Cox model was developed to evaluate to what extent tree location, orchard characteristics, environment, and disease status within the vicinity influenced the risk of infection through time. Eleven variables with potential effect on tree survival (i.e., maintenance of a tree in a disease- free status through time) were selected from survey data and databases created using a geographical information system. Area of the orchard, density of planting, distance of a tree from the edge of the orchard block sharing a boundary with another diseased orchard, and distance to the nearest previously detected symptomatic tree had a significant effect on the risk for a tree to become infected through time. The combined results of this study suggest that new PPV-M infections within orchards subjected to roguing resulted from exogenous sources of inoculum, disease development of latent infected trees, as well as infected trees overlooked within the orchards during visual surveys. A revision of the survey and the roguing procedures used for more effective removal of potential sources of inoculum within the orchards and in the vicinity of the orchards would improve disease control suppression of PPV.