Delson Laranjeira

IN VITRO ACTIVITY OF ESSENTIAL OILS OF Lippia sidoides AND Lippia gracilis AND THEIR MAJOR CHEMICAL COMPONENTS AGAINST Thielaviopsis paradoxa, CAUSAL AGENT OF STEM BLEEDING IN COCONUT PALMS

Essential oils of Lippia sidoides, Lippia gracilis and their main chemical components were investigated for in vitro control of Thielaviopsis paradoxa. Mycelial growth and a number of pathogen conidia were inhibited by the essential oil of L. sidoides at all concentrations tested (0.2; 0.5; 1.0; 3.0 μL mL-1). L. sidoides oil contained 42.33% thymol and 4.56% carvacrol, while L. gracilis oil contained 10% thymol and 41.7% carvacrol. Mycelial growth and conidial production of T. paradoxa were completely inhibited by thymol at a 0.3 μL m-1 concentration. The results suggest that thymol could potentially be used for controlling coconut stem bleeding.

Physiological cost of induced resistance in cotton plants at different nitrogen levels

Resistance induction through the use of chemical inducers often results in physiological costs to the plant. In this study, induced resistance in cotton plants was evaluated with regard to physiological costs in a cultivar susceptible to Colletotrichum gossypii var. cephalosporioides (CNPA GO 2002 - 7997). Plants were cultivated in substrates with two levels of nitrogen and received two applications of acibenzolar-S-methyl (ASM), jasmonic acid (JA) and Agro-Mos® (AM) disease resistance inducers. Plant height (H), internodal length (IL), shoot fresh weight (SFW), root fresh weight (RFW), shoot dry weight (SDW) and root dry weight (RDW) were evaluated. The activity of the phenylalanine ammonia lyase (PAL) and peroxidase (POX) was also determined. The plants treated with ASM presented high physiological costs with an accentuated reduction in H, SFW and SDW, whereas those treated with JA exhibited a significant increase in SDW, and did not significantly differ from H and IL. In the potting mix supplemented with nitrogen, all inducers differed from the control treatment regarding to internodal length, whereas only ASM and AM presented a significant difference between one another in the potting mix without the addition of nitrogen. Significant correlations (P=0.05) were found for most of the variables analyzed, with greater correlations observed between SFW and SDW (0.94); IL and H (0.74); SFW and H (0.70); and SDW and H (0.70). ASM induced the least amount of PAL activity, significantly differing from the remaining treatments. Greater POX activity was observed in ASM, which significantly differed from the control. AM and JA, however, presented lower activity than the control with regard to these enzymes, and it was not possible to confirm induction resistance in these two treatments.

Reação de genótipos de tomateiro às raças 2 e 3 de Fusarium oxysporum f. sp. lycopersici

A murcha-de-fusario, causada por Fusarium oxysporum f. sp. lycopersici, e uma importante doenca do tomateiro (Solanum lycopersicon L.) no Nordeste brasileiro. Visando selecionar genotipos com potencial de utilizacao no manejo da doenca, foram avaliadas 60 linhagens (geracao F7) oriundas do cruzamento entre o acesso BHRS-2,3 e a cultivar Viradoro, em relacao a isolados das racas fisiologicas 2 e 3 de F. oxysporum f. sp. lycopersici. Os isolados foram inoculados em mudas com 21 dias de idade pelo metodo do corte de raizes e imersao na suspensao de conidios do patogeno. A avaliacao foi realizada apos 21 dias, com o auxilio de escala de notas de 1 a 5, para agrupamento dos genotipos em cinco classes de reacao. A maioria dos genotipos (73,3%) se comportou como altamente resistente ao isolado da raca 2, enquanto 45,0% foram classificados como suscetiveis e 28,3% como altamente suscetiveis ao isolado da raca 3. Somente a linhagem L-1 apresentou reacao de alta resistencia aos dois isolados de ambas as racas. A estabilidade da resistencia dessa linhagem foi avaliada em relacao a cinco isolados de cada raca (2 e 3) do patogeno. A linhagem L-1 apresentou reacao de alta resistencia a todos os isolados da raca 2, evidenciado estabilidade da resistencia. No entanto, em relacao aos isolados da raca 3, essa linhagem apresentou tres classes de reacao distintas, variando de altamente resistente a suscetivel, indicando instabilidade da resistencia a essa raca.

Efficacy of plant extracts for anthracnose control in bell pepper fruits under controlled conditions

Anthracnose is an important disease of bell pepper (Capsicum annuum) in Brazil and worldwide. This research investigated the efficacy of plant extracts for control of this disease in bell pepper fruits caused by Colletotrichum acutatum under controlled conditions and analyzed the best treatments in relation to different extract and inoculum concentrations, pathogen isolates, and temperatures. In the preliminary screening, among aqueous or ethanolic extracts of 16 plant species evaluated, the best were 6% aqueous garlic, mallow, and ginger extracts, which reduced disease severity by more than 97%. Garlic extract required the highest concentrations to reduce severity by 75% (CL75) when compared to ginger and mallow extracts, but exhibited the best efficacy in relation to different inoculum concentrations and isolates of C. acutatum. It was also able to maintain greater than 90% efficacy at 20-30oC. The garlic aqueous extract effectively controlled anthracnose caused by C. acutatum in bell pepper fruits under controlled conditions.

Epidemiological correlation between keratinophilic fungi isolated from soil and dermatomycosis agents

This study had the aim of isolating and identifying keratinophilic fungi from soil and correlating them with dermatomycosis agents. According to our results, the predominance of Trichophyton tonsurans as a dermatomycosis agent among children in the city of Recife, PE, is probably due to childrens greater contact with soil.

Selection of cocoa progenies for resistance to witches’ broom

Witch’s broom (WB) and frost pod rot (FPR) are devastating fungal diseases and responsible for severe losses in cacao trees grown in tropical America. To expand and stabilize the resistance to WB in cacao progenies, as well as to incorporate resistance genes to FPR, 17 genotypes were selected from a structured population. These were used in a second selection cycle, in which four gene donors of FPR resistance were included. All but one of the 59 and 52 progenies differed significantly (P < 0.05) from the susceptible controls Catongo and SIC 23, respectively. Nineteen progenies differed significantly (P < 0.05) from the resistance control SCA 6, suggesting high WB resistance. The direct descendants of cacao genotypes from the Brazilian Amazon and from clones carrying FPR resistance showed lower disease index than the resistant control SCA 6, except for some of the progenies of clone ICS 95, which behaved similarly to the susceptible control. The study highlights nine progenies carrying WB resistance genes from several sources and seven of them from parents carrying frosty pod resistance genes.

Murcha de fusário em helicônia: fontes de resistência, método alternativo de detecção e defesa estrutural

ABSTRACT Heliconia grown as a crop has been affected by wilt, caused by Fusarium oxysporum f.sp. cubense . This work aimed to identifygenetic resistances sources, to evaluated the detection of resistancewith an alternative method and to verify the effects of structuralmechanisms in pathogen resistance. The genotypes evaluated were Heliconia bihai, H. psittacorum cv. Golden Torch, H. psittacorum cv. Golden Torch Adrian, H. rostrata, H. stricta Capri , H.psittacorum cv. Sassy, H. caribea, H. latispatha, H. wagneriana,H. psittacorum cv. Alan Carle, H. stricta cv. Fire Bird and H.chartacea cv. Sexy Pink. These genotypes were inoculated with a F. oxysporum f.sp. cubense isolate and the symptoms wereevaluated 40 days after inoculation, based on an disease ratingscale ranging from 1 to 6. The genotypes considered resistant Castro, N.R.; Coelho, R.S.B.; Laranjeira, D.; Pimentel, R.M. de M.; Ferreira, C.P. Heliconia’s Fusarium wilt: resistance sources, alternativemethod of detection and structural mechanisms.