The AAP gene family for amino acid permeases contributes to development of the cyst nematode Heterodera schachtii in roots of Arabidopsis

The beet cyst nematode Heterodera schachtii is able to infect Arabidopsis plants and induce feeding sites in the root. These syncytia are the only source of nutrients for the nematodes throughout their life and are a nutrient sink for the host plant. We have studied here the role of amino acid transporters for nematode development. Arabidopsis contains a large number of different amino acid transporters in several gene families but those of the AAP family were found to be especially expressed in syncytia. Arabidopsis contains 8 AAP genes and they were all strongly expressed in syncytia with the exception of AAP5 and AAP7, which were slightly downregulated. We used promoter::GUS lines and in situ RT-PCR to confirm the expression of several AAP genes and LHT1, a lysine- and histidine-specific amino acid transporter, in syncytia. The strong expression of AAP genes in syncytia indicated that these transporters are important for the transport of amino acids into syncytia and we used T-DNA mutants for several AAP genes to test for their influence on nematode development. We found that mutants of AAP1, AAP2, and AAP8 significantly reduced the number of female nematodes developing on these plants. Our study showed that amino acid transport into syncytia is important for the development of the nematodes

Population dynamics of Heterodera schachtii Schm. and yield response of susceptible and resistant sugar beet (Beta vulgaris L.) after cultivation of susceptible and resistant oilseed radish (Raphanus sativus L.)

Heterodera schachtii zählt zu den wichtigsten Schädlingen der Zuckerrübe. Feldversuche mit dem Ziel, die Ertragsreaktion von Zuckerrübensorten auf Befall mit H. schachtii zu quantifizieren oder den Einfluss der Sorte auf die Populationsdynamik der Nematoden zu beschreiben, werden durch das nesterweise Auftreten im Feld erschwert. Ziel der Untersuchung war es, ein Verfahren zu entwickeln, mit dem eine homogenere Verteilung der Nematoden im Feld erreicht werden kann, sowie den Einfluss unterschiedlicher Populationsdichten von H. schachtii auf den Ertrag einer anfälligen und einer resistenten Zuckerrübensorte zu untersuchen. In den Jahren 2002 bis 2005 wurden 13 Feldversuche in vier Anbauregionen in Deutschland durchgeführt. Im Jahr vor dem Anbau der Zuckerrüben wurden eine anfällige und eine resistente Ölrettichsorte oder eine 50/50-Mischung aus beiden in Streifen angebaut, um die Populationsdichte der Nema­toden an jedem der Standorte zu variieren. Signifikante Unterschiede in der Populationsdichte wurden dabei an sechs der 13 Standorte erzielt. Die anfällige Zuckerrübensorte hatte in allen Versuchen höhere Vermehrungsraten als die resistente, generell nahm die Vermehrungsrate mit steigender Ausgangsdichte der Nematoden (Pi) ab. Mit steigendem Pi-Wert ging der bereinigte Zuckerertrag beider Sorten zurück. Diese Beziehung wurde allerdings nicht an allen Standorten bestätigt. Die Qualität der Rüben wurde nicht durch den Pi-Wert beeinflusst. Insgesamt erscheint die vorgestellte Methodik als zu aufwendig und nicht ausreichend verlässlich für umfangreiche Feldversuchsserien. DOI: 10.5073/JfK.2014.09.01, https://doi.org/10.5073/JfK.2014.09.01Heterodera schachtii is an important pest of sugar beet. Field trials to quantify yield responses of sugar beet varieties to H. schachtii or to assess the effect of variety on population dynamics of the nematode are difficult due to its patchy distribution in the field. The aim of the present study was to develop an experimental method to achieve a more homogeneous distribution of the nematode and to relate yield of susceptible and resistant sugar beet to population density of H. schachtii. From 2002 to 2005, thirteen field trials were conducted in four regions of Germany. In the year prior to sugar beet cultivation, a susceptible and a resistant oilseed radish variety or a 50/50 mix of both were grown in strips to vary population densities of the nematode at each trial site. Significant differences in population densities after oilseed radish cultivation were obtained in six of the thirteen trials. The reproductive rates of H. schachtii were higher under the susceptible than under the resistant sugar beet variety in all trials and generally decreased with increasing initial population density (Pi). In both varieties, white sugar yields decreased with increasing Pi. This relation was not confirmed in all trials. Root quality was not related to Pi. It was concluded that the introduced methodology is too costly and not sufficiently reliable for extensive series of field trials. DOI: 10.5073/JfK.2014.09.01, https://doi.org/10.5073/JfK.2014.09.0

DNA barcoding evidence for the North American presence of alfalfa cyst nematode, Heterodera medicaginis

Specimens of Heterodera have been collected from alfalfa fields in Kearny County, Kansas and Carbon County, Montana. DNA barcoding with the COI mitochondrial gene indicate that the species is not Heterodera glycines, soybean cyst nematode, H. schachtii, sugar beet cyst nematode, or H. trifolii, clover cyst nematode. Maximum likelihood phylogenetic trees show that the alfalfa specimens form a sister clade most closely related to H. glycines, with a 4.7% mean pairwise sequence divergence across the 862 nucleotides of the COI marker. Morphological analyses of juveniles and cysts conform to the measurements of H. medicaginis, the alfalfa cyst nematode originally described from the USSR in 1971. Initial host testing demonstrated that the nematode reproduced on alfalfa, but not on soybeans, tomato, or corn. Collectively, the evidence suggests that this finding represents the first record of H. medicaginis in North America. Definitive confirmation of this diagnosis would require COI sequence of eastern European isolates of this species

Glucosinolate profiles of disomic rapeseed-radish chromosome addition lines

Glucosinolatgehalte und Glucosinolatmuster einer kompletten Serie von neun disomen Raps-Rettich Chromo­somenadditionen (2n = 38 + 2, a bis i) wurden bestimmt und mit denen des Chromosomenspenders Rettich und des Chromosomenempfängers Raps verglichen. Der Effekt einzelner Rettichchromosomen im identischen Rapshintergrund erlaubte die chromosomale Zuordnung von Schritten der Glucosinolat-Biosynthese. Die Addi­tionslinie a wies den fünffachen Glucosinolatgehalt auf wie der Rapselter. Die rettichspezifischen Glucosinolate Glucoraphenin und Glucoerysolin wurden ausschließlich in der Additionslinie g nachgewiesen. In der Additions­linie i wurde außerdem Sinigrin nachgewiesen, welches in keinem der Eltern gebildet wird. Der Glucosinolatgehalt ist nicht mit der Resistenz gegenüber dem Rübenzystennematoden (Heterodera schachtii Schmidt) korreliert.    The glucosinolate (GSL) content and -profile of a complete series of nine disomic rapeseed-radish chromosome addition lines (2n = 38 + 2, a to i) was estimated and compared to that of radish as donor and rapeseed as recipient of the alien chromosomes. Modification of identical genetic rapeseed background by single radish chromosomes allows the assignment of GSL biosynthesis steps to individual radish chromosomes. Addition line a was found to have a five times higher aliphatic GSL content than the rapeseed parent. Radish-specific GSLs, glucoraphenin and glucoerysolin, were synthesized exclusively in addition line g. Addition line i produced sinigrin, not detectable in both parents. The variations in GSL content are not correlated with resistance against beet cyst nematode (Heterodera schachtii Schmidt).   &nbsp

Nuclear magnetic resonance: a tool for imaging belowground damage caused by Heterodera schachtii and Rhizoctonia solani on sugar beet

Belowground symptoms of sugar beet caused by the beet cyst nematode (BCN) Heterodera schachtii include the development of compensatory secondary roots and beet deformity, which, thus far, could only be assessed by destructively removing the entire root systems from the soil. Similarly, the symptoms of Rhizoctonia crown and root rot (RCRR) caused by infections of the soil-borne basidiomycete Rhizoctonia solani require the same invasive approach for identification. Here nuclear magnetic resonance imaging (MRI) was used for the non-invasive detection of belowground symptoms caused by BCN and/or RCRR on sugar beet. Excessive lateral root development and beet deformation of plants infected by BCN was obvious 28 days after inoculation (dai) on MRI images when compared with non-infected plants. Three-dimensional images recorded at 56 dai showed BCN cysts attached to the roots in the soil. RCRR was visualized by a lower intensity of the MRI signal at sites where rotting occurred. The disease complex of both organisms together resulted in RCRR development at the site of nematode penetration. Damage analysis of sugar beet plants inoculated with both pathogens indicated a synergistic relationship, which may result from direct and indirect interactions. Nuclear MRI of plants may provide valuable, new insight into the development of pathogens infecting plants below- and aboveground because of its non-destructive nature and the sufficiently high spatial resolution of the method