Study of Quantitative Trait Loci (QTLs) Associated with Allelopathic Trait in Rice

In rice there are few genetic studies reported for allelopathy traits, which signify the ability of plants to inhibit or stimulate growth of other plants in the environment, by exuding chemicals. QTL analysis for allelopathic traits were conducted with 98 F8 RILs developed from the cross between the high allelopathic parents of ‘Sathi’ and non-allelopathic parents of ‘Nong-an’. The performance of allelopathic traits were evaluated with inhibition rate on root length, shoot length, total length, root weight, shoot weight, and total weight of lettuce as a receiver plant. With 785 polymorphic DNA markers, we constructed a linkage map showing a total of 2489.75 cM genetic length and 3.17 cM of average genetic distance between each adjacent marker. QTL analysis detected on QTL regions on chromosome 8 responsible for the inhibition of shoot length and inhibition of total length. The qISL-8 explained 20.38% of the phenotypic variation for the inhibition on the shoot length. The qITL-8 explained 14.93% of the phenotypic variation for the inhibition on total length. The physical distance of the detected QTL region was 194 Kbp where 31 genes are located.

Major QTLs for seedling traits in barley using a DArT-based linkage map

Seed vigor is considered as the most critical stage for barley production, and cultivar with high early seedling vigour (ESV) allow plants to form a canopy more quickly. In this study, the QTLs of seedling vigour related-traits were investigated using 185 RILs derived from Xena and H94061120 using DArT approach. In total, 46 significant QTLs for ESV related-traits were detected. The total map length was 1075.1 cM with an average adjacent-marker distance of 3.28 cM. Fourteen QTLs for BY were found on all chromosomes, two of them co-located with QTLs on 1H for GY. The related-traits; LL1, LL2, LA1 and LDW1 had high heritability (>60%). Meanwhile, a significant correlation was observed between GY and BY, which provide the clear image of these traits in the selection process. Our results demonstrate that a pleiotropic QTL related to SLA2, BY, and GY was linked to to the DArT markers bPb-9280 and bPb-9108 on 1H, which could be used to significantly improve the seed vigor by marker-assisted selection and possible future map-based cloning of the gene of intrest.

Influence of genetic background and heterozygosity on meiotic recombination in Arabidopsis thaliana

Plant breeding relies on genetic variability generated by meiotic recombination. Control of recombination frequencies is not yet possible, but would significantly extend the options for plant-breeding strategies. A prerequisite would be variability of recombination frequencies. In this study, 15 transgenic kanamycin (KR) and hygromycin (HR) resistance gene insertions mapping to the five Arabidopsis thaliana chromosomes were used as genetic markers. Recombination frequencies were determined from the frequencies of resistance phenotypes within populations segregating for linked KR and HR markers. Recombination frequencies of marker pairs were compared among these four ecotypes, among F1s in both reciprocal forms derived from these ecotypes, and between F1s and their parent lines. On average, the recombination frequencies in F1 crosses were substantially higher (up to 2-fold) than in the homozygous parental ecotypes. A strong negative correlation between genetic similarities of ecotypes and recombination frequencies was detected for two adjacent marker pairs located on the long arm of chromosome 3, but not for marker pairs in other genomic regions. Our results suggest that heterozygosity influences recombination in plant breeding, and cannot be ignored in genetic mapping of genomes.Key Words: meiotic recombination, Arabidopsis, genetic background, heterozygosity, homozygosity.

Fine Structure of Laser Induced Lesions of Rhesus Monkey Retina

The retinas of a rhesus monkey were exposed to mode-locked visible laser pulses operated under the following exposure conditions: pulse train duration, lOmsecj pulse width, ∽250 psec; pulse repetition rate,∽104 mHz; wavelength, 514.5 nm. Two threshold levels were determined on the basis of ophthalmoscopically observed lesions at one hour post treatment and at 24 hours post treatment. One hour lesion threshold was∽430 mW peak pulse power and 24 hour lesion threshold was ∽210 mW peak pulse power. A grid of 16 exposures ranging from 282 to 1587 mW were placed in the macula region of the retina with adjacent marker lesions used for co-ordinate calibration. After six months post treatment, the animal was sacrificed and perfused with 3% glutaraldehyde in 0.1 M sodium cacodylate buffer. The eyes were post fixed in buffered 1% osmium tetroxide, dehydrated and embedded in Spurr plastic.