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1.
R. Chima Wokocha 《Plant and Soil》1988,106(1):146-148
Populations of viable sclerotia ofSclerotium rolfsii were highest in soil in a field in which tomato was planted for three successive years before sampling and in one in which
tomato followed groundnut in the 2 years prior to this study. The lowest sclerotial numbers were recorded in fields in which
groundnut followed maize or in which maize or sorghum was the last crop before sampling. 相似文献
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Summary Nitrate fertiliser labelled with15N was applied to a field grown crop of winter wheat. Uptake and assimilation of fertiliser nitrate was studied by monitoring the appearance of labelled nitrate and labelled amino acids in the xylem sap. Shortly after applying15N-nitrate to the soil about 30 per cent of recently absorbed15N was in the reduced form, indicating that roots of cereal crops can make a substantial contribution in reducing nitrate. Seasonal changes in crop growth andin vivo NRA are also described. 相似文献
4.
Ovenden JR Peel D Street R Courtney AJ Hoyle SD Peel SL Podlich H 《Molecular ecology》2007,16(1):127-138
This study compares estimates of the census size of the spawning population with genetic estimates of effective current and long-term population size for an abundant and commercially important marine invertebrate, the brown tiger prawn (Penaeus esculentus). Our aim was to focus on the relationship between genetic effective and census size that may provide a source of information for viability analyses of naturally occurring populations. Samples were taken in 2001, 2002 and 2003 from a population on the east coast of Australia and temporal allelic variation was measured at eight polymorphic microsatellite loci. Moments-based and maximum-likelihood estimates of current genetic effective population size ranged from 797 to 1304. The mean long-term genetic effective population size was 9968. Although small for a large population, the effective population size estimates were above the threshold where genetic diversity is lost at neutral alleles through drift or inbreeding. Simulation studies correctly predicted that under these experimental conditions the genetic estimates would have non-infinite upper confidence limits and revealed they might be overestimates of the true size. We also show that estimates of mortality and variance in family size may be derived from data on average fecundity, current genetic effective and census spawning population size, assuming effective population size is equivalent to the number of breeders. This work confirms that it is feasible to obtain accurate estimates of current genetic effective population size for abundant Type III species using existing genetic marker technology. 相似文献
5.
M.?A.?Shatnawi K.?A.?JohnsonEmail author 《In vitro cellular & developmental biology. Plant》2004,40(2):239-244
Summary Christmas bush (Ceratopetalum gummiferum Sm) is a shrubby tree species of the east coast of New South Wales in Australia. It is much prized as a cut flower crop because
of its bright, pinky red floral calyces. New varieties are being developed, the storage of which is an important issue. In
this study, it was shown that shoot tips sampled from in vitro plantlets withstood cryopreservation using the encapsulation-dehydration technique. The protocol leading to optimal regrowth
was the following: excised shoot tips were pretreated for 1 d in the dark on hormone-free Murashige and Skoog (MS) medium
with 0.3 M sucrose, then encapsulated in 3% calcium alginate and precultured in liquid MS medium with 0.5 M sucrose for 3 d. Precultured beads were dehydrated for 6 h in the air current of the laminar flow cabinet to 24.3% moisture
content (fresh weight basis) before rapid immersion in liquid nitrogen. Under these conditions, regrowth of shoot tips after
cryopreservation reached 61.4%. Regrowth of cryopreserved shoot tips was not affected by the period of cold acclimation of
in vitro mother plants. 相似文献
6.
William J. Sacks Delphine Deryng Jonathan A. Foley Navin Ramankutty 《Global Ecology and Biogeography》2010,19(5):607-620
Aim To assemble a data set of global crop planting and harvesting dates for 19 major crops, explore spatial relationships between planting date and climate for two of them, and compare our analysis with a review of the literature on factors that drive decisions on planting dates. Location Global. Methods We digitized and georeferenced existing data on crop planting and harvesting dates from six sources. We then examined relationships between planting dates and temperature, precipitation and potential evapotranspiration using 30‐year average climatologies from the Climatic Research Unit, University of East Anglia (CRU CL 2.0). Results We present global planting date patterns for maize, spring wheat and winter wheat (our full, publicly available data set contains planting and harvesting dates for 19 major crops). Maize planting in the northern mid‐latitudes generally occurs in April and May. Daily average air temperatures are usually c. 12–17 °C at the time of maize planting in these regions, although soil moisture often determines planting date more directly than does temperature. Maize planting dates vary more widely in tropical regions. Spring wheat is usually planted at cooler temperatures than maize, between c. 8 and 14 °C in temperate regions. Winter wheat is generally planted in September and October in the northern mid‐latitudes. Main conclusions In temperate regions, spatial patterns of maize and spring wheat planting dates can be predicted reasonably well by assuming a fixed temperature at planting. However, planting dates in lower latitudes and planting dates of winter wheat are more difficult to predict from climate alone. In part this is because planting dates may be chosen to ensure a favourable climate during a critical growth stage, such as flowering, rather than to ensure an optimal climate early in the crop's growth. The lack of predictability is also due to the pervasive influence of technological and socio‐economic factors on planting dates. 相似文献
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MARC KÉRY JOHN H. SPILLMANN CAMILLE TRUONG† ROLF HOLDEREGGER‡ 《Journal of Ecology》2006,94(5):980-986
10.
Risk assessment for engineered bacteria used in biocontrol of fungal disease in agricultural crops 总被引:1,自引:0,他引:1
A plant growth promoting rhizobacterium (PGPR)Pseudomonas fluorescens SBW25 (WT) protects a number of crop plant species from damping-off caused by Pythium ultimum. A genetically modified, phenazine-1-carboxylic acid (PCA) producing variant, 23.10, carries on its chromosome a single copy
of phzABCDEFG, under the control of the P tac constitutive promoter. The genetically modified biological control agent (GM-BCA), 23.10, has improved biocontrol activity
when compared to wild type SBW25, and can effectively suppress Pythium spp. present at up to 100 times normal field infestations. GM-BCA inocula establish high population densities which persist
well in the phytosphere of several crop plants including pea, wheat and sugar beet, effectively suppressed infection and promoted
increase in total plant biomass. It also has an improved spectrum of activity over other plant phytopathogens such as Fusarium spp. Gaeumannomyces graminis var. tritici, Phytophtora cinnamomi and Rhizoctonia solani. However in developing BCAs and in particular GMBCAs it is important to determine whether their use has any adverse effect
in the environment. Any observed changes following inoculation with wild type BCA or GM BCA in microbial diversity (bacteria
and fungi) were negligible when assessed by either quantitive selective plate count methods (CFU/g) or culture independent
molecular assays (SSU rRNA based PCR-DGGE). Rhizosphere community diversity profiles (DGGE) in infected plants in the presence
of inocula were highly similar to disease free systems. Histological assessment of the impact of inocula on established functional
mycorrhizae associations were conducted on cores collected from an established field margin grassland pasture. No adverse
impact on mycorrhizal colonization and root infection were recorded after addition of WT or GM-BCA bacterial inocula as a
soil drench. This approach and the related culturable and culture independent methods have recorded only a minor, transient
perturbation to microbial communities, but as far as we are aware this is the first direct demonstration that a functional,
AFC producing GMM also has only a transient impact on mycorrhizal associations in established plant communities. In all instances
studied the plant species, plant stage of development and disease, damping-off, had a greater impact on changes in rhizosphere
diversity than the presence of an introduced GM bacterial inocula. 相似文献