A simple and reliable method for the screening of transgenic tobacco plants

Even though much improvement has been made in plant transformation methods, the screening of transgenic plants is often a laborious work. Most approaches for detecting the transgene in transformed plants are still timeconsuming, and can be quite expensive. The objective of this study was to search for a simpler method to screen for transgenic plants. The infiltration of kanamycin (100 mg/mL) into tobacco leaves resulted in conspicuous chlorotic spots on the non-transgenic plant leaves, while no spots were seen on the leaves of transformed plants. This reaction occurred regardless of age of the tested plants, and the method has proven to be simple, fast, non-destructive, relatively cheap, and reliable. These results were comparable to those obtained by the polymerase chain reaction (PCR) amplification of the transgene using specific primers.

Genetic variability of Brazilian phytoplasma and spiroplasma isolated from maize plants

The objective of this work was to characterize the genetic variability of phytoplasma and Spiroplasma kunkelii isolated from maize plants showing symptoms of stunt collected from different Brazilian geographic regions. A DNA fragment of 500 base pairs (bp) was amplified from the spiralin gene in S. kunkelii and one fragment of 1,200 bp was generated from 16S rDNA gene in phytoplasma. The partial sequences of the spiralin gene showed similarity of 98% among the isolates of S. kunkelii analyzed. These sequences were compared with the sequence of the spiralin gene from other Spiroplasma species deposited in the GenBank, resulting in a similarity varying from 76.9% to 88.1%. The 16S rDNA sequence from the phytoplasma were completely similar within the Brazilian isolates and showed up to 98% of the similarity with sequences already found from other phytoplasmas. A very narrow genetic variability was detected by these gene fragments within phytoplasma and Spiroplasma analyzed. However, other genomic regions with higher polymorphic levels shall be identified in order to better evaluate the genetic diversity within these microorganisms population.

Rescue of a non-viable accession and rapd analysis of recovered plants of Arachis retusa

In vitro regeneration of Arachis retusa was examined for the purpose of germplasm renewal and conservation. Random amplified polymorphic DNA (RAPD) fingerprinting was used to evaluate the genetic stability of plants derived from embryo axes and apical segments. Ten arbitrary decamer primers were screened and five of them were selected. Ninety genomic regions were evaluated, with an average of 18 loci per clone. All amplified segments were monomorphic. The results indicate that recovered plants are genetically stable at the assessed genomic regions and that both regeneration processes are suitable for in vitro germplasm preservation of Arachis species.

Plants of an Eucalyptus clone damaged by Scolytidae and Platypodidae (Coleoptera)

Species of Scolytidae and Platypodidae were evaluated in a plantation using a clone of Eucalyptus grandis x Eucalyptus urophylla in the State of Minas Gerais, Brazil. Wood disks with galleries were taken from 15 eucalyptus trees between 0.5 and 1.5 m height. After collection, all trees attacked were burned. Woodborers obtained from these disks were identified as Premnobius cavipennis, Premnobius ambitiosus, Dryocoetoides cristatus (Coleoptera: Scolytidae) and Euplatypus parallelus (Coleoptera: Platypodidae). This is the first report of D. cristatus, a Brazilian native species, damaging eucalyptus, which shows its adaptation to this plant.

Spittlebug Cephisus siccifolius damaging eucalypt plants in the State of Bahia, Brazil

Most common pests of eucalyptus plants in Brazil are leaf cutting ants and defoliating caterpillars. Other groups, eventually, feeding on eucalyptus include Heteroptera and cicadas. The objectives of this work were to identify and to describe attack symptoms of Cephisus siccifolius (Walker 1851) (Hemiptera: Aphrophoridae) on eucalyptus trees in a stand of 25.77 hectares in the State of Bahia, Brazil, where 99.3% of them were attacked by this spittlebug. Damage was more severe on branches and leaves. Tree death was, relatively, low while those cut showed 4.7 colonies of this spittlebug with 21.9 nymphs per colony. Cultural control with the removal of trees attacked was recommended.

Photosynthetic responses of young cashew plants to varying environmental conditions

The aim of this study was to characterize gas exchange responses of young cashew plants to varying photosynthetic photon flux density (PPFD), temperature, vapor-pressure deficit (VPD), and intercellular CO2 concentration (Ci), under controlled conditions. Daily courses of gas exchange and chlorophyll a fluorescence parameters were measured under natural conditions. Maximum CO2 assimilation rates, under optimal controlled conditions, were about 13 mmol m-2 s-1 , with light saturation around 1,000 mmol m-2 s-1. Leaf temperatures between 25ºC and 35ºC were optimal for photosynthesis. Stomata showed sensitivity to CO2, and a closing response with increasing Ci. Increasing VPD had a small effect on CO2 assimilation rates, with a small decrease above 2.5 kPa. Stomata, however, were strongly affected by VPD, exhibiting gradual closure above 1.5 kPa. The reduced stomatal conductances at high VPD were efficient in restricting water losses by transpiration, demonstrating the species adaptability to dry environments. Under natural irradiance, CO2 assimilation rates were saturated in early morning, following thereafter the PPFD changes. Transient Fv/Fm decreases were registered around 11h, indicating the occurrence of photoinhibition. Decreases of excitation capture efficiency, decreases of effective quantum yield of photosystem II, and increases in non-photochemical quenching were consistent with the occurrence of photoprotection under excessive irradiance levels.

Influence of substrates and in vitro preconditioning treatments on ex vitro acclimatization of Arachis retusa

The objective of this work was to evaluate the influence of substrate and preconditioning treatments on the acclimatization of in vitro plants of Arachis retusa. Plants were transferred to Plantmax or sand, and fertilized with Hoagland's nutrient solution. Plants maintained in sand, with or without fertilizer, showed the highest survival rates. In order to evaluate the influence of in vitro preconditioning treatments, stem segments were cultured on MS medium supplemented with different sucrose concentrations. The highest survival and developmental rates were observed in plants from two accessions cultured on MS supplemented with 1.5% and 3% sucrose. Flowering and fruit production were observed after five months.

Diets based on soybean protein for Mediterranean fruit fly

The objective of this work was to develop suitable and economic diets for mass rearing Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae). Diets containing sugar beet bagase, wheat bran, brewer yeast, and others with wheat bran and palletized soybean protein from Brazil were tested. Diets based on soybean protein have shown promising results regarding pupal recovery, pupal weight and adult emergence. Soybean bagase in the form of pellets with 60% of protein can be a very important substitute for other expensive sources of protein.

Microclimatic characterization and productivity of coffee plants grown under shade of pigeon pea in Southern Brazil

Recent studies on coffee (Coffea arabica L.) cultivation in agroforestry systems in Southern Brazil have shown the potential of partial shading to improve management of this crop. The objective of this work was to evaluate microclimatic conditions and their effects on coffee production of plants shaded with pigeon pea (Cajanus cajan) in comparison to unshaded ones, from May 2001 to August 2002 in Londrina, State of Paraná, Brazil. The appraised microclimatic characteristics were: global radiation, photosynthetic and radiation balance; air, leaf and soil temperatures; and soil humidity. Shading caused significant reduction in incident global solar radiation, photosynthetically active radiation and net radiation, and attenuated maximum leaf, air and soil temperatures, during the day. Shade also reduced the rate of cooling of night air and leaf temperatures, especially during nights with radiative frost. Soil moisture at 0-10 cm depth was higher under shade. The shaded coffee plants produced larger cherries due to slower maturation, resulting in larger bean size. Nevertheless, plants under shade emitted less plagiotropic branches, with smaller number of nodes per branch, and fewer nodes with fruits, resulting in a large reduction in coffee production. These results show the need to find an optimal tree density and management that do not compromise coffee production and protect against extreme temperatures.

Necrotrophic fungi associated with epidermal microcracking caused by chilling injury in pickling cucumber fruit

The objective of this work was to visualize the association between microcracking and other epidermal chilling injury symptoms, and to identify rots in cucumber fruit (Cucumis sativus L.) by scanning electron microscopy (SEM). Depressed epidermal areas and surface cracking due to damages of subepidermal cells characterized the onset of pitting in cucumber fruit. The germination of conidia of Alternaria alternata, with some of them evident on the fractures in the cultivar Trópico, occurred after damaging on the epidermis. Before, the chilling injury symptoms became visible, Stemphylium herbarum conidia germinated, and mycelium penetrated through the hypodermis using the microcracks as pathway. In the cultivar Perichán 121 the fungus was identified as Botrytis cinerea.

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.

Yield and fruit quality of apple from conventional and organic production systems

The objective of this study was to assess the yield and fruit quality of apple produced with a conventional and an organic production systems in Southern Brazil. The orchards consisted of alternate rows from 10 to 12-year old 'Royal Gala' and 'Fuji' apple trees on M.7 rootstocks, grown as slender spindles, on 4x6 m spacing. Eighteen apple trees of each cultivar and management system were randomly selected and assessed for nutrition, flowering, fruit set, yield, and fruit quality during two growing seasons (2002/2003 and 2003/2004). The organic management system resulted in lower concentrations of K, Mg, and N in leaves and fruits, and in smaller fruits for both cultivars, and lower fruit yield for 'Fuji' than from the conventional production system. For both cultivars, fruits from the organic orchard harvested at commercial maturity had a more yellowish skin background color, higher percentage of blush in the fruit skin, higher soluble solids content, higher density, higher flesh firmness, and higher severity of russet than fruits from the conventional orchard. Fruit from the organic orchard had lower titratable acidity in 'Royal Gala', and higher incidence of moldy core and lower incidence of watercore in 'Fuji', than fruit from the conventional orchard. A non-trained sensory panel detected no significant differences for fruit attributes of taste, flavor and texture between fruit from the production systems for either cultivar.

Preliminary characterization of Psidium germplasm in different Brazilian ecogeographic regions

The objective of this work was to characterize 119 accessions of guava and 40 accessions of "araçá" sampled in 35 Brazilian ecoregions, according to the International Union for the Protection of New Varieties of Plants (UPOV) descriptors. The majority of "araçá" accessions presented wide spacing of leaf veins, while guava accessions presented medium to close spacing. Most fruits of "araçá" accessions were classified as small, contrasting with medium to large fruits of guava accessions. Most of "araçá" accessions (91%) presented white flesh fruit color, while 58% of guava accessions presented pale pink, pink and dark pink colors. Fruit differences among wild and cultivated Psidium species indicate fruit as the most altered trait under artificial selection.

Cell size in trays for the production of strawberry plug transplants

The objective of this work was to evaluate the influence of cell sizes used for strawberry plug production in trays compared to bare root transplants, regarding initial plant size, harvest timing, and total strawberry fruit yield. Plug transplants were produced from runner tips rooted in trays with cell sizes of 26.5, 50, 100 and 150 cm³ filled with Plantmax HA organic substrate. Bare root transplants (control) were produced in a closed soilless system using sand as substrate. A randomized block design was used, with four replicates with 16 plants per plot. Bare root transplants and plug transplants from 100-cm³ cells had larger crown and higher leaf and root dry mass. Early fruit yield was higher in plants propagated from plugs than in those propagated from bare root transplants. Spring and total fruit yield did not differ among treatments, with an average yield of 435 and 874 g per plant, respectively. Earlier strawberry fruit yield was obtained by using plug transplants, even from trays with small cells of 26.5 or 50 cm³.

Postharvest mechanical damage affects fruit quality of 'Montenegrina' and 'Rainha' tangerines

The objective of this work was to evaluate the visual and chemical quality of tangerines after mechanical damage by impacts. The tangerine cultivars Montenegrina and Rainha were submitted to different degrees of impact and evaluated for decay and oleocellosis, loss of fresh weight, total soluble solids, total titratable acidity and ascorbic acid degradation, as well as for epicarp color changes. Experiments with three replicates and experimental units of six fruit for each cultivar were done in a completely randomized design. Impact produced qualitative internal and minor external changes on tangerines. The main modifications produced by impact on the fruit were losses of citric acid and soluble solids, which increased the solid:acid ratio, and losses of ascorbic acid. 'Montenegrina' tangerines are more susceptible to internal quality damage than 'Rainha'.