Genetic Resources (Including Wild and Cultivated Solanum Species) and Progress in their Utilisation in Potato Breeding

The genetic resources available for the improvement of the cultivated potato (Solanum tuberosum) are reviewed along with progress in their utilisation. The conclusions are as follows. The wild and cultivated species of potato have been utilised in potato breeding to good effect, but only a very small sample of the available biodiversity has been exploited. New knowledge and technology will open possibilities for much greater use of these genetic resources in breeding. The strategy for utilising the cultivars native to Latin America will either be the introgression of desirable genes or the direct use of parents from improved populations, depending on how far modern S. tuberosum cultivars have genetically diverged from them and the extent to which S. tuberosum cultivars have been improved in the process. Molecular marker-assisted selection will be used for faster introgression of desirable genes from wild species, and the possibility exists of moving genes directly from wild species to cultivated potato with transgenic methods. New cultivars will continue to come from crosses between pairs of parents with complementary features but adapted to local growing conditions. However, increasingly these parents will possess desirable genes which have been introgressed from wild species and may also be from complementary groups of cultivated germplasm to exploit hybrid vigour. Successful cultivars may be genetically modified, if consumers see benefits in the use of the technology, to introduce genes not present in cultivated potatoes and their wild relatives to achieve novel biochemistry and further desirable improvements.     

Societal Costs of Late Blight in Potato and Prospects of Durable Resistance Through Cisgenic Modification

In the European Union almost 6 Mha of potatoes are grown representing a value of close to €6,000,000,000. Late blight caused by Phytophthora infestans causes annual losses (costs of control and damage) estimated at more than €1,000,000,000. Chemical control is under pressure as late blight becomes increasingly aggressive and there is societal resistance against the use of environmentally unfriendly chemicals. Breeding programmes have not been able to markedly increase the level of resistance of current potato varieties. New scientific approaches may yield genetically modified marker-free potato varieties (either trans- and/or cisgenic, the latter signifying the use of indigenous resistance genes) as improved variants of currently used varieties showing far greater levels of resistance. There are strong scientific investments needed to develop such improved varieties but these varieties will have great economic and environmental impact. Here we present an approach, based on (cisgenic) resistance genes that will enhance the impact. It consists of five themes: the detection of R-genes in the wild potato gene pool and their function related to the various aspects in the infection route and reproduction of the late blight causing pathogen; cloning of natural R-genes and transforming cassettes of single or multiple (cisgenic) R-genes into existing varieties with proven adaptation to improve their value for consumers; selection of true to the wild type and resistant genotypes with similar qualities as the original variety; spatial and temporal resistance management research of late blight of the cisgenic genetically modified (GM) varieties that contain different cassettes of R-genes to avoid breaking of resistance and reduce build-up of epidemics; communication and interaction with all relevant stakeholders in society and transparency in what research is doing. One of the main challenges is to explain the different nature and possible biological improvement and legislative repercussions of cisgenic GM-crops in comparison with transgenic GM-crops. It is important to realize that the present EU Directive 2001/18/EC on GM crops does not make a difference between trans- and cisgenes. These rules were developed when only transgenic GM plants were around. We present a case arguing for an updating and refinement of these rules in order to place cisgenic GM-crops in another class of GM-plants as has been done in the past with (induced) mutation breeding and the use of protoplast fusion between crossable species.     

环介导等温扩增技术及其在转基因作物检测中的应用

转基因作物及其产品的安全性一直存在着较大的争议,人们对转基因产品仍持谨慎态度。因此,快速、准确、灵敏的转基因检测手段对转基因生物的安全监管至关重要。环介导等温扩增(LAMP)是一种恒温核酸扩增的技术,其设备简单、成本低廉、结果可视化,且灵敏度高,现已广泛应用于细菌、病毒、寄生虫、转基因等检测行业。介绍了LAMP技术的原理、特点和联合应用其他技术,及其在转基因作物与产品检测方面的应用情况。     

Genetic variation of wild rice populations from Thailand and the Lao PDR based on molecular markers

The two wild rice species, Oryza rufipogon and O. nivara, which inhabit Thailand and the Lao PDR, are threatened with the loss of their natural habitats. The losses are primarily attributable to human intervention. Before this process advances, it is crucial to obtain basic information on the genetic variations of these species, so important knowledge about the current status of genetic variability. In this study, genetic variation within and between fourteen natural populations of the two populations from Thailand and Lao PDR was investigated at the DNA level by analysis of Polymerase Chain Reaction (PCR) mediate molecular markers. The results illustrated that wild rice from Thailand carried deletion (D) type ORF 100, but deletion and non-deletion type (ND) were found in wild rice samples from the Lao PDR. Five different plastid subtypes (7C7A, 6C8A, 7C6A, 6C7A and 9C7A) were found in the collected samples. Both polymorphism and pattern of distribution of p-SINE1-r2 in the two wild rice species were found among the populations. These data indicated that genetic variation existed in these natural populations of wild rice, suggesting that the strategies should be developed that are conducive to the conservation of wild rice in its natural environment.     

Comparison of reputed duplicate populations in the Russian and US Potato Genebanks using RAPD Markers

The Association of Potato Intergenebank Collaborators (APIC) produced a global inventory of wild potato genetic resources that is available on the Internet (www.potgenebank.org/ipd). This database shows that, in many cases, several genebanks have samples of the progeny from a single original germplasm collection. The assumption has been that these samples are genetically equivalent, so all the characterization and evaluation data gathered on a seedlot from one genebank can be applied to all the other “duplicate” seedlots in other genebanks. This assumption was tested by comparing 25 pairs of reputed duplicates in the VIE (St. Petersburg, Russia) and US (Sturgeon Bay, USA) potato genebanks using RAPDs. In 23 of 25 populations, reputed duplicates among genebanks had significantly less similarity than replicate samples taken from a single population. The average genetic similarity of reputed duplicates was 93%, and the lowest was 81%. Thus, users of germplasm should be aware that reputed duplicate populations from these genebanks may not be genetically identical.     

转mEPSPS基因甘蓝型油菜对根际土壤细菌群落结构和多样性的影响

转基因作物外源基因的表达是否会对土壤微生物生态系统产生不利影响是转基因作物环境安全评价中的重要一环,也关系到作物新品种的应用与推广.为此,本文采用第三代16S扩增子高通量测序技术,对转mEP-SPS基因的甘蓝型油菜甲HX6及其亲本甲9707不同发育阶段的根际土壤细菌群落进行了比较分析.结果显示,样品中油菜根际的优势细菌...     

Wild halophytic species as forage sources: Key aspects for plant breeding

The use of wild halophytic species as forage resources in saline environments has gained increasing attention. Argentina ranks third in area of saline soils in the world, with a third of its territory showing various degrees of salinity, sodicity and/or alkalinity. On this type of soils, rangelands are the main forage resource for livestock production. Many wild species have forage potential and can also be used for the rehabilitation of rangelands and for intercropping. Information about these species, as well as on the physiological and genetic bases associated with salinity tolerance, provides relevant tools for efficient selection methods. This study addresses Argentine wild halophyte species with forage potential and describes selection criteria with an emphasis on the following taxa: (a) Poaceae: subfamily Chloridoideae and tribes Paniceae and Triticeae, (b) Fabaceae and (c) Amaranthaceae (formerly known as Chenopodiaceae). The review is intended to contribute to the general discussion on strategies for the improvement of wild plant genetic resources, using forage species naturally growing in saline soils in Argentina as a case study.     

Salt tolerance inSolanum kurzianum andS. tuberosum cvs Alpha and Russet Burbank

Summary The cultivated potatoSolanum tuberosum cvs Alpha and Russet Burbank and the wild speciesS. kurzianum were compared with respect to salt tolerance. Plants of the wild species were found to be more salt tolerant than those of the cultivated species since their growth was less impaired by the salinity, although they accumulated more sodium and less potassium ions in the shoot. Unlike the whole plant, callus derived from the wild plants was not more tolerant than that from the cultivated species. Differences in the responses to salinity between cultivated and wild plants, and between the whole plants and calli derived from them are discussed. Based on these differences and the similarity of the physiological responses to salt stress betweenS. kurzianum and the wild salt-tolerant relatives of tomato, the former is suggested as a potential source of genes for increasing the salt tolerance of potato.     

Cisgenesis,a New Tool for Traditional Plant Breeding,Should be Exempted from the Regulation on Genetically Modified Organisms in a Step by Step Approach

Modern potato breeding requires over 100,000 seedlings per new variety. Main reasons are (1) the increasing number of traits that have to be combined in this tetraploid vegetatively propagated crop, and (2) an increasing number of traits (e.g., resistance to biotic stress) originates from wild species. Pre-breeding by introgression or induced translocation is an expensive way of transferring single traits (such as R-genes, coding for resistance to biotic stress) to the cultivated plant. The most important obstacle is simultaneous transfer of undesired neighbouring alien alleles as linkage drag. Stacking several genes from different wild sources is increasing this linkage drag problem tremendously. Biotechnology has enabled transformation of alien genes into the plant. Initially, transgenes were originating mainly from microorganisms, viruses or non-crossable plant species, or they were chimeric. Moreover, selection markers coding for antibiotic resistance or herbicide resistance were needed. Transgenes are a new gene source for plant breeding and, therefore, additional regulations like the EU Directive 2001/18/EC were developed. Because of a strong opposition against genetic modification of plants in Europe, the application of this Directive is strict, very expensive, hampering the introduction of genetically modified (GM) crops and the use of this technology by small and medium-sized enterprises (SMEs). Currently, GM crops are almost the exclusive domain of multinationals. Meanwhile, not only transgenes but also natural genes from the plant species itself or from crossable plant species, called cisgenes, are available and the alien selection genes can be avoided in the end product. This opens the way for cisgenic crops without alien genes. The existing EU directive for GM organisms is not designed for this new development. The cisgenes belong to the existing breeders’ gene pool. The use of this classical gene pool has been regulated already in agreements regarding breeders’ rights. We are proposing a step by step approach starting with a crop and gene specific derogation and monitoring towards a general exemption of cisgenic plants from the Directive. Two examples, i.e. development of cisgenic potato for resistance to Phytophthora infestans and cisgenic apple for resistance to Venturia inaequalis are discussed shortly for illustration of the importance of cisgenesis as a new tool for traditional plant breeding. Cisgenesis is simplifying introgression and induced translocation breeding tremendously and is highly recommended for SMEs and developing countries.     

苎麻属植物资源的搜集、保存与开发利用

1995年以来,我所在我国长江流域及以南14个省(市)、自治区搜集到荨麻科植物资源222份,其中苎麻属130份,分属19个种7个变种。根据形态特征,将已搜集到的苎麻属植物划分为腋球苎麻组、帚序苎麻组、苎麻组、序叶苎麻组和大叶苎麻组五个组。苎麻属植物的种群分布与海拔高度有关,按其生态特点可分为湿生性、湿中性、半阴湿性和旱生性四大生态类型。来自于不同地域、不同气候和生态环境的苎麻属植物,异地保存时有的不易成活,建圃保存时要从水分、光照、温度上创造有利条件,满足其生长发育需要。     

Antiviral activities and putative identification of compounds in microbial extracts from the Hawaiian coastal waters

Marine environments are a rich source of significant bioactive compounds. The Hawaiian archipelago, located in the middle of the Pacific Ocean, hosts diverse microorganisms, including many endemic species. Thirty-eight microbial extracts from Hawaiian coastal waters were evaluated for their antiviral activity against four mammalian viruses including herpes simplex virus type one (HSV-1), vesicular stomatitis virus (VSV), vaccinia virus and poliovirus type one (poliovirus-1) using in vitro cell culture assay. Nine of the 38 microbial crude extracts showed antiviral potencies and three of these nine microbial extracts exhibited significant activity against the enveloped viruses. A secosteroid, 5α(H),17α(H),(20R)-beta-acetoxyergost-8(14)-ene was putatively identified and confirmed to be the active compound in these marine microbial extracts. These results warrant future in-depth tests on the isolation of these active elements in order to explore and validate their antiviral potential as important therapeutic remedies.     

RAPD analysis of genetic diversity inSolanum populations to predict need for fine screening

Populations of two wild potato species known to have high levels of green peach aphid, PLRV, and PVY resistance (Solanum polytrichon PI 184170 andS. stoloniferum PI 160226) were assessed for heterogeneity of RAPD markers among plants within these populations and among other populations of the same species. These species are reputed selfers, so were suspected of being relatively inbred. About 75% of the bands segregating within their species were fixed within these populations, and more than 90% of the total bands observed within these populations were fixed. These levels of homogeneity were not significantly different from those of an inbred population ofS. albicans known to be extremely homogeneous. It can be expected that populations such as these, that are relatively homogeneous, are also more likely to be homogeneous for specific traits of interest. Thus, there may be less need for rigorous fine screening of these materials at the genotype level before making breeding crosses.     

Resistance of wild rices, Oryza spp., to the brown planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae)

Of the 128 wild rices screened, 83 accessions were resistant to the brown planthopper Nilaparvata lugens (Stål). Resistant accessions were non-preferred and significantly more individuals settled on susceptible TN1 plants than on resistant ones. The quantity of food ingested and assimilated by N. lugens on resistant accessions was less than on susceptible TN1. N. lugens caged on resistant accessions had slow nymphal development, reduced longevity and low fecundity. Two wild rice species, Oryza officinalis and O. punctata, reduced the percentage hatchability of N. lugens eggs. A significant reduction in population growth was observed on resistant accessions compared with susceptible TN1.     

Identification of late blight, Colorado potato beetle, and blackleg resistance in three Mexican and two South American wild 2x (1EBN)Solanum species

Wild potatoes are important sources of genes for resistance to disease and insect pests. A collection of wild Mexican and South AmericanSolarium species from the US potato Genebank was evaluated under laboratory and/or field conditions for their reaction to late blight (Phytophthora infestans), Colorado potato beetle (CPB,Leptinotarsa decemlineata Say), and blackleg (Erwinia carotovora subsp.atroseptica (van Hall) Dye) in order to identify individual genotypes with multiple resistance genes. Late blight inoculations using aggressive isolates (US-8/A2 and US-11/A1 mating types) of P.infestans revealed a wide range of variation for resistance between and within the accessions of the wild species tested. For late blight, susceptible as well as moderately to highly resistant genotypes were observed in all the species tested. However, at least one accession from the three Mexican and one South American wild diploid species tested showed a relatively uniform high level of resistance toP. infestans. These includedS. bulbocastanum, S. pinnatisectum, S. cardiophyllum, andS. circaeifolium. Two accessions from South American speciesS. commersonii were highly susceptible to late blight. For the Colorado potato beetle test, only one species,S. pinnatisectum appeared uniformly resistant to CPB under field conditions. Results of screening for blackleg resistance showed that there were major differences between genotypes in the wild species. Accessions ofS. circaeifolium PI 498119 andS. bulbocastanum PI 243504 were identified as having significantly higher blackleg resistance than cultivated potato and the other wild species tested. However, genotypes from these two accessions were more susceptible to late blight and CPB. Characterization of theP. infestans isolate P1801C.16 used for late blight evaluation and multi-locus isolate tests using US-8/A2 and US-11/A1 races revealed that the resistance inS. pinnatisectum genotypes tested corresponded to a race-non-specific genetic system, which was different from any existing R genes.Solanum pin-natisectum genotypes with both high levels of late blight and CPB resistance as well as blackleg resistance genotypes identified in the present study represent a diverse gene pool that may be useful for development of new potato cultivars with multiple disease and insect resistance. The potential utilization of these valuable sources for improvement of cultivated potato is discussed.     

Genetic equivalence of putative duplicate germplasm collections held at CIP and US potato genebanks

A common effort among members of the Association of Potato Inter-Genebank Collaborators (APIC) has yielded a global inventory of wild potato genetic resources that is freely accessible to researchers and breeders. In that database there are a number of accessions that originated from distributed progeny of a single original germplasm collection. The logical assumption has been that although these samples are in different locations, they should be genetically equivalent. This study tests this hypothesis by comparing 17 pairs of accessions of 16 different potato species, which are reputed duplicates preserved in the potato genebanks of The International Potato Center (CIP) in Peru and of the U.S.A. (USPG). The RAPD marker analysis revealed that even though the average genetic similarity of reputed duplicates was quite high, there were a few with significant differences. Similarly, SSR markers identified three reputed duplicates that were genetically different. SSRs revealed a loss of markers for some inter-genebank comparisons, a probable indication of genetic drift. Duplicate potato collections between CIP and USPG are in most cases genetically identical. The few exceptions merit further investigation regarding causes and the impact on useful traits.     

Potato viruses in China

Potato (Solanum tuberosum L.) is globally the fourth largest staple crop after rice, wheat and maize. China is the largest potato producer worldwide, accounting for 26.3% and 22.2% of the global total area and yield, respectively. Viral diseases have been a limiting factor for sustainable production of potato in China. This article provides update and comprehensive information on the most important viruses, their effect on yield and their control in China. Meristem culture is currently the most widely used technique for production of virus-free potato plants and these plants are used as nuclear stock for the production of certified seed tubers. Although a significant increase in tuber yield has been achieved using certified seed potatoes, lack of application of a national seed potato production scheme has hindered progress. Conventional breeding using virus-resistant cultivars introduced from other countries as parents has already led to the production of Chinese cultivars. Use of virus-resistant wild Solanum species and genetic transformation techniques will provide new virus-resistant varieties in the future to further enhance control of potato viruses in China.     

WildSolanum species as resistance sources against different pathogens of potato

Summary Resistance screenings againstPhytophthora infestans, Globodera pallida Pa2/3 and the viruses PVY^N, PLRV, PVM and PVS were performed in 98 accessions belonging to 90Solanum wild species. Seventy accessions showed resistance or partial resistance to one or several of these pathogens. Among themS. brachistotrichum exhibited combined resistance to nematodes, late blight and some of the viruses evaluated. Only part of the resistances previously found in different wild species could be confirmed, which might be due to the existing variability within species, the use of different pathogen strains or isolates, or to different methodologies for resistance screening. Several new resistance sources, such asS. andreanum, S. maglia. S. doddsii andS. boliviense, are provided for the different pathogens analyzed. These findings demonstrate that within the gene pool ofSolanum species, still numerous but in part unexploited resistances are available which could be favourably used in potato breeding.     

海南岛兰科植物区系的组成及其特征

海南岛是我国兰科植物分布最集中的地区之一,目前已发现有78属214种。其中,中国特有种31种(包括海南特有种14种),非中国特有种但在中国仅见于海南岛的有20种。种数在10种以上的属有羊耳蒜属(Liparis)、石斛属(Dendrobium)、毛兰属(Eria)、石豆兰属(Bulbophyllum)和兰属(Cymbidium)。海南岛兰科植物属的地理成分可划分为12个分布型和变型,其中热带亚洲成分占总属数的51.3%,热带分布属有71属,占绝对优势。海南岛兰科植物的生活型多样,附生兰有43属,地生兰有32属,腐生兰5属(其中羊耳蒜属和兰属中存在附生和地生2种生活型)。多个种在叶型和花色上变异较大,可作为优良育种材料。与邻近地区相比,海南岛兰科植物与西双版纳共有属最多(为56属),其次依序为台湾、广东、广西和福建。虽然海南岛与台湾和西双版纳同处热带北缘,受热带季风气候影响,但其兰科植物在属、物种和特有种的数量上比后两者要少。总的说来,海南岛的兰科植物区系较为多样,与亚洲热带兰科植物区系亲缘关系密切。     

Pythium soft rot of ginger: Detection and identification of the causal pathogens,and their control

Ginger is considered by many people to be the outstanding member among 1400 other species in the family Zingiberaceae. Not only it is a valuable spice used by cooks throughout the world to impart unique flavour to their dishes but it also has a long track record in some Chinese and Indian cultures for treating common human ailments such as colds and headaches. Ginger has recently attracted considerable attention for its anti-inflammatory, antibacterial and antifungal properties. However, ginger as a crop is also susceptible to at least 24 different plant pathogens, including viruses, bacteria, fungi and nematodes. Of these, Pythium spp. (within the kingdom Stramenopila, phyllum Oomycota) are of most concern because various species can cause rotting and yield loss on ginger at any of the growth stages including during postharvest storage. Pythium gracile was the first species in the genus to be reported as a ginger pathogen, causing Pythium soft rot disease in India in 1907. Thereafter, numerous other Pythium spp. have been recorded from ginger growing regions throughout the world. Today, 15 Pythium species have been implicated as pathogens of the soft rot disease. Because accurate identification of a pathogen is the cornerstone of effective disease management programs, this review will focus on how to detect, identify and control Pythium spp. in general, with special emphasis on Pythium spp. associated with soft rot on ginger.     

Application of Functional Markers to Identify Genes for Bacterial Blight Resistance in Oryza rufipogon

Field resistances of nine accessions of common wild rice (Oryza rufipogon Griff.) and one rice variety (IR24) were evaluated by using nine strains of bacterial blight pathogen (Xanthomonas oryzae pv. oryzae) from the Philippines. IR24 was highly susceptible to all the strains, and six common wild rice accessions resisted all the nine strains, with a resistance frequency of 67%. The accessions Yulin and Wanning were only susceptible to PXO280 and PXO71, respectively. The accession Gaozhou was susceptible to the three strains PXO79, PXO99 and PXO339, whereas resistant to the other six strains. It could be concluded that there is at least one resistance gene in each common wild rice accession. The functional markers of the genes xa5, xa13, Xa21 and Xa27 were used to detect the presence of these resistance genes in the nine tested wild rice accessions, and it was found that four wild rice accessions contained heterozygous xa13. Among the nine common wild rice accessions, five were homozygous for Xa27 and three homozygous for xa27, and the accession Laibin contained neither xa27 nor Xa27. In addition, there were no xa5 and Xa21 in all of these accessions.