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BackgroundThe uneven distribution of recombination across the length of chromosomes results in inaccurate estimates of genetic to physical distances. In wheat (Triticum aestivum L.) chromosome 3B, it has been estimated that 90% of the cross over events occur in distal sub-telomeric regions representing 40% of the chromosome. Radiation hybrid (RH) mapping which does not rely on recombination is a strategy to map genomes and has been widely employed in animal species and more recently in some plants. RH maps have been proposed to provide i) higher and ii) more uniform resolution than genetic maps, and iii) to be independent of the distribution patterns observed for meiotic recombination. An in vivo RH panel was generated for mapping chromosome 3B of wheat in an attempt to provide a complete scaffold for this ~1 Gb segment of the genome and compare the resolution to previous genetic maps.ResultsA high density RH map with 541 marker loci anchored to chromosome 3B spanning a total distance of 1871.9 cR was generated. Detailed comparisons with a genetic map of similar quality confirmed that i) the overall resolution of the RH map was 10.5 fold higher and ii) six fold more uniform. A significant interaction (r = 0.879 at p = 0.01) was observed between the DNA repair mechanism and the distribution of crossing-over events. This observation could be explained by accepting the possibility that the DNA repair mechanism in somatic cells is affected by the chromatin state in a way similar to the effect that chromatin state has on recombination frequencies in gametic cells.ConclusionsThe RH data presented here support for the first time in vivo the hypothesis of non-casual interaction between recombination hot-spots and DNA repair. Further, two major hypotheses are presented on how chromatin compactness could affect the DNA repair mechanism. Since the initial RH application 37 years ago, we were able to show for the first time that the iii) third hypothesis of RH mapping might not be entirely correct.

Goyal A., Beres, B. L., Randhawa, H. S., Navabi, A., Salmon, D. F. and Eudes, F. 2011. Yield stability analysis of broadly adaptive triticale germplasm in southern and central Alberta, Canada for industrial end-use suitability. Can. J. Plant Sci. 91: 125–135. Triticale (×Triticosecale Wittmack) is a cereal crop with high grain yield and biomass potential, which are traits desired in biorefinery processes that currently utilize wheat (Triticum aestivum). This study was conducted to evaluate the performance of introduced germplasm for its adaptability to selected Canadian prairie agroecosystems, and to benchmark both introduced and registered triticale lines against hard red spring wheat. To investigate the genotype×environment interaction effects on the performance of triticale genotypes, 30 genotypes (27 triticale; 3 hard red spring wheat) were grown in three environments for 3 yr (2005–2007) in southern and central Alberta, Canada. Variance due to genotypes, years, locations, and their interactions were studied by employing several stability analysis models. Site Regression Model (SREG) and GGE biplot analysis were conducted to rank the relative yield performance of cultivars and to identify stable genotypes. Triticale consistently produced higher grain and biomass than hard red spring wheat, but some lines were high in pentosan content, produced low test weight, and possessed unacceptable growing degree day requirements. However, several of the introduction lines displayed superior trait performance and high stability. Five advanced to “C” level registration testing with one subsequently recommended for registration. The results provide evidence that some of the global triticale germplasm are well-suited to the production environments of the Canadian prairies, and that triticale has potential to be the ideal cereal platform for future technological and biorefinery end-use applications.

Jute is one of the most important fibre crops, which is second only to cotton in providing environment-friendly (biodegradable and renewable) ligno-cellulose fibre. In order to improve this largely neglected crop, we conducted a preliminary study involving the following: (i) analysis of nature and extent of the genetic variability for fibre yield and four other related traits in a set of 81 genotypes belonging to two commercially cultivated Corchorus species (45 genotypes of C. olitorius + 36 genotypes of C. capsularis), (ii) development and analysis of a set of simple sequence repeat (SSR) markers from C. olitorius, and (iii) use of a sub-set of SSRs for assessment of genetic diversity in the above set of 81 genotypes. The results suggested quantitative nature of fibre yield and other related traits, with a preponderance of dominance component in genetic variance. A sub-set of 45 SSRs derived from C. olitorius, when used for a study of DNA polymorphism and genetic diversity, showed high transferability of these C. olitorius SSRs to C. capsularis. The average number of alleles for individual SSRs was surprisingly low (3.04 for both species, 2.02 for C. capsularis and 2.51 for C. olitorius), and so was the average polymorphic information content (PIC; 0.23 and 0.24 in two species). In the dendrogram obtained using a similarity matrix, the 81 genotypes were grouped into three clusters, which largely corresponded to the two species, Cluster I belonging mainly to C. capsularis and the other two closely related clusters (clusters II and III) belonging to C. olitorius. It was also shown that a minimum of 15 SSRs could give the same information as 41 SSRs, thus making many SSRs redundant. The SSR markers developed during the present study and to be developed in future will prove useful not only for evaluation of genetic diversity, but also for molecular mapping/QTL analysis, and for comparative genome analysis of the two Corchorus species.

BackgroundPlant parasitic nematodes develop an intimate and long-term feeding relationship with their host plants. They induce a multi-nucleate feeding site close to the vascular bundle in the roots of their host plant and remain sessile for the rest of their life. Nematode secretions, produced in the oesophageal glands and secreted through a hollow stylet into the host plant cytoplasm, are believed to play key role in pathogenesis. To combat these persistent pathogens, the identity and functional analysis of secreted effectors can serve as a key to devise durable control measures. In this review, we will recapitulate the knowledge over the identification and functional characterization of secreted nematode effector repertoire from phytoparasitic nematodes.ResearchDespite considerable efforts, the identity of genes encoding nematode secreted proteins has long been severely hampered because of their microscopic size, long generation time and obligate biotrophic nature. The methodologies such as bioinformatics, protein structure modeling, in situ hybridization microscopy, and protein-protein interaction have been used to identify and to attribute functions to the effectors. In addition, RNA interference (RNAi) has been instrumental to decipher the role of the genes encoding secreted effectors necessary for parasitism and genes attributed to normal development. Recent comparative and functional genomic approaches have accelerated the identification of effectors from phytoparasitic nematodes and offers opportunities to control these pathogens.ConclusionPlant parasitic nematodes pose a serious threat to global food security of various economically important crops. There is a wealth of genomic and transcriptomic information available on plant parasitic nematodes and comparative genomics has identified many effectors. Bioengineering crops with dsRNA of phytonematode genes can disrupt the life cycle of parasitic nematodes and therefore holds great promise to develop resistant crops against plant-parasitic nematodes.