Map and sequence-based chromosome walking towards cloning of the male fertility restoration gene Rf5 linked to R11 in sunflower

The nuclear fertility restorer gene Rf5 in HA-R9, originating from the wild sunflower species Helianthus annuus, is able to restore the widely used PET1 cytoplasmic male sterility in sunflowers. Previous mapping placed Rf5 at an interval of 5.8 cM on sunflower chromosome 13, distal to a rust resistance gene R11 at a 1.6 cM genetic distance in an SSR map. In the present study, publicly available SNP markers were further mapped around Rf5 and R11 using 192 F2 individuals, reducing the Rf5 interval from 5.8 to 0.8 cM. Additional SNP markers were developed in the target region of the two genes from the whole-genome resequencing of HA-R9, a donor line carrying Rf5 and R11. Fine mapping using 3517 F3 individuals placed Rf5 at a 0.00071 cM interval and the gene co-segregated with SNP marker S13_216392091. Similarly, fine mapping performed using 8795 F3 individuals mapped R11 at an interval of 0.00210 cM, co-segregating with two SNP markers, S13_225290789 and C13_181790141. Sequence analysis identified Rf5 as a pentatricopeptide repeat-encoding gene. The high-density map and diagnostic SNP markers developed in this study will accelerate the use of Rf5 and R11 in sunflower breeding.

Genotypic Effects on the Response of Soybean (Glycine max (L.) Merrill) to Sulfonylurea Herbicides

In soybean cropping, sulfonylurea (SU) herbicides are a potentially useful alternative to glyphosate-based herbicides. Normally, soybeans are susceptible to SU herbicides, but two unlinked non-GMO genes (ALS1 and ALS2), have been identified that confer SU tolerance. In this project, we explored the effectiveness of these genes in Australian soybean genetic backgrounds. Four lines, carrying both ALS1 and ALS2, were derived by backcrossing different Australian genotypes to a SU-tolerance donor line ‘W4-4’ and then using molecular markers, plants homozygous for both ALS genes were selected. The W4-4 donor and the four derived lines were evaluated in a hydroponic system at increments up to 4× the recommended field rate of metsulfuron-methyl. The ALS genes provided high levels of tolerance, with evidence of some minor interaction with the genetic background. To further test whether there was an effect of background, the five lines were crossed together in a half-diallel mating design and the resulting ten F2 populations were screened hydroponically for tolerance to metsulfuron-methyl herbicide at 4× the recommended field rate. Analyses of seedling dry weight of the five parental lines and their F2 progeny in response to the herbicide, identified differences among the crosses. These results indicated that the development of commercial varieties with maximum herbicide tolerance requires incorporation of both ALS genes, and if combined with selection in segregating populations in the presence of SU herbicide may capture additional tolerance from background genes of minor effect.

DNA markers of AHAS1 gene for screening and identification of sunflower genotypes of hybrid origin

Aim. A molecular genetic study of sunflower F1 and F2 hybrids on a microsatellite markers of mutant AHAS1 gene associated with herbicide resistance was performed. The aim of the work was to screen of F1 and F2 sunflower hybrid populations with usage of DNA markers and identification of homozygous segregants containing of the gene for resistance to SU herbicides. Methods. It was used PCR amplification to detect alleles of microsatellite locus located within the mutant AHAS1 gene. Results. The possibility of identification of hybrid plants with different alleles of the AHAS1 gene was shown. The efficiency of the allele of 191 b. p. in the homo- and heterozygous state for marker selection of genotypes resistant to the herbicide of the sulfonylurea group was confirmed. 10 homozygous F2 plants of SURES-2 x OS 1019B and 18 homozygous F2 plants of SURES-2 x OS 1029B, which according to the genotype correspond to the donor line of the mutant AHAS1 gene, were obtained. Conclusions. F2 plants that are carriers of this gene in the homozygous state can be used as an initial material in breeding for the purpose of creating new inbred lines with genetically determined resistance to SU herbicides. Keywords: DNA markers, AHAS1 gene, sunflower, herbicides, resistance.

Identification of donor lines for improving fruit yield of k 35 x k 12 eggplant hybrid

The aim of this study was to identify an eggplant donor line which possess the largest frequency of favourable alleles that control fruit yield. Such donor line should be used to improve the elite eggplant hybride K35 x K12. The fruit yield of the elite hybrid, its parents and their hybrids with three potential donor lines (K36/1, K11 and K22/2) was examined in a diallel set by means of field trials. The trials were set in a randomized block design in three replications. After the fruit yield had been measured, the modified method of evaluation of relative loci value according to Dudley (1987) was applied. Ali inbred lines expressed positive values of the ?G' parameter. The K11 inbred had the largest ?G' value (2.38) and, also, the lowest frequency of unfavourable alleles on the loci class D (1.33). It was established that the K11 inbred line was more related to the K35 parental inbred line (7.81). Consequently, on the basis of the ?D' values, improvement should be obtained by backcrossing the elite hybrid K35 x K11 to the donor inbred K11.

Genetic lag in a Meishan x Large White pig backcross population: A simulation study

Backcrossing can be used as a tool to introduce new alleles into a population. Having detected an allele of interest in a non-commercial (donor) line, backcrossing methods introduce the allele into a commercial (recipient) population whilst minimising the contribution of the less superior donor genome. Many alleles linked to the desired donor allele are incorporated into the recipient line by a phenomenon called linkage drag. Loci in the region of the target locus may trace back to a common ancestor and become identical by descent (IBD). This leads to a loss of diversity around the target locus. The linkage drag and contributions from ancestral recipient populations mean that the backcross population suffers genetic lag for commercial traits. This study aims to investigate the effect of population size and number of backcross generations on genetic lag, linkage drag and IBD around a target allele reducing back fat found in the Chinese Meishan breed when backcrossed to a commercial Large White population.

DNA fingerprints applied to gene introgression in breeding programs.

An application of DNA fingerprints (DFP) for gene introgression in breeding programs of both farm animals and plants is proposed. DFP loci, detectable by minisatellite probes, are extremely polymorphic. Individuals have unique patterns of DFP and thus can be selected for maximal genomic similarity to the recipient line, and minimal similarity to the donor line, using their DFP patterns as the criterion for similarity. This genomic selection (GS) can be performed at generations BC1, BC2 or both, and thus significantly reduce the required number of backcross generations in introgression breeding programs. The association between genomic and DFP similarity is demonstrated. Theoretical distributions and variances of the relative percentages of the donor and recipient genomes as the basis for the GS approach are presented.