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1.
Nematode pathogenicity experiments on Musa host plants were carried out in pot trials. Both the final nematode population densities and percentages root necrosis on different host plants were higher for the Radopholus similis population from Mbarara than for the populations from Namulonge, Ikulwe and Mukono (Uganda). The R. similis population from Mbarara managed to break the resistance of the diploid banana Pisang Jari Buaya, a known worldwide source of resistance to R. similis. The diploid banana hybrid TMB2× 9128-3 and the triploid dessert banana Yangambi km5 showed resistance against the four R. similis populations. These results indicate that differences in pathogenicity among different R. similis populations exist and should be taken into consideration for plantain and banana germplasm enhancement.  相似文献   

2.
A study to determine the impact of a multispecies nematode population on the root, corm, and shoot growth of East African Musa genotypes was carried out. Eight genotypes comprising the plantain “Gonja” (Musa AAB group), the dessert banana “Sukali Ndizi” (AAB), the beer banana “Kayinja” (ABB), and five East African Highland bananas (AAA-EA) were assessed at flower emergence of the plant crop. Root damage and plant growth characteristics were assessed on both infected and noninfected plants. This study showed that Radopholus similis and Helicotylenchus multicinctus were recovered in highest numbers from infected mother plants. Significantly (P<0.05) higher shoot and root damage was observed in the infested plot compared to the noninfested plot. The differences in nematode damage observed among the different Musa genotypes confirm the variability in susceptibility to nematodes. Most of the East African Highland bananas and “Gonja” had a significant reduction in root system size. In addition, toppling and lengthening of the period to flower emergence of the plant crop was much more pronounced in these genotypes. In contrast to previous reports, this study indicated that a multispecies nematode infection significantly (P<0.05) reduced shoot and root growth of “Kayinja”. “Sukali Ndizi”, however, was observed to be tolerant to nematode infection as a small reduction in the root system size was associated with a negligible effect on the corm and shoot growth characteristics. Therefore, the percentage reduction in root and shoot growth due to nematode infection is not constant but depends on the plant genotype.  相似文献   

3.
Banana (Musa AAA) and plantain (Musa AAB) are important dietary staples for over 70 million people in sub-Saharan Africa. Banana weevil (Cosmopolites sordidus) and nematodes (Radopholus similis, Helicotylenchus multicinctus) are often the largest constraints to production. Leguminous crops in the genera Canavalia, Mucuna and Tephrosia have been reported as having repellent or insecticidal properties. We assessed: weevil and nematode populations and damage; banana growth and development; soil and foliar nutrient concentrations; and soil moisture status in banana intercropped with three legumes (Canavalia ensiformis, Mucuna pruriens and Tephrosia vogelii). The research took place at Kawanda, Uganda, on a field site infested with weevils and nematodes. The legume intercrops did not affect weevil populations or damage. The legumes also provided no benefit in terms of nematode control; in fact, banana root necrosis was higher in the T. vogelii intercrop than in the banana monoculture. Banana fruit yield was not adversely affected by the legume intercrops. The low yield noted across treatments was attributed to the high level of damage by the weevils and the nematodes. Significantly more NO3-N accumulated from 0- to 0.3-m depth in the M. pruriens intercrop than in the other treatments. There was no treatment difference in soil moisture. In summary, there was no significant advantage in banana production associated with the legume intercrops. However, the lack of a significant difference in banana fruit production between the monoculture and the intercrops suggests that land use efficiency may be increased by incorporating food and or/fodder legumes into the banana cropping system.  相似文献   

4.
The burrowing nematode, Radopholus similis (Cobb.) Thorne, causes the most damage to bananas. To minimize nematicide applications, cropping systems that use fallow, crop rotation and clean planting material have been developed in the French West Indies. In order to optimize the benefit of the intercropping period, we studied the survivorship of R. similis in different soil types and conditions. We monitored the survivorship of calibrated populations of R. similis in the laboratory on a Nitisol and on an Andosol, two soils derived from volcanic ashes and pumices. We studied water potentials ranging from 0 to ?700 kPa on undisturbed soil and on soil previously frozen to get rid of living nematodes. Mortality of adult R. similis decreased regularly, and was fairly well described by Teissier's model. In the previously frozen soils, R. similis survived longer in wet soils (half-life of 21–46 days at 0 to ?5 kPa) than in dry soils (half-life of less than 10 days between ?80 and ?250 kPa). In contrast, in undisturbed soils, R. similis survived longer in dry soils: half-lives ranged from 57 days at ?273 kPa to 17 days at water saturation in the Andosol, and 36 days at ?660 kPa to 14 days at water saturation in the Nitisol. These results are consistent with the absence of anhydrobiosis in R. similis, unlike Pratylenchus coffeae. P. coffeae survivorship curves over time do not follow a model derived from exponential decrease like Teissier's model. These results also show that the recommended one year host-free period required to sanitize soils cannot be shortened without risk, even if flooding the soil could improve it.  相似文献   

5.
Mycorrhiza-induced resistance has been observed against a broad range of mainly soil-borne pathogens, including plant-parasitic nematodes, but the modes of action involved remain unclear. In this study the role of mycorrhiza-induced resistance was investigated during the pre-infectional phase of nematode host finding and penetration. Banana plants were colonized by Glomus mosseae or Glomus intraradices, two arbuscular mycorrhizal fungi. The plant-parasitic nematode Radopholus similis was inoculated after establishment of the mycorrhizal colonization. Nematode attraction and penetration were assessed within a 12-day period. In root exudate experiments, root exudates collected from both control and mycorrhizal plants were added both to control and mycorrhizal plants to assess their direct impact on the nematode penetration. In an in vitro chemotaxis bio-assay, the chemotactic behavior of R. similis was determined towards isolated root exudates of control and mycorrhizal plants. The penetration experiments clearly showed lower nematode penetration in mycorrhizal plants and the important contribution of differential root exudation by mycorrhizal plants was demonstrated in the exudate experiments as well as in the in vitro chemotaxis bio-assay, with the largest impact on juveniles. The root exudate experiments and in vitro chemotaxis bio-assay point towards a reduced attraction of the nematodes to the mycorrhizal plant roots. The results demonstrate that a water-soluble compound in mycorrhizal root exudates is at least partially responsible for the mycorrhiza-induced resistance at the pre-infectional level of R. similis infection.  相似文献   

6.
To minimize application of nematicides in banana fields, crop systems have been developed in the French West Indies that combine fallow or rotation crops and nematode-free in vitro plants. After two to four years, populations of the burrowing nematode Radopholus similis have developed enough to cause economic losses, leading banana growers to use nematicides. To understand how banana fields are recontaminated, we studied the dissemination of R. similis by water flow. At a 1-m scale, we analyzed the dispersion of R. similis under a rainfall simulator: we isolated a 1-m2 study plot, placed a R. similis suspension on the upstream soil surface, and simulated a 60 mm/h rainfall for 72 min. We collected soil samples every 10 cm downstream after 12 min of rainfall, and subsequently at 20-min intervals, and extracted the nematodes using a Seinhorst elutriator and then a Baermann funnel. Our results showed that the nematode dissemination follows an inverse exponential law, and depends more on soil moisture at the beginning of rainfall than on the length of rainfall: in fresh soil, 69–80% of the R. similis recovered were found less than 10 cm downstream from the nematode inoculation line, whereas in wetted soil, 76–85% of the recovered individuals were collected in the outlet tub located downstream from the apparatus. This passive dissemination model partially explains the distance covered by individual nematodes but not the low percentage of motile nematodes recovered in the outlet tub (10% and 36% in fresh and wet soils) compared to the percentage of motile nematodes found in the soil (80% and 84% in fresh and wet soils). Indeed, water runoff is likely to disseminate R. similis over long distances only when soil moisture is close to field capacity.  相似文献   

7.
《Applied soil ecology》2001,16(2):179-185
A 60-day glasshouse experiment was conducted to assess the influence of two strains of Pseudomonas fluorescens (GRP3 and PRS9), organic manure, and inorganic fertilizers (urea, diammonium phosphate (DAP), muriate of potash and monocalcium phosphate) alone and in combination on the multiplication of Meloidogyne incognita and growth of tomato. Pseudomonas fluorescens GRP3 was better at improving tomato growth and reducing galling and nematode multiplication than PRS9. Organic manuring resulted in less galling and nematode multiplication than occurred with DAP. However, DAP was found better in reducing nematode multiplication and improving plant growth than urea. Muriate of potash was the inorganic fertilizer least effective in reducing galling and nematode multiplication. Pseudomonas fluorescens GRP3 with organic manure was the best combination for the management of M. incognita on tomato but improved management of M. incognita can also be obtained if DAP is used with the GRP3 strain of P. fluorescens.  相似文献   

8.
Understanding the spatial stability of the plant-feeding nematode (PFN) community in agrosystems represents a fundamental step in the integrated control of some damaging species because modifications of soil properties in intensively managed agrosystems may allow growers to manipulate the balance between pathogenic and non-pathogenic species.In the present study, we tested the hypothesis that a community of four PFN species (Criconemella onoensis, Helicotylenchus erythrinae, Hemicriconemoides cocophillus, and Pratylenchus zeae) in a sugarcane agrosystem is spatially structured according to macro-scale soil properties. This hypothesis was studied by using a sugarcane field in Martinique in which soil properties had been heavily modified by hillock-leveling in the 1970s, resulting in a great variation in soil properties over a small area (20.8 × 16.0 m). The goal of the study was to measure the temporal stability of the PFN community spatial structure and to identify the soil parameters associated with differences in nematode abundance. A systematic sampling design was used to collect data in the field that were analyzed using co-inertia and STATIS-Coa. The field study was complemented by a greenhouse experiment.The field study documented the existence of a stable spatial pattern of the PFN community, a pattern that was structured in relation to macro-scale soil factors such as soil carbon, nitrogen, and phosphorus content and soil texture. The constant spatial pattern of the PFN community results from the differences in distributions among C. onoensis and the three other PFN species. C. onoensis was consistently more abundant in the deeply-leveled areas of the field, while the other PFN species were more abundant in the non-leveled areas. H. erythrinae was consistently more abundant in those parts of the field with higher soil pH and sodium content. These results suggested that soil properties can affect permanently the competitive balance among PFN species.The observed relationships between PFN and these macro-scale factors were validated in a greenhouse experiment with different ratios of soil from the leveled and non-leveled areas of the field site.Modification of some major soil properties (pH, Na+ content, soil organic content) by cultural practices such as hillock-leveling, fertilization, and liming, could greatly affect the balance among PFN species in agricultural fields.  相似文献   

9.
Abstract

The objective of this work was to calibrate, classify, and establish soil and plant reference norms for evaluating the nutritional status of the Horn plantain crop (Musa AAB, subgroup plantain cv. Horn). The sampling unit consisted of the “mother” plant and its corresponding soil at the fertilization band. Soil samples at depths of 0–20 cm and 21–40 cm were analyzed. A total of 221 sampling units were studied, hence, 442 soil and 221 leaf samples were used to develop the reference norms. A regression model with linear combinations of the soil and leaf variables for yield estimation was established by using the stepwise method. The model showed a high significant adjustment of 52% (R2) with normality of the standard residues. Four yield subclasses in kg cluster?1 as 10.9–13.9 (60 units), 14.0–17.9 (92 units), 18.0–19.9 (47 units), and 20 or more (17 units) were defined. With the means of the soil and leaf data linearly related with yield, the reference norms for each subclass were developed. The method thereby established permits to develop reference norms that can be used for the simultaneous interpretation of soil and leaf analysis data and for yield estimation of the Horn plantain crop.  相似文献   

10.
The genus Musa L. comprises of economically important bananas and has been divided into five sections based on their chromosome number and morphological characteristics viz., Australimusa, Callimusa, Eumusa, Rhodochlamys and Ingentimusa. However, this sectional classification has long been disputed. In this study, we present data on sequenced multiple DNA fragments from the maternally inherited chloroplast genome (atpB-rbcL spacer, trnK-matK intron and psbK-psbI spacer) and the biparentally inherited internal transcribed spacers of nuclear ribosomal DNA of three species of Musa along with data available in GenBank database to understand their implications on the sectional relationship and phylogeny of the genus Musa. In our findings, none of the five sections of Musa previously defined based on morphology was recovered in the molecular phylogeny analysis using cpDNA and nrDNA. Instead, the results corroborate with the suggestion that sectional classification in the genus Musa should be reviewed by combining together the section Eumusa and Rhodochlamys as one and section Australimusa and Callimusa as a single different section, along with that of Ingentimusa.  相似文献   

11.
Bananas (Musa spp.), including dessert and cooking types, are of major importance in the tropics. Due to extremely high levels of sterility, the diversity of cultivated bananas is fixed over long periods of time to the existing genotypes. This pattern puts banana-based agrosystems at risk. Therefore, assessing the extent of wild and cultivated banana diversity, conserving it and making it available for further use is a priority. We report here the collection of new wild and cultivated banana germplasm in the Autonomous Region of Bougainville, Papua New Guinea. In total, 61 accessions were collected and their names and uses were recorded when possible. Classification was also provided based on the observations made in the field. Three wild specimens were collected. Among the 58 cultivated accessions, we noted that eight were used as ornamental plants, seven were edible varieties of the Fe’i type and two were natural tetraploids from the Musa section. The ploidy was then checked by flow cytometry and the accessions were genotyped with a set of 19 SSR markers. The genotyping results were merged to the dataset from Christelová et al. (Biodivers Conserv 26:801–824, 2017). This joint analysis helped refine or confirm the classification of the collected accessions. It also allowed to identify 10 private alleles and 35 genotypes or Genotype Groups that were not present in the wider dataset. Finally, it shed light on the diversification processes at work in the region, such as the capture of mutations by farmers and the likely occurrence of geneflow within the cultivated genepool.  相似文献   

12.
The contribution of farmers to the creation and maintenance of genetic diversity is beginning to receive more recognition in developed countries. Although the use of landraces and historic varieties has largely disappeared in countries with industrialized agricultural systems and formal seed markets, certain varieties with particular cultural significance have been continuously cultivated by farmers and other varieties have been preserved ex situ in genebanks. Recently, associations of organic farmers have become involved in the conservation and use of landraces and historic varieties (called farmer varieties in this article) because these varieties possess agronomic and quality traits that they have not found in modern varieties. In this study, eight farmer varieties of bread wheat from Europe selected by participating farmers were evaluated in on-farm trials during 3 years of cultivation. Each variety was grown on each farm, and phenotypic changes in each variety were measured the third year in a replicated split-plot trial on each farm comparing the version of each variety the farmer had multiplied to a sample of each variety from the region of origin. All varieties, including the two modern pureline varieties used as checks, showed statistically significant phenotypic changes over 3 years of multiplication. However, the magnitude of these changes was moderate and did not call into question varietal identity or distinctness. In addition, some traits of putative agronomic and adaptive importance, such as grain weight per spike and thousand kernel weight, did not respond positively to natural selection (environmental conditions and management practices) which suggests the necessity of farmer selection to maintain and improve varietal performance.  相似文献   

13.
Multilocation testing remains the main tool for understanding varietal responses to the environment. Here, Latvian and Norwegian hull-less and hulled barley varieties were tested in field experiments in Latvia and Norway in order to assess the varieties adaptability across environments (sites). Two Latvian (cv Irbe and cv Kornelija) and one Norwegian hull-less barley variety (cv Pihl) were tested along with one Latvian (cv Rubiola) and one Norwegian hulled barley variety (cv Tyra) under conventional and organic management systems. The grain yield, together with physical and chemical grain parameters were compared, and variety yield and protein stability determined. Overall, grain yield of hull-less barley varieties was significantly lower than for hulled barley varieties regardless of climatic conditions and management system. However, in the organic farming systems this difference between barley types was less pronounced. The hull-less barley varieties cv Pihl and cv Irbe, along with both hulled varieties, had good yield stability across environments and were well adapted to both cropping systems. Hull-less barley varieties tended to contain more protein and β -glucans than hulled barley varieties. Despite being bred for local conditions in Norway and Latvia, our study shows that all the varieties used may be successfully transferred across countries.  相似文献   

14.
The Argonaute proteins are key components in the effector complex of RNA silencing pathways which interact with small RNAs to mediate sequence specific silencing of nucleic acid targets. In plants, these proteins are involved in a diversity of biological roles such as antiviral defence, heterochromatin regulation and in the regulation of growth and development. This report describes the study of Argonaute gene sequences in bananas which are an important food staple for many developing nations. This study successfully isolated AGO7-specific PIWI domain genomic sequences from 12 diploid Musa species of three Musa sections and also from Ensete. The Musa AGO7-specific PIWI domain sequences showed the highest similarity to rice AGO7/SHOOTLESS4 with an average amino acid identity of 78%. Phylogenetic analysis of the Musa sequences revealed phylogenetic grouping that agrees fairly well with the present knowledge of the taxonomic classification of Musa species. In addition, this study estimated that there are at least 15 Argonaute genes or loci containing PIWI domain sequences in the genome of Musa acuminata ssp. malaccensis.  相似文献   

15.
Several strains of Bradyrhizobium, Mesorhizobium and Sinorhizobium strains were tested for their compatibility with an Australian acacia: Acacia holosericea. All bacterial strains induced some nodule formation on roots. However, the rhizobia which greatly increased the development of seedlings belonged to the Bradyrhizobium genus. The root-knot nematode Meloidogyne javanica, strongly inhibited the symbiosis with most of the rhizobial strains. The rhizobia had no effect on nematode multiplication except for bacterial strain ORS 1020 where the final nematode population was higher than in the control treatment. The hypothesis concerning the interactions between nematodes and the nitrogen fixative process are discussed. Moreover, this investigation underlines the decreasing effect of nematodes on the potential benefits that may result from growing A. holosericea inoculated with selected rhizobial strains.  相似文献   

16.
Radopholus similis is a worldwide endoparasitic nematode that greatly hampers banana (Musa acuminata, Cavendish subgroup) productivity. Earthworms are known to closely interact with above-ground and under-ground soil biota and particularly with plants and microfaunal communities. This study was aimed at investigating, under greenhouse conditions, the effects of the earthworm Pontoscolex corethrurus on banana growth and nutrient uptake, and assessing the influences of this earthworm on the development of an inoculated population of R. similis. Six-week-old tissue culture banana plants were submitted to four treatments: with P. corethrurus, R. similis, P. corethrurus+R. similis, and a control with no earthworms or nematodes. At the end of the experiment, the P. corethrurus treatments showed significantly higher leaf surface areas, shoot dry root weights, and root fresh weights than those without earthworms. This root growth enhancement probably contributed to the evident but non-significant decrease in the density of nematodes in the roots, even though earthworms did not reduce the total number of nematodes per whole root system. Moreover, the presence of earthworms slightly alleviated the severity of root damage. N bioavailability in the soil, along with N, Ca, and Mg content of banana plants, were also significantly increased in the presence of earthworms. Our results demonstrated that banana plant growth and nutrition were positively influenced by earthworms. Cropping practices that boost the development of earthworm communities in soil should therefore be promoted to enhance sustainability and to naturally alleviate nematode impact.  相似文献   

17.
Understanding how environmental factors structure communities is important in conservation biology and ecosystem management. The aim of this study was to test the hypothesis that a plant-feeding nematode community composed of six species is structured by soil type and climate at the landscape scale, and that niche partitioning via these factors is consistent with the coexistence of the species. Martinique has an impressive diversity of abiotic factors (climate and soil type) over a relatively small land area, which facilitates the study of how soil type and climate affect the nematode community.We conducted this study by building an extensive data set containing the abundance of each nematode species on banana (3708 samples and 5,673,705 nematodes) in a wide range of sites in Martinique. The data set also contained environmental data (soil, climate) and plantation age. We analyzed the response of each nematode species to climate and soil type with a generalized linear model in order to understand whether niche partitioning of factors could contribute to the coexistence of the nematode species.Temperature, rainfall, soil type, and plantation age significantly affected the abundance of the six nematode species. While some pairs of species shared the same environmental niches, other showed clear niche partitioning along climatic axes. The two dominant species, Radopholus similis and Helicotylenchus multicinctus, have similar convergent ecological niches regarding climate, soil type, plantation age, and host range. These two species, which often co-occur, probably have different resources at the root scale. Soil type and climate structure plant-feeding nematode species community at the island scale. Further studies need to evaluate coexistence at the root scale among dominant species.  相似文献   

18.
The effect of grazing by the naked soil amoeba Thecamoeba similis feeding on algae of in vitro phototrophic soil biofilms was investigated in terms of carbon biomass of algae, bacteria and amoebae and compared to shifts in the microbial community determined by 16S rDNA t-RFLP patterns. In a first approach, grazing of T. similis on unialgal Xanthonema hormidioides biofilms growing on regosol was investigated. The growth rate of T. similis was 0.5 divisions per day and the production efficiency reached 25% (allocation of prey-carbon to predator-carbon). The algal biomass decreased from the original 100% down to 7% at the end of the experiment. The increase of egested residues enhanced bacterial growth; the biomass carbon ratio bacteria vs. algae increased from 0.25 to 4.5 indicating the degradation of the algal biofilm, while the 16S rDNA t-RFLP patterns indicated changes in the composition of the microbial community. A subsequent experiment was conducted by inoculating T. similis on a natural biofilm community consisting of trichomes of cyanobacteria, several species of Chlorophyceae and Xanthophyceae. The total algal biomass (including cyanobacteria) remained constant during the experiment. However, 73% of the algal biomass without cyanobacteria was grazed, while the amount of mucous Chlamydocapsa spec. doubled from 32% to 68%. The growth rate of T. similis was 0.4 divisions per day and the production efficiency was only 13%. The 16S rDNA t-RFLP patterns showed a shift of the microbial community. Our results give a first insight into the obviously high potential of naked soil amoebae feeding on algae to change the structures of both the algal and bacterial communities of phototrophic soil biofilms.  相似文献   

19.
A 4-year trial was conducted in the Sudanian area of Senegal to study how the manipulation of the plant composition of a natural fallow might increase soil fertility. The influence of fencing combined with stump removal or planting of Andropogon gayanus on the nematode communities was studied. Apart from fencing, all intervention favoured the multiplication of the plant parasitic nematodes for the duration of the trial. Fencing significantly reduced nematode abundance and modified the balance between the species in the community. The population of Scutellonema cavenessi, a serious pest of food crops in the region, was dramatically reduced to the benefit of the weaker pathogen, Helicotylenchus dihystera. Planting Andropogon increased the H. dihystera population slightly. Disappearance of ligneous plant material by stump removal was associated with the greatest increase in the proportion of S. cavenessi. The results suggested that the soil disturbance when planting, removing stumps, or even grazing could affect the nematode community in the topsoil layer, resulting in a decrease in H. dihystera. This species did not recover during a 4-year fallow, even if a suitable situation was promoted through fencing or the planting of Andropogon, a host plant of H. dihystera.  相似文献   

20.
The organic carbon (OC) fractions and micronutrient status of soil under cashew (Anacardium occidentale), plantain (Musa spp), oil-palm (Elaeis guineensis) and gmelina (Gmelina arborea) plantations were studied to determine their effectiveness for managing converted forest in the derived savanna ecology of southwestern Nigeria. The control secondary forest soil had statistically similar OC (2.11%) at 0–15 cm with gmelina but significantly higher than those of the remaining plantation crops. At deeper depths, however, the OC content of the control forest was lower than those of other plantation crops. Apart from gmelina, other plantation crops had carbon enrichment ratio (CER) <1 at 0–15 cm. Only gmelina sequestered as much non-hydrolysable carbon (NHC) as the control at 0–15 cm depth. Also it was observed that plantain plantation sequestered higher NHC than the control at 15–30 cm depth. At >30 cm depth, however, none of the plantation crops sequestered as much NHC as the control. Using the average NHC at all the soil depth as a quality index, gmelina has a better potential to sequester NHC than the other plantation crops used in this study.  相似文献   

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