Rooting Characteristics of <Emphasis Type="Italic">Solanum chacoense</Emphasis> and <Emphasis Type="Italic">Solanum tuberosum in Vitro</Emphasis>

The precise level of environmental control in vitro may aid in identifying genetically superior plant germplasm for rooting characteristics (RC) linked to increased foraging for plant nitrogen (N). The objectives of this research were to determine the phenotypic variation in root morphological responses of 49 Solanum chacoense (chc), 30 Solanum tuberosum Group Phureja – Solanum tuberosum Group Stenotomum (phu-stn), and three Solanum tuberosum (tbr) genotypes to 1.0 and 0.5 N rate in vitro for 28 d, and identify genotypes with superior RC. The 0.5 N significantly increased density of root length, surface area, and tips. All RC were significantly greater in chc than in either phu-stn or tbr. Based upon clustering on root length, surface area, and volume, the cluster with the greatest rooting values consisted of eight chc genotypes that may be utilized to initiate a breeding program to improve RC in potato.     

Divergent evolution of rice blast resistance <Emphasis Type="Italic">Pi54</Emphasis> locus in the genus <Emphasis Type="Italic">Oryza</Emphasis>

Background

The rice blast resistance gene Pi54 was cloned from Oryza sativa ssp. indica cv. Tetep, which conferred broad-spectrum resistance against Magnaporthe oryzae. Pi54 allelic variants have been identified in not only domesticates but also wild rice species, but the majority of japonica and some indica cultivars lost the function.

Results

We here found that Pi54 (Os11g0639100) and its homolog Os11g0640600 (named as #11) were closely located on a 25 kbp region in japonica cv. Sasanishiki compared to a 99 kbp region in japonica cv. Nipponbare. Sasanishiki lost at least six genes containing one other R-gene cluster (Os11g0639600, Os11g0640000, and Os11g0640300). Eight AA-genome species including five wild rice species were classified into either Nipponbare or Sasanishiki type. The BB-genome wild rice species O. punctata was Sasanishiki type. The FF-genome wild rice species O. brachyantha (the basal lineage of Oryza) was neither, because Pi54 was absent and the orientation of the R-gene cluster was reversed in comparison with Nipponbare-type species. The phylogenetic analysis showed that #11gene of O. brachyantha was on the root of both Pi54 and #11 alleles. All Nipponbare-type Pi54 alleles were specifically disrupted by 143 and 37/44?bp insertions compared to Tetep and Sasanishiki type. In addition, Pi54 of japonica cv. Sasanishiki lost nucleotide-binding site and leucine-rich repeat (NBS–LRR) domains owing to additional mutations.

Conclusions

These results suggest that Pi54 might be derived from a tandem duplication of the ancestor #11 gene in progenitor FF-genome species. Two divergent structures of Pi54 locus caused by a mobile unit containing the nearby R-gene cluster could be developed before domestication. This study provides a potential genetic resource of rice breeding for blast resistance in modern cultivars sustainability.

     

<Emphasis Type="Italic">Prunus persica</Emphasis> var. <Emphasis Type="Italic">platycarpa</Emphasis> (Tabacchiera Peach): Bioactive Compounds and Antioxidant Activity of Pulp,Peel and Seed Ethanolic Extracts

A comparative analysis of ethanol extracts from peel, pulp and seed of Prunus persica var. platycarpa (Tabacchiera peach) was done. The total phenol, flavonoid and carotenoid content as well as the antioxidant properties by using different in vitro assays (DPPH, ABTS, FRAP, Fe-chelating, β-carotene bleaching test) were evaluated. Pulp extract was subjected to liquid chromatography-electrospray-tandem mass spectrometry (HPLC-ESI-MS/MS). Gallic acid, protocatechuic acid, protocatechualdehyde, chlorogenic acid, p-coumaric acid, and ferulic acid were identified as main constituents. Pulp extract was characterized by the highest total phytonutrients content and exhibited the highest antioxidant activity in all in vitro assays (IC₅₀ values of 2.2 μg/mL after 60 min of incubation by using β-carotene bleaching test and 2.9 μg/mL by using Fe-chelating assay). Overall, the obtained results suggest that P. persica var. platycarpa displays a good antioxidant activity and its consumption could be promoted.     

<Emphasis Type="Italic">Lupinus albus</Emphasis> Conglutin Gamma Modifies the Gene Expressions of Enzymes Involved in Glucose Hepatic Production <Emphasis Type="Italic">In Vivo</Emphasis>

Lupinus albus seeds contain conglutin gamma (Cγ) protein, which exerts a hypoglycemic effect and positively modifies proteins involved in glucose homeostasis. Cγ could potentially be used to manage patients with impaired glucose metabolism, but there remains a need to evaluate its effects on hepatic glucose production. The present study aimed to analyze G6pc, Fbp1, and Pck1 gene expressions in two experimental animal models of impaired glucose metabolism. We also evaluated hepatic and renal tissue integrity following Cγ treatment. To generate an insulin resistance model, male Wistar rats were provided 30% sucrose solution ad libitum for 20 weeks. To generate a type 2 diabetes model (STZ), five-day-old rats were intraperitoneally injected with streptozotocin (150 mg/kg). Each animal model was randomized into three subgroups that received the following oral treatments daily for one week: 0.9% w/v NaCl (vehicle; IR-Ctrl and STZ-Ctrl); metformin 300 mg/kg (IR-Met and STZ-Met); and Cγ 150 mg/kg (IR-Cγ and STZ-Cγ). Biochemical parameters were assessed pre- and post-treatment using colorimetric or enzymatic methods. We also performed histological analysis of hepatic and renal tissue. G6pc, Fbp1, and Pck1 gene expressions were quantified using real-time PCR. No histological changes were observed in any group. Post-treatment G6pc gene expression was decreased in the IR-Cγ and STZ-Cγ groups. Post-treatment Fbp1 and Pck1 gene expressions were reduced in the IR-Cγ group but increased in STZ-Cγ animals. Overall, these findings suggest that Cγ is involved in reducing hepatic glucose production, mainly through G6pc inhibition in impaired glucose metabolism disorders.     

Seasonal deviation effects foliar endophyte assemblage and diversity in <Emphasis Type="Italic">Asparagus racemosus</Emphasis> and <Emphasis Type="Italic">Hemidesmus indicus</Emphasis>

Background

Fungal endophytes are the living symbionts which cause no apparent damage to the host tissue. The distribution pattern of these endophytes within a host plant is mediated by environmental factors. This study was carried out to explore the fungal endophyte community and their distribution pattern in Asparagus racemosus and Hemidesmus indicus growing in the study area.

Results

Foliar endophytes were isolated for 2 years from A. racemosus and H. indicus at four different seasons (June–August, September–November, December–February, March–May). A total of 5400 (675/season/year) leaf segments harbored 38 fungal species belonging to 17 genera, 12 miscellaneous mycelia sterile from 968 isolates and 13 had yeast like growth. In A. racemosus, Acremonium strictum and Phomopsis sp.1, were dominant with overall relative colonization densities (RCD) of 7.11% and 5.44% respectively, followed by Colletotrichum sp.3 and Colletotrichum sp.1 of 4.89% and 4.83% respectively. In H. indicus the dominant species was A. strictum having higher overall RCD of 5.06%, followed by Fusarium moniliforme and Colletotrichum sp.2 with RCD of 3.83% and 3%, respectively. Further the overall colonization and isolation rates were higher during the wet periods (September–November) in both A. racemosus (92.22% and 95.11%) and H. indicus (82% and 77.11%).

Conclusion

Study samples treated with 0.2% HgCl₂ and 75% EtOH for 30 s and 1 min, respectively, confirmed most favorable method of isolation of the endophytes. Owing to high mean isolation and colonization rates, September–November season proved to be the optimal season for endophyte isolation in both the study plants. Assessing the bioactive potential of these endophytes, may lead to the isolation of novel natural products and metabolites.

     

<Emphasis Type="Italic">GNS4</Emphasis>, a novel allele of <Emphasis Type="Italic">DWARF11</Emphasis>, regulates grain number and grain size in a high-yield rice variety

Background

Rice plays an extremely important role in food safety because it feeds more than half of the world’s population. Rice grain yield depends on biomass and the harvest index. An important strategy to break through the rice grain yield ceiling is to increase the biological yield. Therefore, genes associated with organ size are important targets for rice breeding.

Results

We characterized a rice mutant gns4 (grain number and size on chromosome 4) with reduced organ size, fewer grains per panicle, and smaller grains compared with those of WT. Map-based cloning indicated that the GNS4 gene, encoding a cytochrome P450 protein, is a novel allele of DWARF11 (D11). A single nucleotide polymorphism (deletion) in the promoter region of GNS4 reduced its expression level in the mutant, leading to reduced grain number and smaller grains. Morphological and cellular analyses suggested that GNS4 positively regulates grain size by promoting cell elongation. Overexpression of GNS4 significantly increased organ size, 1000-grain weight, and panicle size, and subsequently enhanced grain yields in both the Nipponbare and Wuyunjing7 (a high-yielding cultivar) backgrounds. These results suggest that GNS4 is key target gene with possible applications in rice yield breeding.

Conclusion

GNS4 was identified as a positive regulator of grain number and grain size in rice. Increasing the expression level of this gene in a high-yielding rice variety enhanced grain yield. GNS4 can be targeted in breeding programs to increase yields.

     

Identification and fine mapping of <Emphasis Type="Italic">Bph33</Emphasis>, a new brown planthopper resistance gene in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Background

Host-plant resistance is the most desirable and economic way to overcome BPH damage to rice. As single-gene resistance is easily lost due to the evolution of new BPH biotypes, it is urgent to explore and identify new BPH resistance genes.

Results

In this study, using F_2:3 populations and near-isogenic lines (NILs) derived from crosses between two BPH-resistant Sri Lankan rice cultivars (KOLAYAL and POLIYAL) and a BPH-susceptible cultivar 9311, a new resistance gene Bph33 was fine mapped to a 60-kb region ranging 0.91–0.97 Mb on the short arm of chromosome 4 (4S), which was at least 4 Mb distant from those genes/QTLs (Bph12, Bph15, Bph3, Bph20, QBph4 and QBph4.2) reported before. Seven genes were predicted in this region. Based on sequence and expression analyses, a Leucine Rich Repeat (LRR) family gene (LOC_Os04g02520) was identified as the most possible candidate of Bph33. The gene exhibited continuous and stable resistance from seedling stage to tillering stage, showing both antixenosis and antibiosis effects on BPH.

Conclusion

The results of this study will facilitate map-based cloning and marker-assisted selection of the gene.

     

The Low Potential of Teff (<Emphasis Type="Italic">Eragrostis tef</Emphasis>) as an Inoculum Source for <Emphasis Type="Italic">Verticillium dahliae</Emphasis>

Teff (Eragrostis tef) is a fine stemmed annual grass and gluten free small grain that is of interest as a forage, cover, or a rotation crop. Little is known about the susceptibility of teff to many diseases. Teff could be grown in rotation with potato in the northwestern United States provided teff cultivation is economical and does not increase soil populations for pathogens affecting rotation crops such as Verticillium dahliae. Verticillium dahliae infects a wide range of dicotyledonous plants, making it one of the most important fungal pathogens of crop plants in North America, including potato. The objective of this study was to quantify the susceptibility of teff to eight V. dahliae isolates and compare the susceptibility of teff to eggplant. Teff was confirmed as a host for V. dahliae, as indicated by the presence of microsclerotia in teff stems and roots after artificial inoculation in two years of greenhouse studies. The number of microsclerotia produced in teff did not differ between mint and potato pathotypes of V. dahliae. No V. dahliae isolate produced significantly greater numbers of microsclerotia than any of the seven other isolates tested in a two-year study. Microsclerotia production of V. dahliae in teff was consistently less than in susceptible eggplant cv. Night shadow in both greenhouse experiments (P?<?0.02). It is unlikely that teff infected by V. dahliae will proliferate microsclerotia of mint or potato-aggressive pathotypes, especially when compared to susceptible eggplant cultivars.     

Colorimetric Analysis of <Emphasis Type="Italic">Hibiscus</Emphasis> Beverages and their Potential Antioxidant Properties

In food industry, roselle beverages and their subproducts could be functional ingredients since they are an excellent source of bioactive compounds with improved performance due to their important anthocyanins content. The aim of this study was to analyze anthocyanin content and antioxidant properties of aqueous infusions elaborated with color contrasting Hibiscus materials and design a mathematical model in order to predict color-composition relationship. Color measurements of beverages from roselle (Negra, Sudan and Rosa) were made by transmission spectrophotometry, anthocyanins quantification was determined by HPLC, and antioxidant potential was evaluated by in vitro methods (ABTS and FRAP assays). Beverages prepared with particle size minor of 250 μm presented until 4- and 2- times more anthocyanins content and antioxidant capacity respectively, in comparison to beverages prepared with powders with particle size major of 750 μm. Positive correlations among pigments composition and color parameters were found (p?<?0.05), showing that anthocyanins content, antioxidant capacity, C*_ab and h_ab values increased in relation with the smallest particle size of flours. Also, mathematical models were stablished to predict anthocyanin content (r?≥?0.97) and antioxidant capacity (r?≥?0.89) from color data; we propose equations for quick estimation of the antioxidant capacity in the Hibiscus beverages with high anthocyanin content. The obtained models could be an important tool to be used in food industry for pigment characterization or functional compounds with potential health benefits.     

<Emphasis Type="Italic">OsLAP6/OsPKS1</Emphasis>, an orthologue of <Emphasis Type="Italic">Arabidopsis PKSA/LAP6</Emphasis>, is critical for proper pollen exine formation

Background

Male fertility is crucial for rice yield, and the improvement of rice yield requires hybrid production that depends on male sterile lines. Although recent studies have revealed several important genes in male reproductive development, our understanding of the mechanisms of rice pollen development remains unclear.

Results

We identified a rice mutant oslap6 with complete male sterile phenotype caused by defects in pollen exine formation. By using the MutMap method, we found that a single nucleotide polymorphism (SNP) variation located in the second exon of OsLAP6/OsPKS1 was responsible for the mutant phenotype. OsLAP6/OsPKS1 is an orthologous gene of Arabidopsis PKSA/LAP6, which functions in sporopollenin metabolism. Several other loss-of-function mutants of OsLAP6/OsPKS1 generated by the CRISPR/Cas9 genomic editing tool also exhibited the same phenotype of male sterility. Our cellular analysis suggested that OsLAP6/OsPKS1 might regulate pollen exine formation by affecting bacula elongation. Expression examination indicated that OsLAP6/OsPKS1 is specifically expressed in tapetum, and its product is localized to the endoplasmic reticulum (ER). Protein sequence analysis indicated that OsLAP6/OsPKS1 is conserved in land plants.

Conclusions

OsLAP6/OsPKS1 is a critical molecular switch for rice male fertility by participating in a conserved sporopollenin precursor biosynthetic pathway in land plants. Manipulation of OsLAP6/OsPKS1 has potential for application in hybrid rice breeding.

     

Enhanced <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">tuberosi</Emphasis> Resistance in Transgenic Potato Expressing a Rice GLP Superoxide Dismutase Gene

Germin like proteins (GLPs) are a large group of related and ubiquitous plant proteins which are considered to be involved in different processes important for plant development and defense. Multiple functional copies of this gene family have been reported in a number of species (wheat, barley, rice, soybean mosses and liverwort), and their role is being evaluated by gene regulation studies and transgenic approaches. To analyze the role of a rice (Oryza sativa) root expressed germin like protein1 OsRGLP1, for its antifungal activity, transgenic potato plants were developed. These transgenic potato plants were molecularly characterized and biologically assessed after inoculation with Fusarium oxysporum f. sp. tuberosi. Functional analysis showed high accumulation of H₂O₂, increased Superoxide Dismutase (SOD) activity and no oxalate oxidase activity (OxO) in transgenics in comparison to nontransformed control. This increased SOD activity, resistance to heat and sensitivity to H₂O₂ suggest it is a Fe-like SOD. OsRGLP1 expression in potato plants exhibited enhanced resistance in comparison to nontransformed wild type plants suggesting its role in providing protection against Fusarium oxysporum f. sp. tuberosi through elevated SOD level. Overall, results suggest that OsRGLP1 is a candidate for the engineering of potato plants with increased fungal tolerance however, the greater height and tuber number was observed. This phenotype associated with the resistance needs to be evaluated to determine if this is a positive or negative feature.     

Resistance to <Emphasis Type="Italic">Meloidogyne chitwoodi</Emphasis> Identified in Wild Potato Species

Meloidogyne chitwoodi (Columbia root-knot nematode, CRKN) can cause serious damage in potato production systems, decreasing tuber value in the fresh market and processing industries. Genetic resistance to CRKN was first identified from the wild diploid potato species Solanum bulbocastanum accession SB22 and was successfully introgressed into tetraploid potato breeding material. To expand the base of genetic resistance, 40 plant accessions representing nine wild potato species were screened for their resistance to M. chitwoodi. Greenhouse screening identified fifteen clones from S. hougasii, one clone from S. bulbocastanum, and one clone from S. stenophyllidium with moderate to high levels of resistance against three isolates of M. chitwoodi. Geographical mapping showed that the resistance sources identified in this and previous studies primarily originated in the states of Jalisco and Michoacán in west-central Mexico. These new sources of resistance will be introgressed into elite potato populations to facilitate the development of potato cultivars with durable resistance to M. chitwoodi.     

Effect of Inulin on the Viability of <Emphasis Type="Italic">L. plantarum</Emphasis> during Storage and <Emphasis Type="Italic">In Vitro</Emphasis> Digestion and on Composition Parameters of Vegetable Fermented Juices

The prebiotic effect of different concentrations of inulin (0, 1 and 2%) on the growth and survival of Lactobacillus plantarum (LP) CECT 220 in blended carrot and orange juices was investigated after 24 h of fermentation, during 30 days of storage at 4 °C and through the phases of gastrointestinal digestion after different storage periods. Microbiological and chemical determinations were also carried out in all juices. The lactic fermentation increased the shelf life of the fermented juices with inulin. The hygienic-sanitary quality in fermented juices was better than the control juices. During storage, the inulin improved the viability of LP and the monosaccharide concentration remained higher with respect to the juice without inulin (40% lower). At 30 days, the fermented juices with 2% inulin after in vitro digestion presented the highest survival of L. plantarum.     

Proteomic analysis of the defense response to <Emphasis Type="Italic">Magnaporthe oryzae</Emphasis> in rice harboring the blast resistance gene <Emphasis Type="Italic">Piz-t</Emphasis>

Background

Rice blast (caused by Magnaporthe oryzae) is one of the most destructive diseases of rice. While many blast resistance (R) genes have been identified and deployed in rice cultivars, little is known about the R gene-mediated defense mechanism. We used a rice transgenic line harboring the resistance gene Piz-t to investigate the R gene-mediated resistance response to infection.

Results

We conducted comparative proteome profiling of the Piz-t transgenic Nipponbare line (NPB-Piz-t) and wild-type Nipponbare (NPB) inoculated with M. oryzae at 24, 48, 72 h post-inoculation (hpi) using isobaric tags for relative and absolute quantification (iTRAQ) analysis. Comparative analysis of the response of NPB-Piz-t to the avirulent isolate KJ201 and the virulent isolate RB22 identified 114 differentially expressed proteins (DEPs) between KJ201-inoculated NPB-Piz-t (KJ201-Piz-t) and mock-treated NPB-Piz-t (Mock-Piz-t), and 118 DEPs between RB22-inoculated NPB-Piz-t (RB22-Piz-t) and Mock-Piz-t. Among the DEPs, 56 occurred commonly in comparisons KJ201-Piz-t/Mock-Piz-t and RB22-Piz-t/Mock-Piz-t. In a comparison of the responses of NPB and NPB-Piz-t to isolate KJ201, 93 DEPs between KJ201-Piz-t and KJ201-NPB were identified. DEPs in comparisons KJ201-Piz-t/Mock-Piz-t, RB22-Piz-t/Mock-Piz-t and KJ201-Piz-t/KJ201-NPB contained a number of proteins that may be involved in rice response to pathogens, including pathogenesis-related (PR) proteins, hormonal regulation-related proteins, defense and stress response-related proteins, receptor-like kinase, and cytochrome P450. Comparative analysis further identified 7 common DEPs between the comparisons KJ201-Piz-t/KJ201-NPB and KJ201-Piz-t/RB22-Piz-t, including alcohol dehydrogenase I, receptor-like protein kinase, endochitinase, similar to rubisco large subunit, NADP-dependent malic enzyme, and two hypothetical proteins.

Conclusions

Our results provide a valuable resource for discovery of complex protein networks involved in the resistance response of rice to blast fungus.

     

Ephemeral-habitat colonization and neotropical species richness of <Emphasis Type="Italic">Caenorhabditis</Emphasis> nematodes

Background

The drivers of species co-existence in local communities are especially enigmatic for assemblages of morphologically cryptic species. Here we characterize the colonization dynamics and abundance of nine species of Caenorhabditis nematodes in neotropical French Guiana, the most speciose known assemblage of this genus, with resource use overlap and notoriously similar external morphology despite deep genomic divergence.

Methods

To characterize the dynamics and specificity of colonization and exploitation of ephemeral resource patches, we conducted manipulative field experiments and the largest sampling effort to date for Caenorhabditis outside of Europe. This effort provides the first in-depth quantitative analysis of substrate specificity for Caenorhabditis in natural, unperturbed habitats.

Results

We amassed a total of 626 strain isolates from nine species of Caenorhabditis among 2865 substrate samples. With the two new species described here (C. astrocarya and C. dolens), we estimate that our sampling procedures will discover few additional species of these microbivorous animals in this tropical rainforest system. We demonstrate experimentally that the two most prevalent species (C. nouraguensis and C. tropicalis) rapidly colonize fresh resource patches, whereas at least one rarer species shows specialist micro-habitat fidelity.

Conclusion

Despite the potential to colonize rapidly, these ephemeral patchy resources of rotting fruits and flowers are likely to often remain uncolonized by Caenorhabditis prior to their complete decay, implying dispersal-limited resource exploitation. We hypothesize that a combination of rapid colonization, high ephemerality of resource patches, and species heterogeneity in degree of specialization on micro-habitats and life histories enables a dynamic co-existence of so many morphologically cryptic species of Caenorhabditis.

     

Amplification of the <Emphasis Type="Italic">Phytophthora infestans</Emphasis> RG57 loci Facilitates <Emphasis Type="Italic">in planta</Emphasis> T-RFLP Identification of Late Blight Genotypes

Late blight, caused by the oomycete Phytophthora infestans (Mont.) de Bary, is a devastating disease in potato and tomato and causes yield and quality losses worldwide. The disease first emerged in central America and has since spread in North America including the United States and Canada. Several new genotypes of P. infestans have recently emerged, including US-22, US-23 and US-24. Due to significant economic and environmental impacts, there has been an increasing interest in the rapid identification of P. infestans genotypes. In addition to providing details regarding the various phenotypic characteristics such as fungicide resistance, host preference, and pathogenicity associated with various P. infestans genotypes, information related to pathogen movement and potential recombination may also be determined from the genetic analyses. Restriction fragment length polymorphism (RFLP) analysis with the RG57 loci is one of the most reliable procedures used to genotype P. infestans. However, the RFLP procedure requires propagation and isolation of the pathogen and relatively large amounts of DNA. Isolation of the late blight pathogen is sometimes impossible due to the poor condition of the infected tissues or the presence of fungicide residues. In this study, we describe a procedure to identify P. infestans at the molecular level in planta using terminal restriction fragment length polymorphism (T-RFLP) of the RG57 loci. This T-RFLP assay is sufficiently sensitive to detect and differentiate P. infestans genotypes directly in planta without propagation and isolation of the pathogen, to facilitate the timely implementation of best management practices.     

Genetic Diversity of Pathogenic <Emphasis Type="Italic">Fusarium semitectum</Emphasis> Isolates from Potato Tubers,Using PCR-IGS-RFLP Markers

Fusarium semitectum is one of the important causal agents of dry rot of potato tubers in the world. In order to determine genetic variability among 41 isolates of F. semitectum, morphological and molecular studies were carried out. All F. semitectum isolates were recovered from infected potato tubers with dry rot symptoms collected from four provinces in Iran. According to macroscopic and microscopic characteristics, 41 isolates of F. semitectum were classified in two morphotypes (morphotypes I and II). All 41 isolates were evaluated for their pathogenicity on healthy potato tubers. Tuber rot symptoms were observed on the 21st day after inoculation of Fusarium isolates on the tubers tested. The measurement was done by comparing the depth and width of lesion expansion among the isolates. Molecular characterization through PCR-IGS-RFLP analysis by six restriction enzymes (AluI, BsuRI, Eco88I, MspI, TaqI and PstI) divided the 41 isolates of F. semitectum into two separated clusters that were in accordance with the morphological characterization.     

Maturity-Adjusted Resistance of Potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.) Cultivars to Verticillium Wilt Caused by <Emphasis Type="Italic">Verticillium dahliae</Emphasis>

Verticillium wilt is a fungal disease of potato caused by two species of Verticillium, V. dahliae and V. albo atrum. The pathogen infects the vascular tissue of potato plants through roots, interfering with the transport of water and nutrition, and reducing both the yield and quality of tubers. We have evaluated the reaction of 283 potato clones (274 cultivars and nine breeding selections) to inoculation with V. dahliae under greenhouse conditions. A significant linear correlation (r = 0.4, p < 0.0001) was detected between plant maturity and partial resistance to the pathogen, with late maturing clones being generally more resistant. Maturity-adjusted resistance, that takes into consideration both plant maturity and resistance, was calculated from residuals of the linear regression between the two traits. Even after adjusting for maturity, the difference in the resistance of clones was still highly significant, indicating that a substantial part of resistance cannot be explained by the effect of maturity. The highest maturity-adjusted resistance was found in the cv. Navajo, while the most susceptible clone was the cv. Pungo. We hope that the present abundance of data about the resistance and maturity of 283 clones will help potato breeders to develop cultivars with improved resistance to V. dahliae.     

An <Emphasis Type="Italic">In Vitro</Emphasis> Assay Method for Resistance to Bacterial Wilt (<Emphasis Type="Italic">Ralstonia solanacearum</Emphasis>) in Potato

To develop an in vitro assay method for bacterial wilt resistance in potato, resistant and susceptible standard genotypes were grown in vitro, and different conditions of inoculation with Ralstonia solanacearum phylotype I/biovar 4 were examined. The optimal condition was the inoculation of 6–8 leaf stage plants with a bacterial concentration of 10² CFU ml^?1 and an incubation temperature of 28 °C. Evaluation of stem wilting was more reliable than that of leaf wilting. Using this method, nine genotypes with different resistance levels in the field were evaluated. Lower disease indices were obtained for genotypes with high resistance levels in the field, suggesting that this assay is useful for evaluating bacterial wilt resistance in a controlled environment.