Assessing populations of the major cereal pathogens for reduced sensitivity to MBC, DMI and Strobilurin fungicides

End of project reportStudies of eyespot populations in winter wheat crops in the period 2001 to 2003 showed that the R type (Tapesia acuformis) is the dominant strain comprising 77% of isolates. Over 90% of isolates were resistant to MBC fungicides, 53% showed reduced sensitivity to prochloraz and 22% reduced sensitivity to cyprodinil. A study of winter wheat crops in February and March 2003 showed that resistance to strobilurin fungicides was widespread in Mycosphaerella graminicola (Septoria tritici) populations. Resistance was found in all but one of 21 crops sampled, at levels ranging from 9% to 84% with an average of 48%. Subsequent studies of 27 crops over the summer of 2003 showed that strobilunin resistance increased from an average of 31% before the application of the second (T2) spray to an average of 73%, three to four weeks after the application of the final (T3) spray. Strobilurin resistance in M. graminicola remained high in 2004, ranging from 50% to 100% with an average of 83% in populations in winter wheat crops sampled in March. The effect of different fungicide programmes on resistance was studied during summer 2003 at two experimental sites. Levels of strobilurin resistance in M. graminicola populations increased during the summer, in unsprayed plots and plots treated with triazole fungicides as well as in those treated with strobiurin fungicides at both sites. M. graminicola populations in winter wheat crops sampled in 2003 and 2004 were predominantly resistant to MBC-generating fungicides and sensitive to the triazole-based fungicides. Studies of the barley leaf blotch pathogen Rhynchosporium secalis showed that resistance to MBC fungicides occurred in 20% of isolates collected from crops from 2001 to 2003, but all isolates were sensitive to triazole and strobilurin fungicides

New continua for absorption spectroscopy from 40 to 2000 Å

The spectra of plasmas produced by focusing the output of a Q-switched ruby laser (output 1 J) on the rare-earth metals have been studied. From samarium (Z = 70), strong quasi-uniform continua are emitted in the wavelength range 40–2000 Å. Line emission from the target elements is absent over most of this wavelength region, particularly below about 600 Å. The use of these continua as simple, reliable background sources for absorption spectroscopy in the vacuum-ultraviolet and soft x-ray region down to 40 Å is demonstrated

Epidemiology and control of pink rot in potatoes.

End of Project ReportRotting of tubers was reported in early potato crops in Co. Wexford in 1995. Geotrichum candidum, which causes a condition known as rubbery rot, was isolated from a sample of affected tubers. In further investigations in 1996 both G. candidum and Phytophthora erythroseptica, the cause of pink rot, were isolated from diseased tubers. In pathogenicity tests P. erythroseptica re-infected tubers while G. candidum did not. It was concluded that the disease was pink rot. In 1997 foliar applications of the systemic fungicide metalaxyl were evaluated for its control. The level of control obtained was insufficient to overcome the problem which pink rot can cause in early potatoes

Breeding, disease resistance screening and seed production of new potatoe varities.

End of Project ReportThe potato breeding programme at Oak Park was started in the 1960's and has consisted of a number of distinct phases. In the first phase the focus was on the testing of the main domestic and foreign varieties in field trials in the main potato growing areas of the country. This was followed by a breeding programme for the domestic market, with particular emphasis on the production of a blight resistant replacement for Kerr’s Pink. The emphasis then switched to breeding for the export market, with the focus on the UK and Mediterranean markets. Since then the breeding programme has been focused on the domestic, processing and export markets. The process of breeding, testing and multiplying a new potato variety from the making of the initial cross until the new variety can be commercially grown takes about 15 years (see Appendix 2). The objectives of the present Potato Breeding Programme are: 1. Breeding improved varieties for the seed export trade. 2. Developing high yielding early maincrop and maincrop types with resistance to potato cyst eelworm Globodera rostochiensis and or Globodera pallidae with quality suitable for the UK market. 3. Developing a high dry-matter red skinned early maincrop or maincrop variety suitable for the home ware trade with a high level of disease resistance especially to late blight. 4. To select early maincrop or maincrop types suitable for processing into crisps and chips. 5. Breeding 1st and 2nd early varieties suitable for Irish and UK conditions with improved quality and disease resistance

Decision Support Systems For Disease Control in Winter Wheat.

End of Project ReportA leaf diagnostic test and a computer-based decision support system were evaluated for the control of diseases of winter wheat caused by Septoria spp. Fungicide programmes, as dictated by both methods, were compared with a standard routine programme, a reduced-rate programme and an unsprayed control from 1998 to 2000. In some instances fungicide programmes, dictated by leaf diagnostic tests, resulted in lower disease and higher yields than routine programmes but these were not consistent. Fungicide programmes, based on the computer-based decision support system, offered no advantages over routine programmes in terms of lower levels of disease, reduced numbers of fungicide applications or increased yields. Reduced-rate programmes, based on more frequent applications of low rates of fungicides, resulted in substantial savings of fungicides and in 1999 and 2000 better disease control and higher yields than routine programmes

Table-top EUV continuum light source

Work in recent years on the development of a convenient "table-top" source of continuum radiation in the XUV and VUV from 4 to 200 nm is summarized. It was found that laser-produced plasmas on targets of high atomic number (62 leq Z leq 74) emitted apparently line-free continua over very substantial spectral regions in the XUV and VUV. The continua are very intense, reproducible, and relatively insensitive to ambient pressure. The effective absence of line emission can be explained on the basis of the electron configurations of the ionized species responsible for the emission. A high repetition rate modular version of the source is described. Applications and advantages of the light source are presented

Genetic Analysis of Irish Populations of Phytophthora Infestans

End of Project ReportPhytophthora infestans (Mont.) de Bary, the causal agent of potato late blight is best known for its role in the great Irish famine of 1845-1849 which resulted in the deaths of over 1 million people. Since then, the disease has become established in all potato growing countries and is the most important pathogen of potatoes worldwide. The appearance of resistance to the phenylamide fungicides in the late 1970’s indicated that populations of P. infestans were changing. An antiresistance strategy was developed for growers in an effort to reduce the spread of resistant strains. Subsequently the A2 mating type of the fungus was discovered in 1989 promoting fears that a super strain of the fungus could evolve through sexual reproduction. Populations of the fungus have been monitored from 1981 to 1998 for levels of phenylamide resistance and since 1988 for the A2 mating type. Physiological race surveys were conducted in 1983 and 1996. Prior to the 1980s no reliable methods were available for adequate identification of genotypes. Development of molecular markers specific to P. infestans has made this possible and a survey was conducted on isolates from the 1996 population. Results confirm that the anti-resistance strategy for phenylamide based fungicides has been effective in preventing the build up of metalaxyl resistant populations of P. infestans. During the 1990’s the distribution of phenylamide resistance has remained stable at about 50% of crops tested compared to a high of over 80 % in 1981. The level of A2 in the population has also fallen from a high of 35% of isolates tested in 1989 to a static level of 3-4 % in the 1990’s. Physiological race composition has become much more complex since 1983 and 16 different physiological races were found in Ireland in 1996. The population was dominated by race 3.4.7.10.11 which accounted for over 54% of isolates tested. This change has taken place without a corresponding change to varieties with a complex Rgene base. Twelve different genotypes of the fungus were uncovered using the multilocus probe RG57. Races of the fungus were independent of genotype. One particular genotype IE-2 was predominantly associated with phenylamide resistance. The low population diversity discovered suggests that sexual reproduction between A1 and A2 types has not been a major factor in disease epidemiology to date. Super strains similar to those identified in the USA could not be confirmed. The overall level of variation in the Irish isolates of Phytophthora infestans would confirm that the population has become progressively more diverse during the last forty years. However, the population is much less complex than that found in the highland tropics of central Mexico.Teagasc Walsh Fellowship Programm

Effect of early sowing on the growth, yield and quality of sugar beet.

End of Project ReportExperiments have shown that yield of sugar is closely related to the amount of solar radiation intercepted by a sugar beet crop. Early sowing increases leaf area from May onwards when radiation is at its maximum and provides a basis for increasing yields. In the past, bolting has been an undesirable consequence of early sowing but some modern cultivars have good bolting resistance and can be sown early with a limited risk of bolting. This study, conducted from 1994 to 1998, compared the performance of two cultivars, Celt and Monofeb, at three sowing dates and three harvest dates. In replicated experiments, plant establishment, crop development, and root yield and quality were assessed. The effect of sowing date on solar radiation interception was studied. Effects of in-furrow pesticide application on pest numbers and plant damage were also measured. Plant establishment was influenced by sowing date with the early sowings generally giving lower plant numbers than the later ones. The cultivar Celt produced higher populations than Monofeb at all sowing dates. Early sowing increased the leaf area index (a measure of the ratio of leaf to land area) and consequently the amount of solar radiation intercepted. This was particularly so in June when solar radiation levels are highest. Early crop establishment provides the opportunity to exploit good weather conditions which may occur in April or May. Pest numbers generally were small at all the sites. Insecticide had a greater effect on pest numbers and plant damage than it had on plant establishment; the beneficial effects of pesticide were slightly more pronounced for the early and mid-season sowings than for later-sown beet. Seedling diseases were not a problem at any time of sowing. Poor emergence, where it occurred, was not associated with pre-emergence disease. Early to mid-March sowings produced significantly higher yields of roots and sugar than the early or late April sowings over the period of the experiment. Even in years when plant populations from the first sowings were much lower than subsequent sowings, yields tended to be at least equal to those of later sowings. Monofeb produced a slightly higher root yield than Celt, but because it had lower sugar contents there was no difference in sugar yields. Harvesting extended over the period from early October to mid-November and root growth and sugar production increased over that period irrespective of sowing date. Bolting was a problem in 1996 on the early-sown plots, particularly with the cultivar Celt.Teagasc acknowledges the support of Irish Sugar plc and Sugar Beet Levy Farmer Funds in the financing of this projec

Rise and fall of the 4d¹⁰→4d⁹4f resonance in the Xe isoelectronic sequence

The extreme ultraviolet photoabsorption spectrum of a laser-produced lanthanum plasma has been recorded and found to contain a number of discrete features in the 130-eV region. These have been analyzed as 4d10→4d9nf,np transitions in La3+. We show that the 4f transition, which is expected to be the strongest, is not in evidence. The reason is that this resonance, after the collapse of the 4f wave function, has a large autoionization width. We conclude that the 4f orbital in Ba2+ is only partially collapsed, which settles a long-standing discussion of this point

Dramatic changes in the 3s autoionization process at the beginning of the Ar I sequence

The 3s→np resonances were observed to change dramatically in appearance with increasing ionization along the Ar I sequence, and within the 3s→np channel of Ca2+. By applying the Dyson equation method to positive ions for the first time, newly investigated double-electron processes were shown to play a crucial role in the interpretation of the resonance structure. The changes within the resonances result from their position relative to the Cooper minima in the 3s and 3p photoabsorption