Embryonic development in the blue fox

Embryos from vixens at different stages of gestation were measured and photographed. Implantation was observed 16-18 days after breeding. Differentiation and the development of characteristic features were described and embryonic loss was studied in relation to number of corpora lutea.     

Evaluation of maternal parent and puroindoline allele on kernel texture in a reciprocal cross between two hard spring wheat cultivars

Kernel texture is an important characteristic for both the milling and the end-use quality of wheat (Triticum aestivum L.). Gene sequence variation and mutations to the two puroindoline genes (Pina and Pinb), located at the Ha locus on chromosome 5DS, account for the majority of variation in wheat kernel texture. Other factors also influence kernel texture, including effects associated with different maternal parent backgrounds. To investigate the effect of two hard puroindoline alleles in different maternal backgrounds, a population of 228 recombinant inbred lines (RILs) derived from a reciprocal cross between two wheat cultivars ID377s (Pina-D1b/Pinb-D1a) and Klasic (Pina-D1a/Pinb-D1b) were examined in two succeeding generations (F₇ & F₈). Kernel texture was determined using the Single Kernel Characterization System (SKCS) and the RIL puroindoline haplotype was identified by the sequence-specific PCR amplification of each gene. Analysis of variance identified a significant (P 0.001) effect of the maternal parent and puroindoline mutation on kernel texture. RILs containing the Pina-D1b mutation were significantly harder than lines containing the Pinb-D1b mutation. RILs which had Klasic as the maternal parent were significantly harder than those which had ID377s as the maternal parent. When the maternal parent and puroindoline allele were analyzed in combination, RILs derived from Klasic as the maternal parent and the Pina-D1b allele were significantly harder (P 0.001) than those containing the same allele but ID377s as the maternal parent. The same occurred for RILs containing the Pinb-D1b allele, lines with Klasic as the maternal parent were harder than lines with ID377s as the maternal parent. These results corroborate the harder phenotype of the Pina-D1b allele and indicate a significant maternally-inherited contribution to kernel texture variation.     

Identification of triploid Citrus by isozyme analysis

Summary Seedlessness is a desirable horticultural attribute in Citrus and is positively associated with triploidy. The conventional cytological method for triploid identification is a laborious technique involving the preparation of root tips for chromosomal analysis. Digital densitometry of isozymes, however, offers the possibility of distinguishing triploid Citrus from large populations of seedlings both quickly and cheaply. Where there are no gene dosage regulation effects, greater band density should be evident in the allozyme contributed by the diploid gamete for a heterozygous locus. The isozymes of 4 enzymes; malate dehydrogenase, 6-phosphogluconate dehydrogenase, shikimate dehydrogenase, and phosphoglucose isomerase, were investigated with polyacrylamide gel electrophoresis. Band densities of these isozymes for triploid Citrus, their diploid siblings and diploid progenitors were measured using a digital densitometer. Of the 4 enzymes investigated only allozymes for shikimate dehydrogenase exhibited consistent differences over a wide range of Citrus cultivars. Greater band density was evident in the allozyme contributed by the diploid gamete. The band density ratio between allozymes for triploid Citrus was close to 0.5, while for diploid Citrus band density ratios were close to 1.0. This effect is due to the extra protein coded by the additional gene dose and was not observed in diploids. Shikimate dehydrogenase proved to be an accurate molecular marker for distinguishing between diploid and triploid Citrus for heterozygous progeny.Abbreviations PAGE Polyacrylamide gel electrophoresis - MDH malate dehydrogenase - 6PGD 6-phosphogluconate dehydrogenase - SkDH shikimate dehydrogenase - PGI phosphoglucose isomerase     

Fluorescent in situ hybridization as an aid to introducing alien genetic variation into wheat

Summary Fluorescent in situ hybridization (FISH) has been used to assess the occurrence and frequency of wheat-alien chromosome pairing in a wheat/Thinopyrum bessarabicum hybrid and in wheat/rye hybrids with different levels of chromosome pairing by examining pollen mother cells at metaphase I of meiosis. The use of FISH to identify the presence and size of alien chromatin in a wheat background is also demonstrated.The value of FISH as an aid to the introgression of alien genetic variation into wheat is discussed.Abbreviations FISH fluorescent in situ hybridization - GISH genomic in situ hybridization - PRINS primer-induced in situ hybridization     

Reselection of a Pearl Millet Cultivar Utilizing Residual Variability for Downy Mildew Reaction*

‘BJ 104’ was the most widely grown pearl millet hybrid in India until it became susceptible to downy mildew (DM) in 1984—85. Residual variability for resistance was found in both parental lines, 5141 B (maintainer of 5141 A) and J 104, and through four generations of pedigree selection under intense disease pressure in the DM nursery, two lines, IC-MA841 (from 5141 B) and ICMP 84814 (from J 104), were selected resulting in a reconstituted DM resistant hybrid (‘ICMH 84814’) which was equal in yield to the original ‘BJ 104’. The reconstituted hybrid, though phenotypically similar, can be distinguished from “BJ 104” being slightly taller, flowers later, has heavier heads, and 1000-seed weight, but tillers less. A similar exercise was attempted on Tifton 23 B, the female parent of the first widely grown hybrid (‘HB 3’— the male parent was also J 104), but no variability for resistance to DM was found.     

The association of culm anatomy with lodging susceptibility in modern spring wheat genotypes

Selection for lodging resistant cultivars in cereal breeding programs is difficult due to the challenge of screening for this trait under natural field conditions. The identification of easily measurable culm traits related to lodging resistance would simplify the selection process. The present study was conducted to determine if differences in culm anatomy exist among modern wheat genotypes differing in lodging susceptibility, and to determine the association between culm characters and lodging. From a 2-year field study conducted in Edmonton, Alberta, 13 spring wheat cultivars were chosen based on predetermined susceptibility to artificially induced lodging. Morphological and anatomical culm measurements were made visually and with an environmental scanning electron microscope. Genotypes differed (P < 0.05) for plant height, number of internodes per culm, basal internode length and diameter, culm wall thickness and the number of vascular bundles, but not for adventitious root frequency, lumen diameter or sclerenchyma ring thickness. Mean genotype field scores for artificially induced lodging were correlated (P < 0.05) with plant height (r= 0.51) and the length of the fourth basal internode (r= 0.51). Short, wide basal internodes and thick culm walls were characteristic of three lodging tolerant genotypes: Kohika, Sapphire and Olso. Nevertheless, despite such apparent genotype specific association between culm anatomy and field lodging, general applicable associations were not observed for most traits. The most practical and easily selectable trait for lodging resistance within a wheat breeding program remains plant height. This revised version was published online in July 2006 with corrections to the Cover Date.     

Progress in mapping agronomic genes in apple (The European Apple Genome Mapping Project)

Summary The progress of the European Apple Genome Mapping Project is described. Populations segregating for a range of agronomic genes have been established in six European countries. The need for robust methods of analysis has been identified, especially with regard to the development of molecular markers. Isozyme systems, RAPDs, RFLPs and amplified genes are being used to construct a reference genetic linkage map. Standardisation and precise definition of both genotypic and phenotypic measurements has been recognised as being essential for future exploitation of genetic markers in apple breeding. Phenotypic measurements are being replicated in different geographical locations over several years. Statistical and genetic analyses are aimed at defining components of genetic variation which account for ‘genes’, as defined by apple breeders. A relational database is being constructed which will combine disparate sources of data relating to the genetics of apple. Comparative mapping has been identified as an efficient means of expanding genetic knowledge within and between Rosaceae genomes.