Search

The wheat stem rust fungus, Puccinia graminis f. sp. tritici (Pgt), race TTKSK and related races pose a serious threat to world wheat production. Knowing the effectiveness of wheat stem rust resistance (Sr) genes against Pgt race TTKSK is fundamental in mitigating this threat through resistance breeding. Sr15 was previously identified as being ineffective against Pgt race TTKSK. Here, multirace disease phenotyping data, linkage analyses, allelism testing and haplotype analyses are presented to support the conclusion that Sr15 is effective against Pgt race TTKSK. Resistance to race TTKSK was mapped to Sr15 in a biparental population. Thirty‐two accessions with Sr15 displayed seedling resistance phenotypes against race TTKSK. However, these accessions were susceptible as seedlings at high temperatures (22–25 °C), consistent with previous reports that the interaction between avirulent Pgt isolates and Sr15 is temperature‐sensitive. Markers STS638, wri4 and KASP_IWB30995 were found to predict the presence of Sr15, suggesting the utility of these assays for marker‐assisted selection in breeding programmes. The effectiveness of Sr15 to specific Pgt races and temperatures makes it a less‐desirable TTKSK‐effective gene. Wheat lines assayed as resistant to race TTKSK at the seedling stage may possess Sr15 and breeders should be aware of the limitations of Sr15 for conferring stem rust resistance. [ABSTRACT FROM AUTHOR]

Aluminium toxicity is an important abiotic factor limiting the growth and yield of oat plants (Avena sativa L.) and other cultivated species. The objectives of this study were to evaluate the response of oat cultivars at the reproductive stage to aluminium under acid soil conditions and to compare with the responses observed at seedling stage under hydroponic conditions. In the soil, the damage to the above-ground part of the plant was estimated by the morphological response to aluminium, shoot length, shoot dry mass and plant height and, to the below-ground part of the plant as the length of roots and root dry mass. In hydroponics, the primary root regrowth was used to define the level of tolerance. The comparison of the results obtained in acid soil with those obtained in hydroponics demonstrated that both conditions produced essentially the same responses. The use of hydroponic solution can be a valuable tool for phenotyping large populations, especially useful for breeding programmes located in regions were aluminium is not present at toxic levels in the soil. [ABSTRACT FROM AUTHOR]

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.