Spring Barley Responses to Row Spacing and Fungicide Triadimefon in Regions with a Short Crop-growing Season

Aspects of intensive management practices such as high-yielding cultivars, narrow-row spacings and fungicide treatments could potentially increase cereal yields in regions with a short crop-growing season and occasionally dry and hot weather. A field experiment was carried out at McGill University, Canada for three years (1987 to 1989) to test the effects of triadimefon (1-[4-chlorophenoxy]-3,3-dimethyl-1-[1H-1,2,4-triazol-1-yl]-2-butanone, or Bayleton, a trade name) fungicide (0 vs. 140 g a.i. ha⁻¹) and row spacing (10 vs. 20 cm) on the yield components, yield and other agronomic traits (spike emergence, days to maturity, leaf disease and plant height) of spring barley ( Hordeum vulgare L.) cv. Cadette, Laurier and Leger. A cultivar by row spacing interaction resulted in a 11 to 13.5 % increase in grain yield due to narrow rows for Laurier in two out of the three years and up to 16 % for Leger in one year. Over the three years grain yields were on average increased 6 to 12 % due to use of the narrower row spacing. Fungicide application to barley at the early heading stage effectively controlled leaf diseases without influence on yield components or grain yield. Our results indicate that some components of intensive management such as narrow row spacing can be applicable in regions with a short crop-growing season.     

Survival of Leptosphaeria maculans in soil on residues of Brassica napus in South Australia

The survival of Leptosphaeria maculans , which causes phoma stem canker (blackleg), on oilseed rape residues ( Brassica napus ) in South Australia was investigated. Using a quantitative polymerase chain reaction (PCR) assay for L. maculans DNA, the pathogen was mainly detected in the upper 5 cm of the soil profile, including residues on the soil surface. As the size of organic matter particles in the soil decreased, so did the quantity of L. maculans detected in them. To obtain representative data for a field, at least 30 subsamples needed to be collected over the 0·81 ha area studied. In a survey of 49 commercial fields in South Australia, most L. maculans was detected in fields 1 year after oilseed rape had been grown, with less detected after 2 years and negligible amounts 3 years or more after cropping. The diagnostic DNA-based assay for L. maculans reduced the time and cost of studying L. maculans survival in soil and increased the sensitivity and accuracy of results compared with estimates of propagule number of colony-forming units on a semiselective medium.     

Effect of Completion of Vernalization on Generative Development of Winter Rape (Brassica napus L. var. oleifera) Plants

Germinating seeds and young plants of winter rape var. Górczañski were vernalized for 56–63 days under conditions of 9-hour day, at the temperature 2 and 5 °C and in continuous darkness at the temperature 2 °C. After vernalization the plants grew under conditions enabling to complete vernalization: in a glass-house at the temperature day/night 15/10 °C and in semi natural conditions of open vegetation hall in the period from June till August. After sub-optimal vernalization further growth of the plants at lowered temperature increased its effectiveness (completion of vernalization). Depending on the degree of the vernalization of the plants the completion of their vernalization was both obligatory, i.e. conditioning the acquisition of the ability of generative development, and facultative i.e. accelerating this development. It has been demonstrated that the population of plants of the examined variety is strongly differentiated not only with respect of vernalization requirements in the particular plants, but also what regards the effectiveness of vernalization completion. New observations have been made indicating that the mechanisms controlling the successive phases of generative development, i.e. phase of forming flower buds and the flowering phase are not identical which may be interpreted as indicating that the "flowering factor" is polymorphous.     

Acquired resistance triggered by elicitins in tobacco and other plants

Elicitins are a family of proteins excreted byPhytophthora spp. They exhibit high sequence homology but large net charge differences. They induce necrosis in tobacco plants which then become resistant to the tobacco pathogenPhytophthora parasitica var.nicotianae. In stem-treated plants, resistance was not restricted to the site of elicitin application, but could be demonstrated by petiole inoculation at all levels on the stem. Resistance was already maximum after two days and lasted for at least two weeks. It was effective not only towardsP. p. var.nicotianae infection, but also against the unrelated pathogenSclerotinia sclerotiorum. In contrast to dichloroisonicotinic acid, an artificial inducer of systemic acquired resistance, which was increasingly effective with doses ranging from 0.25 to 5mole per plant, the basic elicitin cryptogein exhibited a threshold effect, inducing near total resistance and extensive leaf necrosis above 0.1 nmole per plant. Between 1 and 5 nmole, acidic elicitins (capsicein and parasiticein) protected tobacco plants with hardly any necrotic symptom. Elicitins exhibited similar effects in various tobacco cultivars andNicotiana species, although with quantitative differences, but induced neither necrosis nor protection in other SolanaceÆ (tomato, petunia and pepper). Among 24 additional species tested belonging to 18 botanical families, only some BrassicaceÆ, noticeably rape, exhibited symptoms in response to elicitins, in a cultivar-specific manner. Elicitins appear to be natural specific triggers for systemic acquired resistance and provide a tool for unraveling the mechanisms leading to its establishment.Abbreviations AR acquired resistance - HR hypersensitive response - INA 2,6-dichloroisonicotinic acid - Ppn Phytophthora parasitica var.nicotianae - SAR systemic acquired resistance     

宁夏春小麦磷素利用效率的基因型差异研究

在不同施磷土壤条件下,采用肥料田间试验和测试分析方法,研究了宁夏春小麦磷素利用效率及其有关性状的基因型差异。结果表明,不论施磷与否,小麦籽粒产量、生物学产量、磷肥增产率、地上部茎叶和籽粒中含磷量以及磷素吸收累积量、磷素利用效率等均存在明显基因型差异,且这种差异在低磷条件下更为明显。在低磷条件下,籽粒生产中的磷素利用效率变化在160.1～448.3kg/kg之间,平均为223.1kg/kg,变异系数为23.05％;干物质生产中的磷素利用效率变化在332.6～898.5kg/kg之间,平均为458.4kg/kg,变异系数为22.57％。从中筛选出低磷高产高效品种8个。在较高供磷条件下,籽粒生产中的磷素利用效率变化在150.9～350.9kg/kg之间,平均为229.8kg/kg,变异系数为20.63％;于物质生产中的成素利用效率变化在358.3～746.5 kg/kg之间,平均为482.Ikg地,变异系数为 18.76％。从中筛选出高磷高产高效品种7个。通过相关分析,研究了不同供成条件下磷素利用效率与其它营养性状之间的关系,提出了培育磷高效品种的有用性状指标。     

Variation in the development of secondary dormancy in oilseed rape genotypes under conditions of stress

Summary A substantial amount of seed is left in the fields before and during harvest of oilseed rape. Although this crop exhibits little or no primary dormancy, the absence of certain environmental cues that promote germination of imbibed seeds induces secondary dormancy. The work reported investigated the extent to which environmental stress conditions, including osmotic stress, low oxygen stress and anaerobiosis, induce secondary dormancy in oilseed rape, and examined the variation in development of secondary dormancy between and within genotypes. Osmotic stress was most effective in inducing dormancy. Anaerobic treatment produced very few dormant seeds, as did an atmosphere low in oxygen and high in nitrogen. The development of secondary dormancy under osmotic stress varied considerably between and within genotypes. Dormancy ranged from almost zero to about 60% for winter genotypes and about 85% for spring types. Within genotypes, variations occurred between seed lots and years of harvest. Temperature variations affected the percentage of dormant seeds. More dormant seeds were likely to be produced with incubation under water stress at 20 °C than at 12 °C. In winter genotypes, fewer dormant seeds were produced when incubation temperature and germination test temperatures differed. Thus, incubating at 20 °C and 12 °C, followed by germination tests at 20 °C and 12 °C, respectively, produced most dormant seeds. Also, in the winter genotypes, the potential development of secondary dormancy was positively correlated with the pattern and speed of germination of untreated seeds.     

Sporulation of Pyrenopeziza brassicae (light leaf spot) on oilseed rape (Brassica napus) leaves inoculated with ascospores or conidia at different temperatures and wetness durations

In controlled environment experiments, sporulation of Pyrenopeziza brassicae was observed on leaves of oilseed rape inoculated with ascospores or conidia at temperatures from 8 to 20°C at all leaf wetness durations from 6 to 72 h, except after 6 h leaf wetness duration at 8°C. The shortest times from inoculation to first observed sporulation ( l ₀), for both ascospore and conidial inoculum, were 11–12 days at 16°C after 48 h wetness duration. For both ascospore and conidial inoculum (48 h wetness duration), the number of conidia produced per cm² leaf area with sporulation was seven to eight times less at 20°C than at 8, 12 or 16°C. Values of Gompertz parameters c (maximum percentage leaf area with sporulation), r (maximum rate of increase in percentage leaf area with sporulation) and l ₃₇ (days from inoculation to 37% of maximum sporulation), estimated by fitting the equation to the observed data, were linearly related to values predicted by inserting temperature and wetness duration treatment values into existing equations. The observed data were fitted better by logistic equations than by Gompertz equations (which overestimated at low temperatures). For both ascospore and conidial inoculum, the latent period derived from the logistic equation (days from inoculation to 50% of maximum sporulation, l ₅₀) of P. brassicae was generally shortest at 16°C, and increased as temperature increased to 20°C or decreased to 8°C. Minimum numbers of spores needed to produce sporulation on leaves were ≈25 ascospores per leaf and ≈700 conidia per leaf, at 16°C after 48 h leaf wetness duration.     

Study of Resistance to Orobanche ramosa in Host (Oilseed Rape and Carrot) and Non-host (Maize) Plants

Orobanche ramosa is a parasitic Angiosperm responsible for severe yield losses in several economical crops. It is a serious threat in oilseed rape in France and Morocco and is appearing in carrot crops in Morocco. In this study, several varieties of oilseed rape and carrot were screened in order to identify resistant cultivars and to characterize the resistance mechanisms involved. All the 15 oilseed rape varieties tested were susceptible. In carrot, the varieties 'Colmar à coeur rouge' and 'Nantaise demi-longue' were susceptible, whereas 'Palaiseau' and 'Buror' were resistant. In the susceptible 'Colmar à coeur rouge' carrot no defence reactions were found and the development of the parasite inhibited carrot tap root formation. In the resistant carrot varieties, the parasite germinated, became attached to the host root but became necrotic before emergence. In 'Buror' carrot, formation of a mechanical barrier was associated with the restriction to the cortex of the parasite. In maize cv. 'Vigni', a non-host of O. ramosa, thickening of xylem vessels, cell divisions in the central cylinder and formation of an encapsulation layer were observed in association with restricted development of Orobanche haustoria.     

果梅幼树对春施~(15)N-硫铵的吸收与分配

以盆栽3年生细叶青梅/毛桃为试材,研究了早春施用~(15)N-(NH_4)_2SO_4条件下,果梅对~(15)N的吸收分配规律。结果表明:由于春季土温较低,限制了植株对肥料氮的利用率。在新梢旺长期,植株从肥料氮中吸收的氮素营养主要用于新生器官的建造,且新梢成为~(15)N的主要分配中心,其次即为果实,再其次为细根。至花芽分化期,植株的生长中心已发生转移和分散,但春施氮对促进当年生枝的花芽分化和维持叶片正常光合功能仍有重要作用,此期亦是根系生长的关键时期之一,且与贮氮相比,春施氮更有利于当年新根的萌发和根系的扩大。