Size-hierarchy in a year-class and "condition" of common minnow Esomus danricus (Ham.) in relation to various ecological factors operating in the pond environment

Investigations were made on the existence of size-hierarchy in specimens of Esomus danricus (Ham.) belonging to the same year-class, and the variations in condition factor of the different size-groups. Divergence in the growth rates of individual fish resulted in the development of size-hierarchy in the population. Marked changes seemed to occur in condition factor of the different size-groups. A multitude of factors operating simultaneously in the pond environment appeared to govern the condition factor of fish.     

Haploid Culture and UV Mutagenesis in Rapid-cycling Brassica napus for the Generation of Resistance to Chlorsulfuron and Alternaria brassicicola

The effect of ultra violet (UV) irradiation on cultured isolatedmicrospores of rapid cycling Brassica napus was investigated.The microscpores were highly sensitive to UV, with the calculatedLD₅₀ being an exposure of 20 s. Viability tests suggested thatdeath of the microspores was not immediate, but occurred duringsubsequent incubation (7 d). None of the embryos produced followingUV-irradiation of microscpores showed gross morphological variation.A large number of regenerants was established from embryoidsand grown to flowering. These plants set fertile seed afterselfing. The progenies were assessed for resistance to Alternariabrassicicola and a small number showed increased resistanceto the pathogen, suggesting the generation of novel heritableresistance to this pathogen. In vitro selection revealed heritableresistance to the herbicide ‘Glean’ (active ingredientchlorsulfuron). Brassica napus, microspore culture, UV light, mutagenesis, selection, disease resistance, herbicide, Alternaria brassicicola     

Relative Embryo Growth Rates in the Annual Cicer L. Species

Early embryo growth rates were studied in the nine annual speciesof Cicer L., namely, C. arietinum L., C. bijugum Rech., C. chorassanicum(Bge.) M. Pop., C. cuneatum Rich., C. echinospermum Dav., C.judaicum Boiss, C. pinnatifidum J. and S., C. reticulatum Lad.and C. yamashitae Kit. The number of embryo cells increasedexponentially with time and was log linear in all the species.Species differed in their mean cell doubling time (MCDT). Cicerechinospermum and C. yamashitae had, respectively, the longestand the shortest MCDT which ranged from 9.67 to 16.15 h forthe nine species. Failure of successful interspecific hybridizationbetween C. arietinum and the wild annual species was only partlyexplained by differences in MCDT of the parental species. Relativegenetic closeness still plays the major role in determiningsuccess of interspecific hybridization in Cicer. Chickpea, Cicer, embryo, interspecific hybridization, suspensor     

The Mating System in Saccharomyces

Many, but not all, Saccharomyces species are heterothallic.The mating types in heterothallic species are determined bytwo allelic genes. The mating-type genes occasionally mutatefrom one to the other. Vegetative cells of opposite mating typewere found in some single ascospore colonies. They show conjugationtubes, stimulated by the proximity of cells of the other matingtype. The cultures alao show zygotes, which on sporulation yieldplus(+) and minus(–) progenies. The zygotes bud off diploid vegetative cells which grow fasterthan the original haploid cells and so tend to replace them.If mutation occurs early, replacement is complete and the culturegives no mating reaction but sporulates. If it occurs late,the culture is a mixture of haploid cells giving a mating reactionand diploid cells that will sporulate.