Charakterisierung der Virulenz einer Braunrost-Feldpopulation (Puccinia triticina f. sp. tritici) und Nachweis effektiver Braun-rost-resistenz-gene in Weizen (Triticum aestivum)

Puccinia triticina f. sp. tritici, the causal agent of leaf rust causes yield losses in wheat up to 60%. In order to avoid such losses, leaf rust resistance (Lr-) genes have been incorporated into wheat cultivars. The Lr- genes confer mostly vertical resistance, i.e. they are race specific. Therefore, knowledge of still effective resistance genes is required for efficient breeding of resistant cultivars. To get information on these virulences, a leaf rust population was monitored in field experiments in 2010. For this purpose naturally infection at three different timepoints of wheat development was monitored on Thatcher near isogenic lines (NILs) carrying 37 and accessions carrying 6 additional Lr-genes. Thatcher-NILs carrying Lr2a, Lr9, Lr19, Lr22a, Lr23, Lr24, Lr35, Lr38 and Lr49 showed a significantly lower infection with Puccinia triticina than the susceptible cultivar Thatcher. Thatcher-NILs carrying Lr13, Lr16, Lr37 and Lr46 showed no significant differences in comparison to Thatcher. In order to get information on the effectiveness of resistance genes, P. triticina isolates were collected from the NILs analysed in field trials and a leaf segment test was conducted followed by microscopic analyses. In the field and in the leaf segment test Lr9, Lr19, Lr24 and Lr38 and to some extent Lr3a turned out to be the most effective genes. By microscopic analyses, the infection process as well defense reactions activated before macroscopic symptoms are visible were monitored. By counting haustorial mother cells, it could be demonstrated which Lr-genes provide resistance, which were overcame and whether P. triticina isolates exist already at a low frequency, which may overcome a certain Lr-gene in the future. Thus microscopy offers a timesaving and effective method to detect susceptible or resistant plants and the upcoming of virulent races prior to typical symptom expression.     

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德国及蒙古沙棘品种无性系生物学和观赏性价值评估

沙棘由于其有丰富的内含物和多方面的用途正被作为＂新兴水果＂而赢得了人们越来越多的重视和喜爱.通过在柏林Baumschulenweg的育种工作,到目前为止,已经育成不同成熟期的5个雌性和4个雄性沙棘品种.更多的由欧洲和蒙古原生种产生的杂交选育工作仍在进行中.将这些无性系按照其生物学和果实性状进行评估.就单个性状来讲,各品种之间的差异非常大（比如维生素的含量在17～340mg/100g之间变动,胡萝卜素的变动范围为6.5～23.8mg/100g）.这表明,进一步的育种改良完全有可能.所有用于比较的沙棘品种由在德累斯顿Pillnitz进行的育种工作获得,这些品种将被进一步研究.为了保险起见,以及为了解决后来有可能产生的育种及植物病理学方面的问题,必须尽可能保存现有的所有的某一品种的基因多样性.为此目的,由国家资助扶持的基因库的建立是很有必要的.     

Influence of soil temperature and soil compaction on growth and P uptake of sugar beet

Sugar beet growth is often impaired by cold and compacted soil. The aim of this study was to determine the effect of soil temperature and soil compaction on the growth and function of sugar beet roots. For this purpose a pot experiment with sugar beet (Beta vulgaris) was conducted in a growth chamber in which the soil temperature was kept constant either at 10°C or 20°C and air temperature at 20°C. The soil was uncompacted (1.30 g cm^?3) or compacted to a bulk density of 1.65 g cm^?3. In order to find out whether growth restriction was caused by insufficient P supply of the plant the experiment was run without and with P application (300 mg per kg soil). Root growth was much smaller at 10°C compared to 20°C, whereas root/shoot ratio was not affected by soil temperature. Hence, root and shoot growth was inhibited to the same extent. P content of the plants was not reduced, neither by cold nor by compacted soil, although parameters of acquisition such as root length and morphological root properties were altered. Soil temperature strongly affected P influx, whereas compaction did not. The calculation with a simulation model showed that at 10°C soil temperature the predicted P uptake of the plants agreed with the measured P uptake irrespective of compaction and P application. However, at 20°C the model underestimated the P influx at low soil P availability even if allowance was made for root hairs. It is concluded that under conditions of high shoot P demand and low P availability in soil P has been mobilized by mechanisms not taken into account by the model.