Gisela Jansen

Soft-rot Resistance of Coloured Potato Cultivars (Solanum tuberosum L.): The Role of Anthocyanins

Coloured potatoes (Solanum tuberosum L.) rich in anthocyanins are gaining increasing interest on the markets, mainly due to beneficial health effects. Potato varieties containing colour pigments are therefore utilized more and more in actual breeding programmes. In this study, 10 purple-fleshed potato cultivars were compared in their resistance to soft rot caused by Pectobacterium carotovorum (Pc) with 10 white/yellow-fleshed potato cultivars. The results revealed that coloured potato cultivars exhibited on average better resistance to soft rot than white/yellow-fleshed potato cultivars. On tuber halves of purple-fleshed cultivars, the extent of rotting caused by Pc was on average 28.6% lower than on white/yellow-fleshed cultivars. The greater resistance of coloured potatoes coincided with the presence of anthocyanins, higher concentrations of soluble phenols and elevated polyphenol oxidase activity in tuber tissue. These three components were significantly correlated with the extent of rotting caused by Pc. However, coloured and white/yellow-fleshed cultivars were not very different in phenylalanine ammonia-lyase and peroxidase activity. There were also no significant differences in concentrations of dry matter, starch, crude protein and glycoalkaloids. Key findings reveal that total soluble phenols and anthocyanins contributed crucially to resistance expression in tuber tissue of coloured potato cultivars.

Feeding behavior of aphids on narrow-leafed lupin (Lupinus angustifolius) genotypes varying in the content of quinolizidine alkaloids

Since the beginning of breeding narrow‐leafed lupins [Lupinus angustifolius L. (Fabaceae)] with a low alkaloid content, susceptibility to several aphid species has increased. Therefore, the probing and feeding behavior of Aphis fabae Scopoli, Aphis craccivora Koch, Acyrthosiphon pisum (Harris), Myzus persicae (Sulzer), and the well‐adapted Macrosiphum albifrons Essig (all Hemiptera: Aphididae) was studied over 12 h on narrow‐leafed lupin genotypes containing varying amounts and compositions of alkaloids. We used the electrical penetration graph (EPG) technique to obtain information on the influence of alkaloid content and composition on the susceptibility to various aphid species. Results indicated that the total time of probing of A. fabae, A. craccivora, A. pisum, and M. persicae increased with a reduced alkaloid content, whereas the alkaloid content had no influence on M. albifrons. Almost all of the individuals (>93%) conducted sieve element phases on the highly susceptible genotype Bo083521AR (low alkaloid content). A reduced occurrence of phloem phases was observed during the 12‐h recording on the alkaloid‐rich cultivar Azuro, especially for A. pisum (37.5%) and A. fabae (55.0%). Furthermore, aphids feeding on genotypes with low alkaloid content had in most cases significantly longer sieve element phases than when feeding on resistant genotypes (Kalya: low alkaloid content, yet resistant; Azuro: high alkaloid content, resistant), whereas M. albifrons showed the longest phloem phase on the alkaloid‐rich cultivar Azuro. As most significant differences were found in phloem‐related parameters, it is likely that the most important plant factors influencing aphid probing and feeding behavior are localized in the sieve elements. The aphids’ feeding behavior on the cultivar Kalya, with a low alkaloid content but reduced susceptibility, indicates that not only the total alkaloid content influences the feeding behavior but additional plant factors have an impact.

Effect of the Soil pH on the Alkaloid Content of Lupinus angustifolius

Field studies were conducted in growing seasons 2004, 2005, and 2010 to investigate the effect of different soil pH values on the alkaloid content in seeds of Lupinus angustifolius. Two-year experiments with eleven cultivars were carried out in acid soils with an average of (Mecklenburg-Western Pomerania) and on calcareous soils with an average pH of 7.1 (Bavaria), respectively. In addition, in 2010, eight cultivars were grown in field experiments in soils with pH values varying between and . In all experiments conducted on soils with a higher pH ( and ), a significantly lower alkaloid content was detected in all Lupinus angustifolius cultivars than on soils with a lower pH ( and ). Results clearly show that the alkaloid content is significantly influenced by the soil pH but genotypic differences regarding the reaction to different pH values in the soil were observed.

In vitro method for early evaluation of nitrogen use efficiency associated traits in potato

The objective of the present study was to characterize various traits associated with nitrogen uptake and utilization in a range of potato cultivars. For this purpose an in vitro test system was developed which allows analyzing specific stress responses in a highly controlled environment. Shoot tips were grown fixed in perforated stainless steel plates in 500 ml glass vessels in liquid culture medium at four nitrogen levels, i.e. 60, 30, 15 and 7.5 mmol L-1. At the end of a three weeks’ culture period plant developmental traits were determined and nitrogen uptake and assimilation were analyzed. Reduction of nitrogen in the culture medium differentially affected morphological and physiological features. Highly significant differences were found between different N-levels and cultivars as well as for genotype x nitrogen level interactions. Three groups of cultivars (high, low and intermediate) were distinguished with respect to biomass production and crude protein yield under nitrogen-sufficient conditions of 60 mmol L-1. Genotypes with a low biomass production at full nitrogen availability responded with increased root development under nitrogen deficiency stress and increased their nitrogen utilization capacity in relation to the other cultivars.

Composition, environmental stability and potential of genetic improvement of fatty acids of Lupinus angustifolius

In the last decades procedures for obtaining protein isolates and concentrates derived from narrow-leafed lupins ( L. angustifolius ) for human nutrition have been developed. Since this processes starts with defatting of seeds, lupin oil is obtained in large quantities. Therefore, 50 genotypes of L. angustifolius were analysed regarding the fatty acid (FA) composition of seed oil and the environmental stability of fatty acid contents in order to get information on the application of lupin oil in the food industry. The results revealed an n-3/n-6 poly unsaturated fatty acid ratio of 0.13. Furthermore, the seed oil of L. angustifolius contains rather high amounts of saturated FAs (22%). Significant genotypic differences and a high heritability (h2>85%) for the content of all fatty acids are suggesting that the potential for genetic improvement of fatty acid composition by breeding is given. However, coefficients of variation below 10% for all considered traits point out that a rapid improvement in seed oil quality will be hindered by the narrow genetic base of the breeding material tested.

Temperature stress during flowering time affects yield and quality parameters of waxy barley

Temperatur hat einen Einfluss auf das Wachstum und die Qualitat von Nutzpflanzen. In dieser Studie wurden die Auswirkungen von Temperaturstress wahrend der Blute auf Ertrags- und Qualitatskomponenten von waxyGersten untersucht. Hierfur wurden drei waxyGersten-Linien sowie eine Gerstensorte (Lomerit) mit einer normalen Starkezusammensetzung verschiedenen Temperaturen (10, 20 [Kontrolle] und 30 °C) ausgesetzt. Der Temperaturstress wurde zu Beginn des Ahrenschiebens eingeleitet und endete mit Beginn des Kornansatzes. Es konnte ein hoch signifikanter Einfluss der Bluhtemperatur auf den Ertrag nachgewiesen werden. Hohe Temperaturen (30 °C) fuhrten bei allen Gersten zu einer Reduktion von Kornanzahl und -gewicht pro Pflanze. Ertragssteigerungen wurden vor allem bei niedriger Bluhtemperatur von 10 °C ermittelt. Der Protein- und Starkegehalt sowie die Starkezusammensetzung im Korn wurden ebenfalls von der Bluhtemperatur und vom Genotyp beeinflusst. Alle Linien zeigten infolge einer hohen Temperatur einen erhohten Proteingehalt bei gleichzeitiger Abnahme des Starkegehalts im Vergleich zur Kontrolle (20 °C). Sinkende Protein- und steigende Starkegehalte wurden hingegen bei niedrigen Bluhtemperaturen ermittelt. Der Proteingehalt korrelierte negativ mit dem Starkegehalt und positiv mit der s-Amylaseaktivitat. Verglichen mit Lomerit zeigten die waxyGersten eine starkere Variation der Ertragsparameter in Abhangigkeit der Temperaturstufen und sind somit als temperatursensitiver einzuschatzen.