Morphological traits and high resolution RAPD markers for the identification of the main strawberry varieties cultivated in Argentina

Eight genotypes of the main Fragaria×ananassa cultivars grown in Argentina were analysed using the random amplified polymorphic DNA (RAPD) technique combined with electrophoresis in polyacrylamide gels. The high resolution of this procedure allowed the detection, with only 13 random primers, of 37 genotype‐specific bands that can be used as markers for verifying the identity of cultivars. By using this approach, three different accessions of the cultivar ‘Pájaro’ exhibited differences in amplification profiles, confirming the need for DNA analysis to prevent misidentification of cultivars. In addition, RAPD bands and morphological traits were used to assess genetic relatedness among cultivars. Comparison of both dendrograms revealed that there is no correlation between the clustering obtained with molecular and morphological characters.     

Pistillate-parental differences and the ability to produce interspecific hybrids between Lycopersicon esculentum and 'peruvianum-complex' species (L. peruvianum and L. chilense)

To overcome the cross-breeding barriers between the cultivated tomato Lycopersicon esculentum and the ‘peruvianum-complex’, hybrid production ability (HPA) and pistillate-parental differences were investigated. As a criterion of HPA, the number of germinated ovules per fruit (GPF) was used. GPF was expressed as GPF = OPF × GPO, where OPF is the number of ovules per fruit, and GPO is the proportion of germinated ovules to total ovules obtained. The interspecific crossing between nine varieties and three ‘peruvianum-complex’ accessions revealed that the cultivars ‘Sekaiichi’,‘Ponde Rooza’ and ‘Early Pink’ showed quite high and stable GPF over the years, but the cv.‘Best of All’ produced no hybrids. Variance analysis for GPF, OPF and GPO, and their correlation with seven sexual organ morphological traits and three fruit morphological traits were performed. These results indicated that choosing both the pistillate parents with wider reproductive organs for high OPF and appropriate environmental conditions for high GPO might be significant for enhancing GPF in interspecific crossing.     

New sources of resistance for stripe rust in barley

Eight spring barley accessions from the gene bank in Gatersleben, Germany, and 10 cultivars were tested for stripe rust resistance. Tests were performed at the seedling stage in the growth chamber and as adult plants in the field. All accessions and six cultivars were scored as resistant against race 24 under all test conditions, with very few plants as exceptions, while the susceptible control cultivars ‘Karat’ and ‘Certina’, and four other cultivars were attacked in all cases. Differences between accessions and between cultivars were detected after infection with isolates from ‘Trumpf’ and ‘Bigo’ (seedling tests only). Infection structures within seedling leaves without pustules and for the first time within leaves of adult plants from the field were analysed by fluorescence microscopy. With this method additional genetic Differences in the resistance reaction could be detected which could not to be seen in the resistance test. Crosses between the accessions and the susceptible cultivar ‘Karat’ led to segregating F₂ progenies. The percentage of resistant plants varied between the accessions. This also indicates a different genetic basis of resistance in the accessions. The infection structures observed by fluorescence microscopy stopped earlier in leaves of the two accessions HOR 8979 and HOR 8991 than in leaves of other accessions in all the tests. These accessions were the only ones with more than 50% resistant plants in all F₂ tests. In general, the accessions from the gene bank can be used as new resistance sources against stripe rust.     

Differential fruit gene expression in two strawberry cultivars in response to elevated CO2 during storage revealed by a heterologous fruit microarray approach

The use of a heterologous fruit microarray system to identify differentially expressed genes between strawberry cultivars with different responses to 20 kPa CO₂ (balance air) during storage has been evaluated. Specifically, a tomato cDNA microarray containing approximately 12,000 ESTs (representing 8700 unigenes) was hybridized with strawberry cDNA populations to compare gene expression differences between two cultivars: ‘Jewel’, a cultivar that accumulates acetaldehyde and ethanol in response to elevated CO₂ during storage, and ‘Cavendish’ that does not accumulate these compounds under the same storage conditions. A set of 80 tomato gene sequences gave differential hybridization signals between the two strawberry cultivar probes when they were stored in CO₂ for 48 h, suggesting homologous strawberry genes with differential expression. Within each cultivar, when RNA from fruit stored in air was compared with that from fruit stored in CO₂, 168 sequences suggested differential expression in ‘Jewel’, but only 51 were differentially expressed in ‘Cavendish’ fruit. Strawberry genes with putative homologies to enzymes involved in cell wall metabolism, ethylene action and stress were implicated by the tomato array. This research not only demonstrates the usefulness of using a heterologous microarray platform from a model species (tomato) to study a complex process in strawberry, a crop of economic importance, for which genomic resources are still limited, but also provides a foundation for investigating the molecular basis of responses to elevated CO₂ during strawberry postharvest storage.     

越橘种质资源的CDDP遗传多样性及聚类分析

分析保守DNA序列多态性(CDDP)标记在蓝莓中的分布及其与生物性状之间的联系,为蓝莓种质的科学评价和合理开发提供理论指导及技术支持。通过筛选多态性丰富的CDDP引物,对32份蓝莓种质资源的基因组DNA进行扩增,根据统计结果分析品种的遗传多样性及聚类关系。共筛选出17条多态性高、产物清晰易辨的CDDP引物。32份样品共检测到207条带,其中多态性条带188条,比例为90.82%,特异条带17条,比例为8.21%。可以用2条引物组合完全区分32种蓝莓。在种群水平上,有效等位基因数、Nei’s基因多样性指数和Shannon信息指数分别为1.59、0.37和0.56。样本间的遗传相似系数范围在0.44~1.00之间,平均为0.73。在相似系数为0.69时,32个蓝莓种质分为3类,野生种笃斯越桔单独聚为一类,矮丛品种‘Blomidon’和半高丛品种‘Northblue’聚为一类,其他品种聚为一大类。CDDP标记在蓝莓中具有较高的多态性及特异性,与种质的需冷量、抗寒性及果实颜色具有一定的相关性。CDDP技术可有效用于蓝莓种质资源遗传多样性分析、品种鉴定及分子标记辅助育种。     

Studies on resistance to bacterial speck (Pseudomonas syringae pv. tomato) in tomato cv. Ontario 7710

Plants of 17 tomato cultivars and four wild Lycopersicon accessions were evaluated for their reaction to Pseudomonas syringae pv. tomato (Pst) in a greenhouse following a leaf‐spray inoculation. The genotypes exhibited a large amount of variation in response to Pst infection, with disease severity index (DSI) ratings from 0.2 to 3.9. The cultivar ‘Ontario 7710’ and two accessions of Lycopersicon hirsutum (LA 1773 and LA 1775) were the most resistant, with DSI values of 0.2, 0.4 and 0.6, respectively. Three varieties, M 1812, Kujawski and Warszawski, also showed a high level of tolerance. The most susceptible was ‘A 100’(DSI = 3.9). The inheritance of resistance to bacterial speck was investigated by disease tests in segregated populations obtained by hybridizing the tomato cv. Ontario 7710 with the susceptible variety ‘A 100′. Plants were rated for disease severity by inspecting each plant and were then evaluated according to phenotypic similarity to ‘Ontario 7710’ or ‘A 100’ in respect of the number and size of the spots. Genetic analysis in F1, F2 and backcross segregations indicated that resistance of'Ontario 7710’ to Pst is conferred by one incompletely dominant gene, Pto.     

多酚、黄酮及甾醇与番茄抗晚疫病关系

以对番茄晚疫病抗性较强的番茄品种‘25-1’和易感染番茄晚疫病的品种‘京乐502’为试材,通过人工接种病原的方法,研究多酚、黄酮及甾醇与番茄品种晚疫病抗性之间的关系。结果表明：（1）健康叶多酚类和甾醇类含量在2 个品种间无显著差异;黄酮类含量抗病品种‘25-1’显著高于感病品种‘京乐502’。（2）接种后,多酚类和黄酮类含量在2 个品种中均呈先增后减的趋势。峰值出现时间‘京乐502’晚于‘25-1’。总甾醇含量与番茄晚疫病抗性密切相关。接种晚疫病病原后,2 个品种中总甾醇含量均都呈下降趋势。随着病情的发展,感病品种‘京乐502’的总甾醇含量迅速下降,抗病品种‘25-1’下降较为缓慢。     

Biochemical, sensorial and genomic profiling of traditional Italian tomato varieties

Fruit flavour of traditional tomato ecotypes differs from that of modern varieties, the latter being often blamed for lack of flavour. To respond to consumer complaints breeders should know the range of genetic variability available in tomato resources, including local ecotypes, for improving flavour. For this purpose, multitrait characterization, including biochemical, sensorial and molecular analyses, was performed on 12 Italian tomato ecotypes that belong to different types (San Marzano, Sorrento, and Vesuvio). The ecotypes showed a significant variation both in glucose and citric acid content. As for amino acid determination, lysine, aspartic acid and serine showed significant variation among the three types analyzed. Sensory analysis clearly evidenced differences among genotypes: the San Marzano ecotypes revealed sensory profiles that differ from the control processing variety in perception of sweetness and sourness, whereas the Sorrento and Vesuvio ecotype profiles were similar to the fresh market control. In particular, Vesuvio genotypes exhibited a good intensity of tomato aroma and sweetness and an intermediate level of acidity. Finally, molecular characterization performed through AFLP markers provided evidence for a very high level of polymorphism: an ecotype-specific AFLP pattern was identified for at least 11 genotypes, thus defining their molecular fingerprints.     

Purity control of F1-hybrid tomato cultivars by RAPD markers

Randomly amplified polymorphic DNA (RAPD) markers were applied in purity control of hybrid seed production of tomato (Lycopersicon esculentum Mill.). DNA from three commercial F₁-hybrid cultivars and their parental lines was subjected to RAPD screening with 50 primers. Two of four primers which detected polymorphism between the parents tested, generated paternal-specific RAPDs, enabling a clear distinction to be made between hybrids and their maternal parents. In addition, combination of the polymorphic DNA products generated by these primers exhibited hybrid-specific patterns, enabling each cultivar to be identified. This result indicates the practical usefulness of RAPD markers in hybrid-tomato-seed purity-control tests and cultivar identification. The approach is advantageous in its rapidity and simplicity, particularly as an alternative for those cultivars for which lengthy and costly phenotypic tests are currently used.     

Genetic diversity and relationships in accessions from different cultivar groups and origins in the tree tomato (<Emphasis Type="Italic">Solanum betaceum</Emphasis> Cav.)

Tree tomato (Solanum betaceum) is an Andean small tree cultivated for its juicy fruits. Little information is available on the characterization of genetic resources and breeding of this neglected crop. We have studied the molecular diversity with AFLP markers using 11 combinations of primers of a collection of 25 S. betaceum accessions belonging to four cultivar groups, most of which had been previously morphologically characterized, as well as one accession of the wild relative S. cajanumense. A total of 197 AFLP fragments were scored, of which 84 (43 %) were polymorphic. When excluding S. cajanumense from the analysis, the number of polymorphic AFLP fragments was 78 (40 %). Unique AFLP fingerprints were obtained for every accession, but no AFLP fragments specific and universal to any of the four cultivar groups were found. The total genetic diversity (H _T ) of cultivated accessions was H _T  = 0.2904, while for cultivar groups it ranged from H _T  = 0.1846 in the orange group to H _T  = 0.2498 in the orange pointed group. Genetic differentiation among cultivar groups (G _ST ) was low (G _ST  = 0.2248), which was matched by low values of genetic distance among cultivar groups. The diversity of collections from Ecuador, which we hypothesize is a center of diversity for tree tomato, was similar to that from other origins (H _T  = 0.2884 and H _T  = 0.2645, respectively). Cluster and PCoA analyses clearly separated wild S. cajanumense from the cultivated species. However, materials of different cultivar groups and origins were intermingled in both analyses. The Mantel test correlation coefficient of the matrices of morphological and AFLP distances was low (−0.024) and non-significant. Overall, the results show that a wide diversity is present in each of the cultivar groups, indicate that Ecuador may be regarded as a center of accumulation of diversity for this crop, and confirm that AFLP and morphological characterization data are complementary. The results obtained are of value for the conservation of genetic resources and breeding of tree tomato, as an assessment of the genetic diversity and relationships among different cultivar groups and geographic origins is obtained.     

Hybridization, Through Culture of Embryos and Immature Seeds, of a Range of Tomato Cultivars with a Tomato Somatic Hybrid [Lycopersicon esculentum (+) L. peruvianum]: Emergence of a Possible New Marker Gene for Tomato Breeding

Two hexaploid somatic hybrids [Sh; L. esculentum (+) L. Peruvianum] accessions 6 and 18 were back-crossed with two diploid L. Esculentum cultivars ‘Moneymaker’ (mm) and ‘pusa Ruby’ (pr). Twenty-two plants of the bc2 generation were produced by backcrossing 7 bcl plants (mm x sh, 6, 18) with five tomato cultivars. Fourteen of the bc2 plants were self-fertile, five produced anther cones with anthocyanin pigmentation not present in the parents. A bc3 generation was developed by crossing the four cultivars as female parent with three bc2 generation plants. The bc3 progeny derived from one pollen parent plant were produced without the need to culture immature seeds. They segregated with respect to pigmented anther cones and were self-fertile. The anther cone pigmentation of the pollen parent plant was associated with increased seed set, greater fruit size and an orange-red fruit colour. These features were transmitted to the fertile bc3 generation. Conversely, bc3 offspring involving the other two parent plants were only recovered by culture of immature seeds. The recovery of diploid plants in BCl and self-fertility in BC2 resulted in almost total recovery of the tomato cultivar characteristics (fruit size, colour and number of seeds) by BC3.     

Strawberry-cultivar Identification using Randomly Amplified Polymorphic DNA (RAPD) Markers

Accurate and rapid cultivar identification is important for breeders'-rights protection, especially for vegetatively propagated plants. The objective of this study was to test the feasibility of developing cultivar-specific RAPD markers in commercial strawberries (Fragaria ananassa Dutch). Efforts were focused on distinguishing between two newly developed Volcani cultivars, ‘Ofra’ and ‘Dorit’, and six other cultivars, ‘Douglas’, ‘Chandler’, ‘Oso Grande’, ‘Dover’, ‘Nurit’ and ‘Parker’. Reproducible RAPD fingerprints were generated, each containing at least one polymorphic DNA product. A combination of 10 polymorphic DNA products exhibited cultivar-specific patterns enabling the distinction between closely related varieties, such as ‘Ofra’ (which is the progeny of ‘Dorit’ and ‘Parker’) and ‘Dorit’ (which is the progeny of ‘Nurit’ and ‘Dover’). This study shows that RAPD markers can help in the protection of breeders’ rights to strawberry cultivars.     

Introduction of aromatic fragrance into cultivated tomato from the peruvianum complex'

This study was performed to introduce the distinct aromatic fragrance of Lycopersicon peruvianum LA 1554 into the cultivated tomato, Lycopersicon esculentum. The strong breeding barriers existing between these two distantly related species were circumvented by the ovule selection and culture method. A large BC₁F₁ population was developed and among 127 plants, 36 were self‐compatible and yielded fruits. Fruits of some of these selected plants were found to be enriched with a sweet aromatic flavour. Sensory evaluation of the fruit aroma of these selected plants was performed by a panel of 12 members against one of the best consumer‐rated Japanese commercial tomato cultivars, ‘Momotaro’. Although extensive variation was observed in fruit‐aroma in the BC₁F₁ population, panel opinion on ‘flavour‐desirability’ significantly favoured the BC₁F₁ fruits of some selected plants over the cv. ‘Momotaro’. Therefore, it can be concluded that the aromatic fragrance of a ‘L. peruvianum’ accession has successfully been introduced into the cultivated tomato gene pool.     

Radiomutants of chrysanthemum (Dendranthema grandiflora Tzvelev) of the Lady group: RAPD analysis of the genetic diversity

Random amplified polymorphic DNA (RAPD) markers were used to study the molecular characterization of 10 new radiomutants of chrysanthemum. The original cultivar ‘Richmond’ differed in genetic distance from its Lady group mutants. The analysis of genetic similarity indices revealed low diversity within the radiomutants. The dendrogram obtained after cluster analysis separated the new cultivars as a group that differed from the original cultivar ‘Richmond’. The Lady group cultivars, derived from one original cultivar by radiomutation, could be distinguished from each other by using RAPD markers of only a single primer or sets of two or three primers. Polymerase chain reaction analysis proved the efficiency of the RAPD method for DNA fingerprinting of the original cultivar ‘Richmond’ and its new radiomutants.     

Response of accessions within tomato wild species,Solanum pimpinellifolium to late blight

Late blight (LB), caused by the oomycete Phytophthora infestans, is one of the most devastating diseases of the cultivated tomato (Solanum lycopersicum) worldwide. Most commercial cultivars of tomato are susceptible to LB. Previously, three major LB resistance genes (Ph‐1, Ph‐2, Ph‐3) were identified and incorporated into a few commercial cultivars of tomato. Reduced effectiveness and potential breakdown of the resistance genes has necessitated identification, characterization and utilization of new sources of resistance. We evaluated the response of 67 accessions of the wild tomato species, S. pimpinellifolium to LB, under multiple field and greenhouse (GH) conditions and compared them with six control genotypes. Sixteen accessions were identified with strong LB resistance in both field and GH experiments. However, 12 accessions exhibited resistance similar to a control line which was homozygous for Ph‐2 + Ph‐3. Genotyping accessions with molecular markers for Ph‐2 and Ph‐3 were not conclusive, indicating that resistance in these accessions could be due to these or other resistance genes. Strong correlations were observed between field and GH disease response and between foliar and stem infection.     

Exploitation of wild annual Cicer species for widening the gene pool of chickpea cultivars

Introgression of unadapted genes from the wild Cicer species could contribute to the widening of genetic base of important traits such as yield, yield attributes and resistance to major biotic and abiotic stresses. An attempt was made successfully to intercross two wild annual Cicer species with three cultivated chickpea cultivars. Four interspecific cross‐combinations were made, and their true hybridity was ascertained through morphological and molecular markers. These cross‐combinations were also studied for some important quantitative traits under real field conditions. The range, mean and coefficient of variation of agro‐morphological traits were assessed in the parental lines, their F₁ and F₂ generations to determine the extent of variability generated in cultivated chickpea varieties. A high level of heterosis was recorded for number of pods/plant and seed yield/plant in F₁ generation. Three cross‐combinations of ‘Pusa 1103’ × ILWC 46, ‘Pusa 256’ × ILWC 46 and ‘Pusa 256’ × ILWC 239 exhibited substantially higher variability for important yield‐related traits. The present research findings indicate that these wild annual Cicer species can be easily exploited to broaden the genetic base of cultivated gene pool for improving seed yield as well as adaptation.     

Variation for aphid resistance and insecticidal acyl sugar expression among and within Lycopersicon pennellii-derived inbred backcross lines of tomato and their F1 progeny

Five inbred backcross lines (IBL) were selected for higher relative expression of insecticidal acyl sugars (rank average) from an inbred backcross population derived from the cross Lycopersicon esculentum cultivar ‘Peto 84’×Lycopersicon pennellii accession LA716. These five BC₂S₅ IBLs were crossed in a partial diallel design (Method II), and their self and F₁ progeny and three control cultivars were tested at two California field locations in 1996. Counts of potato aphids, Macrosiphum euphorbiae Thomas, on leaves, as a measure of plant infestation, revealed significant general combining ability (GCA) for lower aphid numbers with IBL44 and IBL59; the F₁ hybrid IBL44 × IBL59 had significantly fewer aphids per leaflet than the susceptible cultivar ‘Alta’. GCA for acyl sugars was associated with IBL59 only. Of all the IBL and IBL × IBL F₁ hybrids, only IBL59 produced significant levels of acyl sugars. Significant within IBL59 variation for acyl sugars was observed, but not for aphid resistance. Our results suggest that factors other than acyl sugars contributed to L. pennellii-derived aphid resistance in IBL × IBL F₁ hybrids and IBL that do not produce significant amounts of acyl sugars. IBL59 and IBL44 may be useful for breeding for aphid resistance in cultivated tomato.     

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.     

番茄品种对南方根结线虫的抗性鉴定

为了明确番茄品种对南方根据线虫的抗性情况,采用温室内盆栽番茄人工接种法, 鉴定了江苏及周边地区栽培的17个番茄品种对南方根结线虫 (Meloidogyne incognita) 的抗性程度。结果表明,天宝316表现高抗;以色列A316和粉果310表现中抗;秦樱3号、布鲁诺以及瑞星华美表现出抗病;奥米多9号、欧亚奇以及美国903表现出感病性;苏红2003、美国大红、合作903、台湾圣女、多彩水果番茄、奥利、黄贵妃樱桃番茄以及荷兰紫圣果表现出高感病性。携带Mi基因的番茄品种能够对南方根结线虫具有很好抗性,笔者利用引物SCAR F及SCAR R进行特异性检测发现,天宝(KF015736)、瑞星华美(KF015735)及多彩水果(KF015734)均获得720bp条带,与Heinz 1706（DQ437766）Mi基因同源性达到100%。