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1.
    
The independent target region amplification polymorphism (TRAP) and single‐nucleotide polymorphism (SNP) marker s were used for genetic evaluation of different selected 47 sugarcane genotypes. A total of 23 pairs of TRAP markers generated 925 alleles, of which 74% alleles were polymorphic. Polymorphism was generally high (>50%), ranging from 54 to 98%. The polymorphism information content (PIC) values 0.20 varied among the primer combination ranging from 0.17 in SAI + Arbi 2 to 0.31 in GL 2+ Arbi 1 with an average of 0.24. However, the Pearson correlation between PIC and power of discrimination (PD) was found to be less significant. Single‐nucleotide polymorphisms were used first time for the assessment of genetic diversity among different species of Saccharum and cultivated sugarcane varieties. The SNPs were detected from 454 sequencing. A total of 245 SNP markers were assayed across the 47 genotypes, and 167 SNPs were found to be polymorphic. The PIC values ranged from 0.04 to 0.38 with an average of 0.21, and their respective PD varied from 0.58 to 0.04 with an average value of 0.31. The obtained results relatively significant were compared with the other marker systems through genetic similarity and the clusters formed in different unweighted pair group method with arithmetic mean clustering dendrogram. The clustering analysis established genetic relationship in the order of Erianthus Sclerostachya Narenga Saccharum spontaneum S. robustum > S. barberi > S. officinarum/cultivars. These results ratify TRAP and SNP marker systems for assessing genetic diversity studies, and more diversified Erianthus spp. can contribute substantially towards sugarcane varietal improvement through breeding with Saccharum spp. or hybrid cultivars.  相似文献   
2.
    
Macrotermes termitaria are conspicuous features of savannah ecosystems in the Sudanian and Sahelian zones of West Africa. The mounds, alive or abandoned, are a major source of heterogeneity in the landscape. The purpose of the present study was to assess the impact of termitaria on tree community in a state forest of the Sudanian regional centre (Tiogo forest, Burkina Faso), under controlled burning and grazing experiments. A comparative inventory was carried out in a split-plot experiment (16 subplots of 2500 m2): 8 subplots where fire regime and grazing were controlled and 8 subplots exposed to grazing and with annual prescribed fire since 1992. All tree individuals (≥1.5 m) were recorded, both on termitaria and outside and their basal area at stump level was measured. A total of 61 observed (or 65.7 ± 2.4 estimated) tree species were recorded on 28 Macrotermes subhyalinus mounds (54 observed species or 60.8 ± 3.3 estimated), the immediate surroundings (44 observed and 59.0 ± 0.0 estimated species) and the rest of subplots (56 observed and 63.6 ± 0.0 estimated). Specific density was higher on mounds in comparison with the surroundings (P < 0.05). Results showed that termitaria played a key role in maintaining higher species diversity as compared to their surroundings (P < 0.05). Differences in species diversity between termitaria and immediate surroundings appeared more pronounced in disturbed plots (submitted to both fire and grazing). Some species, such as Tamarindus indica, Boscia senegalensis, Cadaba farinosa, Capparis sepiaria and Maerua angolensis are found solely on termitaria. Besides, the density of trees was significantly higher on termitaria compared to the surrounding (P < 0.05), as well as total basal area per unit of 100 m2 area (P < 0.05). We concluded that Macrotermes termitaria play an important role as a source of heterogeneity in this Sudanian savannah woodland ecosystem. This role is particularly important in ecosystems under stresses. Termitaria acted as refuge for tree vegetation. The density and dynamics of M. subhyalinus termitaria should, therefore, be taken into account in the global strategy of the forest resources management and conservation.  相似文献   
3.
Grazing behavior, diet selection and weight gain of heifers (with or without social models) were assessed in an unfamiliar site containing high plant diversity. The study was performed within a tropical forest ecosystem containing a mixture of grass forb/herb, shrub and tree species. Ten inexperienced crossbred Bos taurus × Bos indicus heifers (7 ± 1 months old) were randomly assigned to one of two groups: naive or naive + social model (sm) and two experienced heifers (16 months old) were assigned to the second group. Naive heifers were bottle-nursed from days 2 to 90 after birth and began grazing at 1 month of age in tropical grass monocultures, while experienced animals had been foraging in sites containing a high diversity of plant species for 3 months prior to the study. Each group grazed in separate paddocks for a 12-week period during the rainy season, and animals were observed using focal sampling from 7:00 to 19:30 h to assess diet composition based on bite counts. Weight gain was assessed every 14 days. Paddocks contained from 1481 to 1789 kg/ha of herbaceous dry matter, enough to support the heifers throughout the study without affecting diet selection. Shrub and tree cover ranged from 55.2 to 58.4% across treatments. Bites per minute were adjusted to a log-scaled quadratic-plateau model and the curves showed no differences between treatments (P = 0.756). However, diet composition differed between groups (P < 0.001), with naive + sm heifers ingesting a greater proportion of trees (P < 0.001) and shrubs (P = 0.02), while naive heifers ingested more forb/herbs (P = 0.02); no difference in grass consumption was observed (P = 0.92). Heifers in both treatments consumed the same plant species (50 from 26 families). Over time, utilization of several plant species increased or decreased (P < 0.05), eventually leveling off for the remainder of the study. Although differences in diet composition were observed, they did not affect overall weight gain (117 and 113 g/day in the naive and naive + sm groups, respectively; P = 0.913). However, initial post-weaning weight loss was avoided in the naive + sm group. Social learning facilitates a higher use of shrubs and trees in tropical pastures containing a high diversity of plant species with different growth habits. As many plant species have high potential as forage, more effort should be placed on developing mechanisms to increase their dietary inclusion by cattle.  相似文献   
4.
DNA primers, based on the ribosomal sequences of lethal yellowing-type disease (LYD) phytoplasmas, were used to analyse genetic variation within the lethal yellowing-type diseases of coconut in East Africa. Samples were collected from palms in Kenya, Mozambique and high, medium and low disease incidence areas of Tanzania. The mollicute-specific primer pair P1 and P6 amplified a 1.5 kbp product from all diseased palms and no product from symptomless palms, indicating that phytoplasmas were associated with all of these diseases. However, the Rohde forward and Rohde reverse primers (a second rRNA primer pair designed to detect East African LYD-associated phytoplasmas) only amplified products from Tanzanian and Kenyan diseased palms and not from those of Mozambique. Conversely, primers Ghana 813 and AK-SR, designed for specific detection of coconut-associated phytoplasmas in West Africa, amplified products only from the Mozambique palms, indicating that the phytoplasma associated with LYD in Mozambique is more closely related to those from West Africa. This was supported by restriction enzyme digestion of PCR products. DNA sequencing of PCR products from phytoplasmas within Tanzania revealed no detectable differences in the rDNA sequences of isolates from high, medium and low incidence areas.  相似文献   
5.
    
The impact on tree and amphibian diversity of line-planting of tropical hardwoods—mahogany (Swietenia macrophylla × S. mahagoni) and mahoe (Hibiscus elatus)—was studied in a secondary subtropical wet forest of Puerto Rico. Common coqui (Eleutherodactylus coqui) and melodious coqui (E. wightmanae) are the most frequent frog species; forest coqui (E. portoricensis) is less abundant. Although relative abundance means were slightly greater in the undisturbed forest and during the wet season, differences were not statistically significant suggesting that line-planting did not significantly affect amphibian diversity. The line-planted areas had a slightly higher, but not statistically significant diversity, richness, and evenness of tree species than the unplanted forest. Multi-response permutation procedure (MRPP) showed statistically significant community composition differences between line-planting and control plot trees (T = ?5.89, A = .86; p < .001). But mean similarity among plots in both the line-planted and control plots was relatively low at less than 50% of shared species, indicating high diversity of vegetation in the overall forest area. Canopy cover by tree species greater than 3 cm in dbh was much higher in the undisturbed forest but this difference may be reduced as the young line-planted hardwoods mature. Forest enrichment through line-planting of valuable timber species in secondary subtropical wet forest does not significantly affect tree diversity.  相似文献   
6.
    
Trees are able to respond to their local biotic and abiotic environment with morphological adjustments which improve resource acquisition and, thus, growth. In forests, light is broadly recognised as one of the major factors determining growth, and morphological responses comprise changes in crown architecture and stem stature. On sloping terrain, the interplay of phototropism and gravitropism may further affect morphological growth characteristics. However, different tree species are expected to show species-specific responses. In this study, we analysed three growth characteristics of tree individuals belonging to four species of two functional groups (evergreen: Schima superba, Castanopsis eyrei, deciduous: Quercus serrata var. brevipetiolata, Castanea henryi) in a species-rich Chinese subtropical forest. Crown projection area, relative crown displacement and stem inclination were related to biotic (local species richness, functional richness, competition, stand age) and abiotic (slope aspect and inclination, soil depth) variables in the local neighbourhood of the tree individuals. We hypothesised that (i) there are species-specific differences in the morphological response of crown architecture and stem stature and (ii) that crown size and asymmetry as well as stem inclination are influenced by both, biotic and abiotic factors. In contrast to our expectations we were unable to reveal any species-specific differences in any of the three growth characteristics. The results of mixed effects models showed that crown area was mainly affected by the target tree's dbh and biotic variables related to neighbours (competition, functional diversity), whereas stem inclination was mainly influenced by slope. Relative crown displacement was influenced by both, biotic and abiotic variables. We conclude that growth responses resulting in crown displacement and stem inclination seem to be an important mechanism to ameliorate foraging for light in our study area, but that these responses appear to be species-independent. The interplay of stem inclination and crown displacement allows for a plastic response of tree individuals in biotically and abiotically heterogeneous environments. Our results indicate that forest management in this region should focus on functionally diverse stands which are promoting crown area positively resulting in increased growth rates of individual trees.  相似文献   
7.
    
Soybean is the most important oilseed and protein crop worldwide, but in Europe, the acreage is comparably low. Thus, Europe strongly depends on imports of soy products and consequently recent efforts aim at expanding the acreage of soybean, particularly in Central Europe. The aim of this study was, therefore, to assist these breeding efforts by characterizing Central European soybean germplasm, employing a genotyping‐by‐sequencing approach yielding 7741 genomewide distributed markers. Our analysis on genetic diversity and population structure revealed that the Central European lines are most closely related to Swiss and Canadian lines and somewhat more distant from the investigated Chinese and US lines. In addition, we analysed patterns of allelic diversity and the extent of linkage disequilibrium. Collectively, our results can assist breeding of Central European soybean and suggest that further progress can be made by crosses among adapted material but a long‐term success also requires introgression of alleles from non‐European germplasm to further broaden the genetic diversity and incorporate novel traits.  相似文献   
8.
9.
    
T. Yifru    K. Hammer    X. Q. Huang    M. S. Röder 《Plant Breeding》2006,125(2):125-130
This study was conducted to assess regional patterns of diversity of Ethiopian tetraploid wheat accessions and to identify areas of diversity that can be used as source of new germplasm for developing high yielding and stable varieties. A collection of 133 Ethiopian tetraploid wheat accessions and eight introduced cultivars was analysed using 29 wheat microsatellite markers. A total of 383 alleles were detected with an average value of 13.14 alleles per locus. Relatively more alleles were observed in the B genome than in the A genome. Gene diversity indices ranged from 0.08 to 0.95, with a mean value of 0.72. Accessions collected from the same region were pooled and the number of alleles and gene diversity were calculated over the 29 simple sequence repeats for each region. Higher numbers of alleles were detected in the Shewa region (8.72), followed by Tigray (5.86) and Hararghe (5.76). The highest average gene diversity value was found in Shewa (0.65), followed by Gondar (0.64). No significant correlation was observed between geographic distance and genetic distance. Out of 383 different alleles detected, 93 (24.4%) were observed to be region‐specific. Region‐specific alleles were found across all chromosomes except for Xgwm752, Xgwm155 and Xgwm148. Genetic similarity coefficients were estimated for all the possible 55 pairs of regional comparisons and they ranged from 0.16 to 0.52, with a mean value of 0.50. All provinces were differentiated in the UPGMA cluster diagram.  相似文献   
10.
    
R. K. Kapila    R. S. Yadav    P. Plaha    K. N. Rai    O. P. Yadav    C. T. Hash    C. J. Howarth 《Plant Breeding》2008,127(1):33-37
Genetic diversity among 70 maintainers and two pollinators of sub-Saharan and Indian origin was studied for simple sequence repeat (SSR) loci using 34 primer pairs. A total of 213 alleles were detected with an average of 6.26 alleles per locus. Polymorphic information content (PIC) ranged from 0.05 to 0.96 with a mean of 0.58 for the SSR loci. Mean PIC across the linkage groups and number of alleles in dinucleotide motifs varied significantly. The lowest PIC (0.239) for linkage group 6 indicated comparatively conserved nature of this linkage group. Genetic similarity estimates ranged from 0.05 to 0.73 with an average value of 0.29. This indicated sufficient diversity among the maintainer and pollinator lines. The 72 lines fell in five clusters, and the clustering pattern corroborated with their pedigree and characteristic traits. Pollinator ICMR 356 was more diverse from the maintainer lines analysed, and can be a potential parent for pearl millet hybrid development.  相似文献   
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