Pallida Pa3 Research Articles

Microbial Communities in Globodera pallida Females Raised in Potato Monoculture Soil.

Globodera spp. are under strict quarantine in many countries. Suppressiveness to cyst nematodes can evolve under monoculture of susceptible hosts. Females developing in potato monoculture soil infested with G. pallida populations Chavornay or Delmsen were examined for inherent microbial communities. In the greenhouse, nonheated and heat-treated (134°C for 10 min) portions of this soil were placed in root observation chambers, planted with Solanum tuberosum 'Selma', and inoculated with G. pallida Pa3 Chavornay. At harvest in Delmsen soil, cysts had fewer eggs in nonheated than heat-treated soil. In denaturing gradient gel electrophoresis analysis, bacterial and fungal fingerprints were characterized by a high variability between replicates; nonheated soils displayed more dominant bands than heated soils, indicating more bacterial and fungal populations. In amplicon pyrosequencing, females from nonheated portions frequently contained internal transcribed spacer sequences of the fungus Malassezia. Specific for the Chavornay and Delmsen population, ribosomal sequences of the bacteria Burkolderia and Ralstonia were abundant on eggs. In this first report of microbial communities in G. pallida raised in potato monoculture, candidate microorganisms perhaps associated with the health status of the eggs of G. pallida were identified. If pathologies on cyst nematodes can be ascertained, these organisms could improve the sustainability of production systems.

Superoxide dismutase isoelectric focusing patterns as a tool to differentiate pathotypes of Globodera spp.

Abstract Isoelectric focusing was used to separate proteins from cyst extracts of potato cyst nematode (PCN) populations. In a first set of assays, cyst extracts from standard populations of Globodera rostochiensis pathotypes Ro1, Ro2, Ro3, Ro2/3, Ro4, and Ro5, and G. pallida pathotypes Pa2 and Pa3, were loaded on isoelectric focusing gels. Gels were stained for superoxide dismutase (SOD), esterase, and glucose-6-phosphate isomerase (GPI). Twelve bands of SOD activity were detected, six (B1-B6) migrating towards the basic zone and the other six (A1-A6) migrating towards the acidic zone, starting from the loading point. A cluster analysis was carried out based on a data matrix that reported the presence or absence of SOD bands on the isozyme electrophoresis patterns (IEPs). Globodera spp. were clearly distinguished and, within G. rostochiensis, Ro2 and Ro4 shared a high level of similarity, respectively, with Ro3 and Ro5; moreover, Ro1 could be clearly distinguished from Ro2/3 and Ro4/5. Globodera pallida Pa2 and Pa3 also shared a high level of similarity. In contrast, esterase and GPI IEPs did not discriminate among G. rostochiensis standard pathotypes. Subsequently, 14 field populations of G. rostochiensis, five from Italy and nine from Venezuela, and three field populations of G. pallida, two from Italy and one from Chile, were assayed to obtain SOD IEPs. Italian populations had previously been identified at pathotype level by bioassays according to the generally accepted international test using different resistant potato cultivars and clones. The cluster analysis carried out on the SOD IEPs of all the populations tested formed four distinct groups within G. rostochiensis and only one within G. pallida. Pathotype identification of Globodera populations by SOD IEPs was not able to discriminate between bioassay standard couples Ro2/Ro3, Ro4/Ro5 and Pa2/Pa3. Therefore, three groups were assigned to Ro1, Ro2/3 and Ro4/5, and a fourth group to Pa2/Pa3. Four Venezuelan populations, not identified at pathotype level by bioassays, formed a distinct fifth group. By means of the method described herein, four additional unknown Venezuelan populations could be assigned to Ro1 group and one to Ro2/Ro3 group; one G. pallida population from Chile was assigned to Pa2/Pa3 group.

Effects of potential trap crops and planting date on soil infestation with potato cyst nematodes and root‐knot nematodes

SummaryIn 1997 and 1998 the stimulation of hatch of potato cyst nematodes (PCN) by a trap crop was studied at various times during the growing season in a container and a field experiment. Solanum nigrum‘90‐4750‐188’was used as the trap crop in both experiments and was sown on 1 May, 16 June or 1 August in two successive years on different plots. Neither experiment revealed much seasonal variation in hatchability of PCN juveniles under a trap crop. In the container experiment, the hatch of the Globodera pallida Pa3 population was equally and strongly stimulated (89%) at all sowing dates in both years, except for the 1 August sowing in 1998 (when the hatch was 77% under extremely wet soil conditions). In the control treatment with non‐hosts (flax followed by barley) the total spontaneous hatch was 50% over 2 yr. In the field experiment, the hatch of PCN, averaged over the four populations, was also equally stimulated (71%) at all sowing dates in both years. In the control treatment with non‐hosts (flax‐barley) the total spontaneous hatch was 36% over 2 yr. Total hatch under the trap crop over 2 yr varied between the four PCN populations from 63% to 80%.In 1998 and 1999, control of potato cyst nematodes (PCN) by the potential trap crops Solanum sisymbriifolium and S. nigrum‘90‐4750‐188’was studied in the field. Potato was also included as a trap crop. In the 1998 experiment, potato, S. sisymbriifolium and S. nigrum strongly stimulated the hatch of PCN compared with the non‐host white mustard (Sinapis alba). Roots of potato and white mustard were mainly found in the top 10 cm of soil, whereas roots of S. sisymbriifolium and S. nigrum were also abundant at depths of 10–20 cm and 20–30 cm. In the 1999 experiment, soil infestation with PCN decreased markedly with potato and S. sisymbriifolium as trap crops. In plots moderately to severely infested with 2‐yr old cysts (2–29 juveniles ml−1 air dried soil), potato reduced soil infestation by 87% and S. sisymbriifolium by 77%. In plots moderately to severely infested with 1‐yr old cysts the reductions were 74% and 60%, respectively. The reduction was least on plots very severely infested with PCN (110–242 juveniles ml−1 soil): 69% and 52% for potato and S. sisymbriifolium, respectively. Soil infestations of plots that were initially slightly to severely infested with the root‐knot nematode Meloidogyne hapla were greatly reduced under fallow and S. sisymbriifolium but increased under potato. From these and previous experiments it was concluded that, for several reasons, S. sisymbriifolium is a promising trap crop.

Analysis of somatic hybrids between two sterile dihaploid Solanum tuberosum L. breeding lines. Restoration of fertility and complementation of G. pallida Pa2 and Pa3 resistance

Analysis of somatic hybrids between two sterile dihaploid Solanum tuberosum L. breeding lines. Restoration of fertility and complementation of G. pallida Pa2 and Pa3 resistance

Analysis of somatic hybrids between two sterile dihaploid Solanum tuberosum L. breeding lines. Restoration of fertility and complementation of G. pallida Pa2 and Pa3 resistance

Fourteen somatic hybrids generated by electrofusion of mesophyll protoplasts from a non-flowering dihaploid S. tuberosum clone, DHAK-11, and a male-sterile dihaploid clone S. tuberosum, DHAK-33, were grown in the greenhouse and subjected to morphological assessments and tests for fertility and resistance to the white potato cyst nematode Globodera pallida pathotypes Pa2 and Pa3. The ploidy level of the hybrids ranged from 38 to 63 chromosomes. All hybrids developed flowers with violet petals except for one, hy-56, that possessed red petals. The colour of the tuber skin was purple in all hybrids except in hy-56 where the tuber skin was red. All of the hybrids were female fertile and generated viable seeds. Near-tetraploid hybrids produced the highest number of seeds per fruit and these seeds had a normal size. Hybrids with 58 or more chromosomes produced smaller seeds and less seeds per fruit. The germination frequency of the seeds was not influenced by the chromosome number of the hybrids. Pollen viability was determined and the male fertility of three hybrids was tested. Pollination with these three hybrids gave rise to fruit development, but only one produced viable seeds. The hybrids were tested for resistance to G. pallida pathotypes Pa2 and Pa3. A high level of resistance to Pa3, inherited from one parental clone, DHAK-11, and a high level of resistance to Pa2, inherited from the other parental clone, DHAK-33, was combined in four hybrids. These results demonstrate, that protoplast fusion is an efficient method for restoring the fertility of somatic hybrids generated from sterile parent clones, and is a powerful procedure for the complementation of multigenetic disease resistance traits in potato breeding lines.

The inheritance of resistance to the potato cyst nematode Globodera pallida PA3 in wild Solanum species with broad spectrum resistance

A detailed study of the resistance to Globodera pallida and G. rostochiensis populations in eleven selected wild Solanum accessions showed that all the accessions had a high level of resistance to a broad spectrum of G. pallida populations Six of the accessions showed a high level of resistance to G. rostochiensis populations as well. The others were, in comparison with the susceptible cultivar Maritta, partial resistant to G. rostochiensis.

The effect of resistant potato cultivars on a field population of Globodera pallida Pa2 over three years of cropping

SUMMARYSix potato cultivars with different levels of resistance to the white potato cyst nematode (PCN) Globodera pallida Pa2 were grown for three seasons in field plots to which G. pallida Pa2 cysts had been introduced earlier. There were two planting times, corresponding to early and maincrop commercial planting times, and two initial PCN population densities, high and low.The effect of cultivar on PCN population density was far greater than the effect of planting time or initial nematode population. The final PCN populations for the cultivars Ilam Hardy, Wha, 4696A(2), Sovereign, D40/6 and V390 were 151, 74, 27, 1.4, 0.2 and 0.06 eggs per g of soil respectively.It is concluded that resistant potato cultivars can be very effective in controlling G. pallida Pa2 in the field.

Screening for resistance to potato cyst nematodes using bioluminescent photometry

SUMMARYThe measurement of the adenosine triphosphate (ATP) content of cysts by bioluminescent photometry has been used as a screen for assessing the resistance of five potato clones to Globodera rostochiensis Rol and G. pallida Pa3. The multiplication rates (Pf/Pi) of the nematodes are based on the ratio of ATP levels for the cyst inoculum and their progeny. These have been compared to the corresponding ratios based on conventional visual counts of eggs and juveniles. The use of recoverable standard volumes of cysts to inoculate pots has allowed an assessment of the unhatched proportion (Cp) of juveniles from the parental cysts by both methods and an estimate of the corrected multiplication rate (P/P^l‐Cp)). This is an accurate assessment of resistance for a clone and the use of standard inocula and the ATP method will enable the criterion adopted for establishing resistance to be measured rapidly and precisely.

Comparisons of Invasion and Development of Globodera Spp. and European Potato Cyst-Nematode Pathotypes in Roots of Resistant Solanum Sg. Leptostemonum Spp

Populations of Globodera species from the Americas and potato cyst-nematodes G. pallida pathotype Pa2 and G. rostochiensis pathotype Rol from Europe were compared by their relative abilities to invade and develop in roots of eight wild Latin American Solanum sg. Leptostemonum spp. resistant to Globodera and in susceptible S. prinophyllum from Australia. All resistant plants were invaded by second stage juveniles. G. tabacum, a G. rostochiensis population from Bolivia, G. solanacearum and G. virginiae in that order had the greatest invasion rates and development into the third and fourth stages. G. rostochiensis Ro1 and G. pallida Pa2 invaded less numerously and few developed to the third stage. In all combinations fourth stage juveniles were mostly males. Only in Ro1 and Pa2 did males fail to reach adulthood in any plant species. S. quitoense and S. sisymbriifolium, which differentiate Globodera populations and appear to have specific resistance, were most heavily invaded, allowed greatest development of juveniles and produced most adult males. In strongly resistant S. torvum and S. viarum, which appear to have nonspecific resistance, and in S. hirtum juveniles invaded less numerously and rarely developed beyond the early third stage.

Temperature Responses of Three Potato-Cyst Nematode Populations From New Zealand

The effect of temperature on 'survival', fecundity, and multiplication rate of three New Zealand populations of potato cyst-nematodes - CM006, Globodera rostochiensis Rol from Canterbury; CM001, G. pallida Pa3 from Canterbury; and FP001, G. pallida Pa2 from Pukekohe - was studied in the laboratory. Temperature ranges for population increase were: G. rostochiensis 10° to approximately 25°, G. pallida Pa3 9° to 23°, and G. pallida Pa2 8° to 22°. The optimum temperature lay between 15° and 20° for all three populations, but G. rostochiensis increased more rapidly over this range than G. pallida; only below 13°-14° did G. pallida increase more rapidly than G. rostochiensis. The slight but significantly lower temperature range of G. pallida Pa2 than Pa3 may have been a pathotype difference, but could also have been an adaptation of that population to repeated winter cropping with potatoes in soil temperatures of 6°-14° at Pukekohe.