Prospects of breeding for blast disease resistance in the oil palm (Elaeis guineensisJacq.)
SummaryBreeding for nursery blast resistance in the oil palm can reduce blast from around 50% to 1–6% loss, when a parent is carrier of dominant resistant gene(s). At such low blast levels, most of the costly agronomic methods to reduce blast incidence, need not be used.Plant material originating from the arid regions in Nigeria is more blast susceptible than that from the rain forest areas.
A comparative study of the cytological and reproductive behaviour of wheat and triticale subjected to two temperature regimes
SummaryA comparison was made of the meiotic stability and reproductive behaviour ofTriticale hexaploide cv. Rosner andT. aestivum cv. Pitic in response to two temperature regimes (15° and 30°C) imposed continuously from premeiosis to maturity. Mean frequencies of MI open bivalents, univalents, and lagging chromosomes at AI were significantly higher in Rosner than in Pitic. Such irregularity would appear to arise from the asynchronous disjunction of chromosomes between Metaphase I and Anaphase I, resulting in meiotic disturbances and a high frequency of abnormal microspores. Despite such abnormalities, floret fertility was equivalent to that observed in Pitic, and the proportion of aneuploids recovered in the progeny, although greater than expected in wheat, was much lower than would be predicted. It is suggested that there is a strong certation effect in the transmission of aneuploid microspores and that the irregularities observed during microsporogenesis do not apply directly to megasporogenesis.No appreciable effect of temperature on meiotic chromosome behaviour during microsporogenesis was observed in either wheat or Triticale. In Triticale, high temperatures (30°C) substantially reduced spikelet fertility, and in contrast, low temperature (15°C) increased the frequency of aneuploids.
Coexistence of Virulence and Antibiotic Resistance Genes in Pasteurella multocida Isolated from Diseased Rabbits
Pasteurella multocida (P. multocida)is considered a predominant pathogenic bacterial agent causing respiratory manifestations (snuffles) in rabbits with considerable economic losses and unfavorable prognosis in Egypt. A few recent P. multocida strains exhibit resistance to the most commonly used antibiotics in the veterinary field. Therefore, the present study was carried out to investigate the prevalence of both virulence and antibiotic resistance genes among P. multocida isolated from diseased rabbits in Sharkia Governorate, Egypt. Only 10 out of 100 tested rabbits` nasal swabs were finally confirmed positive for P. multocida of serogroup A by polymerase chain reaction (PCR). Antibiotic susceptibility testing of the recovered isolates revealed that they were all multidrug resistant (MDR) with a predominance of resistance to amoxicillin, ampicillin, amoxicillin/clavulanic acid, neomycin and tetracycline (100% each), followed by kanamycin and streptomycin (90% each). All the recovered isolates were further subjected to PCR screening of some common virulence and antibiotic resistance genes of interest . With the exception of toxA gene, the other virulence associated genes (ptfA, Omp87 and nanB) were found among all the examined isolates. Totally, all MDR P. multocida isolates contained at least one antibiotic resistance gene with aphA1 being the most prevalent (100%), followed by ermX gene (40%). Antibiotic resistance genotyping demonstrated the presence of multiple antibiotic resistance genes among majority of the isolates (40%) with only one isolate harboring 4 genes encoding identical resistance phenotypes. Evidentially, all MDR P. multocida isolates possessed at least 3 virulence genes accompanied by the attendance of antibiotic resistance genes. These findings evidenced that rabbits are potential sources of pathogenic P. multocida strains harboring virulence and antibiotic resistance genes. Therefore, it is evident that there is an urgent need for the judicious use of antibiotics in rabbits` treatment systems to successfully mitigate the propagation of drug resistance across P. multocida species.