Guy de Capdeville

Rnai-mediated silencing of the myo-inositol-1-phosphate synthase gene (GmMIPS1) in transgenic soybean inhibited seed development and reduced phytate content

Inositol plays a role in membrane trafficking and signaling in addition to regulating cellular metabolism and controlling growth. In plants, the myo-inositol-1-phosphate is synthesized from glucose 6-phosphate in a reaction catalyzed by the enzyme myo-inositol-1-phosphate synthase (EC 5.5.1.4). Inositol can be converted into phytic acid (phytate), the most abundant form of phosphate in seeds. The path to phytate has been suggested to proceed via the sequential phosphorylation of inositol phosphates, and/or in part via phosphatidylinositol phosphate. Soybean [Glycine max (L.) Merrill] lines were produced using interfering RNA (RNAi) construct in order to silence the myo-inositol-1-phosphate (GmMIPS1) gene. We have observed an absence of seed development in lines in which the presence of GmMIPS1 transcripts was not detected. In addition, a drastic reduction of phytate (InsP6) content was achieved in transgenic lines (up to 94.5%). Our results demonstrated an important correlation between GmMIPS1 gene expression and seed development.

Alternative disease control agents induce resistance to blue mold in harvested 'red delicious' apple fruit.

ABSTRACT Alternative control agents, including UV-type C (254 nm) irradiation, yeasts antagonistic to fungal growth, chitosan and harpin, were evaluated for their ability to induce resistance in cv. Red Delicious apple fruit against postharvest blue mold caused by Penicillium expansum. Freshly harvested and controlled atmosphere (CA)-stored fruit were treated with these agents at different doses and concentrations or with paired combinations of the agents. Treated fruit were inoculated with P. expansum 24, 48, or 96 h following treatment, and stored at 24 degrees C in the dark. The fruit were evaluated for development of disease every 2 days for 14 days by measuring the diameter of lesions that formed. The area under the disease progress curve (AUDPC) was calculated and analyzed statistically. All treatments were effective in reducing the AUDPC; UV-C was most effective, followed by harpin, chitosan, and the yeasts, respectively. Regardless of treatment, fresh fruit were more responsive to treatments than CA-stored fruit. There was a clear time-dependent response of the fruit to the treatments, in which treatments applied 96 h before inoculation provided the best results. In a few situations, the combinations of agents did provide an additive effect, but no synergistic effects were detected. Moreover, disease severity in fruit treated by any combination was markedly better than that in the controls. Although the combinations of treatments was overall less effective than the single treatments, they did provide significant reductions of the progress of disease in comparison with the controls. Because the fungus did not come into contact with any of the control agents, this study showed conclusively that the agents studied were able to induce resistance in the fruit rather than merely inhibit the pathogen directly. It also showed, for the first time, that harpin is able to induce resistance in harvested apple fruit. The use of these control agents may minimize the costs of control strategies and reduce the risks associated with the excessive use of fungicides in harvested apple fruit.

Pre- and Post-harvest Harpin Treatments of Apples Induce Resistance to Blue Mold

Harpin was studied for its ability to induce resistance in apple fruit to blue mold caused by Penicillium expansum after harvest. Red Delicious fruit were harvested and sprayed with harpin at 0, 40, 80, and 160 mg/liter applied as a commercial formulation. At 48, 96, and 144 h after treatment, fruit were wound inoculated with spore suspensions of P. expansum at 103, 5 × 103, or 104 spores/ml. The diameters of the resulting lesions were directly proportional to the inoculum concentration. Fewer fruit treated with harpin became infected relative to the controls, and disease progress was considerably reduced. In a second experiment, apple trees of the cultivars McIntosh, Empire, and Red Delicious were sprayed with different concentrations of harpin 8 or 4 days before harvest. Fruit were harvested, wounded, inoculated with the fungus, and stored in a commercial cold room. Fewer fruit treated with harpin became infected compared with the controls. Greater control resulted from the higher concentrations of harpin, but no difference in control occurred as a function of interval between the spray time and harvest. Spraying apple trees with harpin a few days before harvest is a promising strategy for reducing blue mold decay in storage.

Translocation and insecticidal activity of Bacillus thuringiensis living inside of plants

The major biological pesticide for the control of insect infestations of crops, Bacillus thuringiensis was found to be present naturally within cotton plants from fields that had never been treated with commercial formulations of this bacterium. The ability of B. thuringiensis to colonize plants as an endophyte was further established by the introduction of a strain marked by production of green fluorescent protein (GFP). After inoculation of this preparation close to the roots of cotton and cabbage seedlings, GFP‐marked bacteria could be re‐isolated from all parts of the plant, having entered the roots and migrated through the xylem. Leaves taken from the treated plants were able to cause toxicity when fed to the Lepidoptera Spodoptera frugiperda (cotton) and Plutella xylostella (cabbage). These results open up new horizons for understanding the natural ecology and evolution of B. thuringiensis and use of B. thuringiensis in insect control.

Gray mold severity and vase life of rose buds after pulsing with citric acid, salicylic acid, calcium sulfate, sucrose and silver thiosulfate

O mofo cinzento das roseiras (Rosa hybrida), causado por Botrytis cinerea, requer muitas estrategias de manejo para seu controle. Botoes de rosa (cv Kiss) foram submetidos ao pulsing com solucoes de acido citrico, acido salicilico, sulfato de calcio, sacarose ou tiossulfato de prata (STS), para avaliar o efeito destes tratamentos sobre a severidade do mofo cinzento e a vida de vaso das flores. As solucoes foram aplicadas a hastes colhidas em diferentes tempos em relacao ao ponto de colheita, mas a variacao no ponto de colheita nao produziu efeitos significativos. O tratamento com STS reduziu os valores de area abaixo da curva de progresso da doenca (AACPD) e de severidade maxima em 15% e 55%, respectivamente, e aumentou a vida de vaso das flores em 20%. O sulfato de calcio reduziu consistentemente a AACPD em 66% e a severidade maxima em 88%, alem de aumentar a vida de vaso em 37%. Portanto, o pulsing de botoes de rosa com solucoes de STS e sulfato de calcio e um tratamento potencialmente util para reduzir as perdas devidas ao mofo cinzento e para aumentar a vida de vaso das flores.

The potential of high-resolution BAC-FISH in banana breeding

The genetic complexity in the genus Musa has been subject of study in many breeding programs worldwide. Parthenocarpy, female sterility, polyploidy in different cultivars and limited amount of genetic and genomic information make the production of new banana cultivars difficult and time consuming. In addition, it is known that part of the cultivars and related wild species in the genus contain numerous chromosomal rearrangements. In order to produce new cultivars more effectively breeders must better understand the genetic differences of the potential crossing parents for introgression hybridization, but extensive genetic information is lacking. As an alternative to achieve information on genetic collinearity we make use of modern chromosome map technology known as high-resolution fluorescent in situ hybridization (FISH). This article presents the technical aspects and applications of such a technology in Musa species. The technique deals with BAC clone positioning on pachytene chromosomes of Calcutta 4 (Musa acuminata ssp. burmanicoides, A genome group, section Eumusa) and M. velutina (section Rodochlamys). Pollen mother cells digestion with pectolytic enzymes and maceration with acetic acid were optimized for making cell spread preparations appropriate for FISH. As an example of this approach we chose BAC clones that contain markers to known resistance genes and hybridize them for establishing their relative positions on the two species. Technical challenges for adapting existing protocols to the banana cells are presented. We also discuss how this technique can be instrumental for validating collinearity between potential crossing parents and how the method can be helpful in future mapping initiatives, and how this method allows identification of chromosomal rearrangements between related Musa species and cultivars.

Morphology, distribution and abundance of antennal sensilla in three stink bug species (Hemiptera: Pentatomidae).

The neotropical stink bugs, Euschistus heros, Piezodorus guildinii and Edessa meditabunda, are important pests of soybean and other crops throughout Central America and in South America from Northern Argentina to Brazil. Mate finding and host plant location in these species depend largely on their chemical communication, and semiochemicals are important mediators of these behaviors. In this study scanning electron microscopy was used to examine the external morphology, distribution and abundance of antennal sensilla on males, females and 5th instar nymphs of these species. Nine morphologically different sensilla types were found: trichod sensilla, type 1 and 2 (ST1 and ST2), long and short basiconic sensilla (SB1, SB2, and SB3), slit-tipped and knob-shaped basiconic sensilla, long chaetic sensilla (Sch) and coeloconic sensilla (Sco). Differences were detected in the abundance and arrangement of the sensilla over the antennal segments in individuals of the same species and among the species studied. The Sch, Sco and the slit-tipped and knob-shaped basiconic sensilla accounted for the major difference in sensilla types among the species. The ST1 was the most abundant type and was restricted to the flagellum. The pedicel of E. heros differs from the pedicels of P. guildinii and E. meditabunda mainly by the absence of Sch. There was a sexual dimorphism in ST1, SB1 and SB2, and this may be an indicative of their roles in detection of male-produced sex pheromone and odors derived from the host plants. The SB2 was lacking in the antennal tip of both sexes and 5th instar nymphs, but was abundant on the second flagellar segment of females of the three species. The same types of sensilla were found on 5th instar nymphs, but always in significantly lower numbers. The morphology and putative functions of each sensilla were compared and discussed.

Survival of Botrytis cinerea as mycelium in rose crop debris and as sclerotia in soil

ABSTRACT Botrytis blight caused by Botrytis cinerea is an important disease of rose ( Rosa hybrida ) grown in greenhouses inBrazil. As little is known regarding the disease epidemiology under greenhouse conditions, pathogen survival in crop debrisand as sclerotia was evaluated. Polyethylene bags with petals, leaves, or stem sections artificially infected with B. cinerea were mixed with crop debris in rose beds, in a commercial plastic greenhouse. High percentage of plant parts with sporulationwas detected until 60 days, then sporulation decreased on petals after 120 days, and sharply decreased on stems or leavesafter 90 days. Sporulation on petals continued for 360 days, but was not observed on stems after 150 days or leaves after 240days. Although the fungus survived longer on petals, stems and leaves are also important inoculum sources because highamounts of both are deposited on beds during cultivation. Survival of sclerotia produced on PDA was also quantified. Sclerotiagermination was greater than 75% in the initial 210 days and 50% until 360 days. Sclerotia weight gradually declined but theyremained viable for 360 days. Sclerotia were produced on the buried petals, mainly after 90 days of burial, but not on leavesor stems. Germination of these sclerotia gradually decreased after 120 days, but lasted until 360 days. Higher weight loss andlower viability were observed on sclerotia produced on petals than on sclerotia produced

Some cellular correlates of harpin-induced resistance to blue mold of apples

Harpin is a protein produced by Erwinia amylovora that is involved in its pathogenesis of apple. We studied cellular correlates of harpin-induced resistance in apple fruit to blue mold caused by Penicillium expansum using Light (LM), scanning (SEM) and transmission (TEM) electron microscopy. SEM study of wound surfaces showed the fungus colonizing the wounds within 48 h, and profuse colonization of the wound and penetration of the tissue occurred within 72 h after inoculation of control samples. In harpin-treated samples, spore germination and wound colonization were not evident until 96 h. LM showed that intramural mycelial growth appeared as early as 72 h, and intense tissue colonization occurred by 96 h after inoculation in the control samples. In the harpin-treated fruit, spore germination and wound colonization occurred only by 144 h in the treated specimens. Numerous putative tannin vacuoles and appositions were observed in the epidermal and hypodermal cells of inoculated harpin-treated samples, but only a few appeared in control samples. TEM showed that intramural growth of the fungus occurred frequently in the controls. In harpin-treated specimens, wall depositions and appositions occurred very frequently. The results suggest that harpin may trigger or intensify cellular responses in harpin-treated apples.

Scanning electron microscopy of the interaction between Cryptococcus magnus and Colletotrichum gloeosporioides on papaya fruit

The objective of this work was to investigate possible modes of action of the yeast Cryptococcus magnus in controlling anthracnose (Colletotrichum gloeosporioides) on post harvested papaya fruits. Scanning electron microscopy was used to analyze the effect of the yeast on inoculations done after harvest. Results showed that C. magnus is able to colonize wound surfaces much faster than the pathogen, outcompeting the later for space and probably for nutrients. In addition, C. magnus produces a flocculent matrix, which affects hyphae integrity. The competition for space and the production of substances that affect hyphae integrity are among the most important modes of action of this yeast.O objetivo deste trabalho foi investigar provaveis modos de acao da levedura Cryptococcus magnus , que resultam no controle da antracnose ( Colletotrichum gloeosporioides ) em frutos de mamoeiro na pos-colheita. A microscopia eletronica de varredura foi utilizada para avaliar o efeito da levedura sobre inoculacoes realizadas apos a colheita. Os resultados mostraram que C. magnus e capaz de colonizar a superficie de ferimentos nos frutos e vencer a competicao por espaco e, provavelmente, por nutrientes. Alem disso, C. magnus produz uma matriz de textura caracteristica que afeta a integridade da hifa do patogeno. A competicao por espaco e a producao de substâncias que afetam a integridade das hifas estao entre os mais importantes modos de acao desta levedura.