Physical mapping of wheat and rye expressed sequence tag-simple sequence repeats on wheat chromosomes

Six hundred and seventy two loci belonging to 275 expressed sequence tag-simple sequence repeats [EST-SSRs, including 93 wheat (Triticum aestivum L.) and 182 rye (Secale cereale L.) EST-SSRs] were physically mapped on 21 wheat chromosomes. The mapping involved two approaches, the wet-lab approach involving use of deletion stocks and the in silico approach involving matching with ESTs that were previously mapped. The number of loci per EST-SSR mapped using the in silico approach was almost double the number of loci mapped using the wet-lab approach (using deletion stocks). The distribution of loci on the three subgenomes, on the seven homoeologous groups and on the 21 individual chromosomes was nonrandom (P « 0.01). Long arms had disproportionately (relative to the difference in DNA content) higher number of loci, with more loci mapped to the distal regions of chromosome arms. A fairly high proportion of EST-SSRs had multiple loci, which were largely (81%) homoeoloci. Rye EST-SSRs showed a high level of transferability (≈77%) to the wheat genome. Putative functions were assigned to 216 SSR-containing ESTs through homology searches against the protein database. As many as 104 SSR-containing ESTs (a subset of the above ESTs) were also mapped to the 12 rice chromosomes, which corresponded with the known homology between wheat and rice chromosomes. These physical maps of EST-SSRs should prove useful for comparative genomics, gene tagging, fine mapping, and cloning of genes and QTLs. Dna-based molecular markers, particularly SSRs, have been developed and mapped on chromosomes in a variety of crop plants. In bread wheat, genetic and physical mapping of SSRs has been an ongoing exercise, and, to date, ≈2450 SSRs (1 SSR 1.63 cM-1) have been genetically mapped (for details see Torada et al., 2006) and ≈1320 SSRs (62 SSRs chromosome-1) have been physically mapped (for details see Goyal et al., 2005). With a genome size of ≈16 000 Mbp, it is evident that despite concerted efforts, the density of mapped SSRs in bread wheat remains relatively low and continued efforts are needed to increase the density of these SSRs on available genetic and physical maps. In recent years, emphasis has also shifted from genomic SSRs to EST-SSRs due to the availability of very large databases of ESTs from all of the cereals including bread wheat. Consequently, the number of EST-SSRs in cereals now includes 43 598 from bread wheat (Peng and Lapitan, 2005), 16 917 from rice and 184 from rye (La Rota et al., 2005; Hackauf and Wehling, 2002). The genetic mapping of these EST-SSRs is difficult due to a low level of polymorphism, as a result of their conserved nature. Physical mapping of these EST-SSRs in wheat is equally difficult due to the occurrence of homoeoloci exhibiting no polymorphism. This has discouraged wheat researchers from undertaking a large-scale project to genetically or physically map wheat EST-SSRs although genetic mapping of 325 EST-SSRs (Gao et al., 2004; Nicot et al., 2004; Yu et al., 2004) and physical mapping of 305 EST-SSRs was recently undertaken (Yu et al., 2004; Zhang et al., 2005; Peng and Lapitan, 2005). We previously reported genetic mapping of 58 and physical mapping of 270 genomic SSRs (Gupta et al., 2002; Goyal et al., 2005). The present study is an extension of our earlier studies on physical mapping of SSRs and involved both wet-lab and in silico approaches, leading to the successful mapping of as many as 672 loci. The in silico approach allowed mapping of twice the number of loci (per EST-SSR) mapped using wet-lab analysis

Molecular and Transcriptional Regulation of Seed Development in Cereals: Present Status and Future Prospects

Cereals are a rich source of vitamins, minerals, carbohydrates, fats, oils and protein, making them the world’s most important source of nutrition. The influence of rising global population, as well as the emergence and spread of disease, has the major impact on cereal production. To meet the demand, there is a pressing need to increase cereal production. Optimal seed development is a key agronomical trait that contributes to crop yield. The seed development and maturation is a complex process that includes not only embryo and endosperm development, but also accompanied by huge physiological, biochemical, metabolic, molecular and transcriptional changes. This chapter discusses the growth of cereal seed and highlights the novel biological insights, with a focus on transgenic and new molecular breeding, as well as biotechnological intervention strategies that have improved crop yield in two major cereal crops, primarily wheat and rice, over the last 21 years (2000–2021)

Silicon priming: a potential source to impart abiotic stress tolerance in wheat: A review

Abstract Water deficiency adversely affects a number of physiological and metabolic mechanisms in plants and probably, is a major yield limiting factor. This often put into perspectives, the challenge to produce higher crop yields than ever by conserving and efficiently using the depleting underground water and bringing the marginal water deficit lands under cultivation. A possible potential solution is to induce drought tolerance to mitigate this challenge. The drought resistance recently has drawn the future research focus mainly due to exhausting water table and distribution. Silicon priming is known to enhance crop tolerance against various environmental stresses by tailoring the plant water uptake and transport. Drought tolerance could be induced by modified physio-morphic features such as: adjustment for leaf water potential, stomatal frequency, stomatal size, osmotic adjustments. Silicon priming potentially can induce anatomical changes in cell wall with deposition of silica in the form of polymerized silicon dioxide (SiO 2 ) solid particles , alleviating the oxidative damage of functional molecules and improving anti-oxidative defense abilities. Silicon, actually, induces dehydration tolerance at tissue or cellular levels by improving the water status and hence, facilitates the plant to access photosynthates and this modified adaptability mechanism varies among species. In this review, we discuss the plant drought tolerance adjustments and role of silicon priming to withstand drought stress

DNA repair and crossing over favor similar chromosome regions as discovered in radiation hybrid of Triticum

Background: The 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. Results: A 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. Conclusions: The 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.Keywords: Physical mapping, Deletion mutant, Non homologous end joining, Wheat chromosome 3B, Chromatin\, , Radiation hybrid, Gamma radiatio

Grain Legumes

Grain legumes are a main source of nitrogen-rich edible seeds and constitute a major source of dietary protein in the diets of human population especially for vegetarian diet. Legumes comprise the third largest family of flowering plants and provide important sources of food, fodder, oil, and fiber products. This book focuses on grain legumes production challenges, progress, and prospects. The book comprises a vast array of topics including diversity, biofortification, importance and antioxidant properties of pulse proteins, etc. This volume will serve as an excellent resource for students, researchers, and scientists interested and working in the area of sustainable crop production