Phenotyping Sunflower Genetic Resources for Sclerotinia Head Rot Response: Assessing Variability for Disease Resistance Breeding.

Sclerotinia head rot (SHR) is one of the most serious constraints to sunflower (Helianthus annuus L. var. macrocarpus) production worldwide. Here, we evaluated the response to SHR in a sunflower inbred panel from a large INTA germplasm collection, consisting of 137 inbred lines (ILs). Field trials were performed over five consecutive seasons using a twice-replicated randomized complete-block design. Disease incidence, disease severity, incubation period, and area under disease progress curve for disease incidence and severity were determined after controlled inoculation with the pathogen. Statistical analysis using mixed-effect models detected significant differences among ILs for all variables (P < 0.001). In addition, principal component analysis (PCA) and distance-based methods were used to classify the ILs according to their response to SHR, with ILs ALB2/5261 and 5383 emerging as the most resistant. Broad-sense heritability estimates ranged from 20.64% for disease severity to 10.58% for incubation period. The ample phenotypic variability of our collection, along with the moderate heritability estimates, highlight the importance of molecular breeding approaches to gain new insights into the genetic basis of sunflower resistance to SHR. The exhaustive phenotypic characterization presented here provides a reliable set of variables to comprehensively evaluate the disease and identifies two new sources of resistance to SHR.

Molecular characterization of a putative sucrose:fructan 6-fructosyltransferase (6-SFT) of the cold-resistant Patagonian grass Bromus pictus associated with fructan accumulation under low temperatures.

Fructans are fructose polymers synthesized from sucrose in the plant vacuole. They represent short- and long-term carbohydrate reserves and have been associated with abiotic stress tolerance in graminean species. We report the isolation and characterization of a putative sucrose:fructan 6-fructosyltransferase (6-SFT) gene from a Patagonian grass species, Bromus pictus, tolerant to drought and cold temperatures. Structural and functional analyses of this gene were performed by Southern and Northern blot. Sugar content, quality and fructosyltransferase activity were studied using HPAEC-PAD (high-pH anion-exchange chromatography with pulsed amperometric detection), enzymatic and colorimetric assays. The putative 6-SFT gene had all the conserved motifs of fructosyl-transferase and showed 90% identity at the amino acid level with other 6-SFTs from winter cereals. Expression studies, and determination of sugar content and fructosyl-transferase activity were performed on five sections of the leaf. Bp6-SFT was expressed predominantly in leaf bases, where fructosyltransferase activity and fructan content are higher. Bp6-SFT expression and accumulation of fructans showed different patterns in the evaluated leaf sections during a 7 d time course experiment under chilling treatment. The transcriptional pattern suggests that the B. pictus 6-SFT gene is highly expressed in basal leaf sections even under control temperate conditions, in contrast to previous reports in other graminean species. Low temperatures caused an increase in Bp6-SFT expression and fructan accumulation in leaf bases. This is the first study of the isolation and molecular characterization of a fructosyltransferase in a native species from the Patagonian region. Expression in heterologous systems will confirm the functionality, allowing future developments in generation of functional markers for assisted breeding or biotechnological applications.

Cooked garlic and antioxidant activity: Correlation with organosulfur compound composition.

The antioxidant properties and the main beneficial organosulphur compounds of home-cooked garlic samples were studied in order to establish relationships between them. Antioxidant activity was tested by free radical scavenging against 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and 2,2'-azino-bis-(3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS+), Fe(III) reducing ability (FRAP) and linoleic acid co-oxidation initiated by soybean lipoxygenase in a micelle system. DPPH, ABTS and FRAP assays showed the highest activity for raw garlic samples, while ß-carotene bleaching assay yielded the highest activity for stir-fried garlic. Pure organosulphur compounds tested by DPPH, FRAP and ß-carotene bleaching assays showed that allicin had an antiradical action mechanism, as well as iron reducing capacity; while antioxidant activity was the main mechanism for ajoenes and 2-VD. To our knowledge, this study is the first demonstration that home-cooked garlic retains its antioxidant activity, and, at the same time, elucidates the mechanisms involved in this activity.