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991.
One hundred and forty-seven Chinese barley varieties maintained at the Gene Bank of the National Barley Improvement Centre,
Zhejiang, and 84 progenies from these varieties were tested at the seedling stage for their reaction to 32 selected pathotypes
of Blumeria graminis f. sp. hordei. Eighteen resistance spectra were identified comprising single or combined resistances from eight known (Ml(Bw), Ml(Ch), Mla7, Mla8, Mla9, Mla13, MlaRu4 and Mlg) and six unknown resistance genes. The most frequent gene was Ml(Bw), which was found in 69 varieties and previously detected in only a few European winter barley varieties. The genes Mla8 and Ml(Ch) were also often present, but other resistance genes were rare. After inoculation, considerably fewer pathogen colonies were
observed in ‘Aiganqi’ and one line of ‘Tong5’. Twenty varieties were composed of lines with different resistance genes. China
is likely to be a region of origin of the genes Ml(Bw), Mla7, as well as three unknown genes found in original landraces and perhaps another three unknown genes detected in cultivars
bred in China. The resistances of varieties from the Zhejiang province and those originating from 11 other Chinese provinces
were quite different. Unfortunately, none of the varieties are promising sources of resistance to powdery mildew and China
does not seem to be a region suitable for identifying such sources. 相似文献
992.
Mohammad Reza Naghavi Mohsen Mardi Seyed Mostafa Pirseyedi Mehrbanu Kazemi Payam Potki Mohammad Reza Ghaffari 《Genetic Resources and Crop Evolution》2007,54(2):237-240
Genetic diversity of 54 accessions of Aegilops tauschii from five countries was assessed using sequence-tagged microsatellites (or simple sequence repeats, SSRs) and amplified fragment
length polymorphisms (AFLPs). In the case of AFLP analysis, a total of 256 amplification products obtained, 234 of them were
polymorphic across all the 54 accessions. A total of 224 fragments were obtained from the 24 SSR primers and 219 of fragments
were polymorphic across all the genotypes screened. Based on both AFLP and SSR markers, the highest percentage of polymorphisms
were obtained in Iranian and accessions of unknown origin. The highest polymorphic information content (PIC) value was observed
for SSRs (0.82) while the highest marker index (MI) value was for AFLPs (8.5) reflecting the hyper-variability of the first
and the distinctive nature of the second system. Principal co-ordinate analysis (PCO) revealed congruent patterns of genetic
relationships for both data sets, but did not group accessions strictly according to their geographical origins. Poor correlation
was found between AFLP and SSR marker loci. This low association may be due to low number of AFLP and SSR markers. These results
show that molecular markers can help to organize the genetic variability and expose useful diversity for breeding purposes. 相似文献
993.
Sarah I. Beldin Bruce A. Caldwell Phillip Sollins Elizabeth W. Sulzman Kate Lajtha Susan E. Crow 《Biology and Fertility of Soils》2007,43(6):837-841
The cation exchange capacity (CEC) of a soil depends on the type and amount of both mineral and organic surfaces. Previous
studies that have sought to determine the relative contribution of organic matter to total soil CEC have not addressed differences
in soil organic matter (SOM) composition that could lead to differences in CEC. The objectives of this study were (1) to compare
the CEC of two distinct SOM pools, the “light fraction (LF)” composed of particulate plant, animal, and microbial debris,
and the “heavy fraction (HF)” composed of mineral-bound organic matter; and (2) to examine the effects of differences in aboveground
vegetation on CEC. Soil samples were collected from four paired grassland/conifer sites within a single forested area and
density fractionated. LF CEC was higher in conifer soils than in grassland soils, but there was no evidence of an effect of
vegetation on CEC for the HF or bulk soil. LF CEC (but not HF CEC) correlated well with the C concentration in the fraction.
The mean CEC of both fractions (per kg fraction) exceeded that of the bulk soil; thus, when the LF and HF CEC were combined
mathematically by weighting values for each fraction in proportion to dry mass, the resulting value was nearly twice the measured
CEC of bulk soil. On a whole soil basis, the HF contributed on average 97% of the CEC of the whole soil, although this conclusion
must be tempered given the inflation of CEC values by the density fractionation procedure. 相似文献
994.
Long-term effect of chemical fertilizer,straw, and manure on labile organic matter fractions in a paddy soil 总被引:2,自引:0,他引:2
To assess the effect of long-term fertilization on labile organic matter fractions, we analyzed the C and N mineralization
and C and N content in soil, particulate organic matter (POM), light fraction organic matter (LFOM), and microbial biomass.
Results showed that fertilizer N decreased or did not affect the C and N amounts in soil fractions, except N mineralization
and soil total N. The C and N amounts in soil and its fractions increased with the application of fertilizer PK and rice straw.
Generally, there was no significant difference between fertilizer PK and rice straw. Furthermore, application of manure was
most effective in maintaining soil organic matter and labile organic matter fractions. Soils treated with manure alone had
the highest microbial biomass C and C and N mineralization. A significant correlation was observed between the C content and
N content in soil, POM, LFOM, microbial biomass, or the readily mineralized organic matter. The amounts of POM–N, LFOM–N,
POM–C, and LFOM–C closely correlated with soil organic C or total N content. Microbial biomass N was closely related to the
amounts of POM–N, LFOM–N, POM–C, and LFOM–C, while microbial biomass C was closely related to the amounts of POM–N, POM–C,
and soil total N. These results suggested that microbial biomass C and N closely correlated with POM rather than SOM. Carbon
mineralization was closely related to the amounts of POM–N, POM–C, microbial biomass C, and soil organic C, but no significant
correlation was detected between N mineralization with C or N amounts in soil and its fractions. 相似文献
995.
Amer Ibrahim Basha Stefano Padulosi Kamel Chabane Adnan Hadj-Hassan Ehsan Dulloo Mario Augusto Pagnotta Enrico Porceddu 《Genetic Resources and Crop Evolution》2007,54(8):1807-1816
Pistachio (Pistacia vera L.) is a strategic nut tree species in the Middle East which holds comparative advantage over other fruit trees in view of
its hardiness, income generation opportunities and benefits for the ecosystem. Yet pistachio cultivation depends on a very
narrow genetic base, in spite of the existence of many varieties still marginally exploited. Syria is an important center
of diversity for pistachio. A country wide ecogeographic survey in this country was carried out to determine the extent of
pistachio genetic diversity and its use. As a whole, 114 accessions were collected from 37 farms to assess diversity at morphological
and molecular level. Molecular evaluation was carried out using Amplified Fragment Length Polymorphism (AFLP) technique and
performed using seven primer pair combinations. Results from the studies allowed the identification of 25 pistachio female
varieties in Syria, some of which unique and described for the first time. Three groups of pistachio diversity were identified
by cluster analysis which provides useful information about the distribution of genetic diversity in Syria for enhanced use
and sustainable conservation. 相似文献
996.
The effect of soil freeze–thaw cycles on the denitrification potential was examined based on the C2H2 inhibition method. The gross N2O production curve of the soil sample (incubation with C2H2) showed minor changes between the freeze–thaw treatment and the unfrozen control. However, kinetics analysis revealed that
the initial production rate, an indicator of the population density of denitrifying communities, decreased (P = 0.043) and the specific growth rate constant, an indicator of the activity of denitrifying communities, increased (P = 0.039) as a result of the freeze–thaw cycles in five of six soil samples examined. The increase in the specific growth
rate constant suggested the stimulation of the activity of denitrifying communities that survived after the freeze–thaw cycles
and may explain the minor suppression on the gross N2O production in spite of decreasing the population density of denitrifying communities that was suggested by the initial production
rate. The net N2O production curve of the soil sample (incubation without C2H2) showed a remarkable change in one out of six soil samples, and in that one soil sample, N2O release to the atmosphere was largely stimulated (7.6 times) by the freeze–thaw cycles. However, the stimulation of the
N2O release by the freeze–thaw cycles was even observed in two other selected soil samples (4.6 and 1.8 times), suggesting that
an imbalance in the N2O-producing and N2O-reducing activities of denitrifying communities might complementally explain the N2O release stimulated by the freeze–thaw cycles. 相似文献
997.
A. de Varennes M. O. Torres C. Cunha-Queda M. J. Goss C. Carranca 《Biology and Fertility of Soils》2007,44(1):49-58
We investigated conservation and cycling of N under oat–oat and lupine–oat rotations in disturbed and undisturbed soil, when
roots or roots plus aboveground residues were retained. Crop residues were labelled with 15N in Year 1, and differential soil disturbance was imposed after harvest. In Year 2, plant growth, N transfer from residue
into the various sinks of the second crop (plant, soil, and residual residues), and changes in microbial activity and numbers
were determined. Oat biomass was greater after lupine than after oat due to differences in supply of N from these residues.
Buried residues of both crops appeared to decompose faster than when left on the soil surface. Lupine residues decomposed
faster than oat residues. Oat biomass was not affected by soil disturbance if grown after lupine but decreased when oat straw
was buried in the soil. More residue N was recovered from soil than from the crop. Most 15N was recovered from disturbed soil, which also had greater dehydrogenase activity and more culturable fungi. At the end of
the oat–oat rotation, 20 and 5 kg N ha−1 were derived from the roots of the first crop in undisturbed or disturbed soil, respectively. Equivalent values for the lupine–oat
rotation were 18 and 44 kg N ha−1. Returning aboveground residues provided an extra 52–80 kg N ha−1 for oat and 61–63 kg N ha−1 for lupine relative to treatments where they were removed. Over a year, lupine contributed 9 to 20 kg N ha−1 more to the agroecosystem than did oat. 相似文献
998.
Paula Martins-Lopes José Lima-Brito Sónia Gomes Julieta Meirinhos Luís Santos Henrique Guedes-Pinto 《Genetic Resources and Crop Evolution》2007,54(1):117-128
Thirty Portuguese and eight foreign olive (Olea europaea L.) cultivars were screened using Random Amplified Polymorphic DNA (RAPD) and Inter-Simple Sequence Repeat (ISSR) markers.
Twenty RAPD primers amplified 301 reproducible bands of which 262 were polymorphic; and 17 ISSR primers amplified 204 bands
of which 180 were polymorphic. The percentage of polymorphic bands detected by ISSR and RAPD was similar (88 and 87%, respectively).
The genetic variability observed was similar in the Portuguese and foreign olive cultivars. Seven ISSR and 12 RAPD primers
were able to distinguish individually all 38 olive cultivars. Twenty specific molecular markers are now available to be converted
into Sequence Characterised Amplified Region (SCAR) markers. Relationships among Portuguese and foreign cultivars is discussed. 相似文献
999.
Chris Klok Jack Faber Guido Heijmans Jos Bodt Annemariet van der Hout 《Biology and Fertility of Soils》2007,43(5):549-556
In this paper we report on the influence of clay content and acidity of soil on growth and reproduction of the epigeic earthworm
species Lumbricus rubellus (Hoffm.), which is common in most temperate soils and abundant in grasslands. Growth, cocoon production and survival of L. rubellus were tested in 12 Dutch soils which differed in soil properties. A matrix model was used to assess the population-level consequences
of changes in growth and reproduction. Soil acidity had a strong negative effect on earthworm survival, and the maturation
weight decreased with clay content. Individual weight gain in L. rubellus decreased with both acidity and clay content. The acidity of soils had a larger influence on population growth rate than
the clay content. The acidity of the soil also changed the population composition towards younger age classes, whereas in
soils rich in clay, the population composition did not change. The average individual weight of L. rubellus in clayey soils, however, was lower compared with that in soils low in clay, a result that agrees with literature data. 相似文献
1000.