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1.
Resistance of sugar beet seedlings to Rhizoctonia damping-off caused by Rhizoctonia solani has not been described. A series of preliminary characterisations using a single susceptible host and four different R. solani isolates suggested the disease progression pattern was predictable. Two AG-4 isolates and a less virulent AG-2-2 isolate (W22) showed a comparable pattern of disease progression in the growth chamber where disease index values increased for the first 5–6 days, were relatively constant for the next 7–8 days, and declined thereafter. Seedlings inoculated with a highly virulent AG-2-2 isolate (R-1) under the same conditions showed similar patterns for the first 4 days post-inoculation; however disease index values continued to increase until seedling death at 13–14 days. Similar results were observed in the greenhouse, and a small expanded set of other germplasm lines were screened. One tested germplasm accession, EL51, survived seedling inoculation with R. solani AG-2-2 R-1, and its disease progress pattern was characterised. In a field seedling disease nursery artificially inoculated with R. solani AG-2-2 R-1, seedling persistence was high with EL51, but not with a susceptible hybrid. Identification of EL51 as a source of resistance to Rhizoctonia damping-off may allow investigations into the Beta vulgaris–Rhizoctonia solani pathosystem and add value in sugar beet breeding.  相似文献   

2.
Web blight, an important foliar disease of dry beans in the Americas, is a challenge to manage. We studied genetic variation of 92 isolates of Rhizoctonia solani subgroups AG-1-IE and AG-1-IF using DNA fingerprinting methods and mycelial compatibility grouping. The isolates were collected over 13 years from bean fields in the Dominican Republic, Honduras and Puerto Rico. Cluster and AMOVA analysis of combined data from two universal rice primers and two internal sequence repeats revealed significant genetic variation among and within populations of both subgroups. Variation was influenced by geographic origin and sampling year for AG-1-IE isolates and geographic origin for AG-1-IF isolates. Mycelial compatibility of paired isolates was mostly scored as incompatible in both subgroups and supported many unique phenotypes. Only two isolates of AG-1-IE displayed mycelial compatibility and DNA fingerprints, suggesting clonal origin. Genetic variation in these AG-1-IE and AG-1-IF isolate populations may explain the lack of durable resistance to web blight reported in dry beans.  相似文献   

3.
Leaf blight, sheath blight, and web blight are major diseases caused by Rhizoctonia species on both Fabaceae and Poaceae plant hosts in the Brazilian Amazon agroecosystem. To determine the diversity of Rhizoctonia species associated with foliar diseases on fabaceous (cowpea and soybean) and poaceous (rice and signal grass [Urochloa brizantha]) hosts, a broad survey was conducted in Pará, Rondônia, Roraima, and Mato Grosso, in the Amazon, from 2012 to 2013. We extended our survey to Cerrado areas of Mato Grosso, and the lowlands of Paraíba Valley, in São Paulo, where these Rhizoctonia foliar diseases have not been reported so far. Our findings revealed that these diseases are caused by a diversity of Rhizoctonia solani AG-1 complex. We detected that R. solani AG-1 IA (sexual phase Thanatephorus cucumeris) was the predominant pathogen associated with signal grass leaf blight and collar rot diseases in the Amazon, especially in Rondônia and northern Mato Grosso. In addition, a subgroup of R. solani (AG-1 IF), not previously reported in Brazil, was associated with leaf blight on cowpea and soybean, in Roraima. Another subgroup (AG-1 ID) was also detected in Roraima. In Mato Grosso Cerrados we did not find any of the major Rhizoctonia foliar pathogens. Instead, R. oryzae (Waitea circinata) was the predominant species associated with a collar rot on U. brizantha. In the lowlands of São Paulo, R. oryzae-sativae (Ceratobasidium oryzae-sativae) was the predominant pathogen detected causing the rice sheath spot disease.  相似文献   

4.
Leaf blight is a common disease affecting Sansevieria trifasciata in many countries, including Malaysia. In the present study, Fusarium isolates were consistently recovered from the diseased leaves collected from various locations throughout the country. Based on morphology and multigene phylogenetic analysis using mitochondrial small subunit (mtSSU), intergenic spacer region (IGS) and translation elongation factor 1-α (TEF1-α) gene sequences, seven Fusarium species were identified, with F. oxysporum being the most prevalent (67.6%) among 34 isolates. Pathogenicity tests resulted in the discovery of pathogenic isolates that belonged to F. oxysporum, F. proliferatum, and F. pseudocircinatum, whereas all isolates of F. brachygibbosum, F. concentricum, F. mangiferae, and F. solani were nonpathogenic. The results suggest that several Fusarium species are accountable for causing disease on S. trifasciata in Malaysia.  相似文献   

5.
Rhizoctonia solani causes pre- and post-emergence damping-off, root and hypocotyl rot and foliar blight in soybean. Foliar blight has resulted in yield losses of 31–60% in north and northeast Brazil. The aim of this study was to characterize isolates of R. solani associated with soybean in Brazil. Among 73 Rhizoctonia isolates examined, six were binucleate and 67 were multinucleate. The multinucleate iso1ates were characterized according to hyphal anastomosis reaction, mycelial growth rate, thiamine requirement, sclerotia production, and RAPD molecular markers. Four isolates that caused hypocotyl rot belonged to AG-4 and using RAPD analysis they grouped together with the HGI subgroup. Another isolate that caused root and hypocotyl rots was thiamine auxotrophic, grew at 35°C, and belonged to AG-2-2 IIIB. All 62 isolates that caused foliar blight belonged to AG-1 IA. RAPD analysis of R. solani AG-1 IA soybean isolates showed high genetic similarity to a tester strain of AG-1 IA, confirming their classification. The teleomorph of R. solani, Thanatephorus cucumeris was produced in vitro by one AG-1 IA isolate from soybean. The AG-4 and AG-2-2 IIIB isolates caused damping-off and root and hypocotyl rots of soybean seedlings cv. FT-Cristalina, under greenhouse conditions. The AG-2-2 IIIB isolate caused large lesions on the cortex tissue, that was distinct from the symptoms caused by AG-4 isolates. The AG-1 IA isolates caused foliar blight in adult soybean plants cv. Xingu under the greenhouse and also in a detached-leaf assay.  相似文献   

6.
Abstrast  Three-hundred-twenty-five isolates ofRhizoctonia (215R. solani and 110 binucleateRhizoctonia) were obtained from roots and crowns of alfalfa, sainfoin and common vetch grown in Erzurum, Turkey. The isolates were assigned to five anastomosis groups (AG) ofR. solani (AG-2-1, AG-3, AG-4, AG-5, and AG-10) and two anastomosis groups of binucleateRhizoctonia (AG-I and AG-K). In pathogenicity tests on alfalfa, sainfoin and common vetch, the highest disease severities were caused by isolates of AG-4 and AG-5. Isolates of AG-10 and AG-I were not pathogenic on the three tested forage legumes, whereas isolates of AG-K on alfalfa and sainfoin, and of AG-2-1 on sainfoin, were moderately virulent. Alfalfa isolate AG-3 was moderately virulent on sainfoin. This is the first report ofR. solani AG-3, AG-5, AG-10 and binucleateRhizoctonia AG-I on alfalfa. In addition, all theR. solani and binucleateRhizoctonia groups isolated from sainfoin and common vetch were recovered from these crops for the first time in Turkey. http://www.phytoparasitica.org posting Dec. 16, 2002.  相似文献   

7.
The population structure of Rhizoctonia solani AG-1 IA causing rice sheath blight from India was evaluated for 96 isolates using seven RFLP loci. Nineteen of the isolates did not hybridise to R. solani AG-1 IA RFLP probes and rDNA analyses subsequently confirmed that they were either Ceratobasidium oryzae-sativae isolates or another Rhizoctonia sp. The population structure of the remaining 77 R. solani AG-1 IA Indian isolates was similar to that of a previously characterized Texas population. Clonal dispersal of R. solani AG-1 IA in India was moderate within fields and no clones were shared among field populations. Low levels of population subdivision and small genetic distances among populations were consistent with high levels of gene flow. Frequent sexual reproduction was indicated by the fact that most populations were in Hardy–Weinberg equilibrium (HWE). The two loci (R68 and R111) that deviated significantly from HWE showed an excess of heterozygosity. Although Texas and Indian populations were geographically very distant, they exhibited only moderate population subdivision, with an FST value of 0.193.  相似文献   

8.
Sheath blight, caused by Rhizoctonia solani AG1‐IA, is one of the most serious diseases of rice. In this study, a total of 175 isolates of R. solani AG1‐IA were collected from five rice‐growing regions in China. Pathogenicity tests revealed that all isolates were virulent to five cultivars with different levels of resistance at the rice seedling stage in the greenhouse. There was considerable variation in aggressiveness, and the isolates were classified into three pathotypes based on disease severity, with moderately virulent isolates prevalent in the population. Forty‐three haplotypes were identified based on ITS sequencing, and 39 haplotypes were distinct among isolates. There were high levels of haplotype diversity and nucleotide diversity within the populations of R. solani AG1‐IA. High gene flow (Nm = 1·63–5·22) was detected, consistent with relatively low differentiation between pairs of populations. Five populations were divided into two distinct clusters by the unweighted pair group method with arithmetic mean (UPGMA), and no spatial population differentiation was discernible. The majority (97·8%) of genetic diversity was distributed among isolates within populations, with only 2·2% of the genetic diversity attributed to differences among populations. The star‐like shape of the haplotype network provided evidence of signatures of population expansion in recent history. No significant relationships were found between the genetic diversity and aggressiveness or geographic origin among populations of R. solani AG1‐IA. These results highlight that the population characteristics of R. solani AG1‐IA should be taken into account in evaluating the germplasm resistance of rice cultivars to sheath blight.  相似文献   

9.
水稻纹枯病生防细菌筛选及其与病原菌侵染垫形成的关系   总被引：3，自引：0，他引：3  
为筛选对立枯丝核菌Rhizoctonia solani具有拮抗作用的生防细菌,利用稀释涂布平板法,从吉林省水稻纹枯病样中分离筛选出对立枯丝核菌AG-1A具有高拮抗活性的生防菌株,通过gyrB基因序列分析鉴定其分类地位,并采用离体侵染试验和温室防治试验测定筛选生防菌株对水稻纹枯病的防效,在显微镜下观察生防菌株预处理后接种病原菌的水稻叶片表面的菌丝生长情况,分析其生防机理。结果显示,从水稻纹枯病样中共分离获得35株菌株,其中菌株ND11对立枯丝核菌AG-1A的抑制率和抑菌圈直径最大,分别为74.12%和31.50 mm。基于gyrB基因序列分析最终将菌株 ND11鉴定为短小芽胞杆菌Bacillus pumilus;该菌株能够减缓立枯丝核菌AG-1A的侵染速度,抑制其侵染垫的形成,对水稻纹枯病的温室防效达70.69%以上。表明短小芽胞杆菌菌株ND11能够通过抑制立枯丝核菌侵染垫的形成来防治水稻纹枯病,且防效较好,具有开发为生防菌剂的潜力。  相似文献   

10.
Sixty-eight Rhizoctonia solani isolates (31 AG-1, 37 of AG-2-2) associated with web blight (WB) of common bean, Phaseolus vulgaris, were examined for sequence variations in the ITS-5.8S rDNA region. The isolates were collected in bean-growing lowland and mountainous regions in Central and South America. Sequences of these isolates were aligned with other known R. solani sequences from the NCBI GenBank and distance and parsimony analysis were used to obtain phylogenetic trees. WB isolates of AG-1 formed two clades separated from known AG-1 subgroups. WB isolates of AG-2-2 formed one clade separated from known AG-2-2 subgroups. Other isolates belonged to AG-1 IA and AG-1 IB. Based on phylogenetic analysis, we confirmed that at least five genetically different subgroups incite WB of common beans. Three new subgroups of R. solani have been identified and designated as AG-1 IE, AG-1 IF and AG-2-2 WB. DNA sequences of these isolates provided needed information to design taxon-specific primers that can be employed in ecological/epidemiological studies and seed health tests.  相似文献   

11.
During surveys conducted in 2010–2012 Rhizoctonia symptoms were observed on 30 ornamental species in different nurseries located in eastern Sicily (Southern Italy). Eighty-eight isolates of Rhizoctonia spp. were obtained from symptomatic leaves, roots and stems. Fifty-six of the isolates were binucleate and 32 were multinucleate Rhizoctonia. Characterisation of anastomosis groups (AGs) was performed using morphological characteristics and sequence analysis of the internal transcribed spacer of ribosomal DNA ( rDNA-ITS) region. Most isolates collected were Rhizoctonia solani AG-4 HG-I (35.2% of all isolates) and one isolate was AG-2-2 IIIB. The binucleate isolates belonged to AG-R (27.3%), AG-A (21.6%), AG-G (12.5%), AG-V (1.1%) and AG-Fb (1.1%). The pathogenicity of 38 representative isolates collected from each host was tested on seedlings or cuttings grown in a growth chamber. All R. solani AG-4 HG-I isolates, most of the binucleate AG-R, AG-A and AG-G and AG-V were pathogenic and reproduced symptoms identical to that observed in nurseries, while binucleate AG-Fb and R. solani AG-2-2 IIIB isolates were nonpathogenic. This is the first report of the occurrence of Rhizoctonia species on some ornamental plants and the first report of binucleate Rhizoctonia AG-R and AG-V in Europe.  相似文献   

12.
Fusarium graminearum species complexes (FGSCs), such as Fusarium asiaticum and F. graminearum, are important pathogens that cause Fusarium head blight (FHB) in several cereal crops worldwide. In this study, we collected 342 gramineous weed samples in the proximity of rice fields from May to June 2018 in Korea. Among the 500 Fusarium isolates from the weed samples, 13 species of Fusarium were identified, and F. asiaticum (41.2%), F. avenaceum (18.0%), F. acuminatum (16.4%) and F. graminearum (14.8%) were the most frequently isolated. The trichothecene genotype analysis showed that 206 F. asiaticum strains consisted of the nivalenol (NIV) genotype (n = 195, 94.7%) and 3-acetyldeoxynivalenol (3ADON) genotype (n = 11, 5.3%), whereas 74 F. graminearum strains consisted of the 15-acetyldeoxynivalenol (15ADON) genotype (n = 58, 78.4%) and 3ADON genotype (n = 16, 21.6%). Geographical differences were observed in the FGSC and trichothecene genotype compositions, which appeared host-dependent between the southern provinces and mid-eastern provinces. The aggressiveness assessment of FHB showed that the 3ADON chemotype was most aggressive followed by the 15ADON and NIV chemotypes in wheat, while the NIV chemotype was most aggressive followed by the 3ADON and 15ADON chemotypes in rice. The F. asiaticum strains grew slowly and produced fewer conidia and perithecia than the F. graminearum strains, regardless of their chemotypes. The results of this study suggest that F. asiaticum with the NIV chemotype has a host preference for rice, and FHB-causing pathogens can be harboured in gramineous weeds, which play a role in the dispersal of FHB pathogens to rice and other cereal crops.  相似文献   

13.
Ageratum conyzoides L. is an annual herb in the tropics and subtropics whose extracts are known to possess pharmacological and biocidal activity. We report on the bioactivity of a secondary metabolite (a chromene) isolated from the shoots ofA. conyzoides against some plant pathogenic fungi. Organic solvent extracts from the shoots were tested for antifungal activity against the plant pathogenic fungiRhizoctonia solani, Sclerotium rolfsii, Botryodiplodia theobromae, Phomopsis theae andFusarium species growingin vitro on potato dextrose agar medium. The cruden-hexane extract completely inhibited the growth ofR. solani andS. rolfsii. Then-hexane extract was chromatographed over a column of silica gel followed by activity-guided fractionation to give an antifungal principle. Structure elucidation by detailed analysis of1H,13C NMR and mass spectroscopy identified the active compound as precocene II. The growth ofR. solani andS. rolfsii was completely inhibited by precocene II at a concentration of 80–100 ppm. The sclerotia ofR. solani andS. rolfsii were also completely suppressed by 150 ppm of precocene II. Sub-culture of these inhibited fungi onto precocene II-free medium restored growth of the fungus, indicating that precocene II is fungistatic. Crude or refined extracts fromA. conyzoides offer the possibility of biocontrol of plant pathogenic fungi. http://www.phytoparasitica.org posting Feb. 11, 2004.  相似文献   

14.
A decline of unknown aetiology has become a major problem for commercial orchid production in Hawaii, one of the primary orchid‐producing states in the USA. The major symptoms of decline include root degradation, foliar blight, pseudobulb rot and sheath rot. It was unclear whether all these symptoms are caused by the same or different pathogens, but preliminary research indicated that Fusarium species may be involved. In this study, the incidence of Fusarium species was examined across 186 plants, from 29 orchid genera and intergeneric hybrids across three islands in the state of Hawaii. The main five species associated with diseased orchids were F. proliferatum (38% of samples), F. solani (16%), F. oxysporum (16%) and two previously undescribed species (8% for both species combined). The two undescribed species were similar in appearance to F. subglutinans, and were designated FS‐A and FS‐B. Pathogenicity tests established that both F. proliferatum and FS‐B caused foliar spots, foliar blight and pseudostem rot on Dendrobium orchids, and that F. proliferatum isolates from diseased tissue of several genera could also induce symptoms on Dendrobium orchids. Although orchids have increasing importance in floriculture, relatively little is known about orchid pathogens, and previous studies focused primarily on Cymbidium and Phalaenopsis. This study provides new information concerning Dendrobium orchid pathogens and suggests a much wider host range than previously recognized for the five Fusarium species recovered from tissue with symptoms. These findings can contribute to better management of Fusarium diseases, which represent a significant challenge to orchid production in Hawaii.  相似文献   

15.
Early blight of tomato (Lycopersicon esculentum) caused by Alternaria solani has the potential to become one of the most serious diseases throughout the tomato‐producing regions of Greece. Controlled environment experiments were conducted to study the virulence of A. solani isolates and the susceptibility of commercial tomato cultivars and hybrids to early blight. The isolates used, derived from naturally infected tomato plants during the period 1997/1998, differed significantly (P>0.05) in the rate of mycelial growth as well as in their ability to sporulate in vitro. No correlation (R2= 0.33) was found between mycelial growth and conidia production. Isolates of A. solani were virulent to young tomato plants (cv. Ace 55VF), although they differed significantly (P>0.05) in the intensity of symptoms produced on leaves, stems, petioles and flowers. Defoliation was linearly related (R2= 0.87) to the percentage of leaf area with symptoms. Twenty‐three tomato cvs. or F1 hybrids were evaluated for their susceptibility to early blight. The cultivars or hybrids were arbitrarily categorized as immune, highly tolerant, tolerant, moderately tolerant, susceptible and highly susceptible based on a percent disease index range: 0%, 1‐9%, 10‐24%, 25‐49%, 50‐74% and 75% or more respectively. None of the cultivars or hybrids tested was immune or tolerant to A. solani infection.  相似文献   

16.
Early blight caused by Alternaria solani is a highly destructive disease of potatoes. Control of early blight mainly relies on the use of preventive fungicide treatments. Because of their high efficacy, azoxystrobin and other quinone outside inhibitors (QoIs) are commonly used to manage early blight. However, loss of sensitivity to QoIs has previously been reported for A. solani in the United States. Two hundred and three A. solani field isolates collected from 81 locations in Germany between 2005 and 2011 were screened for the presence of the F129L mutation in the cytochrome b gene; of these, 74 contained the F129L mutation. Sequence analysis revealed the occurrence of two structurally different cytb genes, which differed in the presence (genotype I) or absence (genotype II) of an intron, with genotype I being the most prevalent (63% of isolates). The F129L mutation was detected only in genotype II isolates, where it occurred in 97%. Sensitivity to azoxystrobin and pyraclostrobin was determined in conidial germination assays. All isolates possessing the F129L mutation had reduced sensitivity to azoxystrobin and, to a lesser extent, to pyraclostrobin. Early blight disease severity on plants treated with azoxystrobin was significantly higher for A. solani isolates with reduced fungicide sensitivity in the conidial germination assay compared with sensitive isolates. Data suggest an accumulation of F129L isolates in the German A. solani population over the years 2009–2011. It is assumed that the application of QoIs has selected for the occurrence of F129L mutations, which may contribute to loss of fungicide efficacy.  相似文献   

17.
Artificial suppression of radish damping-off disease was induced by repeated soil inoculations with Rhizoctonia solani, binucleate Rhizoctonia (BNR) and Sclerotium rolfsii in pot systems. Soils repeatedly inoculated with R. solani and BNR showed suppressive to disease caused by R. solani and S. rolfsii, while soils repeatedly inoculated with S. rolfsii were suppressive to disease caused by S. rolfsii but not by R. solani. Species of Trichoderma were consistently isolated from soils repeatedly inoculated with R. solani, BNR and S. rolfsii. These Trichoderma spp. accumulated selectively in relation to the fungal species that was repeatedly added to the soils. The ratios of the frequencies of T. viride, T. harzianum and T. hamatum were 5:2:2 and 8:5:2 in soils repeatedly inoculated with R. solani and BNR, respectively. In S. rolfsii- inoculated soils, T. koningii was predominantly isolated. T. viride, T. harzianum and T. hamatum isolates obtained from either R. solani or BNR after repeated additions to the soils suppressed radish damping-off disease caused after challenge inoculations with R. solani or S. rolfsii. Among the Trichoderma species, T. viride consistently yielded high levels of suppression. However, isolates of T. koningii obtained from S. rolfsii-infested soils suppressed disease caused by S. rolfsii but failed to suppress disease caused by R. solani. Generally, the species of Trichoderma accumulated in a selective pattern that was closely related to the species of fungal pathogen used to induce the suppressive soil.  相似文献   

18.
The objective of this study was to evaluate the potential role of gramineous weeds present near paddy fields as alternative hosts for the Fusarium graminearum species complex (FGSC) that causes fusarium head blight (FHB) in rice. A total of 142 weed samples were collected from 10 gramineous weed species near paddy fields from August to October 2018 in Jiangsu Province, China. Of the 145 isolates of seven Fusarium species isolated from the weed samples, F. asiaticum was the most abundant (86.9%), followed by F. fujikuroi (5.5%), F. proliferatum (2.8%), F. graminearum (2.1%), F. tricinctum (1.4%), F. acuminatum (0.7%), and F. sporotrichioides (0.7%). Genotype and mycotoxin analyses confirmed that 72.2% of F. asiaticum isolates were producers of deoxynivalenol (DON) with 3-acetyl deoxynivalenol (3ADON), and the remainder were nivalenol (NIV) producers. Pathogenicity assays showed that both 3ADON and NIV chemotypes of F. asiaticum could cause FHB in rice, but NIV chemotypes were significantly (p < .05) more aggressive than 3ADON chemotypes. Three Fusarium mycotoxins, DON, NIV, and zearalenone, occurred naturally at low concentrations in the weed samples. Taken together, this study provides insight into the mycotoxin production and aggressiveness of F. asiaticum isolates from gramineous weeds in China.  相似文献   

19.
In 1990–91, 96% of the test plants in a barley (Hordeum vulgare L.) winter nursery in Puerto Rico was lost toSclerotium rolfsii. Small necrotic lesions (1–3 mm long) developed at the base of the stem, followed by wilting and general chlorosis as the lesions progressed and eventually girdled the base of the stem. Sclerotia then developed on the plants at the stem base. Two morphologically different strains ofS. rolfsii that were mycelial incompatible were isolated. This is the first report of a destructive blight due toS. rolfsii on field barley in the Caribbean. The apparent rate of disease increase (r) was estimated to be 12.2% per day using the logistic model, with an initial disease incidence of 0.042% (R2=0.89, p<-0.001).  相似文献   

20.
The cultivation of aerobic rice in the tropics enables farmers to save water without lowering productivity. Unfortunately, this system suffers from declining yields due to a disease complex involving nematodes, pathogenic Pythium spp. and nutrient deficiencies. Assessing the impact of each underlying factor can contribute to efficient disease control measures. This study therefore investigated pathogenic and genotypic variability among Pythium species from affected aerobic rice fields in the Philippines using pathogenicity assays and sequence information from the internal transcribed spacer (ITS) region and β‐tubulin gene. Three closely related Pythium spp., P. arrhenomanes, P. graminicola and P. inflatum, were recovered from affected aerobic rice fields. All P. arrhenomanes isolates reduced rice seedling growth, whereas only a few P. graminicola isolates and no P. inflatum isolates were pathogenic, indicating that P. arrhenomanes is probably the most important species affecting rice. Both P. arrhenomanes and P. graminicola isolates showed little genetic variation, despite the observed pathogenic variation within P. graminicola. Intraspecific variation was higher among P. inflatum isolates, but again no correlation was observed with phenotype. When screening P. arrhenomanes isolates from other hosts such as sugarcane, maize and several grasses, a link between pathogenic and genetic variability was detected. However, rice and maize isolates seemed to lack host specificity, and therefore crop rotation with maize might be a risky strategy to manage yield decline in Philippine aerobic rice fields.  相似文献   

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