Variation at the b Mating Type Locus of Ustilago maydis

ABSTRACT Population level diversity at the Ustilago maydis b mating type locus was determined in samples from four Minnesota locations using a combination of plate mating techniques and a polymerase chain reaction (PCR)-based assay. The PCR method allows rapid identification of b types from samples of natural populations and utilizes the hypervariable regions of the b locus that determine mating type specificity. Results demonstrated high levels of b diversity within populations, with one population yielding 17 of the total 18 b types found in the study. Pairwise G(ST) values were in the range of 0.02 to 0.05, and common b mating types were found across broad geographic distances. These data demonstrated that very low levels of differentiation among U. maydis populations occur with respect to b locus variation. Consistent with frequency-dependent selection models, b types were represented at approximately equal frequencies within the entire Minnesota population. However, neutral evolutionary models for patterns of geographic distribution and variation at b cannot be entirely excluded. The importance to agricultural practices of understanding population genetic processes is discussed.     

小麦矮秆突变体的遗传分析

对辐射诱发的小麦矮秆突变系进行了遗传分析,鉴定出这些矮秆突变系主要受1～2个主要的隐性矮秆基因所控制,而且这些隐性矮秆基因并未带有不良的基因多效性,即胚芽鞘相应地缩短而影响出苗率,说明辐射诱变方法可以创造自然界所缺少的矮源。     

Effects of age at inoculation and induced molt on the recovery of Mycoplasma gallisepticum from layer chickens.

An experiment was conducted to determine the effects of age at inoculation and induced molt on the reisolation of Mycoplasma gallisepticum (MG) from commercial leghorn hens that had been eyedrop-inoculated with F strain MG at either 10 or 66 wk of age. Chickens were maintained in biological isolation units from 10 wk of age through 78 wk of age. At 70 wk of age (premolt), hens were swabbed, cultured for MG, and molted. Swabs were taken both at the end of molt (postmolt [74 wk]) and again 4 wk later (postmolt+4 [78 wk]). A significant (P < or = 0.05) decrease in MG isolations was observed in the postmolt swabs as compared with the premolt swabs of hens inoculated at either 10 or 66 wk of age. A significant (P < or = 0.05) increase in isolations was observed in the postmolt+4 swabs as compared with the postmolt swabs of hens inoculated at either 10 or 66 wk of age. For the hens inoculated at 10 wk, no significant difference was found in premolt as compared with postmolt+4 MG isolations; however, for hens inoculated at 66 wk, a significant (P < or = 0.05) decrease was observed between premolt and postmolt+4 isolations. Significantly (P < or = 0.05) fewer MG isolations were obtained from the premolt swabs of hens inoculated at 10 wk as compared with hens inoculated at 66 wk. No significant difference in MG isolations was observed in either the postmolt or postmolt+4 swabs between hens inoculated at either 10 or 66 wk.     

The effects of F strain Mycoplasma gallisepticum, Mycoplasma synoviae, and the dual infection in commercial layer hens over a 44-week laying cycle when challenged before beginning of lay. II. Egg size distribution.

In each of two trials, 160 commercial pullets were separated into four treatments with four replicates of 10 chickens in each treatment. Forty pullets were designated as controls and received no inoculation; 40 pullets received F strain Mycoplasma gallisepticum (FMG); an additional 40 pullets received Mycoplasma synoviae (MS); and the final 40 pullets were inoculated with both FMG and MS (dual). All inoculations occurred at 10 wk of age. Eggs from all treatments were collected daily, Monday-Thursday, and individually weighed. No significant difference was observed among the treatments for percentages of jumbo, extra-large, medium, small, peewee, or undergrade eggs. As a percentage of eggs laid for the 4 days of each week over the 44-wk laying cycle of each trial, the FMG hens laid significantly fewer large size eggs (43.2%) as compared with either controls (51.17%) or dual-infected hens (49.95%). No significant difference was found in percentage of large eggs laid by FMG hens when compared with MS hens.     

Analysis of information used in the management of plant genetic resources: a case study from northwestern Mato Grosso,Brazil

Evaluation and monitoring are critical to agroforestry (AFS) project management, especially if they aim to contribute to use and conservation of biodiversity and plant genetic resources. A methodology to analyze information used in decision-making processes was developed and applied in a biodiversity conservation project in the Brazilian Amazon. Quality of information gathered at landscape, AFS, species (Bactris gasipaes Kunth, both wild and cultivated varieties) and genetic diversity levels in three dimensions was analyzed. The information at the landscape level was good, while that in the organizational-institutional and socio-economic dimensions was acceptable; information gaps were serious in the genetic-ecological dimension. Ecological and economic functionality assessment based on indicators built upon reported administrative actions suggests that information related to conservation played a greater role in decision-making and management than information associated with use and development. The application of the methodology proved instrumental for enhancing efficacy of decision-making within an adaptive management approach to plant genetic resources use and conservation.     

Feline discrete high‐grade gastrointestinal lymphoma treated with surgical resection and adjuvant CHOP‐based chemotherapy: retrospective study of 20 cases

The aim of this retrospective study was to evaluate the outcome of cats treated with surgical intervention for a discrete intermediate‐/high‐grade gastrointestinal lymphoma prior to CHOP‐based chemotherapy. Variables including sex, breed, haematocrit, white blood cell count, serum albumin concentration, clinical stage of disease, gastrointestinal obstruction and peritonitis were assessed for their effect on survival. Twenty cats met the inclusion criteria with three cats still alive at the time of data analysis. The overall median survival time (MST) was 417 days (range: 12–2962 days). The disease‐free interval (DFI) was 357 days (range: 0–1585 days) with six cats still deemed in remission prior to death. Only clinical stage had a significant effect on both MST and DFI. Cats with discrete intermediate/high‐grade gastrointestinal lymphoma that undergo surgical resection followed by adjuvant CHOP chemotherapy may achieve acceptable overall survival times.