Behavior of new entries and developed tomato hybrids carrying Ty-2 gene

Tomato yellow leaf curl disease (TYLCD) is a serious problem hampering tomato production worldwide. In the Mediterranean Basin, disease incidence and severity are higher in the dry season increasing whitefly (Bemisia tabaci) populations. Effectiveness of resistance to Tomato yellow leaf curl virus (TYLCV) depends on both tomato host resistance and TYLCV complex species. So far, six different Ty tomato resistance genes have been identified. Two main TYLCV complex species, Tomato yellow leaf curl virus-Israel (TYLCV-Is) and Tomato yellow leaf curl Sardinia virus (TYLCSV), have been identified in Tunisia. The present work aimed to evaluate entries heterozygous for Ty-2 gene to help predict hybrid performance. Two tomato entries homozygous for the Ty-2 TYLCV resistance gene, one tomato hybrid homozygous for Ty-2 and two heterozygous hybrids were included, besides two susceptible tomato entries. Resistance response to TYLCD was recorded based on disease incidence and severity levels. Data analysis was performed according to presence/absence of Ty-2 gene and taking into account homozygosity and heterozygosity of Ty-2. Generalized linear model analysis was applied to check significance of individual factors' effects (i.e. effect of tomato entries or tomato groups of entries based on presence or absence of homozygous/heterozygous Ty-2 gene, block unit within the field trial and the year of the trial) on the dependent variables (disease incidence and severity). Further multi-comparison tests gave evidence on significant effect of Ty-2 homozygous gene tomato entries on TYLCD incidence and severity levels. The results were discussed with special focus on the relevance use of heterozygous hybrid tomato varieties

Value adding search among a selection of Tunisian fennel (Foeniculum vulgare Mill.) cultivars: Nutritional composition, chlorophyll and β-carotene contents of fennel seeds

Foeniculum vulgare has an important medicinal and economic role due to the frequent use of different parts of the plant. However, fennel seeds are the most exploited especially in culinary preparations and food industries. In order to highlight the benefits of this spice, physico-chemical composition of 7 fennel cultivars was carried out. Results revealed high contents of sugars, proteins and ash, and low contents of fat and water. The highest sugar content was displayed by the cultivar Cv2 (61±1.87 %) and the lowest one was obtained by cultivar Cv5 (31.41±1.77 %). Statistically significant differences between the 7 fennel cultivars were shown among their respective protein contents. Interestingly, all of the 7 cultivars, except one (Cv3: 7.91±0.07 %), revealed high levels of protein contents. Moreover, assessment of physiological parameters of the 7 cultivars gave evidence of high β-carotene contents. Despite, chlorophyll assessment results gave moderate content levels. Taking into account results from the present work, in addition to our previous published findings, 4 fennel cultivars were selected, essentially, based on their nutritional composition while searching for future potential industrial applications

Value adding search among a selection of Tunisian fennel (Foeniculum vulgare Mill.) cultivars: Diversity assessment and selection among a local fennel germplasm

Fennel (Foeniculum vulgare Mill.) is a very popular, aromatic, herbaceous plant that belongs to the Apiaceae family. It is among most important spices and medicinal species over the world. Nevertheless, in Tunisia fennel cultivation doesn't cover the local market needs. Also, fennel seeds are produced by farmers traditionally, and none of the local cultivars is named nor labelled in the market. Efforts have been deployed during the present work aiming to the characterization and valorization of genetic fennel resources. Hence, morphological diversity assessment was carried out among 62 entries of fennel acquired from different origins. Two steps principle component analysis (PCA) were applied. It came out with 7 selected cultivars of fennel representative of the initial diversity as assessed within the 62 collected fennel entries. Interestingly, among these latter, some of them exhibited particular phenotypic features linked to production traits

Genomes of three tomato pathogens within the Ralstonia solanacearum species complex reveal significant evolutionary divergence

<p>Abstract</p> <p>Background</p> <p>The <it>Ralstonia solanacearum </it>species complex includes thousands of strains pathogenic to an unusually wide range of plant species. These globally dispersed and heterogeneous strains cause bacterial wilt diseases, which have major socio-economic impacts. Pathogenicity is an ancestral trait in <it>R. solanacearum </it>and strains with high genetic variation can be subdivided into four phylotypes, correlating to isolates from Asia (phylotype I), the Americas (phylotype IIA and IIB), Africa (phylotype III) and Indonesia (phylotype IV). Comparison of genome sequences strains representative of this phylogenetic diversity can help determine which traits allow this bacterium to be such a pathogen of so many different plant species and how the bacteria survive in many different habitats.</p> <p>Results</p> <p>The genomes of three tomato bacterial wilt pathogens, CFBP2957 (phy. IIA), CMR15 (phy. III) and PSI07 (phy. IV) were sequenced and manually annotated. These genomes were compared with those of three previously sequenced <it>R. solanacearum </it>strains: GMI1000 (tomato, phy. I), IPO1609 (potato, phy. IIB), and Molk2 (banana, phy. IIB). The major genomic features (size, G+C content, number of genes) were conserved across all of the six sequenced strains. Despite relatively high genetic distances (calculated from average nucleotide identity) and many genomic rearrangements, more than 60% of the genes of the megaplasmid and 70% of those on the chromosome are syntenic. The three new genomic sequences revealed the presence of several previously unknown traits, probably acquired by horizontal transfers, within the genomes of <it>R. solanacearum</it>, including a type IV secretion system, a rhi-type anti-mitotic toxin and two small plasmids. Genes involved in virulence appear to be evolving at a faster rate than the genome as a whole.</p> <p>Conclusions</p> <p>Comparative analysis of genome sequences and gene content confirmed the differentiation of <it>R. solanacearum </it>species complex strains into four phylotypes. Genetic distances between strains, in conjunction with CGH analysis of a larger set of strains, revealed differences great enough to consider reclassification of the <it>R. solanacearum </it>species complex into three species. The data are still too fragmentary to link genomic classification and phenotypes, but these new genome sequences identify a pan-genome more representative of the diversity in the <it>R. solanancearum </it>species complex.</p

Novel Source of Resistance against Root Necrosis and Plant Wilting Disease Caused by Phytophthora nicotianae in Capsicum annuum

Phytophthora nicotianae the causal agent of root necrosis in pepper was isolated and identified for the first time in Tunisia in 1995. It causes plant wilting and might induce considerable damage especially in infested soils grown with pepper varieties lacking genetic resistance. This disease was observed in green houses as well as in open fields. The present study aimed to identify sources of resistance against P. nicotianae in a collection of pepper accessions from the WorldVeg (The World Vegetable Center, previously named AVRDC for Asian Vegetable Research and Development Center) gene bank. These WorldVeg accessions include 28 chili and 12 sweet peppers together with 8 chili and one sweet local cultivars. Seedling reaction to the pathogen was determined one month after inoculation by the zoospores of a highly aggressive isolate deposited at the seedling crown. Results showed that 12 accessions (11 chili and 1 sweet peppers) displayed good resistance to this oomycete. However, fruit quality and productivity of these resistant accessions need to be verified. It is of importance to carry out an analysis on genetic control of such resistance by performing crosses between susceptible and resistant ones, besides studying the suitable use of the unveiled resistance according to the pathogenicity and virulence of the pathogen strains. Therefore, appropriate resistance sources can be used as genitors in a breeding program

Specific Genes from the Potato Brown Rot Strains of Ralstonia solanacearum and Their Potential Use for Strain Detection

International audienceRalstonia solanacearum is the agent of bacterial wilt infecting >200 different plant species covering >50 botanical families. The genus R. solanacearum can be classified into four phylotypes and each phylotype can be further subdivided into sequevars. The potato brown rot strains of R. solanacearum from phylotype IIB, sequevar 1 (IIB1), historically known as race 3, biovar 2 strains, are responsible for important economic losses to the potato industry and threaten ornamental crop production worldwide. Sensitive and specific detection methods are required to control this pathogen. This article provides a list of 70 genes and 15 intergenes specific to the potato brown rot strains of R. solanacearum from phylotype IIB1. This list was identified by comparative genomic hybridization on microarray and subsequent polymerase chain reaction validation with 14 IIB1 strains against 45 non-IIB1 strains that covered the known genetic diversity in R. solanacearum. The microarray used consisted of the previously described microarray representative of the phylotype I strain GMI1000, to which were added 660 70-mer oligonucleotides representative of new genomic islands detected in the phylotype IIB1 strain IPO1609. The brown rot strain-specific genes thus identified were organized in nine clusters covering 2 to 29 genes within the IPO1609 genome and 6 genes isolated along the genome. Of these specific genes, 29 were parts of mobile genetic elements. Considering the known instability of the R. solanacearum genome, we believe that multiple probes are required to consistently detect all IIB1 strains and we recommend the use of probes which are not part of genetic mobile elements

Value adding search among a selection of Tunisian fennel (Foeniculum vulgare Mill.) cultivars: Diversity assessment and selection among a local fennel germplasm

Fennel (Foeniculum vulgare Mill.) is a very popular, aromatic, herbaceous plant that belongs to the Apiaceae family. It is among most important spices and medicinal species over the world. Nevertheless, in Tunisia fennel cultivation doesn't cover the local market needs. Also, fennel seeds are produced by farmers traditionally, and none of the local cultivars is named nor labelled in the market. Efforts have been deployed during the present work aiming to the characterization and valorization of genetic fennel resources. Hence, morphological diversity assessment was carried out among 62 entries of fennel acquired from different origins. Two steps principle component analysis (PCA) were applied. It came out with 7 selected cultivars of fennel representative of the initial diversity as assessed within the 62 collected fennel entries. Interestingly, among these latter, some of them exhibited particular phenotypic features linked to production traits

Value adding search among a selection of Tunisian fennel (Foeniculum vulgare Mill.) cultivars: Nutritional composition, chlorophyll and β-carotene contents of fennel seeds

Foeniculum vulgare has an important medicinal and economic role due to the frequent use of different parts of the plant. However, fennel seeds are the most exploited especially in culinary preparations and food industries. In order to highlight the benefits of this spice, physico-chemical composition of 7 fennel cultivars was carried out. Results revealed high contents of sugars, proteins and ash, and low contents of fat and water. The highest sugar content was displayed by the cultivar Cv2 (61±1.87 %) and the lowest one was obtained by cultivar Cv5 (31.41±1.77 %). Statistically significant differences between the 7 fennel cultivars were shown among their respective protein contents. Interestingly, all of the 7 cultivars, except one (Cv3: 7.91±0.07 %), revealed high levels of protein contents. Moreover, assessment of physiological parameters of the 7 cultivars gave evidence of high β-carotene contents. Despite, chlorophyll assessment results gave moderate content levels. Taking into account results from the present work, in addition to our previous published findings, 4 fennel cultivars were selected, essentially, based on their nutritional composition while searching for future potential industrial applications