No abstract

We developed highly reliable co-dominant SCAR markers linked to the Frl gene. FORL testing is difficult. The marker is expected to be quickly adapted for MAS by tomato breeders. Fusarium oxysporum f. sp. radicis-lycopersici causes Fusarium crown and root rot (FCR), an economically important soil-borne disease of tomato. The resistance against FCR is conferred by a single dominant gene (Frl) located on chromosome 9. The aim of this study was to develop molecular markers linked to the Frl gene for use in marker-assisted breeding (MAS) programs. The FCR-resistant 'Fla. 7781' and susceptible 'B560' lines were crossed, and F1 was both selfed and backcrossed to 'B560' to generate segregating F2 and BC1 populations. The two conserved set II (COSII) markers were found linked to the Frl gene, one co-segregated with FCR resistance in both F2 and BC1 populations and the other was 8.5 cM away. Both COSII markers were converted into co-dominant SCAR markers. SCARFrl marker produced a 950 and a 1000 bp fragments for resistant and susceptible alleles, respectively. The linkage of SCARFrl marker was confirmed in BC2F3 populations developed by backcrossing the resistant 'Fla. 7781' to five different susceptible lines. The SCARFrl marker has been in use in the tomato breeding programs in BATEM, Antalya, Turkey, since 2012 and has proved highly reliable. The SCARFrl marker is expected to aid in the development of FCR-resistant lines via marker-assisted selection (MAS).

-Eruca sativa L. (rocket or arugula) and Diplotaxis tenuifolia L. (perennial wall-rocket)

No abstract

The Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is an important pest of small‐grain cereals, particularly wheat, worldwide. The most efficient strategy against the RWA is to identify sources of resistance and to introduce them into susceptible wheat genotypes. This study was conducted to determine the mode of inheritance of the RWA resistance found in ICARDA accession IG 100695, to identify wheat microsatellite markers closely linked to the gene and to map the chromosomal location of the gene. Simple sequence repeat (SSR) marker scores were identified in a mapping population of 190 F2 individuals and compared, while phenotypic screening for resistance was performed in F2 : 3 families derived from a cross between ‘Basribey’ (susceptible) and IG 100695 (resistant). Phenotypic segregation of leaf chlorosis and rolling displayed the effect of a single dominant gene, temporarily denoted Dn100695, in IG 100695. Dn100695 was mapped on the short arm of chromosome 7D with four linked SSR markers, Xgwm44, Xcfd14, Xcfd46 and Xbarc126. Dn100695 and linked SSR markers may be useful for improving resistance for RWA in wheat breeding.

Rocket (Eruca spp. and Diplotaxis spp.) is widely cultivated as a green vegetable in Mediterranean countries, Europe, United States and Brazil, but few rocket cultivars are available and limited variety selection has taken place. Plant genetic resources and germplasm are fundamental sources for plant breeding, and the assessment of the genetic diversity among germplasm accessions is useful to facilitate the more efficient use of plant genetic resources. The objective of this study was to characterize phenotypic diversity and relationships among genotypes of Eruca and Diplotaxis originating from 11 countries across three regions (Europe, Africa and Asia). Principal component analyses explained over 85% of total variation for 51 qualitative and quantitative agromorphological traits. Cluster analyses divided the accessions into five major clusters according to plant traits, siliqua properties and geographical origin of genotype with a few exceptions. These findings indicate a number of useful traits in the gene pool and a wide range of phenotypic variation that provides a good source of diversity for use in modern Eruca breeding programmes.

High-Throughput Illumina Sequencing (HTS) can be used to study metagenomes, for example, those of importance for plant health. However, protocols must be optimized according to the plant system in question, the focal microorganisms in the samples, the marker genes selected, and the number of environmental samples. We optimized the protocol for metagenomic studies of aspen leaves, originating from varied genotypes sampled across the growing season, and consequently varying in phenolic composition and in the abundance of endo- and epiphytic fungal species. We optimized the DNA extraction protocol by comparing commercial kits and evaluating five fungal ribosomal specific primers (Ps) alone, and with extended primers that allow binding to sample-specific index primers, and we then optimized the amplification with these composite Ps for 380 samples. The fungal DNA concentration in the samples varied from 561 ng/µL to 1526 ng/µL depending on the DNA extraction kit used. However, binding to phenolic compounds affected DNA quality as assessed by Nanodrop measurements (0.63–2.04 and 0.26–2.00 absorbance ratios for 260/280 and 260/230, respectively), and this was judged to be more important in making our choice of DNA extraction kit. We initially modified the PCR conditions after determining the concentration of DNA extract in a few subsamples and then evaluated and optimized the annealing temperature, duration, and number of cycles to obtain the required amplification and PCR product bands. For three specific Ps, the extended Ps produced dimers and unexpected amplicon fragments due to nonspecific binding. However, we found that the specific Ps that targeted the ITS2 region of fungal rDNA successfully amplified this region for every sample (with and without the extension PP) resulting in the desired PCR bands, and also allowing the addition of sample-specific index primers, findings which were successfully verified in a second PCR. The optimized protocol allowed us to successfully prepare an amplicon library in order to subject the intended 380 environmental samples to HTS.

No abstract