Distribution of Vegetatively Compatible Populations of Rhizoctonia solani AG1-IA in a Field Planted with Different Host Species

To understand the distribution pattern and divergence of Rhizoctonia solani in a field over a 4-year period, R. solani AG1-IA isolates were collected from diseased tissues of several crops. Pairing tests between isolates to detect hyphal anastomosis and vegetatively compatible population (VCP) groupings were done on 2% water agar and potato dextrose agar. A single VCP of R. solani AG1-IA dominated a large upland crop field at the Institute of Plant Breeding, University of the Philippines at Los Ba?os. The VCP changed more slowly and at a lower frequency as compared to other reports. Received 27 September 1999/ Accepted in revised form 3 February 2000     

Interaction between jasmonic and gibberellic acids on in vitro tuberization of potato plantlets

Summary A reverse of the delaying effect of gibberellic acid (GA₃) was observed in in vitro tuberization of potato plantlets when the medium contained 0.8×10⁻⁵ M jasmonic acid (JA). The promoting effect of JA seemed to be correlated with the initial absence of growing roots, probably through direct activity of JA in microtuber-producing buds in the stoloniferous shoots. This is based on the fact that JA did not inhibit root growth a posteriori. Endogenous gibberellins (GAs) synthesized by roots did not interfere with the previous activity of JA in tuberization. The absence of a JA promoting-effect on tuberization of previously-rooted plantlets could be related to the capacity of potato roots to synthesize endogenous GAs which might antagonize the JA effect on buds of stoloniferous shoots.     

Soil organic carbon in cropping sequences with predominance of soya bean in the argentinean humid Pampas

Soya bean (Glycine max (L.) Merr.) monoculture can lead to a decrease in labile fractions of soil organic carbon (SOC). This study sought to evaluate the effects of cover crops (CC), application of fertilizer, and crop rotation on SOC, particulate organic carbon (POC), and soil carbon input in soya bean-based crop sequences under a no-till cropping system in the Argentinean Humid Pampas. Five crop sequences at two sites differing in initial SOC were evaluated: continuous soya bean (Sb), continuous soya bean fertilized with phosphorus (P) and sulphur (S) (Sbf), grass CC / PS-fertilized soya bean (CC/Sbf), nitrogen (N)-fertilized CC / PS-fertilized soya bean (CCf/Sbf) and NPS-fertilized crop rotation with high intensification sequence index (ISI) (Rot). At 0–5 cm, SOC and POC were higher (p < .05) in the sequences with higher residue-C supply (CC/Sbf; CCf/Sbf and Rot) at both sites. Changes in SOC at 0–20 cm simulated by AMG model closely tracked measured results at 0–20 cm. Findings from this study suggest that the inclusion of CC or crop rotation with high ISI improved C balance in soils under crop sequences with soya bean predominance.     

PREPUBIC AND TRANSRECTAL ULTRASONOGRAPHY OF THE CANINE PROSTATE: A COMPARATIVE STUDY

A comparative study was conducted in ten dogs with signs of prostatic disease in order to evaluate the usefulness of the prepubic and transrectal ultrasonography for the examination of the prostate gland and for prostate biopsy guidance. Both techniques were adequate to identify the prostate gland and prostatic urethra. Transrectal ultrasound found 5 occurrencies of parenchymal echogenicity changes whereas the prepubic technique found only 2. Lesions in the cranial prostatic margin (two dogs) were detected only by prepubic ultrasound. Lesions of the caudal prostatic margin (six dogs), prostatic urethra disruption (two dogs) and prostatic capsule abnormalities (five dogs) were only recognized by the transrectal approach. Prepubic ultrasonography was useful for biopsy guidance of cranial prostatic lesions and transrectal ultrasonography was a good means for biopsy guidance of caudal lesions.     

Animal medical genetics: a perspective on the epidemiology and control of inherited disorders

This perspective considers genetic disorders of domestic animal populations, in particular their epidemiology and control. Inherited disorders of animals share the same basic molecular biology as those of human beings, but they differ in their epidemiology due largely to the breed structure of the various species, human control of breeding and a greater influence of the founder effect, particularly due to extensive use of a limited number of sires, and inbreeding. Control of genetic disorders in animals is also more practical through extensive screening for disease, or heterozygous animals within defined breed populations, followed by exclusion of affected or carrier animals from breeding. This is assisted by the fact that, within a breed, many inherited monogenic disorders are associated with a single mutation. However some of the more important disorders may be inherited in a non-Mendelian manner, being influenced by multiple genes as well as environmental factors. These aspects are discussed and contrasted with similar aspects in human medical genetics.     

Effect of adding crude glycerine to diets with feed additives on the feed intake,ruminal degradability,volatile fatty acid concentrations and in vitro gas production of feedlot Nellore cattle

The effects of adding crude glycerine with sodium monensin or essential oils to beef cattle diets on the intake, degradability of DM and nutrients, rumen concentration of volatile fatty acids (VFA) and in vitro gas production were evaluated. Five ruminally cannulated Nellore steers were randomly assigned to a 5 × 5 Latin square design. The treatments were as follows: CONT, without crude glycerine and additives; EO, with essential oils and without crude glycerine; MON, with sodium monensin and without crude glycerine; EOG, with essential oils and crude glycerine; MONG, with sodium monensin and crude glycerine. Treatments with essential oil and sodium monensin increased the NDF and STC intake and the DM degradability. When crude glycerine was combined with either sodium monensin or essential oil, there was a reduction in DM, NDF and STC intake and an increase in DM and CP degradability of the diets. The adding crude glycerine to essential oil diets reduced the CH₄ production. Sodium monensin treatments reduced DM and NDF intake and the production of total gas, CH₄, total VFA and acetic acid concentration. In conclusion, the adding crude glycerine (200 g/kg DM) with either sodium monensin (0.03 g/kg DM) or essential oil (0.5 g/kg DM) can be utilized in diets for Nellore cattle without causing detrimental effects on feed intake and improving the DM degradability.     

Cytoplasmic and nuclear genetic components of membrane stability of winter wheat plants exposed to sub‐zero temperatures

Winter wheat (Triticum aestivum L.) is seeded in the autumn and harvested the following summer, and therefore, must survive multiple episodes of subfreezing temperatures throughout the winter months. Cellular membrane stability following exposure to subfreezing temperatures contributes to the ability to survive these episodes. This study investigated the inheritance of the ability to tolerate subfreezing temperatures with a seven‐parent diallel cross analysis of cellular membrane integrity as measured by electrolyte leakage after exposure to ?10 or ?14 °C. Significant differences in membrane stability were found among the parent lines. The inheritance of the freezing tolerance as measured by electrolyte leakage was complex and characterized by significant additive, dominant and cytoplasmic effects. General combining ability, indicative of additive genetic effects, were significant at both test temperatures, but accounted for 25.5% of the variance at the ?10° C test temperature, and only 4% of the variance at the ?14 °C test temperature. Specific combining ability, indicative of genetic dominance effects, were significant at both test temperatures, but accounted for only 14.6% of the variance at the ?10 °C test temperature, and 38% of the variance at the ?14 °C test temperature. Reciprocal (cytoplasmic) effects were significant and accounted for about 20% of the variance at both test temperatures. Cytoplasmic effects contributing to greater membrane stability were especially apparent in the cultivar Tiber when crossed to Masami, Lewjain, or Hatton. These results suggest that efforts to improve freezing tolerance are complicated by differing gene action at different test temperatures and also may benefit from identifying specific combinations of nuclear and cytoplasm sources that are most conducive to membrane stability following freezing.