Prevention of preharvest aflatoxin contamination through genetic engineering of crops

Current practices on prevention of aflatoxin contamination of crop species include time consuming, expensive agronomic practices. Of all the methods available to-date, conventional breeding and/or genetic engineering to develop host plant-based resistance to aflatoxin-producing fungi appear to be valuable for several reasons. However, breeding for disease-resistant crops is very time consuming, especially in tree crops, and does not lend itself ready to combat the evolution of new virulent fungal races. Moreover, availability of known genotypes with natural resistance to mycotoxin-producing fungi is a prerequisite for the successful breeding program. While it is possible to identify a few genotypes of corn or peanuts that are naturally resistant toAspergillus we do not know whether these antifungal factors are specific toA. flavus. In crops like cotton, there are no known naturally resistant varieties toAspergillus. Availability of transgenic varieties with antifungal traits is extremely valuable as a breeding tool. Several antifungal proteins and peptides are available for genetic engineering of susceptible crop species, thanks to the availability of efficient modern tools to understand and evaluate protein interactions by proteomics of host, and genomics and field ecology of the fungus. Transgenic approaches are being undertaken in several industry and academic laboratories to prevent invasion byAspergillus fungi or to prevent biosynthesis of aflatoxin. Recent trends in reducing aflatoxin contamination through genetic engineering of cultivated crop species with antifungal proteins are summarized in this report. Presented at the EU-USA Bilateral Workshop on Toxigenic Fungi & Mycotoxins, New Orleans, USA, July 5–7, 2005     

Variations and Transmission of QTL Alleles for Yield and Fiber Qualities in Upland Cotton Cultivars Developed in China

Cotton is the world’s leading cash crop, and genetic improvement of fiber yield and quality is the primary objective of cotton breeding program. In this study, we used various approaches to identify QTLs related to fiber yield and quality. Firstly, we constructed a four-way cross (4WC) mapping population with four base core cultivars, Stoneville 2B, Foster 6, Deltapine 15 and Zhongmiansuo No.7 (CRI 7), as parents in Chinese cotton breeding history and identified 83 QTLs for 11 agronomic and fiber quality traits. Secondly, association mapping of agronomical and fiber quality traits was based on 121 simple sequence repeat (SSR) markers using a general linear model (GLM). For this, 81 Gossypium hirsutum L. accessions including the four core parents and their derived cultivars were grown in seven diverse environments. Using these approaches, we successfully identified 180 QTLs significantly associated with agronomic and fiber quality traits. Among them were 66 QTLs that were identified via linkage disequilibrium (LD) and 4WC family-based linkage (FBL) mapping and by previously published family-based linkage (FBL) mapping in modern Chinese cotton cultivars. Twenty eight and 44 consistent QTLs were identified by 4WC and LD mapping, and by FBL and LD mapping methods, respectively. Furthermore, transmission and variation of QTL-alleles mapped by LD association in the three breeding periods revealed that some could be detected in almost all Chinese cotton cultivars, suggesting their stable transmission and some identified only in the four base cultivars and not in the modern cultivars, suggesting they were missed in conventional breeding. These results will be useful to conduct genomics-assisted breeding effectively using these existing and novel QTL alleles to improve yield and fiber qualities in cotton.     

不同抗虫遗传背景对棉花经济性状的影响

为培育高产、优质、抗病虫的棉花新品种,本实验以一组转基因抗虫棉为材料,对不同类型抗虫棉的经济性状,农艺性状,早熟性,抗红铃虫和抗黄萎病进行了研究。结果表明,转(Bt CpTI)基因抗虫杂交棉新组合667表现为高产,纤维品质优良,高抗红铃虫、耐黄萎病,综合性状好。在参试材料中,双价抗虫棉优于单价(Bt)抗虫棉;杂交抗虫棉优于常规抗虫棉。利用外源抗虫基因转导的棉花新材料为杂交亲本,可以培育出丰产优质的高抗虫的棉花新品种。     

Silencing GhNDR1 and GhMKK2 compromises cotton resistance to Verticillium wilt

Cotton is an important cash crop worldwide, and is a significant source of fiber, feed, foodstuff, oil and biofuel products. Considerable effort has been expended to increase sustainable yield and quality through molecular breeding and genetic engineering of new cotton cultivars. Given the recent availability of the whole-genome sequence of cotton, it is necessary to develop molecular tools and resources for large-scale analysis of gene functions at the genome-wide level. We have successfully developed an Agrobacterium-mediated virus-induced gene silencing (VIGS) assay in several cotton cultivars with various genetic backgrounds. The genes of interest were potently and readily silenced within 2 weeks after inoculation at the seedling stage. Importantly, we showed that silencing GhNDR1 and GhMKK2 compromised cotton resistance to the infection by Verticillium dahliae, a fungal pathogen causing Verticillium wilt. Furthermore, we developed a cotton protoplast system for transient gene expression to study gene functions by a gain-of-function approach. The viable protoplasts were isolated from green cotyledons, etiolated cotyledons and true leaves, and responded to a wide range of pathogen elicitors and phytohormones. Remarkably, cotton plants possess conserved, but also distinct, MAP kinase activation with Arabidopsis upon bacterial elicitor flagellin perception. Thus, using gene silencing assays, we have shown that GhNDR1 and GhMKK2 are required for Verticillium resistance in cotton, and have developed high throughput loss-of-function and gain-of-function assays for functional genomic studies in cotton.     

植物抗虫基因工程研究进展

植物抗虫基因工程为防治农业害虫提供了一条崭新途径。本文对植物抗虫基因工程近年来所取得的某些研究进展,包括目前已发现和利用的抗虫基因、提高抗虫基因在植物体内表达的方法以及防止或延缓害虫产生抗性的策略等方面进行了综合评述,并对植物抗虫基因工程中有待解决的问题和发展前提提出了自己的看法。     

Genetic approaches to sustainable pest management in sugar beet (Beta vulgaris)

Sugar beet (Beta vulgaris) is an important arable crop, traditionally used for sugar extraction, but more recently, for biofuel production. A wide range of pests, including beet cyst nematode (Heterodera schachtii), root‐knot nematodes (Meloidogyne spp.), green peach aphids (Myzus persicae) and beet root maggot (Tetanops myopaeformis), infest the roots or leaves of sugar beet, which leads to yield loss directly or through transmission of beet pathogens such as viruses. Conventional pest control approaches based on chemical application have led to high economic costs. Development of pest‐resistant sugar beet varieties could play an important role towards sustainable crop production while minimising environmental impact. Intensive Beta germplasm screening has been fruitful, and genetic lines resistant to nematodes, aphids and root maggot have been identified and integrated into sugar beet breeding programmes. A small number of genes responding to pest attack have been cloned from sugar beet and wild Beta species. This trend will continue towards a detailed understanding of the molecular mechanism of insect–host plant interactions and host resistance. Molecular biotechnological techniques have shown promise in developing transgenic pest resistance varieties at an accelerated speed with high accuracy. The use of transgenic technology is discussed with regard to biodiversity and food safety.     

Genome editing for resistance against plant pests and pathogens

The conventional breeding of crops struggles to keep up with increasing food needs and ever-adapting pests and pathogens. Global climate changes have imposed another layer of complexity to biological systems, increasing the challenge to obtain improved crop cultivars. These dictate the development and application of novel technologies, like genome editing (GE), that assist targeted and fast breeding programs in crops, with enhanced resistance to pests and pathogens. GE does not require crossings, hence avoiding the introduction of undesirable traits through linkage in elite varieties, speeding up the whole breeding process. Additionally, GE technologies can improve plant protection by directly targeting plant susceptibility (S) genes or virulence factors of pests and pathogens, either through the direct edition of the pest genome or by adding the GE machinery to the plant genome or to microorganisms functioning as biocontrol agents (BCAs). Over the years, GE technology has been continuously evolving and more so with the development of CRISPR/Cas. Here we review the latest advancements of GE to improve plant protection, focusing on CRISPR/Cas-based genome edition of crops and pests and pathogens. We discuss how other technologies, such as host-induced gene silencing (HIGS) and the use of BCAs could benefit from CRISPR/Cas to accelerate the development of green strategies to promote a sustainable agriculture in the future.

     

Genetic transformation of wheat: current status and future prospects

Genetic transformation is a reverse genetics tool for validation of target genes and crop improvement. However, due to its low efficiency and genotype dependency, wheat is considered a recalcitrant plant for genetic transformation. During the last 20 years, various in vitro and in planta transformation methods have been reported in wheat. Until now, biolistic particle and Agrobacterium-mediated wheat transformation methods using immature embryos as explants have been the two major transformation approaches. In addition to immature embryos, other explant types, such as mature embryos, anther-derived calli, inflorescences, apical meristems, and other floral organs, have been employed; however, they need further optimization. In addition to the common marker genes, such as bar, hpt and gus, other effective markers, ALS, AtMYB12 and pmi, have been successfully used for selection of positive transgenic plants. Numerous agronomic trait genes such as biotic stress resistance or tolerance genes have been transferred into wheat plants. Future prospects, such as recipient wheat cultivars and explants, marker free issues, and transgene silencing, are discussed. The objective of this review is to summarize current successful techniques for wheat transformation and stimulate further research into long-term wheat improvement by genetic engineering approaches.     

High-resolution sequencing of nine elite upland cotton cultivars uncovers genic variations and breeding improvement targets

Structural variations (SVs) are critical factors affecting genome evolution and important traits. However, identification results and functional analyses of SVs in upland cotton are rare. Here, based on the genetic relationships, breeding history and cumulative planting area of upland cotton in China, nine predominant cultivars from the past 60 years (1950s–2010s) were selected for long read sequencing to uncover genic variations and breeding improvement targets for this crop. Based on the ZM24 reference genome, 0.88–1.47 × 10⁴ SVs per cultivar were identified, and an SV set was constructed. SVs affected the expression of a large number of genes during fiber elongation, and a transposable element insertion resulted in the glandless phenotype in upland cotton. Six widespread inversions were identified based on nine draft genomes and high-throughput chromosome conformation capture data. Multiple haplotype blocks that were always associated with aggregated SVs were demonstrated to play a pivotal role in the agronomic traits of upland cotton and drove its adaptation to the northern planting region. Exotic introgression was the source of these haplotype blocks and increased the genetic diversity of upland cotton. Our results enrich the genome resources of upland cotton, and the identified SVs will promote genetic and breeding research in cotton.     

Production of transgenic rice with agronomically useful genes: an assessment

Rice is the most important food crop in tropical and subtropical regions of the world. Yield enhancement to increase rice production is one of the essential strategies to meet the demand for food of the growing population. Both abiotic and biotic features limit adversely the productivity of rice growing areas. Conventional breeding has been an effective means for developing high yielding varieties, however; it is associated with its own limitations. It is envisaged that recent trends in biotechnology can contribute to the agronomic improvement of rice in terms of yield and nutritional quality as a supplement to traditional breeding methods. Genetic transformation of rice has demonstrated numerous important opportunities resulting in the genetic improvement of existing elite rice varieties and production of new plant types. Significant advances have been made in the genetic engineering of rice since the first transgenic rice plant production in the late 1980s. Several gene transfer protocols have been employed successfully for the introduction of foreign genes to rice. In more than 60 rice cultivars belonging to indica, japonica, javanica, and elite African cultivars, the protocol has been standardized for transgenic rice production. Selection and use of appropriate promoters, selectable markers, and reporter genes has been helpful for development of efficient protocols for transgenic rice in a number of rice cultivars. The present review is an attempt to assess the current state of development in transgenic rice for the transfer of agronomically useful genes, emphasizing the application and future prospects of transgenic rice production for the genetic improvement of this food crop.     

外源基因转化棉花育种研究的进展与应用

棉花作为重要的经济作物,新品种的选育和应用对于促进棉花生产至关重要。通过转基因技术将外源基因转化棉花,是棉花育种的新手段。尤其是抗逆、抗除草剂、抗虫、抗病和提高棉花品质的转基因技术研究,有助于加速棉花新品种的培育。棉花的转基因技术主要包括农杆菌介导法、基因枪轰击法和花粉管通道法。利用不同的转基因技术在棉花外源基因遗传转化的育种研究中取得了明显成效,探讨外源基因转化棉花育种研究的进展与应用,为新疆陆地棉的转基因育种研究提供重要参考。     

The influence of genetics on future crop production strategies: from traits to genes, and genes to traits

This paper discusses how a genetical approach to plant physiology can contribute to research underpinning the production of new crop varieties. It highlights the interactions between genetics and plant breeding and how the current advances in genetics and the new science of genomics can contribute to our understanding of the genetical control of key agronomic traits ‐ the process of ‘translating’ traits to identified and mapped genes. Advances in genomics, such as the sequencing of whole genomes and expressed sequence tags, are producing information on genes and gene structures, but without knowing their function. A great deal more biology will be necessary to translate gene structure to function ‐ the process of translating genes to traits. Combining these ‘forward’ and ‘reverse’ genetic approaches will allow us to get comprehensive knowledge of the biology of agronomic traits at the physiological, biochemical and molecular levels, so that the ‘circuitry’ of our crop plants can be elucidated. This will enable plant breeders to manipulate crop phenotype using marker‐assisted breeding or genetic engineering approaches with a precision not previously possible.     

Genetic mapping and quantitative trait locus analysis of fiber quality traits using a three-parent composite population in upland cotton (Gossypium hirsutum L.)

Composite cross populations (CP) developed from three or more cultivars/lines are frequently used to improve agronomic and economic traits in crop cultivar development programs. Employing CP in linkage map construction and quantitative trait locus (QTL) mapping may increase the marker density of upland cotton (Gossypium hirsutum L.) genetic maps, exploit more adequate gene resources and facilitate marker-assisted selection (MAS). To construct a relatively high-density map and identify QTL associated with fiber quality traits in upland cotton, three elite upland cultivars/lines, Yumian 1, CRI 35 and 7,235, were used to obtain the segregating population, Yumian 1/CRI 35//Yumian 1/7,235. A genetic map containing 978 simple sequence repeat (SSR) loci and 69 linkage groups was constructed; the map spanned 4,184.4 cM, covering approximately 94.1% of the entire tetraploid cotton genome. A total of 63 QTL were detected, explaining 8.1–55.8% of the total phenotypic variance: 11 QTL for fiber elongation, 16 QTL for fiber length, 9 QTL for fiber micronaire reading, 10 QTL for fiber strength and 17 QTL for fiber length uniformity. The genetic map and QTL detected for fiber quality traits are promising for further breeding programs of upland cotton with improved fiber quality.     

Transgenic cotton resistant to herbicide bialaphos

Resistance to bialaphos, a non-selective herbicide, was intro duced into cotton through genetic engineering. A gene encoding phosphinothric in acetyltransferase (bar) from Streptomyces hygroscopicus was inserted into elite varieties of cotton through particle bombardment. Based on the marker gene, -glucuronidase (gus) expression, a total of 18 Pima (Gossypium barbadense), 45 DP50 (G. hirsutum L.), 20 Coker 312 (G. hirsutum) and 2 El Dorado (G. hirsutum) transgenic plants were recovered. Integration of the bar gene into cotton genomic DNA was confirmed by Southern blot analysis and gene expression was confirmed by northern blot and enzyme assays. Herbicide (Basta®) tolerance up to 15 000 ppm was demonstrated in greenhouse trials. The newly introduced herbicide tolerance trait is inherited in a Mendelian fashion in the progenies of germline transformants. This study demonstrates the potential for particle bombardment to introduce commerically important genes directly into elite varieties of cotton. This mode of gene transfer can expedite the introduction of transgenic cotton products into world markets     

Correlation of vector Aphids activity,physiological characteristics and environmental condition with the severity of PVY and PLRV viruses on potato cultivars

Abstract

Aphids have serious damage and well known of the most important pests, which may transmit different viruses on potato. Potato has immense significance as a food crop throughout the world. In the last research, the most important and different aspects of predominant potato varieties; Agria, Arinda, Fontane, Banba and Sante were studied during 2015–2016 in Karaj, Iran. This research has been conducted into several disparate categories: the effect of environmental conditions on the physiological trends, aphid characteristics and virus infection. The results showed that potato fields had an increasing trend to the end of season in the aspect of infestation by Aphis gossypii Glover and Myzus persicae Sulzer. The potato cultivars showed the same reaction in the lab and no host preference was observed between them against cotton aphid (A. gossypii). Finally, Arinda, and Agria varieties had the most photosynthesis activity, chlorophyll concentration, and leaf dry weight values and had the least electrical conductivity and susceptibility to some potato virus diseases. These results may help to provide better potato varieties by considering to the important physiological characteristic related to some destructive pests.     

The development and application of molecular markers for abiotic stress tolerance in barley

This article represents some current thinking and objectives in the use of molecular markers to abiotic stress tolerance. Barley has been chosen for study as it is an important crop species, as well as a model for genetic and physiological studies. It is an important crop and, because of its well-studied genetics and physiology, is an excellent candidate in which to devise more efficient breeding methods. Abiotic stress work on cultivated gene pools of small grain cereals frequently shows that adaptive and developmental genes are strongly associated with responses. Developmental genes have strong pleiotropic effects on a number of performance traits, not just abiotic stresses. One concern is that much of the genetic variation for improving abiotic stress tolerance has been lost during domestication, selection and modern breeding, leaving pleiotropic effects of the selected genes for development and adaptation. Such genes are critical in matching cultivars to their target agronomic environment, and since there is little leverage in changing these, other sources of variation may be required. In barley, and many other crops, greater variation to abiotic stresses exists in primitive landraces and related wild species gene pools. Wild barley, Hordeum spontaneum C. Koch is the progenitor of cultivated barley, Hordeum vulgare L. and is easily hybridized to H. vulgare. Genetic fingerprinting of H. spontaneum has revealed genetic marker associations with site-of-origin ecogeographic factors and also experimentally imposed stresses. Genotypes and collection sites have been identified which show the desired variation for particular stresses. Doubled haploid and other segregating populations, including landrace derivatives have been used to map genetically the loci involved. These data can be used in molecular breeding approaches to improve the drought tolerance of barley. One strategy involves screening for genetic markers and physiological traits for drought tolerance, and the associated problem of drought relief-induced mildew susceptibility in naturally droughted fields of North Africa.     

抗真菌植物基因工程的策略和进展

所有高等植物都受多种真菌的侵害,水稻的240多种病害中真菌性痫害占90％。,可见真菌病害是世界范围内危害作物产蘑的主要因素之一,是长期以来作物育种学家一直在努力攻克的难题。目前国     

Direct DNA transfer using electric discharge particle acceleration (ACCELL™ technology)

Direct DNA transfer methods based on particle bombardment have revolutionized plant genetic engineering. Major agronomic crops previously considered recalcitrant to gene transfer have been engineered using variations of this technology. In many cases variety-independent and efficient transformation methods have been developed enabling application of molecular biology techniques to crop improvement. The focus of this article is the development and performance of electric discharge particle bombardment (ACCELL™) technology. Unique advantages of this methodology compared to alternative propulsion technologies are discussed in terms of the range of species and genotypes that have been engineered, and the high transformation frequencies for major agronomic crops that enabled the technology to move from the R&D phase to commercialization. Creation of transgenic soybeans, cotton, and rice will be used as examples to illustrate the development of variety-independent and efficient gene transfer methods for most of the major agronomic crops. To our knowledge, no other gene transfer method based on particle bombardment has resulted in variety-independent and practical generation of large numbers of independently-derived crop plants. ACCELL™ technology is currently being utilized for the routine transfer of valuable genes into elite germplasm of soybean, cotton, bean, rice, corn, peanut and woody species.