Effects of UV-B radiation on the antagonistic ability of Clonostachys rosea to Botrytis cinerea on strawberry leaf disc

Human activities are altering the concentrations of ozone in the troposphere and hence in the incidence of ultraviolet-B (UV-B) on Earth’s surface. Although representing only five percent of UV-B radiation striking the Earth's surface, this radiation has the potential to cause effects on biologically active molecules. Sensitivity to UV-B radiation is one of the limitations of biological control of plant pathogens in the field. The objectives of this work were to evaluate the effects of UV-B on several isolates of Clonostachys rosea, and the ability of an isolate of C. rosea, previously selected for its tolerant to UV-B radiation, to control Botrytis cinerea on strawberry leaves in controlled conditions (strawberry leaf discs). The germination of C. rosea conidia was inversely proportional to the irradiance. The most tolerant strain (LQC62) had relative germination of about 60% after irradiation of 4.2kJ/m2, and this strain was selected to be used in the subsequent studies. The data showed that even with exposure to UV-B radiation, C. rosea LQC62 controlled the pathogen. Conidial concentrations of strain LQC62 above 105 conidia/ml showed higher tolerance to UV-B radiation and increased ability to control more than 75% of the B. cinerea even with exposure to radiation. According to our results, in addition to showing less growth under UV-B, conidia of C. rosea had lower antagonistic ability. Further studies are needed to observe the tolerance of B. cinerea conidia to UV-B radiation and thereby prove that an environment with increased UV-B radiation may be favoring the pathogen due to a lower ability of C. rosea to control the pathogen in conditions of increased UV-B.

Resistance of three different populations of mulberry silkworm (Bombyx mori L.) to Bacillus thuringiensis

The relative resistance levels of three different populations of mulberry silkworm, Bombyx mori L. to Bacillus thuringiensis (Bt) has been studied. All three populations (two Australian and one Indonesian) were observed for similar characteristics including 3rd instar larval mortality at 24, 48, 72 and 96 h after treatment (HAT), LD50 ratio and probit mortality. Among the Australian two populations, the QuBill (yellow coloured, oval shaped cocoon) population showed higher larval mortality to Bt toxicity compared to the QuBite (white coloured, oval shaped cocoon) population. When all the populations were compared, the Insab (Indonesian population with white Coloured, peanut shaped cocoon) showed lower larval mortality and highest LD50 ratio up to 48 HAT. The Insab population also showed a 24 It longer incubation/latent period prior to the start Of Mortality.

Endophytic microorganisms isolated from coffee leaves, roots and branches as plant growth promoters and biocontrol agents of coffee leaf rust

Suppression of plant diseases and growth promotion due to the action of endophytic microorganisms has been demonstrated in several pathosystems. Experiments under controlled conditions involving 234 endophytic bacteria and fungi isolated from coffee leaves, roots and branches were conducted with the objective of evaluating the germination inhibition of Hemileia vastatrix urediniospores, the control of coffee leaf rust development in tests with leaf discs and on plastic bags seedling, and to promote growth of coffee seedlings. None of the fungal isolates induced plant growth or reduced disease severity. The bacterial isolates (identified by the fatty acids profile analysis) 85G (Escherichia fergusonii), 161G, 163G, 160G, 150G (Acinetobacter calcoaceticus) and 109G (Salmonella enterica) increased plant growth, the maximum being induced by 85G. This isolate produced in vitro phosphatase and indol acetic acid. In assay to control rust on coffee leaf disc, nine bacterial isolates, 64R, 137G, 3F (Brevibacillus choshinensis), 14F (Salmonella enterica), 36F (Pectobacterium carotovorum), 109G (Bacillus megaterium), 115G (Microbacterium testaceum), 116G and 119G (Cedecea davisae) significantly reduced disease severity, when applied 72 or 24h before challenging with the pathogen. In seedling tests most disease severity reduction was achieved by the isolates 109G and 119G. There was no correspondence between the organisms that promoted seedling growth and those that reduced rust severity on seedlings or leaf discs.

Effects of elevated atmospheric carbon dioxide on the biological control of coffee leaf rust under controlled conditions

The effect of elevated atmospheric CO2 concentration on biological control of coffee leaf rust, caused by Hemileia vastatrix, was evaluated by leaf disc assay, under controlled conditions. The biocontrol agents Bacillus subtilis, Bacillus pumilus and Lecanicillium longisporum were applied 24h before, 24h after, and simultaneously with the H. vastatrix on leaf discs (diameter of 1.5cm). The CO2 concentrations tested were: 380, 430, 700 and 1300ppm for B. subtilis and B. pumilus; and 380, 430, 670 and 1200ppm for L. longisporum. The antagonists were not affected by CO2 concentrations. B. subtilis was the most effective in controlling the disease when applied before and simultaneously with pathogen.

Predation and reproductive output of the ladybird beetle Stethorus tridens preying on tomato red spider mite Tetranychus evansi

Predatory behaviour and reproductive output of the ladybird beetle Stethorus tridens Gordon as function of the tomato red spider mite (TRSM), Tetranychus evansi Baker & Pritchard, densities was investigated in the laboratory. Adult female of S. tridens were isolated in cylindrical plastic arenas, containing a leaf disc of Solanum americanum Mill. with 5, 20, 40, 60, 80 or 100 T. evansi nymphs. The number of prey consumed and eggs laid were evaluated daily for ten consecutive days, starting at the oviposition. Oviposition of S. tridens was positively correlated with prey consumption and lower threshold prey consumption for S. tridens laying eggs was 16.3 mites per day. The instantaneous rate of attack (ca. discovery area) and the handling time were 0.0062 h(-1) and 0.83 h, and 0.00254 h(-1) and 0.78 h, respectively, for predators at the 1st- and 10th-oviposition day. The predator exhibited a type II functional response at 1st- and 10th-oviposition day with a maximum consumption per predator of 33 T. evansi nymphs per day at the highest prey density. The ladybird beetle S. tridens is often collected associated with red spider mite colonies on solanaceous wild plants and the results suggest the potential of this ladybird beetle to control T. evansi in tomatoes crops.

DNA polymorphism in Cab locus of tomato induced by tissue culture

Plants were regenerated from callus induced from leaf disc explants of a tomato F, hybrid heterozygous for three marker loci (a), without anthocyanin (aw), and hairless (hl). Regenerants were studied for somaclonal variation at the phenotypic level by scoring for variation in the marker loci, and at the DNA level by probing geomic DNA blots with a chlorophyll a/b binding protein (Cab-3C) cDNA sequence. While no variation was observed at the phenotypic level in over 950 somaclones studied, DNA polymorphism for the Cab locus could be detected in two out of 17 somaclones tested. Tissue culture induced variation at the phenotypic level for specific loci is very low (less than 0.001 for a, awor hl) but DNA sequence changes are induced at much greater frequency (- 0.1 for a multicopy gene family such as Cab).

Evaluation of Somaclonal Variation in Callus Cultures of Jatropha curcas Maintained on Different Hormonal Combinations Using RAPD Markers

Random genetic changes generated during in vitro culture are not desirable for plant micropropagation and genetic transformation. RAPD markers were used to detect the variation in leaf disc callus cultures of Jatropha curcas, maintained in Murashige and Skoog (MS) medium with different auxin and cytokinin combinations. In total 41 scorable bands were produced with 11 primers. Out of 41 bands, 37 were polymorphic (91.12%). The average number of polymorphic bands was 3.36 per primer. The highest similarity (0.82) with mother plant was seen in callus maintained on MS with hormonal combination Indole butyric acid - 0.4mg/l+ N6-benzyladenine purine - 4.0 mg/l. The callus grown on MS with hormonal combinations IBA- 0.4mg/l+ BAP- 2.0mg/l, IBA- 0.4mg/l+ BAP- 2.5mg/l and IBA- 0.6 mg/l+ BAP- 2.0 mg/l also showed similarity with the mother plant. Callus maintained on MS with hormonal combination IBA- 0.2mg/l+ BAP- 2.0 mg/l was found to show least similarity (0.53) with mother plant

Genetic variation of and environmental effects on inducibility of resistance in tomatoes (Solanum lycopersicum L.) to Phytophthora infestans (Mont) de Bary

Many plant strengtheners are promoted for their supposed effects on nutrient uptake and/or resistance induction (IR). In addition, many organic fertilizers are supposed to enhance plant health and several studies have shown that tomatoes grown organically are more resistant to late blight, caused by Phytophthora infestans to tomatoes grown conventionally. Much is known about the mechanisms underlying IR. In contrast, there is no systematic knowledge about genetic variation for IR. Therefore, the following questions were addressed in the presented dissertation: (i) Is there genetic variation among tomato genotypes for inducibility of resistance to P. infestans? (ii) How do different PS compare with the chemical inducer BABA in their ability to IR? (iii) Does IR interact with the inducer used and different organic fertilizers? A varietal screening showed that contrary to the commonly held belief IR in tomatoes is genotype and isolate specific. These results indicate that it should be possible to select for inducibility of resistance in tomato breeding. However, isolate specificity also suggests that there could be pathogen adaptation. The three tested PS as well as two of the three tested organic fertilisers all induced resistance in the tomatoes. Depending on PS or BABA variety and isolate effects varied. In contrast, there were no variety and isolate specific effects of the fertilisers and no interactions with the PS and fertilisers. This suggests that the different PS should work independent of the soil substrate used. In contrast the results were markedly different when isolate mixtures were used for challenge inoculations. Plants were generally less susceptible to isolate mixtures than to single isolates. In addition, the effectiveness of the PS was greater and more similar to BABA when isolate mixtures were used. The fact that the different PS and BABA differed in their ability to induce resistance in different host genotype -pathogen isolate combinations puts the usefulness of IR as a breeding goal in question. This would result in varieties depending on specific inducers. The results with the isolate mixtures are highly relevant. On the one hand they increase the effectiveness of the resistance inducers. On the other hand, measures that increase the pathogen diversity such as the use of diversified host populations will also increase the overall resistance of the hosts. For organic tomato production the results indicate that it is possible to enhance the tomato growing system with respect to plant health management by using optimal fertilisers, plant strengtheners and any measures that increase system diversity.

The use of bioluminescence for monitoring in planta growth dynamics of a Pseudomonas syringae plant pathogen

The use of bioluminescence was evaluated as a tool to study Pseudomonas syringae population dynamics in susceptible and resistant plant environments. Plasmid pGLITE, containing the luxCDABE genes from Photorhabdus luminescens, was introduced into Pseudomonas syringae pv. phaseolicola race 7 strain 1449B, a Gram-negative pathogen of bean (Phaseolus vulgaris). Bacteria recovered from plant tissue over a five-day period were enumerated by counting numbers of colony forming units and by measurement of bioluminescence. Direct measurement of bioluminescence from leaf disc homogenates consistently reflected bacterial growth as determined by viable counting, but also detected subtle effects of the plant resistance response on bacterial viability. This bioluminescence procedure enables real time measurement of bacterial metabolism and population dynamics in planta, obviates the need to carry out labour intensive and time consuming traditional enumeration techniques and provides a sensitive assay for studying plant effects on bacterial cells.

Não preferência para alimentação e aspectos biológicos de Spodoptera eridania em cultivares de feijão-caupi

The aim of this paper was to evaluate the no-preference for feeding and biological aspects of Spodoptera eridania fed on cowpea cultivars BR17 Gurgueia, BRS Urubuquara, BRS Nova Era, Sempre Verde, BRS Milenio and BR3 Tracuateua. In free-choice test, leaf discs were placed in Petri dishes where one third instar larvae per cultivar was released, whereas in no-choice test one leaf disc was placed per Petri dish where one caterpillar per cultivar was released, evaluating their attractiveness after 1, 3, 5, 10, 15, 30, 60, 120, 360 and 720 minutes, as well as the leaf area consumed. Randomized blocks and complete randomized blocks design were used for free-choice and no-choice tests, respectively, with six treatments and 10 replications. The evaluation of the biological parameters of S. eridania was carried out in Petri dishes where recently hatched caterpillars were transferred in the proportion of one per dish, and the leafs of the cultivars were offered to them during the whole larval period, and we evaluated: periods and viabilities of larvae and pupae, overall viability, weight of larvae and pupae, sex ratio, longevity and overall cycle. Complete randomized design was used with six treatments and 30 replications. In no- preference for feeding free-choice test the cultivars Sempre Verde and BR17 Gurgueia were the most and the least consumed, respectively. Regarding the effects of cowpea cultivars on larval viability we can infer that BRS Urubuquara and Sempre Verde show antibiosis-type resistance to S. eridania.

Feeding of Spodoptera eridania (Lepidoptera: Noctuidae) on soybean genotypes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biologia de aphis gossypii em plantas infectadas pelo vírus do mosaico das nervuras do algodoeiro

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Indirect method for quantifying the content of photosynthetic pigments in genotypes of dwarf elephant grass

O objetivo deste ensaio foi determinar equações que indiretamente associem os valores obtidos no medidor de clorofila SPAD-502 aos teores de clorofila e carotenóides de genótipos de capim-elefante anão. Folhas de genótipos de capim-elefante anão foram utilizadas e, depois de coletadas, foram transportadas em caixas de isopor, protegidas da luz, até o laboratório de Fisiologia Vegetal da UENF. Posteriormente, os discos foliares de área conhecida foram extraídos. Com o auxílio do medidor portátil de clorofila (MPC) SPAD-502, foi obtida a média de 5 leituras/disco foliar e utilizaram-se 6 discos para cada intervalo, distribuídos de acordo com a seguinte escala de valores do MPC: 0-10; 10-20; 20-30; 30-40; 40-50; 50-60. O medidor de clorofila SPAD-502 possibilitou uma rápida e eficaz estimativa do conteúdo de clorofila total, clorofila-a e clorofila-b em genótipos de capim-elefante anão.

Efeito de cultivares de repolho e doses de extrato aquoso de nim na alimentação e biologia de Plutella xylostella (linnaeus) (lepidoptera: Plutellidae)

The isolated and associated effects of cabbage cultivars Ruby Ball and Chato de Quintal and aqueous extract of seeds of fruits of neem (Azadirachta indica A. Juss.) were evaluated in the concentrations of 5 and 10% on Plutella xylostella (L.) attractiveness, feeding and development. In free-choice no-preference for feeding test, leaf discs of each treatment were placed in Petri dishes where three caterpillars/treatment were released while in no-choice test two caterpillars were placed in Petri dishes with one leaf disc in each dish. In the biology test, neonate larvae were transferred to Petri dishes in the proportion of one per dish, whereas the biological parameters were evaluated: larvae mortality after 1, 3 and 5 days; pupae mortality; total mortality; six day-old larvae weight; 24 hour-old pupae; and adult longevity. Cultivar Ruby Ball showed lower attractiveness to the caterpillars in free-choice test. Neem extract in both concentrations was repellent to the caterpillars in free-choice test. There were no differences in the dry mass consumed by the caterpillars in free-choice and no-choice tests. There were no differences in larval, pupal and total mortality between the cultivars. Both doses of neem extract were equally efficient in the mortality of the diamondback moth. There were no differences in caterpillars and pupae weight and in the longevity of the adults of P. xyostella between the cultivars.

Tipos e graus de resistência de genótipos de soja a Spodoptera eridania (Cramer, 1782) (Lepidoptera: Noctuidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)