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Multiflorous spikelets are found in several grass species of agricultural and economic interest. In oat, this morphological characteristic is associated with the production of naked grains. Although many genetic studies have been performed over the past century, the inheritance of the multiflorous spikelet trait is not fully understood in oat. The objectives of this study were to evaluate environmental effects on the multiflorous spikelet trait, to estimate the number of genes controlling the trait, and to clone and characterize sequences of the AP2 gene in oat. Two genetic populations of recombinant inbreed lines were screened for the multiflorous spikelet trait from different years and sowing dates under field experiments. Normal, multiflorous, and mosaic spikelets were analyzed in the whole panicle for both years and sowing dates. Specific primer pairs for the AP2 gene was utilized to amplify and clone oat sequences. The results demonstrate that under higher temperature and day-length conditions, the variable expressivity of the multiflorous spikelet trait was less pronounced in both populations. Genetic analyses indicated the action of one major gene and two or three modifying genes controlling the expression of the multiflorous spikelet trait in oat, depending on the genetic background. Sequences with similarity to the AP2 gene were isolated from the oat lines UFRGS 017004-2 and URS Taura, and genetic polymorphisms were identified, which are valuable to confirm the action of AP2 on the multiflorous spikelet trait. Our results provide information to assist in the development of future studies of the multiflorous spikelet trait in oat.

The objective of this study was to evaluate whether the oxidative stress caused by aluminum (Al) toxicity is a symptom that can trigger root growth inhibition in oat genotype seedlings. Oat seedlings were grown in a nutrient solution (pH 4.0) with 0 and 370 μM Al. At 12, 24, and 36 h after Al addition, growth (root length) and biochemical parameters (catalase - CAT, ascorbate peroxidase - APX, and superoxide dismutase - SOD activities, lipid peroxidation, ascorbic acid (ASA) and non-protein thiol group (NPSH) concentration) were determined. The aluminum content was measured in oat seedlings. Regardless of the exposure time, root of the tolerant genotype grew normally with any Al treatments. Al supply caused lipid peroxidation only in the Al-sensitive genotype in roots and shoots (at 12, 24, and 36 h). In sensitive genotype seedlings, CAT, APX, and SOD were activated only at 24 or 36 h. In tolerant and intermediate genotypes, CAT, APX, and SOD were activated at 12, 24, and 36 h. Data for root growth and lipid peroxidation suggested that lipid peroxidation in the sensitive genotype may be an effect of Al toxicity on root growth. Therefore, the tolerant, intermediate, and sensitive genotypes differ in the expression of the amount, type of antioxidants, and speed of activation of antioxidant system, suggesting a varying capacity of these genotypes to deal with oxidative stress, which resulted in varying sensitivity and tolerance to Al., (© 2013.)

The phytotoxic effects of aluminum and the mechanisms of genetically-based Al tolerance have been widely investigated, as reported in many papers and reviews. However, investigations on many Al-sensitive and Al-resistant species demonstrate that Al phytotoxicity and Al-resistance mechanisms are extremely complex phenomena. The objective of the present study was to analyze the effects of aluminum on the activity of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX). Also was evaluated the lipid peroxidation, H(2)O(2) content, levels of ascorbic acid (ASA), non-protein thiols (NPSH) and Al content in three genotypes of oat, Avena sativa L. (UFRGS 930598, UFRGS 17, and UFRGS 280). The genotypes were grown in different concentrations of Al ranging from 90 to 555 μM for 5 days. The antioxidant system was unable to overcome toxicity resulting in negative effects such as lipid peroxidation and H(2)O(2) content in UFRGS 930598. The results showed that UFRGS 930598 was the most sensitive genotype. UFRGS 17 and UFRGS 280 were more resistant to Al toxicity. These results suggest that UFRGS 17 has mechanisms of external detoxification and UFRGS 280 has mechanisms of internal detoxification. The different behavior of enzymatic and non-enzymatic antioxidants of the genotypes showed that aluminum resistance in UFGRS 17 and UFRGS 280 may be related to oxidative stress.

Background: Genomic discovery in oat and its application to oat improvement have been hindered by a lack of genetic markers common to different genetic maps, and by the difficulty of conducting whole-genome analysis using high-throughput markers. This study was intended to develop, characterize, and apply a large set of oat genetic markers based on Diversity Array Technology (DArT)., Results: Approximately 19,000 genomic clones were isolated from complexity-reduced genomic representations of pooled DNA samples from 60 oat varieties of global origin. These were screened on three discovery arrays, with more than 2000 polymorphic markers being identified for use in this study, and approximately 2700 potentially polymorphic markers being identified for use in future studies. DNA sequence was obtained for 2573 clones and assembled into a non-redundant set of 1770 contigs and singletons. Of these, 705 showed highly significant (Expectation < 10E-10) BLAST similarity to gene sequences in public databases. Based on marker scores in 80 recombinant inbred lines, 1010 new DArT markers were used to saturate and improve the 'Kanota' x 'Ogle' genetic map. DArT markers provided map coverage approximately equivalent to existing markers. After binning markers from similar clones, as well as those with 99% scoring similarity, a set of 1295 non-redundant markers was used to analyze genetic diversity in 182 accessions of cultivated oat of worldwide origin. Results of this analysis confirmed that major clusters of oat diversity are related to spring vs. winter type, and to the presence of major breeding programs within geographical regions. Secondary clusters revealed groups that were often related to known pedigree structure., Conclusion: These markers will provide a solid basis for future efforts in genomic discovery, comparative mapping, and the generation of an oat consensus map. They will also provide new opportunities for directed breeding of superior oat varieties, and guidance in the maintenance of oat genetic diversity.

Flowering time (or days to heading) is an important characteristic in crop plants that affects adaptation to cropping cycles and growing seasons. The objectives of this study were to identify molecular markers associated with flowering time in 3 oat populations developed from Brazilian oat varieties, and to compare their map locations with those of other loci that might influence flowering time. Flowering time was studied in recombinant inbred lines from 3 hexaploid oat populations: UFRGS 8 x Pc68/5*Starter; UFRGS 881971 x Pc68/5*Starter; and UFRGS 8 x UFRGS 930605. Bulked segregant analysis, using amplified fragment length polymorphism, was followed by selective mapping in each population and in a reference population, 'Kanota' x 'Ogle' (KxO). One quantitative trait locus (QTL) with major effects on flowering time was identified in each cross. Comparative mapping showed that a major QTL, with earliness alleles originating from UFRGS 8 and UFRGS 881971, is in a region with close homology to KxO linkage group 17 and to a locus that reportedly confers day-length insensitivity in oat (Di1). This is the first report to identify the map location of the Di1 locus, and putatively confirm the presence of Di1 alleles in new germplasm. Further comparative mapping and the alignment of mapped oat markers with the sequenced rice genome suggest that this QTL and (or) Di1 is orthologous to the Hd1 locus in rice and the CONSTANS gene in Arabidopsis and other species. A different QTL with major effects segregated in the UFRGS 8 x UFRGS 930605 cross, where the early-flowering allele for Di1 was probably fixed. Two additional QTLs with smaller effects were identified in the UFRGS 8 x Pc68/5*Starter population. These results suggest that the Brazilian oat line UFRGS 8 contains an optimal set of alleles conditioning earliness under the short-day conditions of the Brazilian winter growing season, and that molecular selection could be used to introgress these alleles into other breeding material.