Cyst Nematode Infection Research Articles

In plantamonitoring of the activity of two constitutive promoters, CaMV 35S and TR2′, in developing feeding cells induced byGlobodera rostochiensisusing green fluorescent protein in combination with confocal laser scanning microscopy

Under the control of either the constitutive CaMV 35S or the mannopine synthase TR2′ promoter, the green fluorescent protein (GFP) from the jellyfishAequorea victoriawas expressed in transgenic potato (Solanum tuberosum) plants. Confocal laser scanning microscopy (CLSM) was applied to observe GFPin plantaand, subsequently, to investigate promoter activity in developing feeding cells developed during potato cyst nematode (Globodera rostochiensis) infection. Both the CaMV 35S and the TR2′ promoter were strongly upregulated in young feeding cells in less than 4 days upon infection byG. rostochiensis,whereas the GFP level in the surrounding tissues remained low. Optical sectioning revealed intense green fluorescence in the dense cytoplasm of the entire syncytial cell, including the most distal cell. Furthermore, GFP was observed within the digestive system of the feeding nematode, showing that proteins with an apparent molecular weight of 32 kDa can be taken up by parasitic juveniles ofG. rostochiensis. Provided CLSM is used, GFP was shown to be a powerful tool that allowsin vivomonitoring of gene expression inside young developing feeding cells. Finally, the transcriptional regulation of the CaMV 35S and TR2′ promoter in plant–nematode interactions is discussed.

Effects of soil characteristics on the relationship between potato cyst nematodes and yield. II. Acidity (soil pH)

The sandy and sandy peat soils of the northeast of The Netherlands are mineralogically very poor and acid. Independently of potato cyst nematode infestations, there is a considerable negative effect of increasing soil pH on potato tuber yield. Potato cyst nematode infections aggravate the effect of soil pH in depressing yield. It was shown that both potato cyst nematode infection and increasing soil pH values reduce the buffering capacity of the root system. Testing for yield as well as for tolerance to potato cyst nematode infection should be made at a range of soil pH values, similar to those found in the target area. This refers to active breeding programmes as well as to the selection of cultivars for yield trials.

Relationship between potato cyst nematodes and their principal host. IV. Tolerance of potato cultivars and the effect of potato cyst nematode on initial plant growth

Greenhouse experiments on the effects of white potato cyst nematode infestations (Globodera pallida Stone) on initial growth and development of a series of potato cultivars are compared with the results of field experiments on sandy and sandy-peat soils on the effect of nematode density on tuber yield. A simple greenhouse test, assessing root growth response to potato cyst nematode infection, provided a good insight into a cultivar's tolerance performance in the field early in the growing season. As a very limited number of plants is needed for the greenhouse test, screening for tolerance can be conducted in the early stages of a breeding programme.

Induction of cdc2a and cyc1At expression in Arabidopsis thaliana during early phases of nematode-induced feeding cell formation.

Root-knot and cyst nematodes are plant parasites that induce large multinucleated feeding cells in the roots of their hosts. Cytological observations have shown that root-knot nematodes induce giant cells by cycles of mitosis without cytokinesis whereas cyst nematodes provoke cell wall degradation leading to the formation of a large syncytium. This study was intended to characterize and compare the ability of both types of nematodes to induce progression through the cell cycle. For this purpose, the expression, upon nematode infection, of two cell cycle markers was followed: a marker for division competence, the cyclin-dependent kinase cdc2a and a marker for the G2 phase, the mitotic cyclin cyc1At. For both types of nematodes, transcriptional activation of these markers was correlated with early phases of feeding cell development. Using molecular markers, it was thus possible to confirm and extend the observations of repeated mitosis in root-knot nematode-induced giant cells. Surprisingly, promoter activation of both cdc2a and cyc1At markers was also found upon cyst nematode infection, in feeding cells in which mitosis has not been clearly reported. Incorporation of tritiated thymidine in these syncytia confirms that they progress through the S phase of the cell cycle. One possibility is that cyst nematodes induce cycles of DNA endoreduplication shunting the M phase. Despite obvious differences in ontogeny, common molecular mechanisms, involving cycles of DNA endoreduplication and cdc2a and cyc1At expression, might thus be involved in the formation of a giant cell or a syncytium.

The influence of cyst nematodes and drought on potato growth. 1. Effects on plant growth under semi-controlled conditions

Potatoes were grown under a permanent rain shelter in mobile containers in soil with or without potato cyst nematodes (Globodera pallida). The plants were subjected to an early drought stress period starting at planting until 43 days after planting, to a late drought stress period starting at 43 days until senescence at 92 days and to a drought control. Dry matter weight and characteristics of leaves, stems, stolons and roots were determined at periodic harvests. The early drought stress and nematode infection affected many plant organ characteristics in similar ways. Numbers of leaves, specific leaf area, plant height, specific stem weight, leaf area ratio, mean tuber weight and harvest index were reduced by both stress factors at early stages of growth. Later on, interactions between both stress factors which influence the development rate of the plants led to more diverse plant reactions. Plants of all treatments rapidly senesced at about 90 days after planting. Uninfected plants had then depleted the soil nutrient supply whereas the plants grown in the inoculated soil senesced as a result of the potato cyst nematode infection.

The effect of manganese deficiency and cereal cyst nematode infection on the growth of barley

Two factorial pot experiments, each with four rates of soil-applied manganese (Mn), four levels of cereal cyst nematodes (CCN) and four replicates, were conducted under controlled environmental conditions to investigate the interaction of these factors on growth of barley. The experiments were harvested sequentially to count numbers of nematodes at two developmental stages. Development of the nematodes was independent of the Mn status of the host, indicating no effect of Mn on host resistance. In the absence of CCN, decreased Mn had a small effect on vegetative growth, not significantly decreasing dry weight of tops but tolerance at the higher densities of CCN was considerably reduced at low Mn supply, both vegetative growth and grain yield being depressed. Increasing CCN density exerted little effect on the growth of Mn sufficient hosts. Two field surveys supported conclusions from the pot experiments in that increasing nematode densities were correlated with decreasing plant size only at the site where plants were low in Mn. An implication for the field is that crops infected with the nematode and also low in Mn may yield less than expected because the two factors interact to reduce growth and retard development.