A Model of Growth of the Fifth Leaf of Tomato

Some measurements on the fifth leaf of the tomato plant aredescribed: these include length, area, dry weight and freshweight. A model, which attempts to describe and interpret someof the data, is constructed. After fitting the model to thedata, it is used to rank the physiological and environmentalparameters, in terms of how much they affect the contributionthat the fifth leaf makes to the carbon economy of the wholeplant.     

Developmental Anatomy of the Leaf of L. Ficus religiosa

The leaves of Ficus religiosa show a more or less sigmoid growthpattern, and under the conditions prevailing in Delhi each leafincreases in size in 9 days from about 425 to 4025 mm²(as judgedby the average mature leaf size) after its emergence from thespathe. The leaf is hypostomatic and has paracytic and anomocyticstomata between polygonal epidermal cells. The frequency ofstomata per mm² increases from 33.3 to 400 and the number oflower epidermal cells decreases from about 11 300 to about 3040per mm² with the growth of the leaves while the number of upperepidermal cells decreases from 5600 to 1110. The vasculaturecomprises a single main vein (the mid rib), secondaries, tertiaries,quaternaries, and intermediaries. The number of areoles permm² decreases from 15.5 to 2.7 while the numbers of vein endingsand vein tips per areole show no correlation either with oneanother or with leaf size.     

A Leaf Spot of Water Hyacinth Caused by Drechslera spicifera

In the present study, corn meal agar was found as the best medium for growth of Drechslera spicifera, a pathogen of water hyacinth. Small water hyacinth plants exhibited a smaller number of lesions/leaf when inoculated with D. spicifera compared with inoculated medium and large plants. However, percentage total diseased area/leaf was almost the same among the different plant sizes. The pathogen did not interfere with the vegetative plant growth, since, both infected and healthy water hyacinth plants of the same age showed similar percentages of new leaf growth. Leaf diffusates of water hyacinth plants significantly reduced conidiospore germination in D. spicifera.     

草果叶斑病防治初步研究

从发病的草果叶片上分离得到草果叶斑病病原菌,进行药剂筛选试验,把不同处理的哈茨木霉(Tri-choderma harzimum)菌株和病原菌对峙培养,结果表明:春雷霉素400倍药液下病菌菌丝无法生长,金歌1 500倍、多菌灵800倍、易保1000倍、春雷霉素500倍药液对病原菌菌丝生长抑制率在61%以上;不同处理的哈茨木霉菌株对草果叶斑病病原菌均有抑制效果,且药物诱变和紫外线诱变的突变菌株比野生型菌株抑菌效果显著。     

番茄抗黄化曲叶病毒育种研究进展

本文分别对近年番茄抗黄化曲叶病毒的传统育种、分子辅助育种、基因工程育种进展进行了综述.栽培番茄均不抗番茄黄化曲叶病毒,所以传统育种采用从野生近缘种中筛选抗性材料,以其为亲本与栽培番茄进行杂交来获得抗性;野生近缘种中的抗性位点Ty-1、Ty-2和Ty-3及一些QTLs先后被定位,也筛选出了可鉴定Ty-1基因的SSR-47标记及鉴定Ty-3的SCAR标记;通过转基因技术获得抗性是研究热点之一,目前转入番茄后表现出抗性的序列有TYLCV病毒的CP基因、尺EP基因的部分序列或反义序列、不编码的保守序列以及源于白粉虱的GroEL基因.同时讨论了今后的主要发展方向.     

A New Leaf Spot of Ginger in Southern Africa and its Control

Khuskia oryzae Hudson was consistently isolated from ginger plants with a severe leaf spot disease, and its pathogenicity confirmed experimentally. All available commercial ginger selections were found to be susceptible to the disease in field and glasshouse trials, selection Gl being the most susceptible. In chemical control trials in the field, iprodione and a mixture of benomyl, mancozeb and soluble boron gave the best control. Soil fumigation with hot methyl bromide also reduced disease.     

Transcriptome Analysis of Poplar during Leaf Spot Infection with Sphaerulina spp.

Diseases of poplar caused by the native fungal pathogen Sphaerulina musiva and related species are of growing concern, particularly with the increasing interest in intensive poplar plantations to meet growing energy demands. Sphaerulina musiva is able to cause infection on leaves, resulting in defoliation and canker formation on stems. To gain a greater understanding of the different responses of poplar species to infection caused by the naturally co-evolved Sphaerulina species, RNA-seq was conducted on leaves of Populus deltoides, P. balsamifera and P. tremuloides infected with S. musiva, S. populicola and a new undescribed species, Ston1, respectively. The experiment was designed to contain the pathogen in a laboratory environment, while replicating disease development in commercial plantations. Following inoculation, trees were monitored for disease symptoms, pathogen growth and host responses. Genes involved in phenylpropanoid, terpenoid and flavonoid biosynthesis were generally upregulated in P. balsamifera and P. tremuloides, while cell wall modification appears to play an important role in the defense of P. deltoides. Poplar defensive genes were expressed early in P. balsamifera and P. tremuloides, but their expression was delayed in P. deltoides, which correlated with the rate of disease symptoms development. Also, severe infection in P. balsamifera led to leaf abscission. This data gives an insight into the large differences in timing and expression of genes between poplar species being attacked by their associated Sphaerulina pathogen.     

草坪草离蠕孢叶枯病菌生物学特性的研究

对草坪离蠕孢叶枯病病原菌进行分离鉴定,并对其生物学特性进行了研究。结果表明:该病害由禾草离蠕孢(Bipolaris sorokiniana)引起。该病原菌的菌丝生长及产孢的最适温度为30℃,孢子萌发最适温度为25℃,菌丝的致死温度为65℃,而孢子的致死温度则为55℃;该菌对酸碱度的适应能力较强,中性偏酸性的条件对菌丝的生长有利,而pH值为8.0时最易产孢;各碳源对菌丝的生长均有促进作用,但不同碳源对产孢量的影响很大,单糖和双糖利于产孢,多糖对产孢的影响不大。氮源对菌丝生长和产孢量非常重要,无机氮效果较好,硝态氮好于氨态氮,有机氮效果最差。花粉、叶面物质和草坪草汁液可促进孢子萌发。     

A Developmental Model for Branching Morphogenesis of Lake Cress Compound Leaf

Lake cress, Rorippa aquatica (Brassicaceae), is a semi-aquatic plant that exhibits a variety of leaf shapes, from simple leaves to highly branched compound leaves, depending on the environment. Leaf shape can vary within a single plant, suggesting that the variation can be explained by a simple model. In order to simulate the branched structure in the compound leaves of R. aquatica, we implemented reaction-diffusion (RD) patterning onto a theoretical framework that had been developed for serration distribution in the leaves of Arabidopsis thaliana, with the modification of the one-dimensional reaction-diffusion domain being deformed with the spatial periodicity of the RD pattern while expanding. This simple method using an iterative pattern could create regular and nested branching patterns. Subsequently, we verified the plausibility of our theoretical model by comparing it with the experimentally observed branching patterns. The results suggested that our model successfully predicted both the qualitative and quantitative aspects of the timing and positioning of branching in growing R. aquatica leaves.     

番茄黄化曲叶病毒对番茄叶片光合特性和叶绿体超微结构的影响

以番茄为试验材料,研究番茄黄化曲叶病毒(TYLCV)侵染对植株叶片叶绿素含量、净光合速率、气孔导度、胞间CO2浓度和叶绿体超微结构的影响.结果表明:TYLCV侵染番茄后,叶片叶绿素a、b以及总叶绿素含量分别下降50.2%、24.19%和43.84%,叶片净光合速率和气孔导度分别下降43.28%、27.07%,胞间CO2浓度增加13.04%.与健康叶片相比,叶绿体变形,叶绿体基质片层大部分消解,基粒结构消失,叶绿体外膜和内膜剥离,质壁分离和细胞膜内陷,细胞器消解.研究表明,TYLCV侵染破坏了番茄叶片的叶绿体结构,严重影响番茄叶片的光合作用.     

Morphology of Leaf Surfaces of Tomato Cultivars in Relation to Possible Invasion into the Leaf by Pseudomonas syringae pv. tomato

The role of morphological characteristics of tomato leaves inthe infection process of the pathogen Pseudomonas syringae pv.tomato was studied in 15 cultivars of varying susceptibility.Natural openings such as stomata, broken trichomes and cuticularcracks were counted. It was found that susceptibility increasedin proportion to the number of these potential penetration sites.However, their role is probably limited because even in thehighly resistant cultivars there are enough natural openingsto enable successful bacterial penetration. Bacterial speck of tomato, Lycopersicon esculentum, phytopathogenic bacteria, plant morphology, Pseudomonas syringae pv. tomato, tomato     

A Model Integrating Components of Rate-reducing Resistance to Cercospora Leaf Spot in Sugar Beet

Four components of rate-reducing resistance to Cercospora leaf spot in sugar beet (infection efficiency of conidia RC₁, incubation period RC₂, size of necrotic spots RC₃ and spore yield RC₄), previously measured in single infection cycle experiments, were integrated into a model simulating the chain of infection cycles under field conditions, as influenced by weather. To integrate resistance components, variables accounting for infection frequency, incubation period, affected leaf area, and infectiousness – which are computed for a susceptible cultivar – were modified by means of coefficients which reduced (RC₁, RC₃, RC₄) or increased (RC₂) them. Outputs obtained by running the model and changing resistance components actually reduced the rate of disease progress and the area under the disease progress curve of epidemics (AUDPC), as happens at field level; therefore, the approach may be considered successful. Changes in single resistance components were closely correlated with changes in AUDPC: improvements in RC₁, RC₃ or RC₄ reduced AUDPC by the same, over the whole range of variation in infection frequency, affected leaf area, and infectiousness; on the contrary, little improvements in RC₂ were more effective than stronger ones. When components acted simultaneously, each of them reduced disease progress in proportion to its magnitude; when all components were improved by the same amount, they had about the same effectiveness in slowing the epidemic. Changing more components simultaneously reduced the disease development slightly more than additively. Advantages for plant breeders in improving their selection strategies are outlined.     

Factors Affecting Survival of Bacteriophage on Tomato Leaf Surfaces

The ability of bacteriophage to persist in the phyllosphere for extended periods is limited by many factors, including sunlight irradiation, especially in the UV zone, temperature, desiccation, and exposure to copper bactericides. The effects of these factors on persistence of phage and formulated phage (phage mixed with skim milk) were evaluated. In field studies, copper caused significant phage reduction if applied on the day of phage application but not if applied 4 or 7 days in advance. Sunlight UV was evaluated for detrimental effects on phage survival on tomato foliage in the field. Phage was applied in the early morning, midmorning, early afternoon, and late evening, while UVA plus UVB irradiation and phage populations were monitored. The intensity of UV irradiation positively correlated with phage population decline. The protective formulation reduced the UV effect. In order to demonstrate direct effects of UV, phage suspensions were exposed to UV irradiation and assayed for effectiveness against bacterial spot of tomato. UV significantly reduced phage ability to control bacterial spot. Ambient temperature had a pronounced effect on nonformulated phage but not on formulated phages. The effects of desiccation and fluorescent light illumination on phage were investigated. Desiccation caused a significant but only slight reduction in phage populations after 60 days, whereas fluorescent light eliminated phages within 2 weeks. The protective formulation eliminated the reduction caused by both of these factors. Phage persistence was dramatically affected by UV, while the other factors had less pronounced effects. Formulated phage reduced deleterious effects of the studied environmental factors.     

Effect of Leaf Age on Potassium Efflux and Net Flux in Tomato Leaf Slices

The effects on leaf age on K (⁸⁶Rb) efflux, influx and net fluxinto lamina slices from leaf 7 on a tomato plant (Lycopersiconesculentum Mill.) were determined. The ontogenetic trend inK efflux was dependent on the external K concentration. At externalKCI concentrations between 0.5 and 10.0 mM, K efflux rates increasedduring leaf elongation. Only a small increase in efflux occurredin mature leaves with increasing age. It is suggested that thetonoplast retains its structural integrity through the initialstages of leaf senescence. In fully expanded leaves, a zeronet K flux (a balance between influx and efflux) was achievedat external KCI concentrations between 1.0 and 3.5 mM. The Kcontent of lamina slices from leaves 5 and 13 remained constantwhen bathed in a solution containing 2 to 3 mM K. It is suggestedthat the decline in K concentration in mature tomato leaf tissueis due to a decline in leaf free space K concentrations below1 to 3 mM which would result in a net efflux out of leaf cells. Lycopersicon esculentum Mill., tor ato, free space, ion fluxes, leaf age, leaf ontogeny, potassium