This ebook is the first authorized digital version of Kernighan and Ritchie's 1988 classic, The C Programming Language (2nd Ed.). One of the best-selling programming books published in the last fifty years, "K&R" has been called everything from the "bible" to "a landmark in computer science" and it has influenced generations of programmers. Available now for all leading ebook platforms, this concise and beautifully written text is a "must-have" reference for every serious programmers digital library.

As modestly described by the authors in the Preface to the First Edition, this "is not an introductory programming manual; it assumes some familiarity with basic programming concepts like variables, assignment statements, loops, and functions. Nonetheless, a novice programmer should be able to read along and pick up the language, although access to a more knowledgeable colleague will help."

The C programming language

In mammals, cadmium is widely considered as a non-genotoxic carcinogen acting through a methylation-dependent epigenetic mechanism. Here, the effects of Cd treatment on the DNA methylation patten are examined together with its effect on chromatin reconfiguration in Posidonia oceanica. DNA methylation level and pattern were analysed in actively growing organs, under short- (6 h) and long- (2 d or 4 d) term and low (10 mM) and high (50 mM) doses of Cd, through a Methylation-Sensitive Amplification Polymorphism technique and an immunocytological approach, respectively. The expression of one member of the CHROMOMETHYLASE (CMT) family, a DNA methyltransferase, was also assessed by qRT-PCR. Nuclear chromatin ultrastructure was investigated by transmission electron microscopy. Cd treatment induced a DNA hypermethylation, as well as an up-regulation of CMT, indicating that de novo methylation did indeed occur. Moreover, a high dose of Cd led to a progressive heterochromatinization of interphase nuclei and apoptotic figures were also observed after long-term treatment. The data demonstrate that Cd perturbs the DNA methylation status through the involvement of a specific methyltransferase. Such changes are linked to nuclear chromatin reconfiguration likely to establish a new balance of expressed/repressed chromatin. Overall, the data show an epigenetic basis to the mechanism underlying Cd toxicity in plants.

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In Posidonia oceanica cadmium induces changes in DNA methylation and chromatin patterning

Whiteflies of the Bemisia tabaci species complex are economically important pests of cassava. In Africa, they cause greatest damage through vectoring viruses responsible for cassava mosaic disease and cassava brown streak disease. Several cryptic species from the B. tabaci complex colonize cassava and neighboring crops, but the feeding interactions between the different crops and B. tabaci species are unknown. The electrical penetration graph (EPG) technique makes it possible to conduct detailed feeding studies of sap-sucking insects by creating an electric circuit through the insect and the plant. The apparatus measures the voltage fluctuations while the wired-up insect feeds and produces graphs that describe feeding behavior. We utilized EPG to explore the feeding behavior of cassava-colonizing whiteflies (SSA1-SG3) on cassava, sweet potato, tomato, and cotton; and sweet potato-colonizing whiteflies (MED and IO) on cassava and sweet potato. Results show that: (1) feeding of SSA1-SG3 is not restricted to cassava. The least preferred host for SSA1-SG3 was tomato, where probing was delayed by 99 min compared to 10 min on other hosts, furthermore mean duration of phloem ingestion events was 36 min compared to 260 min on cassava. (2) Feeding of MED on cassava appeared to be non-functional, as it was characterized by short total phloem ingestion periods ( 5 h). (3) Wire diameter affects the feeding in a statistically and practically significant manner. Implications for whitefly control and studies of host whitefly resistance are discussed.

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Impact of Host Plant Species and Whitefly Species on Feeding Behavior of Bemisia tabaci.

The grapevine (Vitis spp.) undoubtedly represents one of the woody crops most widely grown in temperate climates, and a highly valuable agricultural commodity. As most of the vegetatively propagated crops, grapevines are exposed to the attacks of a variety of pests and pathogens among which infectious intracellular agents (viruses, viroids, phloem‑ and xylem‑limited prokaryotes) play a major role, causing heavy losses, shortening the productive life of vineyars, and endangering the survival itself of affected vines. The importance of the grapevine industry and the magnitude of the problems caused by these pathogens has generated wide interest which, in turn, has fostered intensive research which has been especially active at the international scale from the late 1950’s onwards.

Directory of virus and virus-like diseases of the grapevine and their agents

Grapevine leafroll-associated virus 2 (GLRaV-2) was recognized in 1984, but its nomenclature was settled only in 1995. It is one of the five viruses involved in grapevine leafroll disease. It is also associated with graft incompatibility disorders. Because of peculiar genome structure and evolutionary history, GLRaV-2 belongs to the genus Closterovirus in the family Closteroviridae. The GLRaV-2 genome is a single-stranded, positive-sense RNA of ca. 16,500 nucleotides that is presumably capped at the 5′ terminus but lacks a poly(A) tail at the 3′ end. The nine ORFs encoded by GLRaV-2 comprise three functional modules, including the replication module, the quintuple gene block module, and the module for RNA silencing suppressors. The translation product of ORF1a lacks an AlkB domain, unlike all members of the genus Ampelovirus that infect the grapevine. The genetic diversity of GLRaV-2 is very high, with six lineages that are characterized by up to 25% nucleotide divergence and different biological behavior on plant hosts. All Vitis vinifera, rootstocks, and interspecific hybrids are susceptible to GLRaV-2. The identification of GLRaV-2 in wild Vitis spp. native to the American continent supports the hypothesis that the virus originated from North America. The virus is restricted to the phloem tissue, and infected cells are characterized by a massive presence of membranous vesicles that are typical of infection by members of the genus Closterovirus. No arthropod vector is known for GLRaV-2, but the virus is graft transmissible and mechanically transmissible to some herbaceous hosts, unlike other GLRaVs. Management of GLRaV-2 is through the use of virus-tested, clean propagation materials. The recent development of infectious GLRaV-2 clones sets the foundation for studies on gene function, virus replication, pathological properties, as well as virus-host interactions.

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Grapevine leafroll-associated virus 3

Excel Workbook for automatic parameter calculation of EPG data

Several vineyards in Rias Baixas and one in the Ribeira Sacra (Spain) were monitored and the spatial pattern of leafroll-diseased grapevine was analysed at several dates. Unidimensional aggregation analysis (ordinary runs), bidimensional analysis, and disease gradients analysis were used as methods of study of spatial aspects of epidemics of GLRaV. At very low insect populations the mealybug Planococcus citri transmitted the GLRaV-3 from infected plants to healthy ones planted between them in an experimental plot at Beluso; an initial focus of leafroll-infected grapevines was detected 2 years after planting at the area where the vectors had been located infesting the old plants. Within 8 years some new foci appeared and coalesced, and the incidence reached >80%. In three commercial plots where no vectors were observed, the spatial analysis of the diseased plants showed three different situations. In Meano, the study of the evolution of the spatial patterns of diseased plants between 1992 and 2005 suggested slow vectorial field transmission of GLRaV-3. In Goian the analysis for only 2 years suggested random distribution; therefore the viruses were arriving with the planting material, but the runs analysis of some lines suggested incipient spread of GLRaV-3. In Portomarin the incidence of both GLRaV-2 and 3 was low and their distribution was random, without any evidence of field spread. These examples of the study of the spatial analysis of leafroll-infected plants may be helpful to determine whether or not spread of the viruses is occurring, and the best control measures to take.

Spatial analysis of epidemics of Grapevine leafroll associated virus-3

The citrus mealybug, Phnococcus citri (Risso) (Hemiptera: Pseudococcidae), is a vector of Grapevine leafroll-associated virus 3 (GLRaV-3), which causes severe damage to grapevines (Vitis spp.) worldwide. We studied the feeding behavior of P. citri on grapevine leaves and whole plants infected with GLRaV-3 and on artificial feeding membranes using DC-electrical penetration graphs (EPGs). P. citri ingested from phloem sieve elements, but it also spent long intervals in the xylem. Waveforms, not described before for mealybugs, were characterized, some of them resembling those of aphids: 1) one new pattern occurring within the phloem phase, named E23, correlated with honeydew excretion and positive ninhydrine reaction and therefore was associated with sap ingestion from the phloem sieve elements; and 2) an extracellular waveform, named G, also possibly associated with ingestion in artificial membranes, which probably represented xylem ingestion. The potential drops (pd) of P. citri showed two distinc...

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Characterization of the probing and feeding behavior of Planococcus citri (Hemiptera: Pseudococcidae) on grapevine.

Grapevine leafroll-associated virus 3 (GLRaV-3) is a mealybug-transmissible ampelovirus. Though the transmission mechanism has been described as semipersistent on the basis of temporal parameters, definitive proof of this mechanism has never been provided. In the present study, we carried out preliminary assays to establish the location of the virus in its vector, Planococcus citri. After dissecting the insects, GLRaV-3 was detected by means of IC-RT-PCR in the salivary glands, intestine and Malpighian tubes, but not in the sucking apparatus. Immunogold labelling of the capsid protein revealed the presence of the virus in some cells of the primary salivary glands, but not in the alimentary channel of the stylet, or in the accessory salivary glands. The strong labelling of the electron-dense secretion vesicles in some cells of the primary salivary glands, together with the non-detection of the virus in the sucking apparatus suggests that the transmission mechanism may be different from that previously described. We propose a circulative transmission mechanism based on a specific transportation route for the viral particles from the midgut or hindgut to the salivary glands. As the transmission mechanism is generally a common feature of a viral genus, the existence of a circulative transmission mechanism for other mealybug-transmitted ampeloviruses is expected. Organ by organ analysis of GLRaV-1, another ampelovirus not transmissible by P. citri, showed the absence of the virus in the salivary glands, thus providing further, though indirect, evidence in favour of circulative transmission for this virus genus.

Presence of Grapevine leafroll-associated virus 3 in primary salivary glands of the mealybug vector Planococcus citri suggests a circulative transmission mechanism

The citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae), is the main grapevine pest in vineyards in some countries, such as Spain and Brazil. In Galician vineyards (northwestern Spain), mealybug population levels are low because the accumulated degree-days are lower than in other grapevine-growing areas. The main problem caused by mealybugs is the transmission of viruses, even at low infestation levels. The active period of citrus mealybug in the study vineyard lasted from July until December, with an important movement peak at the end of July and August and a lower peak in November. The mealybug mainly moved upward along arbor-trained plants, and there were no important downward movements at the end of the season as has been described for other grapevine mealybugs. The mealybugs were normally restricted to the woody organs and were only present on leaves, branches, and green canes (always close to woody parts) in plants with high infestations. The movement of mealybugs between plants does not seem to take place by contact between green organs. Passive aerial transport and movement of pruning remains may play an important role in mealybug movement and thus in spread of the virus. The number of mealybugs carrying Grapevine leafroll-associated virus 3 (GLRaV-3) was found to represent approximately 75% of mealybugs caught in a GLRaV-3 infected vineyard.

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Miguel Cid

Papers

Excel Workbook for automatic parameter calculation of EPG data

Spatial analysis of epidemics of Grapevine leafroll associated virus-3

Characterization of the probing and feeding behavior of Planococcus citri (Hemiptera: Pseudococcidae) on grapevine.

Presence of Grapevine leafroll-associated virus 3 in primary salivary glands of the mealybug vector Planococcus citri suggests a circulative transmission mechanism

Citrus mealybug (Hemiptera: Pseudococcidae) movement and population dynamics in an arbor-trained vineyard.