Plant Breeding and Genomics News

Rice is one of the most important crops worldwide, both as a staple food and as a model system for genomic research. In order to systematically assign functions to all predicted genes in the rice genome, a large number of rice mutant lines, including those created by T-DNA insertion, Ds/dSpm tagging, Tos17tagging, and chemical/irradiation mutagenesis, have been generated by groups around the world. In this study, we have reviewed the current status of mutant resources for functional analysis of the rice genome. A total of 246 566 flanking sequence tags from rice mutant libraries with T-DNA, Ds/dSpm, orTos17 insertion have been collected and analyzed. The results show that, among 211 470 unique hits, inserts located in the genic region account for 68.16%, and 60.49% of nuclear genes contain at least one insertion. Currently, 57% of non-transposable-element-related genes in rice have insertional tags. In addition, chemical/irradiation-induced rice mutant libraries have contributed a lot to both gene identification and new technology for the identification of mutant sites. In this review, we summarize how these tools have been used to generate a large collection of mutants. In addition, we discuss the merits of classic mutation strategies. In order to achieve saturation of mutagenesis in rice, DNA targeting, and new resources like RiceFox for gene functional identification are reviewed from a perspective of the future generation of rice mutant resources.

Why is cassava important?

Cassava (Manihot esculenta), a major staple crop, is the main source of calories for 500 million people across the globe. No other continent depends on cassava to feed as many people as does Africa. Cassava is indispensable to food security in Africa. It is a widely preferred and consumed staple, as well as a hardy crop that can be stored in the ground as a fall-back source of food that can save lives in times of famine. Despite the importance of cassava for food security on the African continent, it has received relatively little research and development attention compared to other staples such as wheat, rice and maize. The key to unlocking the full potential of cassava lies largely in bringing cassava breeding into the 21st century.

Why genomic selection?

Genomic Selection is a new plant breeding method that uses statistical modeling to predict how a plant will perform, before it is field-tested. Novel statistical models and bioinformatics tools, combined with increasingly abundant genomic information, have enabled the deployment of prediction-based breeding methods such as Genomic Selection in crop breeding programs. Giving breeders the ability to select based on predictions rather than observations will result in much improved genetic gains and efficiency.

 

CassavaBase

Access to data and tools for breeders and researchers, including genomic selection algorithms and analysis capacity, a cassava genome browser, cassava ontology tools, phenotyping tools, and social networking.

Hop-derived aroma characteristics in beer are very important for the quality of beer. This study compared the differences of hop aroma characteristics and the compounds contained in beer by changing the variety of hops applying the idea of “food metabolomics” on the GC×GC/TOF-MS analysis data, to clarify which aroma compounds contribute to the differences of hop aroma profiles indicated by sensory descriptors. As a result, by focusing only on hop-derived compounds, 67 compounds were strongly correlated with one or more of the sensory descriptors. Furthermore, the odor descriptions of each key compound corresponded well to each sensory descriptor. Thus, these compounds are likely to be the key compounds explaining the differences of hop aroma characteristics in beer. This study led to the suggestion that understanding the relationship between the comprehensive nontarget analysis by GC×GC-TOF/MS and organoleptic evaluation using PCA is effective in estimating the key compounds.

Hybrid weakness is an important reproductive barrier that hinders genetic exchange between different species at the post-zygotic stage. However, our understanding of the molecular mechanisms underlying hybrid weakness is limited. In this study, we report discovery of a novel interspecific hybrid weakness in a rice chromosome segment substitution line (CSSL) library derived from a cross between the indicavariety Teqing (Oryza sativa) and common wild rice (O. rufipogon). The dominant Hybrid weakness i1(Hwi1) gene from wild rice is genetically incompatible with Teqing and induced a set of weakness symptoms, including growth suppression, yield decrease, impaired nutrient absorption, and the retardation of crown root initiation. Phytohormone treatment showed that salicylic acid (SA) could restore the height of plants expressing hybrid weakness, while other phytohormones appear to have little effect. Fine mapping indicated that Hwi1 is located in a tandem leucine-rich repeat receptor-like kinase (LRR–RLK) gene cluster. Within the 13.2-kb candidate region on the short arm of chromosome 11, there are two annotated LRR–RLK genes, LOC_Os11g07230 and LOC_Os11g07240. The Teqing allele ofLOC_Os11g07230 and the wild rice allele of LOC_Os11g07240 encode predicted functional proteins. Based on the genetic inheritance of hybrid weakness, LOC_Os11g07240 is implicated as the candidate gene for Hwi1. Functional analysis of Hwi1 will expand our knowledge of the regulation of hybrid weakness in rice.

Abiotic Stress - Plant Responses and Applications in Agriculture. Edited by: Kourosh Vahdati and Charles Leslie. ISBN 978-953-51-1024-8, Published 2013-03-13

 

"This book is not intended to cover all known abiotic stresses or every possible technique used to understand plant tolerance but, instead, to describe some of the widely used approaches to addressing such major abiotic stresses as drought, salinity, extreme temperature, cold, light, calcareous soils, excessive irradiation, ozone, ultraviolet radiation, and flooding, and to describe major or newly emerging techniques employed in understanding and improving plant tolerance. Among the strategies for plant stress survival, examples of both avoidance and tolerance are presented in detail and comprehensive case studies of progress and directions in several agricultural crops such as apple, walnut, grape and wheat are included."

  

One of the major concerns of the general public about transgenic crops relates to the mixing of genetic materials between species that cannot hybridize by natural means. To meet this concern, the two transformation concepts cisgenesis and intragenesis were developed as alternatives to transgenesis. Both concepts imply that plants must only be transformed with genetic material derived from the species itself or from closely related species capable of sexual hybridization. Furthermore, foreign sequences such as selection genes and vector-backbone sequences should be absent. Intragenesis differs from cisgenesis by allowing use of new gene combinations created by in vitrorearrangements of functional genetic elements. Several surveys show higher public acceptance of intragenic/cisgenic crops compared to transgenic crops. Thus, although the intragenic and cisgenic concepts were introduced internationally only 9 and 7 years ago, several different traits in a variety of crops have currently been modified according to these concepts. Five of these crops are now in field trials and two have pending applications for deregulation. Currently, intragenic/cisgenic plants are regulated as transgenic plants worldwide. However, as the gene pool exploited by intragenesis and cisgenesis are identical to the gene pool available for conventional breeding, less comprehensive regulatory measures are expected. The regulation of intragenic/cisgenic crops is presently under evaluation in the EU and in the US regulators are considering if a subgroup of these crops should be exempted from regulation. It is accordingly possible that the intragenic/cisgenic route will be of major significance for future plant breeding.

Increased phenotyping accuracy and throughput are necessary to improve our understanding of quantitative variation and to be able to deconstruct complex traits such as those involved in growth responses to the environment. Still, only a few facilities are known to handle individual plants of small stature for non-destructive, real-time phenotype acquisition from plants grown in precisely adjusted and variable experimental conditions. Here, we describe Phenoscope, a high-throughput phenotyping platform that has the unique feature of continuously rotating 735 individual pots over a table. It automatically adjusts watering and is equipped with a zenithal imaging system to monitor rosette size and expansion rate during the vegetative stage, with automatic image analysis allowing manual correction. When applied to Arabidopsis thaliana, we show that rotating the pots strongly reduced micro-environmental disparity: heterogeneity in evaporation was cut by a factor of 2.5 and the number of replicates needed to detect a specific mild genotypic effect was reduced by a factor of 3. In addition, by controlling a large proportion of the micro-environmental variance, other tangible sources of variance become noticeable. Overall, Phenoscope makes it possible to perform large-scale experiments that would not be possible or reproducible by hand. When applied to a typical quantitative trait loci (QTL) mapping experiment, we show that mapping power is more limited by genetic complexity than phenotyping accuracy. This will help to draw a more general picture as to how genetic diversity shapes phenotypic variation.

Genomics-based breeding of economically important crops such as banana, coffee, cotton, potato, tobacco and wheat is often hampered by genome size, polyploidy and high repeat content. We adapted the sequence-based Whole Genome Profiling (WGP ) technology to gain insight into the polyploidy of the model plant Nicotiana tabacum (tobacco). N. tabacum is assumed to originate from a hybridization event between Nicotiana sylvestris and Nicotiana tomentosiformis about 200,000 years ago. This resulted in tobacco having a haploid genome size of 4,500 million base pairs, about four times larger than the related tomato and potato genomes. In this study a physical map containing 9,750 contigs of bacterial artificial chromosomes (BACs) was constructed. The average contig size was 462 kbp, and the calculated genome coverage equaled the estimated tobacco genome size. We used a method for determination of the ancestral origin of the genome by annotation of WGP sequence tags. This assignment agreed with the ancestral annotation available from the tobacco genetic map and may be used to investigate the evolution of homoeologous genome segments after polyploidization. The map generated will be an essential scaffold for the tobacco genome. We propose the combination of WGP physical mapping technology with tag profiling of ancestral lines as a generally applicable method to elucidate the ancestral origin of genome segments of polyploid species. The physical mapping of genes and their origins will enable application of biotechnology to polyploid plants aimed at accelerating and increasing the precision of breeding for abiotic and biotic stress resistance. This article is protected by copyright. All rights reserved.