Biomedical subjects

Christine A Hackett

Publications and source records attributed to Christine A Hackett.

5 recordsLinked to original sources

PubMed2006

Detection of a quantitative trait locus for both foliage and tuber resistance to late blight [Phytophthora infestans (Mont.) de Bary] on chromosome 4 of a dihaploid potato clone (Solanum tuberosum subsp. tuberosum).

Linkage analysis, Kruskal-Wallis analysis, interval mapping and graphical genotyping were performed on a potato diploid backcross family comprising 120 clones segregating for resistance to late blight. A hybrid between the Solanum tuberosum dihaploid clone PDH247 and the long-day-adapted S. phureja clone DB226(70) had been crossed to DB226(70) to produce the backcross family. Eighteen AFLP primer combinations provided 186 and 123 informative maternal and paternal markers respectively, with 63 markers in common to both parents. Eleven microsatellite (SSR) markers proved useful for identifying chromosomes. Linkage maps of both backcross parents were constructed. The results of a Kruskal-Wallis analysis, interval mapping and graphical genotyping were all consistent with a QTL or QTLs for blight resistance between two AFLP markers 30 cM apart on chromosome 4, which was identified by a microsatellite marker. The simplest explanation of the results is a single QTL with an allele from the dihaploid parent conferring resistance to race 1, 4 of P. infestans in the foliage in the glasshouse and to race 1, 2, 3, 4, 6, 7 in the foliage in the field and in tubers from glasshouse raised plants. The QTL was of large effect, and explained 78 and 51% of the variation in phenotypic scores for foliage blight in the glasshouse and field respectively, as well as 27% of the variation in tuber blight. Graphical genotyping and the differences in blight scores between the parental clones showed that all of the foliage blight resistance is accounted for by chromosome 4, whereas undetected QTLs for tuber resistance probably exist on other chromosomes. Graphical genotyping also explained the lack of precision in mapping the QTL(s) in terms of lack of appropriate recombinant chromosomes.

Chromosome Mapping↗

PubMed2006

Soil microbial and faunal community responses to bt maize and insecticide in two soils.

The effects of maize (Zea mays L.), genetically modified to express the Cry1Ab protein (Bt), and an insecticide on soil microbial and faunal communities were assessed in a glasshouse experiment. Soil for the experiment was taken from field sites where the same maize cultivars were grown to allow comparison between results under glasshouse conditions with those from field trials. Plants were grown in contrasting sandy loam and clay loam soils, half were sprayed with a pyrethroid insecticide (deltamethrin) and soil samples taken at the five-leaf stage, flowering, and maturity. The main effect on all measured parameters was that of soil type and there were no effects of Bt trait or insecticide on plant growth. The Bt trait resulted in more soil nematodes and protozoa (amoebae), whereas insecticide application increased plant Bt concentration and altered nematode community structure. The only significant effects on soil microbial community structure, microarthropods, and larvae of a nontarget root-feeding Dipteran, were due to soil type and plant growth stage. The results indicate that, although there were statistically significant effects of the Bt trait on soil populations, they were small. The relative magnitude of the effect could best be judged by comparison with the insecticide treatment, which was representative of current best practice. The Bt trait had no greater effect than the insecticide treatment. Results from this glasshouse experiment were in broad agreement with conclusions from field experiments using the same plant material grown in the same soils.

Animals↗

PubMed2004

Interval mapping of quantitative trait loci for resistance to late blight [Phytophthora infestans (Mont.) de Bary], height and maturity in a tetraploid population of potato (Solanum tuberosum subsp. tuberosum).

Interval mapping of quantitative trait loci (QTL) for resistance to late blight, height, and maturity was performed on a tetraploid full-sib family of potato comprising 227 clones from a cross between a susceptible parent, 12601ab1, and a resistant cultivar, Stirling, which were of similar height and main crop maturity. Thirty-eight AFLP primer combinations provided 585 informative markers, and 23 SSRs proved useful for identifying linkage groups (LGs). A simplex QTL allele was found on LGV of Stirling close to marker STM3179, which was associated with early maturity, short plants, and susceptibility to blight and explained 54.7, 26.5, 26.3, and 17.5% of the variation for maturity, height, tuber blight, and foliage blight. When the residuals from the regressions of foliage and tuber blight on maturity were analyzed, there was no significant effect of a QTL on LGV, but a duplex QTL allele for resistance was found on LGIV of Stirling, which explained 30.7 and 13.6% of the variation for foliage and tuber blight on an additive model. Partial dominance for resistance explained even more of the variation, up to 37.2% for foliage blight. A major gene for blight resistance in Stirling was also mapped to LGXI.

Chromosome Mapping↗

PubMedDate not supplied

Analysis of simple sequence repeats (SSRs) in wild barley from the Fertile Crescent: associations with ecology, geography and flowering time.

Wild barley, Hordeum spontaneum C. Koch, is the progenitor of cultivated barley, Hordeum vulgare. The centre of diversity is in the Fertile Crescent of the Near East, where wild barley grows in a wide range of conditions (temperature, water availability, day length, etc.). The genetic diversity of 39 wild barley genotypes collected from Israel, Turkey and Iran was studied with 33 SSRs of known map location. Analysis of molecular variance (AMOVA) was performed to partition the genetic variation present within from the variation between the three countries of origin. Using classification tree analysis, two (or three) specific SSRs were identified which could correctly classify most of the wild barley genotypes according to country of origin. Associations of SSR variation with flowering time and adaptation to site-of-origin ecology and geography were investigated by two contrasting statistical approaches, linear regression based on SSR length variation and linear regression based on SSR allele class differences. A number of SSRs were significantly associated with flowering time under four different growing regimes (short days, long days, unvernalised and vernalised). Most of the associations observed could be accounted for by close linkage of the SSR loci to earliness per se genes. No associations were found with photoperiodic and vernalisation response genes known to control flowering in cultivated barley suggesting that different genetic factors may be active in wild barley. Novel genomic regions controlling flowering time in wild barley were detected on chromosomes 1HS, 2HL, 3HS and 4HS. Associations of SSRs with site-of-origin ecological and geographic data were found primarily in genomic regions determining plant development. This study shows that the analyses of SSR variation by allele class and repeat length are complementary, and that some SSRs are not necessarily selectively neutral.

Alleles↗

PubMedDate not supplied

Statistical methods for QTL mapping in cereals.

This paper gives an overview of the statistical theory suitable for mapping quantitative trait loci in experimental populations derived from inbred parents, with a particular emphasis on methodology for cereal crops. The basic theory is described, and some new areas of statistical research appropriate for mapping in cereal crops are discussed.

Chromosome Mapping↗