Genotypic variability and genotype by environment interactions for inulin content of Jerusalem artichoke germplasm

Genetic variations in germplasm and genotype × environment interaction (G × E) are important for crop improvement. The objectives were to explore genetic variation in Jerusalem artichoke germplasm and to evaluate G × E interaction for inulin content. Seventy-nine accessions of Jerusalem artichoke were evaluated in a randomized complete block design with two replications for three seasons. Significant variation in inulin content (55.3–74.0% dry weight) was observed and the genotypes with high inulin content could be identified although there was intermediate G × E interaction. Genotypes were also significantly different for days to maturity, fresh tuber yield, biomass and harvest index and G × E interactions for these traits were also significant. The correlation between inulin content and days to maturity was not significant (r = −0.20), whereas inulin content and fresh tuber yield were significantly associated (r = 0.22). JA 37 and CN 52867 are promising for high yield and inulin content.     

Indicators of resistance of sunflower plant to basal stalk rot (Sclerotinia sclerotiorum): Symptomatological,biochemical, anatomical,and morphological characters of the host

Summary The object of this work was a study of the relationship between the field reactions of different sunflower genotypes to basal stalk rot (in terms of severe (dead plants) and incipient wilting, and lesion length) and some biochemical (phenol concentration), morphological (plant height, and stem and flower-bud diameters) and anatomical (xylem and cortical indexes) characters of the host. Plants from 8 inbred lines at closed flower-bud stage were artificially inoculated with mycelium at the base of the stem. The percentage of dead plants for each inbred line and the lesion length and wilting range for individual plants after 7 days were recorded.A positive and highly significant correlation coefficient between the percentage of dead plants and lesion length was found for the three years of the study (r=0.83; P<0.01). A highly significant association between lesion length and wilting range for individual plants was always found (P=0.00). Postinfectional phenol content exhibited a strong negative correlation with lesion length and the percentage of dead plants in all the experiments (P=0.05). Association between postinfectional phenol content and wilting range for individual plants was significant for all the years studied (P<0.05). No correlation between phenol levels in healthy plants of the different sunflower genotypes and their susceptibility was found. Morphological characters positively correlated with lesion length but only plant height exhibited significant values for the three years. Associations between wilting range and morphological characters for individual plants were significant for one of the two years analyzed (P<0.05). Xylem index showed a negative correlation with lesion length which was significant one of the two years studied.The lesion length measure seems to be a simple and direct method for resistance screening before the flowering period. Although strong relations with postinfectional phenol levels were found, their determinations would be too much time consuming and not completely reliable. The relationships between other characters measured and disease resistance would indicate that physiological mechanisms could be related to resistance.     

257份菊芋种质资源表型性状的遗传多样性

为有效利用我国菊芋种质资源的遗传多样性,分析了257份菊芋种质资源,表明12个数量性状的变异系数(CV)在6%～50%之间,平均为24.75%,单株块茎重的变异系数最大(50%),生育期的变异系数最小(6%),多样性指数(H')分布在1.24～1.53之间,平均为1.44,单株块茎数的多样性指数最高(1.53),叶宽的多样性指数最低(1.24);8个质量性状的多样性指数在0.85～1.08之间,平均为0.98,以块茎习性最大,块茎整齐度最小,大部分性状表现出丰富的遗传多样性; 257份菊芋资源的隶属函数均值介于0.12～0.58之间,其中JA1095材料最高(0.58),其花数和单株块茎重具有明显优势。菊芋资源12个数量性状的相关性分析表明,茎粗、叶长、花和花盘大小可作为今后选育高产菊芋品种的指导目标性状;主成分分析结果表明,7个主成分因子的累计贡献率达66.794%,其中花数量、单株块茎数量、块茎毛根量、块茎表皮光滑程度4个性状是构成菊芋种植表型差异的主要因素;以20个性状为基础的聚类分析将257份种质材料分为5类,其中,第I类和第II类占总资源量的85%。本研究结果为菊芋种质资源的利用及品种选育等提供了重要参考。     

半干旱地区菊芋品系植株表型与光合特性分析

为了加快半干旱地区的新型资源作物菊芋品种的选育进程,探讨菊芋产量及相关性状表型和光合生理基础是必要的。选用本课题组收集和培育的4个品系( 2个高产,2个低产品系),设置随机区组试验,比较菊芋高产和低产品系与产量形成相关的生物量累积、植株表型和光合特性的差异。结果表明,高产菊芋品系的地上生物量、块茎产量及根生物量显著高于低产品系;高产品系整体表现出明显的生长优势,其株高、基径、叶面积和叶片数均显著高于低产品系。气体交换参数分析表明,高产品系的光补偿点和暗呼吸速率显著小于低产品系,而其他各项参数差异不显著。相关性分析表明,菊芋块茎产量与株高、基径、叶面积、叶片数、地上生物量和根生物量呈显著正相关,而与光补偿点和暗呼吸速率呈显著负相关。建议多的叶片数、大的叶面积和发达的根系作为半干旱地区菊芋高产品系田间选育指标,而低的光补偿点和暗呼吸速率在高产品系选育中也具参考价值。     

Selection of pea genotypes with partial resistance to <Emphasis Type="Italic">Sclerotinia sclerotiorum</Emphasis> across a wide range of temperatures and periods of high relative humidity

Partial resistance to Sclerotinia sclerotiorum based on stem lesion advancement was assessed for nine wild pea genotypes from five geographic origins and two cultivated genotypes, when peas were inoculated and incubated at all combinations of five temperatures (15.6, 18.3, 21.1, 23.9, 29.4°C) and four period(s) of high relative humidity (PHRH; 12, 24, 48, 72 h). PHRH of 12 and 24 h should not be used when screening plants for resistance to S. sclerotiorum regardless of the incubation temperature, since stem lesions are rarely (2.7%) visible at 12 h and there were no significant differences (P ≤ 0.05) in lesion lengths among and within genotypes at all temperatures assessed after 24 h. However, PHRH of 48 and 72 h are recommended for use to assess partial resistance since significant differences in stem lesion length among the genotypes were observed and characterized for these periods. Genotypes with cool (15.6 and 18.3°C) versus warm (23.9 and 29.4°C) temperature partial resistance to S. sclerotiorum were identified, and genotypes PI 240515 and PI 169603 appear to have the best cool and warm temperature partial resistance, respectively, among the genotypes assessed. A temperature of 21.1°C was the optimal temperature favouring lesion advancement for the majority of the genotypes evaluated. PI 169603 demonstrated the best partial resistance to S. sclerotiorum across the widest temperature and PHRH ranges and is recommended to plant breeders as the best single genotype to develop future cultivars with improved partial resistance to S. sclerotiorum based on stem lesion advancement.     

黑腐病对花椰菜（Brassica oleracea L. var. botrytis）幼苗根系形态和生理的影响

为了阐明黑腐病对苗期花椰菜的根系形态和生理的影响,对建立花椰菜抗黑腐病根系育种新途径提供依据,利用黑腐病菌感染花椰菜抗病品种雪峰的叶片后,研究植株根系发生的一系列形态和生理变化。结果表明,接种7天后的植株根长、根干重、地上部干重、根系活力比接种后2天的显著增加。接种处理的植株根长、根干重和地上部干重明显比未接种对照（CK）低,但是接种幼苗的根系活力比未接种对照的根系活力高。接种3天后,接种处理的根系可溶性蛋白质含量一直显著高于未接种对照;接种后0~4天,接种处理的根系超氧化物歧化酶（SOD）活性明显低于未接种对照,但到接种后5~7天,接种处理的根系SOD活性又高于未接种对照;根系多酚氧化酶（PPO）活性和脱落酸（ABA）含量在植株接种后都显著高于未接种对照。但是,黑腐病病原菌没有提高根系过氧化物酶（POD）活性。以上结果说明,黑腐病菌引起了花椰菜幼苗根部一系列形态变化,并通过诱导植株根系中防御酶活性和调控内源激素等抵御病原菌的进一步侵染。     

Screening techniques and sources of resistance to root rots and wilts in cool season food legumes

Soilborne, fungal pathogens of cool season food legumes, including seed and seedling blights, rot rots, and wilts are described. Seed and seedling diseases are caused primarily by Pythium and Rhizoctonia spp. The most important fungi causing root rots include Aphanomyces euteiches, Fusarium solani, Pythium spp., Sclerotium rolfsii, and Macrophomina phaseolina. Wilt is caused primarily by various host-specific forms of Fusarium oxysporum. This paper discusses these diseases and screening procedures that emphasize standardization of inoculum levels, maintenance of virulent pathogen cultures, inoculum growth media, environmental conditions, and host plant age. Sources of resistance to these diseases are discussed.     

Identification of QTL associated with durable adult plant resistance to stem rust race Ug99 in wheat cultivar ‘Pavon 76’

Stem rust of wheat, caused by Puccinia graminis f. sp. tritici, was under control worldwide for over 30 years by utilizing genetic resistance. The emergence of stem rust in 1998 in eastern Africa in form of race Ug99 and its evolving variants with virulence to many resistance genes were recognized as potential threats to wheat production. In this study we identified genomic regions contributing to putatively durable, adult plant resistance (APR) to wheat stem rust. A recombinant inbred line (RIL) population of 298 lines was previously developed at CIMMYT from a cross between ‘Avocet S’ and ‘Pavon 76’. Pavon 76 has been described to carry APR to stem rust. Avocet S carries the race-specific resistance gene Sr26. A subset of RILs without Sr26 segregated for APR to stem rust race Ug99 when evaluated in Kenya for three years. Single year and joint year analysis by inclusive composite interval mapping using 450 DArT markers identified five quantitative trait loci (QTL) that contributed to the resistance of wheat to stem rust race Ug99. Three of these, including QSr.cim-3B, which probably represents the Sr2 gene, were contributed by Pavon 76 whereas the remaining two QTL were contributed by Avocet S. QSr.cim-3B, or putatively Sr2, on chromosome arm 3BS explained 32 % of the phenotypic variation while the additional QTL in Pavon contributed 24 and 20 %, respectively. Two QTL from Avocet S explained 8 and 6 % of phenotypic variance, respectively. A combination of APR QTL from the two parents resulted in transgressive segregants expressing higher levels of resistance than Pavon 76. Our results indicate that it is possible to accumulate several minor resistance genes each with a small to intermediate effect resulting in a variety that exhibits negligible disease levels even under high stem rust pressure.     

品种基因型和温度对马铃薯脱毒试管苗农艺性状的影响

以大西洋、克新1号、青薯168脱毒基础苗为试验材料,采用二因素随机区组设计,研究不同基因型品种、不同温度对马铃薯脱毒基础苗苗鲜重、根鲜重、苗干重、根干重、叶片数、株高、茎粗、根长和根条数影响,培养14d时,测定各性状指标.结果表明,3个不同成熟期基因型品种、3种不同培养温度处理对马铃薯单株平均根鲜重、叶片数、株高影响有显著性交互作用(p＜0.05),其余性状受品种基因型和温度交互作用影响不显著.不同基因型品种对苗干重、根干重、叶片数、根条数农艺性状指标影响显著(p＜0.05),其余性状指标未达显著影响;不同培养温度对马铃薯单株平均苗鲜重、根鲜重、苗干重、根干重、茎粗、根长、根条数(p＜0.05)农艺性状指标有显著性影响(p＜0.01),其余性状指标未达显著影响;3个不同基因型品种所需的适宜培养温度为(23±2)℃,此培养温度时,3个品种基因型的农艺性状表现最好.     

Relationship of morphological variables to rubber production in guayule

Summary The objective of this study was to find measurable characters to aid the plant breeder in predicting both rubber percentage and rubber yield of guayule (Parthenium argentatum Gray). A field of 234 guayule breeding lines was harvested by clipping in February 1986. Forty-two of these lines were selected for further evaluation on the basis of superior regrowth, rubber content and yield. These 42 lines were reharvested in February 1987. Nineteen variables were evaluated including percent rubber and resin, rubber and resin yield (g/plant), plant height (cm), width (cm), and volume (m³), fresh and dry weight (kg/plant), percent dry weight, stem number, mean stem diameter (cm), total and mean stem circumference (cm), total and mean stem area (cm²), total stem circumference/total stem area (cm^-1), and regeneration at two dates. Dry weight (kg/plant) had the best correlation to rubber yield (r=0.85), and plant volume best predicted dry weight (r=0.83). These variables did not correlate as highly with percent rubber. The best statistical regression model for percent rubber included four variables, fresh and dry weight, percent dry weight, and plant volume. This model accounted for 51% of the variation. In comparison, the best regression of rubber yield had an R²=0.85 for plant height and width, volume, and dry weight.     

Genetics and population improvement of resistance to bacterial soft rot in Chinese cabbage

Resistance to bacterial soft rot caused by Erwinia carotovora subsp. carotovora is a quantitative trait. The narrow-sense heritability was from 42% to 60% in the studied populations. Griffing's diallel analysis and generation mean analysis indicated that additive genetic effects were most significant, and the resistant sources involved in this study appeared to have different genes or alleles. Recurrent phenotypic selection was used for improving the resistance level by combining different resistance genes from the selected genotypes of Chinese cabbage. After 3 cycles of recurrent selection, the level of resistance increased markedly. When the cycle 3 population was compared with the cycle 0 population, the mean disease severity rating was reduced 38% from 6.3 to 3.9, and the percentage of plant survival increased from 65% to 97% based on the mean of two years experiments using mist-chamber seedling inoculation methods. The improvement of resistance was also demonstrated in field assays. This revised version was published online in July 2006 with corrections to the Cover Date.     

The variation of relative water content,SPAD chlorophyll meter reading,stomatal conductance,leaf area,and specific leaf area of Jerusalem artichoke genotypes under different durations of terminal drought in tropical region

This work assessed the responses of Jerusalem artichoke (JA) genotypes experienced to different durations of terminal drought for relative water content (RWC), SPAD chlorophyll meter reading (SCMR), stomatal conductance (SC), leaf area (LA) and specific leaf area (SLA), investigated the significant contributor of physiological traits to yield and yield reduction and diversity of physiological traits in terminal drought tolerance genotypes. Field research was conducted during the late-rainy season for 2 years using a split-plot design with four replications. The three irrigation treatments involved no-drought (SD0), short (SD1) and long (SD2) durations of terminal drought were arranged as main plots, and sub-plots were six genotypes of JA. The current study revealed that RWC, SC, LA, and SLA, were drastically reduced whilst SCMR values slightly increased under SD1 and SD2 compared to SD0. According to multiple linear regression indicated that SLA (SD0), and RWC (SD1 and SD2) had high contributions to tuber fresh weight (TFW), whereas SC had a high contribution to TFW reduction under terminal drought. Principal component analysis also confirmed that the diversity of LA, RWC, and SLA had maximized contributing traits, followed by HI, SCMR and SC in these breeding materials of JA under three irrigation treatments. Our finding emphasized that JA125 (low SLA), HEL256 and JA37 (high SLA) lead to the high performance of TFW under SD0, and they exhibited high TFW under SD1 by performing medium RWC. Likewise, JA4 and JA37 had high TFW under SD2 caused by medium RWC. HEL253 and JA60 were identified as terminal drought-tolerant genotypes because of performed medium SC, which contributed to a low reduction in TFW. Our promising results are the basis for further studies, SLA, RWC and SC are an important keys for screening drought tolerance (low economic yield reduction) and these genotypes studied could be used for parental lines to improved drought tolerance progenies through breeding programs under different durations of terminal drought-prone areas.     

Screening for resistance to clover rot (Sclerotinia spp.) among a diverse collection of red clover populations (Trifolium pratense L.)

Red clover (Trifolium pratense) is an important perennial forage crop that is widely cultivated in Europe. Clover rot remains a major disease in red clover, but resistance breeding is hampered by the lack of available sources of resistance. Moreover, little is known about the factors that influence clover rot resistance. In this paper we evaluated the variation in clover rot susceptibility among a diverse collection of 113 red clover accessions, with the aim of identifying more resistant accessions. Clover rot susceptibility was assessed with a high throughput bio-test on young plants. We found significant variation in clover rot susceptibility, within and among accessions. ‘Tedi’, ‘Maro’ and ‘No 292’ were the most resistant accessions. Fifteen diploid accessions were more susceptible than the average accession with the cultivar ‘Nemaro’ being the most susceptible. Clover rot susceptibility was not correlated with isoflavone levels from Mullaney et al. (Agronomy abstract. ASA, Madison, p 195, 2000). Cultivars were more resistant than landraces and wild accessions and tetraploid cultivars were more resistant than diploid cultivars. Besides the in-depth analysis for clover rot susceptibility, possible correlations with plant architecture and other diseases were investigated. Growth habit, branching, plant yield, flowering date and susceptibility to mildew, virus and rust diseases were investigated in a 3-year field trial. Unlike previously suggested, clover rot susceptibility was not correlated with branching or with plant yield over three years. On the other hand, late flowering accessions and accessions with erect growth habit were less susceptible to clover rot. Clover rot susceptibility was not correlated with susceptibility to rust disease (Uromyces trifolii) or viral diseases, but negatively with susceptibility to mildew (Erysiphe polygoni). Because no completely resistant accessions were found, the best way to improve clover rot resistance would be to select recurrently for resistant genotypes among diverse cultivars and landraces with lower susceptibility. Tetraploidisation of diploid populations with a higher resistance level can provide an additional level of protection.     

Identification of QTLs for agronomic traits using association mapping in lentil

A diverse panel of 96 genotypes of lentil was used in this study to identify QTL for nine agronomic traits through marker-trait association analysis. This study showed significant genetic variability among the lentil genotypes for nine agronomic traits and had medium to large broad sense heritability estimates (h² =?0.58–0.95). Screening of 534 SSR markers resulted in 266 polymorphic loci that generated 697 alleles ranging from 2 to 16 alleles per locus across the genotypes. The model-based population structure analysis identified two distinct subpopulations among lentil genotypes and each subpopulation did not show any admixture. Marker trait association (MTA) analysis following ML model resulted in the identification of 24 MTAs for nine traits at P?<?0.01. The per cent of phenotypic variation explained by each associated marker with particular agronomic trait ranged from 7.3 to 25.8%. The highest proportion of total phenotypic variation (23.1–25.8%) was explained by the QTLs controlling the primary branches/per plant. In the present study, few EST-SSR markers showed significant association with days to maturity, pods/plant, secondary branches/plant, 100 seed weight, yield/plant and reproductive duration and explained large phenotypic variation (7.3–23.8%). Hence, these markers can be used as functional markers in lentil breeding program for developing improved cultivars.     

Pathogenic diversity of Phytophthora sojae and breeding strategies to develop Phytophthora-resistant soybeans

Phytophthora stem and root rot, caused by Phytophthora sojae, is one of the most destructive diseases of soybean [Glycine max (L.) Merr.], and the incidence of this disease has been increasing in several soybean-producing areas around the world. This presents serious limitations for soybean production, with yield losses from 4 to 100%. The most effective method to reduce damage would be to grow Phytophthora-resistant soybean cultivars, and two types of host resistance have been described. Race-specific resistance conditioned by single dominant Rps (“resistance to Phytophthora sojae”) genes and quantitatively inherited partial resistance conferred by multiple genes could both provide protection from the pathogen. Molecular markers linked to Rps genes or quantitative trait loci (QTLs) underlying partial resistance have been identified on several molecular linkage groups corresponding to chromosomes. These markers can be used to screen for Phytophthora-resistant plants rapidly and efficiently, and to combine multiple resistance genes in the same background. This paper reviews what is currently known about pathogenic races of P. sojae in the USA and Japan, selection of sources of Rps genes or minor genes providing partial resistance, and the current state and future scope of breeding Phytophthora-resistant soybean cultivars.     

Introgression of hexaploid sources of crown rot resistance into durum wheat

Triticum turgidum ssp. durum (tetraploid durum) germplasm is very susceptible to crown rot, caused by the fungus Fusarium pseudograminearum. Screening activities to date have failed to identify even moderately susceptible lines. In contrast partial resistance to this disease has been identified in a number of Triticum aestivum (hexaploid wheat) lines, including 2-49 and Sunco. This study describes the successful introgression of partial crown rot resistance from each of these two hexaploid wheat lines into a durum wheat background. Durum backcross populations were produced from two 2-49/durum F₆ lines which did not contain any D-genome chromosomes and which had crown rot scores similar to 2-49. F₂ progeny of these backcross populations included lines with field based resistance to crown rot superior to that of the parent hexaploid wheat.     

Competition and Control of Volunteer Jerusalem Artichoke in Various Crops

A major production constraint in Jerusalem artichoke ( Helianthus tuberosus L.) is caused by tubers which are not recovered at harvest. Such lost tubers raise a serious weed problem the following season. Winter wheat, oat, spring oilseed rape, sugarbeet, maize and ryegrass were grown in a field which had Jerusalem artichoke as the preceding crop in order to obtain information about their competitive ability and the efficacy of various control measurements against Jerusalem artichoke infestation. The Jerusalem artichoke treatments in these crops were: total control by regular hand weeding (TOC), mechanical/chemical control (MCC), and no control (NOC). Under the NOC treatment, Jerusalem artichoke infestation at harvest was variable among crops, with the number of shoots ranging from 9 to 25 m⁻² in oat and maize stands respectively. The number of Jerusalem artichoke shoots in the MCC plots was reduced by 50 to 99 % in oat and maize, respectively. The highest crop yields in each of the six species were realized under the TOC treatment. Insignificant yield reductions were observed in the NOC treatment of wheat, oat, rape and ryegrass. However, under this management yield reductions of 91 and 81 % occurred in sugarbeet and maize respectively. Depending on the preceding crop, 1–9 shoots m⁻² of Jerusalem artichoke were still recorded under the MCC plots in the following season. Consequently, for complete elimination of infestation, volunteers must be controlled in the second and probably in the third year following a Jerusalem artichoke crop.     

Management of potato dry rot

Dry rot is a postharvest fungal disease affecting potato (Solanum tuberosum L.) tubers. The disease, caused by several species of Fusarium such as F. solani var. coeruleum, F. sambucinum, F. oxysporum, F. avenaceum, F. culmorum, results in significant yield losses. Some Fusarium species associated with the disease produce toxins, which are implicated in mycotoxicoses of humans and animals. The pathogens cannot penetrate the tuber through the lenticels or in the absence of wounds and cause infection only if the potato skin is ruptured. The seed tuber is considered as the main source of inoculum although soil infested by Fusarium spp. also constitutes a source of inoculum. Control of the disease, once provided by the fungicide thiabendazole, is now difficult due to the appearance of thiabendazole-resistant strains and the lack of potato cultivars with high levels of resistance to dry rot. An integrated disease management program including detection strategies, appropriate cultural practices and storage conditions (including a wound healing period) along with the use of synthetic chemical fungicides as seed tuber and/or postharvest treatment is recommended to reduce incidence and severity of dry rot. Recent studies also indicate the possibility that generally recognized as safe (GRAS) compounds and microbial antagonists could eventually be integrated into dry rot management strategies.     

大豆倒伏性及其相关性状的QTL分析

利用来自中豆29×中豆32的165个重组自交系F₁₀进行2年田间试验, 以复合区间作图法检测与大豆倒伏及形态性状有关的QTL。结果表明, 2年分别检测到25个和19个与大豆倒伏及茎杆性状和根系性状有关的QTL, 分布于A2、C1、C2、D1a、F、G、I和L连锁群, 可解释4.4%~50.1%的表型变异。在F连锁群上, 2年均检测到倒伏主效QTL(qLD-15-1)和株高主效QTL(qPH-15-2);G连锁群和L连锁群上分别有1个主茎节数QTL和2个根重QTL在2个年份重复出现。在倒伏QTL的附近检测出株高、根重、茎叶重、茎粗、主茎节数和分枝数QTL, 表明植株地上部和地下部性状与抗倒性普遍关联;QTL定位结果与表型相关分析一致, 反映了这些形态性状表型相关的遗传特性。部分性状QTL存在共位性, 但是未在2个年份稳定表达。     

Number of involved genes and heritability of clover rot (Sclerotinia trifoliorum) resistance in red clover (Trifolium pratense)

European red clover (Trifolium pratense) crops are challenged by clover rot, a devastating disease caused by Sclerotinia trifoliorum or, in some cases by S. sclerotiorum. No completely resistant cultivars are available and resistance breeding is hampered by the lack of knowledge on the number of involved resistance genes and the heritability of clover rot resistance. In this study, we estimated the number of major genes contributing to clover rot resistance by analysing 15 F₁ progeny populations from pair crosses between ramets of resistant and susceptible genotypes. Parent plants were chosen from diverse, diploid populations, including wild material, landraces and cultivars. Young progeny plants were inoculated with ascospores, evaluated phenotypically and the segregation of disease scores was studied. Our results indicated that clover rot resistance may be conferred by three major effect genes, although segregation patterns suggested that there may be numerous minor effect genes involved as well. No proof was found for a maternal inheritance of clover rot resistance. To get insight in the heritability of clover rot resistance, we applied divergent selection by our high-throughput bio-test on an experimental diploid population: the original population (70.5 %), the first generation after selection for susceptibility (79.2 %) and the first generation after selection for resistance (62.3 %) differed significantly in susceptibility (p < 0.001). The second generation after selection for resistance (60.0 %) was not more resistant than the first generation after selection for resistance. In the first generation of selection the heritability (h²) was on average 0.34. In the second generation of selection h² was 0.07. These findings have important implications for resistance breeding.