施氮量对小麦旗叶光合速率和光化学效率、籽粒产量与蛋白质含量的影响

为给小麦高产高效栽培提供依据,在大田高产条件下,研究了施氮量对开花后小麦旗叶光合速率和光化学效率、旗叶和籽粒蔗糖含量及籽粒产量和蛋白质含量的影响。结果表明,适量施氮有利于提高灌浆中、后期的旗叶光合速率、旗叶PSⅡ实际光化学效率,以及灌浆末期旗叶PSⅡ最大光化学效率;施氮过多不仅不能继续提高旗叶光合速率,而且使PSⅡ实际光化学效率降低。施氮有利于提高旗叶蔗糖含量,促进灌浆前期籽粒中蔗糖的供应;施氮较多的处理中,灌浆后期有较多蔗糖滞留于旗叶中,致使施氮处理间籽粒蔗糖含量无显著差异。与不施氮的处理相比较,施氮105~195 kg.ha-1显著提高籽粒产量,施氮105~240 kg.ha-1显著提高籽粒蛋白质含量;继续增施氮肥至285 kg.ha-1,籽粒蛋白质含量、粒重和籽粒产量均降低。综合考虑籽粒产量和蛋白质含量,施氮量以150~195 kg.ha-1为宜。     

外源脱落酸对苗期野生大豆抗盐能力的影响

以山东阳谷县境内野生大豆为材料.通过外施10μmol·L-1的脱落酸研究其对苗期野生大豆抗盐能力的影响.不同浓度的NaCl盐处理都抑制了野生大豆株高的生长.降低叶色值,并且严重降低光合系统Ⅱ(PS Ⅱ)的光能转换效率,Rubisco含量减少,SOD活性增加,MDA含量上升,喷施脱落酸后可以在不同程度上缓解上述情况,脱落酸处理可以在叶色值、PSⅡ的光能转换效率和Rubisco含量方面明显减轻盐胁迫对野生大豆的损害,差异显著(P＜0.05).ABA喷施对不间浓度的盐处理缓解程度也不尽相同,除株高及SOD活性指标外,ABA喷施对0.9%的盐胁迫缓解能力最强.     

新美洲星和6-BA对低温胁迫下稻茬小麦光合和产量的影响

为了解植物生长调节剂6-苄氨基腺嘌呤（6-BA）和叶面肥6-BA和对稻茬小麦低温胁迫伤害的缓解效应,以半冬性小麦品种烟农19和弱春性小麦品种淮麦30为材料,通过盆栽试验研究了喷施6-BA和新美洲星对分蘖期-10 ℃和拔节期0 ℃低温胁迫下小麦叶片光合参数、叶绿素荧光参数及产量性状的影响。结果表明,与喷施蒸馏水的对照相比,喷施6-BA和新美洲星处理显著降低了两个小麦品种的叶片初始荧光,显著提高了叶片净光合速率、气孔导度、PSⅡ光化学效率、光化学猝灭系数,增加了穗粒数、千粒重和产量。说明喷施6-BA和新美洲星能有效缓解分蘖期和拔节期低温胁迫对小麦功能叶片光合性能和产量的影响。     

尿素对骠马胁迫紫苏幼苗的缓解效应

为探讨尿素对骠马胁迫紫苏幼苗的缓解效应,阐明适宜紫苏生长的最佳除草施肥条件。采用随机区组试验设计,在紫苏六叶期喷施不同浓度的尿素(0、1、2、4和8g/L)和6.9 %骠马水乳剂(0、1.33、2.66、5.32和 7.98 mL/L),分析其对紫苏光合特性指标、荧光特性、杂草防效和籽粒产量的影响。结果表明,骠马显著降低紫苏叶片的叶绿素含量指数（CCI）,净光合速率（Pn）和气孔导度（Gs）也均不同程度降低,胞间CO2浓度（Ci）升高,说明骠马显著抑制紫苏的光合特性,且表现出一定的剂量-效应关系;叶绿素荧光分析表明,除草剂显著降低了PSⅡ最大光化学效率（Fv/Fm）、PSⅡ潜在活性（Fv/Fo）、PSⅡ实际光化学效率（ФPSⅡ）及光化学荧光淬灭系数（qP）,非光化学淬灭系数（NPQ）则呈一定的上升趋势。表明在除草剂骠马胁迫下紫苏叶片发生了光抑制,PSⅡ复合体受到损伤伴随着光合电子传递受阻;8 g/L的尿素处理效果相同;而1～4g/L浓度的尿素处理则效果相反。1～4 g/L的尿素和不同浓度的骠马先后处理,比单用骠马处理效果好,A组的P1N3处理可使籽粒产量比单独施用骠马增产11%,杂草防效提高11.35%,表明先施4 g/L的尿素再施1.33 mL/L 的骠马,能显著缓解骠马对紫苏的胁迫,提高其光合性能,并使其光系统Ⅱ维持较高的光化学效率,该施药模式具有平衡除草施肥技术,安全高产等特点,有较高的推广价值。     

化控对不同种植密度下东北春玉米光合特性及产量的影响

选用东农253为试验材料,设5万、6万、7万、8万株/hm2共4个种植密度,于拔节期叶面喷施"玉黄金",研究化控对不同种植密度下东北春玉米叶片光合特性及产量的影响。结果表明,与清水处理相比,"玉黄金"的施用改善了叶片的光合性能,增加了叶片的叶绿素SPAD值和净光合速率Pn,提高最大光化学效率Fv/Fm、实际量子产量Y(Ⅱ)、光化学淬灭系数q P,降低非调节性能量消耗的量子产量Y(NO)、非光化学淬灭系数q N。在7万株/hm2种植密度下,"玉黄金"处理获得最高产量,达11 428.18 kg/hm2。     

硫素对玉米光合特性及产量的影响

以郑单958为材料,在大田试验中设置0(S0)、40(S1)、80(S2)、120(S3)、160 kg/hm2(S4)5个施硫(硫磺)水平,研究不同施硫量对玉米光合特性及产量的影响。结果表明,从抽雄吐丝期至灌浆期,S2、S3处理玉米一直保持较高的叶面积指数(LAI)和叶绿素含量(SPAD)。施硫量为S2处理时,玉米净光合速率(P_n)、气孔导度(G_s)均表现为最大值,分别较S0处理提高19.08%、76.7%,且达到显著水平。胞间二氧化碳浓度(C_i)、蒸腾速率(T_r)分别在S3、S4处理时达到最大值,且显著高于S0处理。施用硫肥能够显著降低玉米气孔限制值(L_s),且施硫量为S2时达最小值,与S0处理达到差异显著水平。施用硫肥能显著提高PSⅡ的潜在活性(F_v/F_o)、PSⅡ原初光能转化效率(F_v/F_m)、PSⅡ有效光化学量子产量(F_v’/F_m’)和光化学猝灭系数(qP),显著降低非光化学猝灭系数(NPQ)。施用硫肥能够显著提高玉米产量,增产幅度为7.0%~18.1%。施硫量为S2时,玉米产量最高,为12 978.3 kg/hm~2。     

烟嘧磺隆对糯玉米光合特性和叶绿素荧光参数的影响

以沈糯509抗、不抗近等基因系为试材,研究烟嘧磺隆除草剂对玉米光合色素含量、叶片光合特性和叶绿素荧光参数的影响。结果表明,烟嘧磺隆处理使沈糯509抗、不抗近等基因系的叶绿素含量、净光合速率和PSⅡ光化学效率等均不同程度的降低,使胞间CO₂浓度和非光化学猝灭系数呈升高趋势,且表现出一定的剂量-效应关系。在供试浓度范围内,抗系各参数变化幅度均小于不抗系,说明抗系具有较强的光合调节机制,用以减轻或消除烟嘧磺隆的胁迫反应。     

CO2浓度升高对玉米叶片光合生理特性的影响

以沈糯3号为研究材料,利用开顶式气室(OTCs)法研究了二氧化碳(CO2)浓度升高处理下,玉米叶片叶绿素含量、光合生理特性及其子粒产量的变化,揭示CO2浓度升高对玉米光合生理特性及子粒产量的影响机理.结果表明,在整个生育期内,与对照相比,高浓度CO2处理下,玉米叶片叶绿素a、叶绿素b及叶绿素(a+b)的含量增加,而叶绿素a/b的值则先升高后降低;在整个处理期间,净光合速率均高于对照(p＞0.05),升高幅度为12.6%～71.1%,气孔导度低于对照(p＞0.05),其降低幅度为2.9%～18.8%.处理至抽雄期和灌浆期,胞间CO2浓度分别增加152%和161%,均极显著高于对照(p＜0.01);蒸腾速率的变化较小.高浓度CO2处理下,玉米穗粒数和穗粒重均明显高于对照(p＜0.05).CO2浓度升高在一定程度上促进了玉米的光合作用,从而使玉米子粒产量增加.     

庐山不同海拔茶树光合响应差异研究

为明确茶树光合活性和光系统Ⅱ(PSⅡ)的光抑制对海拔梯度的响应规律,以茶树品种庐山本地群体种为材料,观测了庐山5个不同海拔高度茶树叶片的光合气体交换和叶绿素荧光参数。结果表明,叶片厚度、最大净光合速率(Pnmax)、PSⅡ最大相对电子传递速率[rETR(Ⅱ)max]、光补偿点(Ic)、光饱和点(Isat)、半饱和光强(Ik)、水分利用效率(WUE)等随海拔升高呈增加趋势,水汽压亏缺(VPD)、气孔导度、蒸腾速率、胞间CO2浓度、暗呼吸速率(Rd)等随海拔升高而呈下降趋势。PSⅡ潜在最大光化学量子产量(Fv/Fm)随海拔升高而增加;PSⅡ非调节性能量耗散量子产量[Y(NO)]随海拔升高而降低。PSⅡ实际光化学量子产量[Φ(Ⅱ)]、光化学淬灭(qP)、PSⅡ相对电子传递速率[rETR(Ⅱ)]均随海拔升高而增加。综上分析,茶树在庐山低海拔处的光合作用和PSⅡ活性显著低于高海拔处,这与低海拔处叶片PSⅡ受到光抑制密切相关。     

外源ABA对干旱条件下小麦冠层温度及光合同化物积累与分配的调控效应

为给外源脱落酸(ABA)在小麦抗旱栽培中的合理利用提供理论依据,以耐旱型品种山农20和水分敏感型品种辐287为材料,研究外源ABA对花后干旱条件下小麦冠层温度、光合特性、籽粒灌浆及产量的影响。结果表明,干旱处理显著降低了小麦吸收光能性能指数(PI_(abs))及被捕获电子传递到电子传递链Q_A~-中下游其他电子受体的概率(φ_0),尤其在灌浆后期,PI_(abs)及φ_0降幅均达到50%以上,导致叶片净光合速率、蒸腾速率及气孔导度显著下降和冠层温度显著升高。同时,干旱处理下两品种的最大灌浆速率及平均灌浆速率均呈现降低趋势。两品种花后光合积累量及花后贮藏同化物转运量对籽粒产量的贡献率均显著降低,辐287降幅大于山农20。最终表现为粒重及产量显著降低。干旱条件下喷施ABA可以显著提高PI_(abs)值、φ_0值、净光合速率及叶绿素相对含量,延缓叶绿素降解,诱导气孔适当关闭,减少水分散失,降低冠层温差。同时ABA处理提高了强势粒最大灌浆速率、平均灌浆速率,延长了生长活跃期,降低穗叶温差,花后光合积累量及花后同化物转运量对籽粒产量的贡献率显著升高,最终表现为粒重及产量提高。这说明耐旱型小麦品种叶片光合同化力强,花后干物质转运效率较高,有利于籽粒灌浆增重,实现产量提高;外源喷施ABA可以提高灌浆期水分亏缺条件下小麦的光合性能,显著降低穗叶温差,优化同化物分配比例,最终实现小麦的抗旱稳产。     

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.