The etiology of foul brood]

Five hundred and thirty-six samples of honeycombs were examined in a laboratory in the years 1971-1974. In all the samples clinically determined as the foul brood, B. alvei was isolated as a pure culture, and enterococci, or both microorganisms were isolated in mixed form. Twenty-five strains of the isolated streptococci were analyzed microbiologically and biochemically; on the basis of their culture and biochemical characteristics five strains were designated as Streptococcus faecalis, 14 strains as Streptococcus faecalis var. liquefaciens, five strains as Streptococcus faecium and one strain as Streptococcus durans. After checking the used taxonomic key of the culture and biochemical classification of B. alvei it may be stated that the culture and biochemical characteristics are stable. The strains of B. alvei (very dried strains), which persisted in the dried slant meat-peptone agar, were viable under the laboratory conditions, which proves the high resistance of the spores to the environment.     

Validation of the two-gene epistatic model for vernalization response in a winter × spring barley cross

A two gene epistatic model in which a dominant “winter growth habit” allele at Vrn-H2 encodes a repressor with a corresponding binding site in a recessive vrn-H1 allele explains the vernalization response phenotypes in an array of barley germplasm. In order to validate the model genetically, we developed an F ₂ population (and F ₂-derived F ₃ families) from the cross of Hardy (winter) × Jubilant (spring). Using gene-specific primers, we determined the Vrn-H1 and Vrn-H2 allele architecture of each F ₂ plant and we measured the growth habit phenotype of each F ₂ plant via phenotyping of its F ₃ progeny under controlled environment conditions. We used a set of treatments involving plus/minus vernalization under long photoperiod and vernalization under short photoperiod. Alleles at the two loci showed expected patterns of segregation and independent assortment. Under long day conditions, the two Vrn genes were the primary determinants of heading date, regardless of the vernalization treatment. Under short photoperiod, the effects of these loci were not significant. There was incomplete dominance at Vrn-H1: heterozygotes were significantly later to head than Vrn-H1Vrn-H1 genotypes. Vrn-H2 genotypes were also significantly later to head, even when plants were vernalized. These results validate the two-gene epistatic model for vernalization response under long-day conditions. The results under short photoperiod, and the variance in flowering with vernalization, confirm that while the two Vrn genes are the primary determinants of vernalization response, they are part of a larger interactome that determines the timing of the vegetative to reproductive transition.     

Successful Hybridization of Acipenser Species Using Cryopreserved Sperm

Successful hybridization of sterlet (Acipenser ruthenus) × Siberian sturgeon (Acipenser baeri), sterlet × Russian sturgeon (Acipenser gueldenstaedti) and sterlet × European sturgeon (Acipenser sturio) was carried out for the first time using cryopreserved semen of sturgeon males and sterlet × sterlet crosses as controls. Sperm of all three species was diluted with a cryodiluent composed of 23.4 mM sucrose, 0.25 mM KCl, 30 mM Tris (pH 8.0) and 10% methanol. The samples were frozen in plastic straws in the vapor of liquid nitrogen at the height of 3 cm above the level of nitrogen for 3 min. Following thawing approximately 3000 sterlet eggs were fertilized with six straws of frozen-thawed sperm. The hatching rate with sterlet sperm was 30.6% while the hatching rate of A. ruthenus × A. baeri, A. ruthenus × A. gueldenstaedti and A. ruthenus × A. sturio hybrids was 50, 17.4 and 34%, respectively. Morphometric markers as well as random amplified polymorphic DNA (RAPD) assay was used to verify interspecific hybridization.