Relationships between land use, fertility and Andisol behaviour: examples from volcanic islands

Abstract. Soils developed on volcanic parent materials have many intrinsic qualities favourable to cropping. However, fertility decreases dramatically when they are badly managed. A short review and case studies from Réunion and Guadeloupe highlight the special characteristics of these soils, and their response to management.
The interplay of cropping systems and physical characteristics of Andisols is first considered through the example of Pelargonium and food crop systems in Réunion. Progressive decrease in production and cropping potential shows in falling yields as well as in the overall decline of the system. The example of banana production in Guadeloupe highlights the increase in inputs needed to realise the land's potential and to maintain yields, in particular more tillage and pest treatment.
In both cases, these trends are connected to the co-evolution of soil characteristics and cropping systems. They lead to an increase of risks with less security and less scope in the choice of cropping systems. Technical solutions in the form of erosion-control measures, rotation and planting techniques have been developed and prove to be relevant and consistent in their benefit.     

香蕉受枯萎病菌侵染后内源激素含量的变化

对香蕉受枯萎病菌Fusarium oxysporum f.sp．cubense侵染后体内赤霉酸（GA3）、吲哚乙酸（IAA）和脱落酸（ABA）3种内源激素含量的变化进行了测定．结果表明：接种的香蕉苗体内的GA3、IAA和ABA的含量均高于未接种的对照,表明香蕉枯萎病菌的侵染引起了香蕉体内GA3、IAA和ABA的积累,此3种植物内源激素与香蕉受枯萎病菌感染的病程相关．     

Development of a specific molecular tool for detecting Xanthomonas campestris pv. musacearum

A specific and rapid diagnostic tool has been developed to detect Xanthomonas campestris pv. musacearum, the causal agent of bacterial wilt of banana. PCR primers were developed from intergenic regions of X. campestris pv. musacearum following its partial sequence. A total of 48 primers were tested for specificity to X. campestris pv. musacearum strains collected from various regions in Uganda. These were also tested for specificity against related Xanthomonas species from the vasicola group, Xanthomonas species pathogenic to other crops, and against those existing saprophytically on banana plants. Seven primer sets (Xcm12, Xcm35, Xcm36, Xcm38, Xcm44, Xcm47 and Xcm48) were found to be very specific to X. campestris pv. musacearum. These primer sets directed the amplification of the expected product for all 52 strains of X. campestris pv. musacearum collected from different locations in Uganda. No amplification products were obtained with unrelated phytopathogenic bacteria or endophytic/epiphytic bacteria from banana. A detection limit of 10³ CFU mL^?1 corresponding to about four cells per PCR reaction was observed when X. campestris pv. musacearum cells were used for all the seven primer sets. The DNA samples from symptomless plant tissues also tested positive with primer set Xcm38. The specific PCR method described here is a valuable diagnostic tool which can be used to detect the pathogen at early stages of infection and monitor disease.     

基于近红外光谱的香蕉品质检测方法研究

研究提出了近红外光谱技术无损检测香蕉品质指标的新方法。采用The Unscramble 9.7分析软件,建立了香蕉糖度、坚实度和粘度的预测模型。根据定标集样品常规方法测定结果和所扫描得到的香蕉未剥皮和剥皮的光谱信号间的拟合关系,采用偏最小二乘法建立香蕉糖度、坚实度和粘度的定标模型,并用未参与定标的一组样品作为预测集对模型进行检验。未剥皮香蕉的糖度、坚实度和粘度的预测决定系数分别为0.94,0.95,0.93,剥皮香蕉的糖度、坚实度和粘度的预测决定系数分别为0.92,0.97,0.95,预测精度较高。结果表明,香蕉皮对其的影响不大,近红外光谱技术可应用于未剥皮香蕉品质检测,实现了香蕉品质的快速、无损检测,为香蕉品质的无损检测提供了理论依据。     

Porosity and soil water properties of Caribbean volcanic ash soils

Abstract. Volcanic ash soils are generally recognized as soils with excellent and stable physical properties. Here we characterized the porosity and water properties of volcanic ash Andosols and Nitisols from Guadeloupe in contrasting banana systems: (1) perennial crop without mechanization, (2) mechanized and regularly replanted crop. Desiccation from 1 kPa to 1550 kPa moisture tension leads to significant shrinkage in the Andosol, representing a 50% reduction of the void space. The clayey Nitisol exhibited limited shrinkage. Soil clods from the mechanized plots had a significantly smaller macroporosity than that from perennial plots. The soil hydraulic conductivity was also drastically reduced in the compacted layers of the mechanized plots. However, Nitisols appeared to be less affected than Andosols. Laboratory compression tests showed that both soils were susceptible to compaction at soil moisture close to field capacity. The shrinkage properties of the Andosol were due to microaggregation of non-crystalline components upon drying. The relative stability of the macroporosity in the Nitisol was probably related to the presence of stable microaggregates made of halloysite and iron oxide. Two major processes promote soil structure degradation in the Andosol under mechanized banana cropping, surface desiccation and soil compaction. They are both induced by repeated tillage after clearing.     

香蕉受枯萎病菌侵染后酚类物质含量的变化

对人工接种香蕉枯萎病菌Fusarium oxysporum f.sp．cubense后香蕉体内总酚及阿魏酸含量的变化进行了研究．结果表明：接种的和对照的香蕉体内的总酚和阿魏酸含量总体上都呈上升趋势,这可能是由于香蕉本身就是一类多酚植物,香蕉体内酚类物质含量随植株生长而增加的缘故．然而,接种的香蕉体内的总酚和阿魏酸含量明显高于对照的香蕉体内的总酚和阿魏酸含量,例如,接种WG5菌株28d后粉蕉的总酚和阿魏酸含量分别为546和74．8μg／mL,而对照的相应品种在同一时间的总酚和阿魏酸含量分别为184和68．6μg／mL,表明罹病香蕉体内高水平的酚类物质含量与香蕉枯萎病菌的侵染有关．     

香蕉种质资源超低温保存技术研究进展

香蕉是一种大型草本植物,多数品种没有种子或单性结实,通常以无性繁殖方式为主.由于其生殖特征,难以通过传统杂交育种的方法来进行品种改良,而多是采用体细胞突变的方法来选育新品种.因此,香蕉资源的多样性对香蕉新品种改良尤为重要.但由于常(低)温离体保存、田间活体保存方法易受到生物或非生物胁迫等影响因素限制费力、耗能,其种质资...     

干旱胁迫下香蕉miRNAs的表达分析

以干旱驯化和未驯化的香蕉幼苗为研究材料,采用实时荧光定量PCR方法检测干旱胁迫过程中6个miRNAs的表达变化。结果表明:6个miRNAs在所有香蕉幼苗的干旱胁迫响应过程中均有表达,但其表达模式存在差异,在直接干旱处理下,mi R156k、mi R160a、mi R162a、mi R164a、mi R166d的表达均呈现升高-降低的趋势,mi R397b的表达则呈现升高-降低-升高-降低的趋势;在驯化后干旱处理下,mi R156k、mi R162a、mi R166d、mi R397b的表达均呈现升高-降低的趋势,mi R160a、mi R164a的表达则呈现升高-降低-升高-降低的趋势。干旱胁迫响应过程中(除处理后第10天外),驯化后的香蕉幼苗中miRNAs的表达量基本上高于未驯化香蕉幼苗中miRNAs的表达量,同时还发现mi R160a和mi R164a的表达量都非常高。上述研究结果将为香蕉干旱胁迫应答研究奠定基础。     

香蕉吸芽生长特性与除芽技术研究进展

香蕉是世界重要的热带亚热带水果,我国是香蕉生产和消费大国。吸芽是从香蕉地下球茎上腋芽发育而成的后代,其维管束与原球茎是相通的。吸芽作为香蕉继代母株,在香蕉生育期持续抽生几十个不等,但是过多吸芽会导致母株生长缓慢、抽蕾开花迟、果实成熟晚等问题,生产上因除芽任务繁重、除芽不及时或除芽不尽而造成大量减产,及时清除吸芽对提高香蕉果实产量、改善品质具有重要意义。本文从吸芽分类、生长规律、除芽技术研究现状等进行综述,以期为香蕉除芽技术研发与应用提供借鉴。     

Fish-toxicity problems of pesticides in Japan - the present situation and the policies of the Ministry of Agriculture and Forestry

Abstract

A survey of termite damage to groundnuts and an estimation of loss in yield was made between 1977 and 1979 in northern Nigeria. The foliage was attacked by Odontotermes. Damage was restricted to the Sudan savanna and loss in yield was less than 5%. Much more important was the damage caused by Microtermes lepidus Sjöstedt which attacked the pods, the tap root and the haulms. There was a linear relationship between the percentage of stands with the tap root invaded by Microtermes and the loss in yield. Damage varied from year to year, but the higher yield losses (up to 40%) were consistently recorded in the Sudan savanna. There was a significant relationship between the level of Microtermes damage and rainfall, the latter having a marked influence on foraging behaviour and the level of foraging activity. The chemical control of termites is economically viable on mechanised farms in the Sudan savanna, but cannot be justified on peasant farms, where yields are too low.