Coat Color Roan Shows Association with KIT Variants and No Evidence of Lethality in Icelandic Horses

Roan (Rn) horses show a typical seasonal change of color. Their body is covered with colored and white hair. We performed a descriptive statistical analysis of breeding records of Icelandic horses to challenge the hypothesis of roan being lethal in utero under homozygous condition. The roan to non-roan ratio of foals from roan × roan matings revealed homozygous roan Icelandic horses to be viable. Even though roan is known to be inherited in a dominant mode and epistatic to other coat colors, the causative mutation is still unknown. Nevertheless, an association between roan phenotype and the KIT gene was shown for different horse breeds. In the present study, we identified KIT variants by Sanger sequencing, and show that KIT is also associated with roan in the Icelandic horse breed.

Marker-assisted pyramiding of two major broad-spectrum bacterial blight resistance genes,Xa21andXa33into an elite maintainer line of rice, DRR17B

Bacterial blight (BB) disease reduces the yield of rice varieties and hybrids considerably in many tropical rice growing countries like India. The present study highlights the development of durable BB resistance into the background of an elite maintainer of rice, DRR17B, by incorporating two major dominant genes,Xa21andXa33through marker-assisted backcross breeding (MABB). Through two sets of backcrosses, the two BB resistance genes were transferred separately to DRR17B. In this process, at each stage of backcrossing, foreground selection was carried out for the target resistance genes and for non-fertility restorer alleles concerning the major fertility restorer genesRf3andRf4, using gene-specific PCR-based markers, while background selection was done using a set of 61 and 64 parental polymorphic SSR markers respectively. Backcross derived lines possessing eitherXa21orXa33along with maximum genome recovery of DRR17B were identified at BC3F1generation and selfed to develop BC3F2s. Plants harboringXa21orXa33in homozygous condition were identified among BC3F2s and were intercrossed with each other to combine both the genes. The intercross F1plants (ICF1) were selfed and the intercross F2(ICF2) plants possessing bothXa21andXa33in homozygous condition were identified with the help of markers. They were then advanced further by selfing until ICF4generation. Selected ICF4lines were evaluated for their resistance against BB with eight virulent isolates and for key agro-morphological traits. Six promising two-gene pyramiding lines of DRR17B with high level of BB resistance and agro-morphological attributes similar or superior to DRR17B with complete maintenance ability have been identified. These lines with elevated level of durable resistance may be handy tool for BB resistance breeding.

Evaluasi Molekuler dan Lapangan terhadap Galur-galur Padi Berumur Genjah dan Produktivitas Tinggi Turunan Ciherang

Improving Ciherang rice variety for earliness and higher productivity was obtained using Marker Assisted Backcrossing (MAB). Among 78 lines of BC2F4 generation of Ciherang x Nipponbare were obtained from greenhouse and molekuler analysis selection. Field evaluations were conducted at two locations, namely field station of Sukamandi (Indonesian Center for Rice Research, West Java), and field station of Maros (Indonesian Cereals Research Institute, South Sulawesi). Molecular analysis was performed using markers RM1362 and RM7601 which are flanking markers for the QTL region for Hd2 gene, located on chromosome 7. Flowering time and grain yield were evaluated among BC2 F4 lines. Five lines flowered earlier and yielded higher than Ciherang were selected for background analysis using microsatellites covering the rice chromosomes. The earliest flowering line was BC2F4 CihNip-60 (at 74 days, 4 days earlier than that of Ciherang), and the highest yield (which flowered earlier than Ciherang) was BC2 F4 CihNip-23, namely (2.20 t/ha higher than Ciherang). A total of 74 (95%) BC2 F4 lines showed QTL region of Hd2 gene in homozygous condition. This showed that molecular selection from F1 generation of BC2 F4 was able to identify homozygous gens and almost free of contaminant plant. Genetic backgrounds of the five BC2 F2 selected lines were similar to that of Ciherang. Based on the agronomic and molecular marker, twenty five lines of BC2 F4 flowered earlier than did Ciherang and yielded higher than did Ciherang. These lines should be further evaluated for their stability

Production of haploids and double haploids in annual (Lolium multiflorum) and perennial (L. perenne) ryegrasses

Anthers from 32 genotypes from one line of annual ryegrass (Lolium multiflorum) and 229 genotypes from 15 cultivars of perennial ryegrass (L. perenne) were tested for the production of haploids and double haploids. Six (23%) annual and 71 (31%) perennial ryegrass genotypes produced calli ranging from 1.3-16% and 0.8- 12.2% respectively. However none of the annual ryegrass genotypes produced green plants and only one genotype (Option WH-1) of perennial ryegrass produced 16 (1.8%) green plants. The remaining produced only albino regenerates. Twelve of the 16 green plants were evaluated cytologically for chromosome numbers. Four were haploids thus confirming their origin from haploid pollen. The remaining eight were all diploids. One haploid and one diploid were tested for their homozygous condition using seven simple sequence repeat (SSR) markers and were found to be homozygous at all seven loci. In order to increase the recovery of green regenerates, we have used the responsive genotype Option WH-1 in crosses with three other perennial ryegrass genotypes and the progenies are currently been grown for anther culture

Replicase-Derived Resistance Against Pea early browning virus in Nicotiana benthamiana Is an Unstable Resistance Based upon Posttranscriptional Gene Silencing

Virus resistance in Nicotiana benthamiana plants containing a translatable Pea early browning virus (PEBV) 54K sequence from the 201K replicase gene has been reported previously. Resistant plants contain multiple transgene copies divided between two loci. Analysis of a genetic series containing the two loci in separate homozygous or heterozygous condition suggest that only one of the loci is necessary to induce the resistance. The resistance observed in R2 and R3 generations of lines containing both transgene loci in homozygous condition became less consistent in R4 and R5 generations. This inversely correlated with steady-state transgene transcript levels of the segregating populations. The use of recombinant Potato virus X vectors carrying PEBV 54K sequences showed that the resistance is based upon posttranscriptional gene silencing, is non-strand specific, and recognizes 3′ located sequences within the PEBV 54K sequence.

Introduction of the D-genome chromosomes from bread wheat into hexaploid triticale with a complete rye genome

Hexaploid triticale (× Triticosecale Wittmack) lines selected from the progeny of octoploid × tetraploid triticale hybrids were karyotyped using C-banding. The number of D-genome chromosome pairs substituted for A- and (or) B-genome chromosomes ranged from 0 to 4, averaging 2.1 substitutions per line. Every D-genome chromosome was present in at least 1 of the 70 lines analyzed. The most frequent were chromosomes 3D and 6D, followed by 1D. Of the 14 possible substitutions, 12 were present in the homozygous condition, 1 (4D/4B) was still segregating, and 6D/6B was absent. With the exception of one 1D/1R substitution and one 7RS/4DS translocation, all lines had a complete rye genome. Key words: triticale, chromosome substitutions, D genome.

THE GENETIC FACTORS ALTERED IN HOMOZYGOUS abo STOCKS OF DROSOPHILA MELANOGASTER

ABSTRACT Females homozygous for the maternal-effect mutation abo (2-44.0) produce a large fraction of eggs which arrest during embryogenesis. Increasing doses of defined heterochromatic regions inherited by offspring of abo mothers from their fathers function zygotically to bring about a partial rescue of the abo-induced embryonic lethality. Another property of the abo mutation is that the severity of the maternal effect decreases when an abo stock is maintained in homozygous condition for a number of generations. Here, we show that the factors which change in homozygous abo stocks to result in the decrease in maternally induced embryonic lethality, act zygotically, dominantly and additively. More importantly, we show that the X and second chromosomes, but not the Y and third chromosomes, derived from homozygous abo stocks are, when inherited from males, more effective in promoting zygotic rescue of the abo-induced lethality than are the equivalent chromosomes derived from an abo stock maintained in heterozygous condition. The chromosomal locations of the factors altered in the homozygous stock, as well as their behavior, strongly suggest that the same heterochromatic elements that are responsible for rescuing embryos from the abo-induced maternal effect are altered in homozygous abo flies in such a way that the maternal effect itself is less severe.

High levels of fitness modifiers induced by hybrid dysgenesis in Drosophila melanogaster

SummaryWild-type chromosomes of D. melanogaster mutagenized by passage through a single generation of hybrid dysgenesis have been compared against identical chromosomes passed through a reciprocal, non-dysgenic cross. Fitness of the chromosome in homozygous condition has been examined in population cages using the technique of balancer chromosome equilibration. The results indicate that amongst chromosomes with no lethal or visible mutation, more than 50% have suffered a measurable decline in fitness. The magnitude of this decline is estimated to be in the range 10–20%.