基于COI基因解析我国茶网蝽种群遗传多样性和遗传结构

茶网蝽(Stephanitis chinensis)是我国西南茶区的重要害虫，近年有入侵成灾事件发生。为解析茶网蝽的生态适应机制和成灾规律，测定了茶网蝽12个种群共240头成虫COI基因序列，利用Dna SP 6.12.03、Arlequin3.5.2.2、MEGA 7.0.26等软件进行了遗传分化程度、基因流(N_m)以及分子变异情况的分析。结果显示，茶网蝽12个地理种群的240条COI基因序列共包含75个变异位点和38个单倍型，其中仅Hap13是共享单倍型。茶网蝽总群体的单倍型多样性指数(H_d)为0.827 79，地理种群的H_d在0.00～0.85，总群体的遗传分化固定系数(F_ST)为0.864 26,N_m为0.039 87，表明我国茶网蝽群体遗传分化程度较高，基因交流较小。重庆城口、重庆巫溪、湖北恩施、湖北十堰、陕西汉中等5个种群相互之间遗传分化程度较低，基因交流频繁(F_ST<0.06,N_m>4.50)，其他种群对之间...     

基于COI基因的橡胶树六点始叶螨遗传多样性分析

六点始叶螨是橡胶树上的重要害螨之一,具有分布范围广、危害重等特点。为了研究其遗传多样性和遗传分化,本研究利用线粒体COI（mitochondrial cytochrome oxidase subunit I）基因序列对采自海南、云南、越南河内等地区橡胶树上的11个不同地理种群的165头样本进行了种群的遗传多样性分析。获得的六点始叶螨线粒体COI基因片段长度均为658 bp,分析发现可变位点30个,其中简约信息点15个,单变异位点15个,单倍型15种;种群间F_ST值为0.34698,Nm值为0.47,G_ST值为0.19660,表明11个种群的六点始叶螨存在一定的遗传分化。     

多基因序列比较分析海南橡胶树炭疽病菌遗传种群

橡胶树炭疽病是橡胶树上一种重要叶部病害,已知病原菌有胶孢炭疽菌和尖孢炭疽菌,它们是复合种群,群下种类多,遗传多样性丰富。利用ITS、GAPDH、CHS-1和ACT基因的部分序列,对来自海南省橡胶树不同植胶地点的16株炭疽菌,进行基因谱系比较分析。结果显示,采用单基因部分序列和4基因拼接序列都能将供试菌株分为两大类群:胶孢炭疽菌复合群和尖孢炭疽菌复合群。其中,来自于儋州HN06、乐东志仲HN02和保亭大本HN16的3个菌株聚类于尖孢炭疽菌复合群,其余13个菌株聚类于胶孢炭疽菌复合群。4基因拼接序列分析还可以看出,胶孢炭疽菌复合群下参试的9个菌株都属于分支Musae Clade。但是采用单基因或4基因拼接序列均不能将海南橡胶炭疽菌鉴定到复合群下的具体种。     

基于COⅠ基因片段的瓜实蝇遗传多样性分析

瓜实蝇是一种重要入侵害虫,广泛分布于热带和部分亚热带国家和地区,寄主广,危害性大。本研究对中国6个主要分布省份、19个地区瓜实蝇线粒体COⅠ基因中的部分序列进行了测定,分析了种群的遗传学关系并建立系统进化树。结果表明,在获得的640 bp的DNA序列中,可变位点16个,其中简约性信息位点7个,单变异位点9个。Fst值为0.107 88,Nm值为2.07,遗传距离为0~0.001 8。单倍型多样性云南、广西最高。聚类分析发现国内各地理种群间差异不显著。中国19个种群的瓜实蝇存在一定的遗传分化,但分化程度很低。     

东亚和北美裸大麦(青稞)籽粒硬度基因HINA的分子进化分析

随着现代经济社会的发展,裸大麦(青稞)的多元化加工也成为裸大麦(青稞)口粮外的另一类发展趋势,籽粒硬度是决定裸大麦加工用途的一个重要品质性状,HINA基因编码的HINA蛋白是影响籽粒硬度性状的一个重要蛋白。本研究通过对108份来自北美和东亚(中国青藏高原)6个地区裸大麦(青稞)HINA基因进行重测序,结果在群体序列中发现58个多态性位点(包括30个SNP和28个Indel),可以将群体序列分成13种单倍型。其中单倍型1(Hap1)和单倍型4(Hap4)是分布范围最为广泛的2种单倍型。各地区的单倍型多样性指数范围为0.000~0.833,总群体单倍型多样性指数为0.575,各地区核苷酸多样性系数范围为0.000~0.010,总群体的核苷酸多样性系数为0.007,6个地区群体的基因序列配对分化系数(Fst)范围为-0.08~0.16,分子方差分析显示东亚和北美群体的基因遗传变异主要是由群体内的变异为主(总群体中91.16%的基因变异来源于群体内,8.84%的变异来源于群体间)。群体结构分析将所有材料的HINA基因序列分成2个亚群群体。材料的地理来源与亚群分类相关性较低。利用中性检测及错配分析对选择压力与群体HINA基因遗传分化的关系进行考察,发现中性检验值在东亚(中国青藏高原)、北美和总群体中均为负值,同时群体错配曲线为多峰曲线,说明群体在HINA基因位点上是稳定群体,这些结果为了解HINA基因在裸大麦(青稞)遗传特征上的作用提供了理论依据。     

CsSSK1基因调控暹罗炭疽菌胁迫应答和致病性的功能分析

暹罗炭疽菌（Colletotrichum siamense）是热带、亚热带地区许多农林作物炭疽病的主要病原菌。SSK1是双组分系统中的应答调节蛋白,已有研究显示病原真菌中的SSK1与病原菌的形态建成、胁迫反应、耐药性和致病力有关,但在不同菌中其功能存在差异。为了解暹罗炭疽菌中同源基因CsSSK1的功能,本研究利用同源重组法构建了CsSSK1基因缺失突变体ΔCsSSK1和回补菌株ΔCsSSK1(CsSSK1),对其进行表型观察。结果显示：与野生型菌株相比,形态发育上,缺失突变体ΔCsSSK1的菌丝生长速率略有降低,分生孢子较短且产孢量低,孢子萌发率也降低;胁迫应答上,ΔCsSSK1显著提高了炭疽菌对NaCl、山梨醇、蔗糖、葡萄糖、刚果红胁迫的敏感性,提高了对氟康唑和戊唑醇的敏感性,但降低了对咯菌腈的敏感性;致病功能方面,CsSSK1基因缺失明显降低了致病力。研究结果表明CsSSK1基因参与调控暹罗炭疽菌的形态建成,应答盐胁迫、渗透胁迫、刚果红胁迫反应,参与药剂敏感性调控,影响暹罗炭疽菌的致病能力。本研究结果为深入了解暹罗炭疽菌CsSSK1基因功能,解析病原真菌应答胁迫反应的分子机理奠定基...     

玉米耐盐基因ZmHKT1的序列变异分析

HKT(High-affinity potassium transporter,高亲和性钾转运蛋白)基因所编码的蛋白能起到维持植物体内的Na+/K+平衡的作用。在作物中HKT蛋白主要通过排出叶片中的Na+,从而提高植物耐盐性。对54份玉米自交系材料的Zm HKT1基因及上游序列进行多态性分析。结果表明,在3 784 bp的序列中,共有194个SNP和32个In Del。大部分变异集中在基因上游序列和内含子区,编码区的变异相对较少,说明编码区在进化和人工选择中承受了更大的选择压力。根据序列变异情况可将54份玉米自交系材料划分为15个单倍型,上游序列主要存在3种单倍型,而基因序列存在9种单倍型。遗传重组和连锁不平衡分析发现,全长序列只有3次重组事件发生,上游序列存在着非常强的连锁不平衡。     

海南台农芒采后果实炭疽病病原鉴定

刺盘孢属(Colletotrichum)真菌是芒果的重要病原菌。本研究采用形态和分子生物学鉴定了海南省台农芒果实采收后炭疽病的病原菌。从台农芒发病果实上总共分离纯化获得38株刺盘孢属真菌。基于形态学特征和多基因序列(核糖体转录间隔区、钙调蛋白、3-磷酸甘油醛脱氢酶、谷氨酰胺合成酶、肌动蛋白、微管蛋白),确定引起台农芒采后炭疽病的病原为暹罗炭疽菌(C.siamense)、亚洲炭疽菌(C.asianum)和果生炭疽菌(C.fructicola)。其中果生炭疽菌是我国芒果炭疽病原的首次报道。     

暹罗炭疽菌中脂滴包被蛋白Cap20与乙酸激酶CsAck的互作研究

暹罗炭疽菌（Colletotrichum siamense）是一种重要的病原真菌,是我国橡胶树炭疽病（Colletotrichum leaf disease, CLD）的田间优势病原种,也是热带、亚热带地区许多其他农林作物炭疽病的主要病原种。脂滴是细胞的中性脂,存在于绝大多数真核细胞中,是细胞内甘油三酯的主要贮存形式。脂滴在细胞内可以参与脂质代谢、膜转运、蛋白降解和信号传导等。包被蛋白（perilipin）是脂滴表面最丰富的脂质相关蛋白,主要存在于动植物体内,对细胞内脂滴代谢起着重要的调控作用。Cap20是暹罗炭疽菌中包被蛋白的同源蛋白,前期证实Cap20是一个致病相关蛋白,它参与了炭疽菌附着胞膨压形成、脂滴数量和致病性。了解其互作蛋白和互作的生物学意义可能为深入了解脂滴包被蛋白参与的致病分子机制具有重要意义。课题组前期通过酵母双杂交技术在暹罗炭疽菌cDNA文库中筛选到一个与Cap20互作的候选蛋白乙酸激酶,本研究克隆了该乙酸激酶的编码基因,并进行了蛋白结构和同源蛋白聚类分析。结果表明,乙酸激酶编码基因的DNA大小为1312 bp,包括一个内含子,cDNA为1248 bp,编码415个氨基酸,含有一个乙酸激酶结构域,命名为CsAck。然后构建含6×his标签的原核表达载体PET32a-CsAck,利用其和含GST标签的pGEX6p-1-Cap20（先前构建）进行蛋白表达和纯化,获得含有6×His标签的融合蛋白CsAck和含有GST标签的Cap20。通过Pull down验证了Cap20和CsAck蛋白之间的体外互作。最后,构建含有潮霉素转移酶基因HPH的表达载体PXY203-CsAck-S和含有氯嘧磺隆抗性基因ILV1的表达载体pCB1532-GFP-Cap20,将它们共同转化暹罗炭疽菌野生型菌株获得转化子。Co-IP（Co-immunoprecipitation）的结果证实Cap20和CsAck在暹罗炭疽菌中可以相互作用。该结果证实了致病性相关蛋白Cap20和乙酸激酶CsAck在体外和体内均可发生蛋白互作,可为进一步研究Cap20在暹罗炭疽菌中的致病功能和调控机制奠定基础。     

黑龙江省马铃薯晚疫病菌线粒体DNA单倍型分析

为明确黑龙江省马铃薯晚疫病菌线粒体DNA单倍型组成和分布情况,采用PCR-RFLP方法分析了2015～2020年采自黑龙江省7个马铃薯种植区的193份马铃薯晚疫病菌株的线粒体DNA单倍型及频率分布。结果表明,IIa单倍型为优势线粒体DNA单倍型,占比89.12%,Ia和Ib两种单倍型也均有发现,分别占比9.84%和1.04%,所有样品中未发现IIb单倍型。与前人研究相比较,黑龙江省线粒体DNA单倍型存在动态变化,因此,加强对晚疫病菌群体遗传结构的监测,对更好地进行马铃薯晚疫病防控具有重要意义。     

Pharmacokinetics of Marine-Derived Drugs

Marine organisms represent an excellent source of innovative compounds that have the potential for the development of new drugs. The pharmacokinetics of marine drugs has attracted increasing interest in recent decades due to its effective and potential contribution to the selection of rational dosage recommendations and the optimal use of the therapeutic arsenal. In general, pharmacokinetics studies how drugs change after administration via the processes of absorption, distribution, metabolism, and excretion (ADME). This review provides a summary of the pharmacokinetics studies of marine-derived active compounds, with a particular focus on their ADME. The pharmacokinetics of compounds derived from algae, crustaceans, sea cucumber, fungus, sea urchins, sponges, mollusks, tunicate, and bryozoan is discussed, and the pharmacokinetics data in human experiments are analyzed. In-depth characterization using pharmacokinetics is useful for obtaining information for understanding the molecular basis of pharmacological activity, for correct doses and treatment schemes selection, and for more effective drug application. Thus, an increase in pharmacokinetic research on marine-derived compounds is expected in the near future.     

La pourriture fongique des tubercules de pomme de terre en atmosphère contrôlée

Résumé Fusarium culmorum et, dans une moindre mesure,F. avenaceum, F. sambucinum, Colletotrichum coccodes etCylindrocarpon sp. ont été isolés de tubercules entreposés en atmosphère contr?lée (AC) et atteints de pourriture grave. Des expériences d'inoculation de tubercules avec 10 espèces ou variétés fongiques et conservation en AC à 8 et 10°C ont montré que: 1) les champignons non pathogènes en atmosphère normale (ex.:Cylindrocarpon sp.) le devenaient en AC, 2) ceux qui étaient faiblement pathogènes en atmosphère normale étaient nettement plus virulents en AC (ex.:F. culmorum), 3) les espèces ou variétés virulentes en conditions d'air normales (Fusarium sulphureum etPhoma exigua var.foveata) ne provoquaient pas de pourriture plus grave en AC et leur activité pouvait même être légérement freinée.

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Summary The extensive rotting of tubers which occurred during storage trials in controlled atmospheres has led to a mycological and pathological study of the rots. The most frequently isolated species wasFusarium culmorum althoughF. avenaceum, F. Sambucinum, Coletotrichum coccodes and aCylindrocarpon sp. were also present. Tubers of cvs Bintje and Ulla were inoculated with 19 isolates of 10 fungal species or varieties associated with rotting of stored tubers (Table 1). The tubers were incubated at 8 or 10°C in normal or controlled (2% O₂:1% CO₂, 2% O₂:6% CO₂, 2% O₂:12% CO₂, 6% O₂:6% CO₂) atmospheres and the extent of rotting was determined a month later (Tables 2 and 3 and Fig. 2). Species which were weakly virulent in a normal atmosphere (variousFusarium spp. andPhoma exigua var.exigua) were clearly more aggressive in the controlled atmosphere and this was especially evident in the case ofF. culmorum. Species ot pathogenic in a normal atmosphere under experimental conditions (Colletotrichum coccodes, Cylindrocarpon sp.,Phoma eupyrena) caused rotting in the controlled atmosphere. The two species which were virulent in a normal atmosphere (F. sulphureum andP. exigua var.foveata) were also virulent in the controlled atmosphere and in some cases the extent of rotting was even less. As a general rule, rotting caused by weakly virulent fungi was greater in both cultivars in the controlled than in a normal atmosphere.

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Zusammenfassung Eine starke F?ulnis von in Kontrotrollierter Atmosph?re gelagerten Kartoffelknollen veranlasste eine mykologische und pathologische Untersuchung. Der am h?ufigsten isolierte Pilz warFusarium culmorum. F. avenaceum, F. sambucinum, Colletotrichum coccodes undCylindrocarpon sp. wurden ebenfalls bestimmt. Neunzehn St?mme von 10 Pilzsorten oder-Arten welche bei Lagerf?ulnis vorkommen (Tab. 1) wurden auf Knollen der Sorten Bintje und Ulla inokuliert. Die Lagerung wurde bei 8 oder 10°C under Normalbedingungen oder kontrollierter Atmosph?re durchgeführt (2% O₂:1% CO₂, 2% O₂:6% CO₂, 2% O₂:12% CO₂, 6% O₂:6% CO₂). Der F?ulnisgrad (Abb. 1) wurde nach einem Monat bonitiert. Die Ergebnisse sind in den Tabellen 2 und 3 dargestellt und in der Abb. 2 illustriert. Unter in Normalbedingungen nur schwach virulente Arten (verschiedeneFusarien undPhoma exigua var. exigua) waren deutlich aktiver in kontrollierter Atmosph?re. Dies was besonders der Fall fürF. culmorum. Pilze, die im Versuch unter Normalbedingungen nicht pathogen waren (Colletotrichum coccodes, Cylindrocarpon sp., Phoma eupyrena), haben unter kontrollierter Atmosph?re Sch?den verursacht. Hingegen werden die beiden unter Normalbedingungen sehr pathogenen Arten (F. sulphureum undP., exigua var.foveata), durch kontrollierte Atmosph?re wenig beeinflusst. Es wurde sogar in einigen F?llen eine gewisse Verringerung des F?ulnisbefalls beobachtet. Ganz allgemein haben die getesteten kontrollierten Bedingungen die Entwicklung der Pilzf?ulnis an beiden Kartoffelsorten gef?rdert, speziell durch Pilzarten, welche unter Normal-bedingungen wenig Sch?den verursachen.

     

Marine Pharmacology in 2016–2017: Marine Compounds with Antibacterial,Antidiabetic, Antifungal,Anti-Inflammatory,Antiprotozoal, Antituberculosis and Antiviral Activities; Affecting the Immune and Nervous Systems,and Other Miscellaneous Mechanisms of Action

The review of the 2016–2017 marine pharmacology literature was prepared in a manner similar as the 10 prior reviews of this series. Preclinical marine pharmacology research during 2016–2017 assessed 313 marine compounds with novel pharmacology reported by a growing number of investigators from 54 countries. The peer-reviewed literature reported antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral activities for 123 marine natural products, 111 marine compounds with antidiabetic and anti-inflammatory activities as well as affecting the immune and nervous system, while in contrast 79 marine compounds displayed miscellaneous mechanisms of action which upon further investigation may contribute to several pharmacological classes. Therefore, in 2016–2017, the preclinical marine natural product pharmacology pipeline generated both novel pharmacology as well as potentially new lead compounds for the growing clinical marine pharmaceutical pipeline, and thus sustained with its contributions the global research for novel and effective therapeutic strategies for multiple disease categories.     

Effects of Micronutrient Deficiencies on Human Health: Its Status in South Asia

SUMMARY

Vitamin A, iodine, and iron deficiencies affect large numbers of people worldwide. A deficiency of one or more of these micronutrients adversely affects the physical and mental abilities of humans. South Asia contains a high percentage of these individuals, not just because of its large population, but also the prevalence of deficiency is higher there than in many other parts of the world. The reasons for the high rates of deficiency in South Asia are many, but they include inadequate availability of micronutrient-rich foods, sub-optimal dietary habits, and high rates of infection. Across the region, national plans vary from (a) increasing availability of appropriate foods, (b) introducing new dietary behaviors, (c) improving health status, and (d) directly addressing deficiency through intervention programs. The extent to which each of the countries is making progress toward the goals of these plans can help in understanding the priorities for future efforts to address micronutrient malnutrition. This article discusses the adverse effects of micronutrient deficiencies in humans with special reference to South Asia.     

Irrigation but not N fertilization enhances seedhead density in plains rough fescue ( F estuca hallii)

Plains rough fescue ( F estuca hallii) is an important forage grass species in western Canada. Seed for use in pastures and ecological restoration is in high demand but supply is limited because F. hallii is an erratic seed producer. Seed producers require an understanding of the factors that influence flowering and seed set in this species. The aim of this study was to assess the effect of irrigation and nitrogen fertilization on the flowering and growth of F. hallii in a native rough fescue prairie in Alberta, Canada. Irrigation had a strong positive effect on seedhead density, whereas fertilization had limited effects on growth and reproduction of F. hallii. These results demonstrate that under field conditions, available moisture is likely to be a key factor driving flowering and seed production in F. hallii.     

Management of Soil Micronutrient Deficiencies in the Rice-Wheat Cropping System

Summary

Within the last three decades, the rice-wheat cropping system has triggered, and with time, aggravated soil micronutrient deficiencies in the Indo-Gangetic Plains (IGP). This has largely been due to the shift from an earlier rice and wheat monoculture with low yielding, long duration indigenous varieties, to an intensive rice-wheat rotation cropping system with short duration modern high yielding varieties on the same piece of land. The problems related to micronutrient deficiency in the IGP are more due to the size of its available pools in the soil rather than its total contents and are greatly influenced by crop management, or rather its mismanagement. Deficiency of zinc is widespread in the IGP, but with the extensive use of zinc sulfate, zinc deficiency has reduced in some areas of the region. Meanwhile, the deficiency of Fe, Mn and B has increased in the IGP. Deficiency of Cu and Mo is location specific and can limit rice and wheat yields. The adoption and spread of the rice-wheat system in permeable coarse textured soils, particularly in the western IGP, not only caused iron deficiency in rice but also resulted in the emergence of manganese deficiency in wheat. In highly calcareous and acidic soils, boron is the next limiting micronutrient in crop production after zinc. Bumper rice and wheat harvests in the past decade, the declining use of organic manures in the region and except for the widespread use of zinc sulfate, a general lack of awareness amongst farmers on micronutrient deficiency problems has contributed to micronutrients limiting rice and wheat yields in the IGP. Approaches to alleviating micronutrient deficiencies include matching the crop removals of the micronutrients with its replenishments through their respective external carriers, supplementation through organic sources and mobilization/utilization through cultivation of micronutrient efficient crop cultivars. Identification of efficient micronutrient carriers and finding the optimum rate, mode and time of its application is important in ameliorating the micronutrient deficiencies. This article reviews the extent of micronutrient deficiency and discusses various management options available to reduce micronutrient deficiency induced crop yield reduction for rice and wheat in the Indo-Gangetic Plains.     

Marine Drugs Regulating Apoptosis Induced by Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL)

Marine biomass diversity is a tremendous source of potential anticancer compounds. Several natural marine products have been described to restore tumor cell sensitivity to TNF-related apoptosis inducing ligand (TRAIL)-induced cell death. TRAIL is involved during tumor immune surveillance. Its selectivity for cancer cells has attracted much attention in oncology. This review aims at discussing the main mechanisms by which TRAIL signaling is regulated and presenting how marine bioactive compounds have been found, so far, to overcome TRAIL resistance in tumor cells.     

Biochemical and morphological characterization of potato clones differing in their resistance to late blight

Summary Morphological and biochemical parameters that could be involved in resistance to late blight were studied in non-infected and in infected potato hybrids resulting from a cross betweenSolanum phureja, resistant toPhytophthora infestans, and a susceptibleSolanum tuberosum. Some morphological differences between resistant and susceptible hybrids, indicating a positive correlation between stem diameter and phloem thickness in the stem and resistance toP. infestans, were observed. The lignin content in the leaves of the resistant hybrid rose upon infection byP. infestans. In the leaves of the susceptible hybrid, a diminution of the lignin content could be observed upon infection byP. infestans. In the same context, peroxidasic activity raised upon infection byP. infestans in both resistant and susceptible hybrids. Further characterization of the hybrid clones based on the polymorphism of peroxidases was attempted using isoelectric focusing.     

Applied Biotechnology to Combat Late Blight in Potato Caused by <Emphasis Type="Italic">Phytophthora Infestans</Emphasis>

Potato is an important crop, grown worldwide. It suffers from many pests and diseases among which late blight, caused by the oomycete Phytophthora infestans, is the worst. The disease is still causing major damage in many potato production areas and control is only possible by applying fungicides frequently. The knowledge on the molecular biology and genetics of the interaction between the plant and the oomycete is developing rapidly. These are relevant fields of study, currently dominated by the discovery of many resistance genes and numerous effector proteins and the analysis of their specific mode of action. These studies may yield essential information needed for the development of durable resistance. The long-term and worldwide effort to breed for resistance so far has had little effect. A novel breeding approach may change this. It is based on cisgenic modification (CM) consisting of marker-free pyramiding of several resistance genes and their spatial and temporal deployment yielding dynamic varieties that contain potato genes only. It is envisioned that this CM approach with potato’s own genes will not only prove societally acceptable but may also result in simplifications in the legislation on use of the CM approach. Various parties in the potato research arena intend to cooperate in this novel approach in a number of developing countries where potato substantially contributes to food security. The use of resources such as land, water and energy improves when the effect of late blight is markedly reduced.     

Resistance to <Emphasis Type="Italic">Potato virus Y</Emphasis> in a Multitrait Potato Breeding Scheme without Direct Selection in Each Generation

In an experimental breeding scheme to improve late blight (Phytophthora infestans) and white potato cyst nematode (Globodera pallida) resistance of tetraploid potato over three generations of crossing and selection, 15 clones survived the final selection, and these were derived from 15 great-grandparents. There was no direct selection for resistance to Potato virus Y (PVY), but 14 out of the 15 great-grandparents were resistant to PVY and three had extreme resistance. Thirteen of the 15 descendants had PVY resistance and one extreme resistance. This was within the range expected for a random (unselected) sample from the genotypes of the great-grandparents. Hence, we found no evidence for any positive or negative association between PVY resistance and the attributes selected. The conclusion is that laborious selection is not required in every generation when many parents have PVY resistance, including some with more than one copy of a PVY resistance gene or resistance at more than one locus. However, in the future, determining the major virus resistance genes present in potential parents in each generation using diagnostic molecular markers would prevent susceptible × susceptible crosses being made and maximise the number of resistant × resistant ones.