Postharvest of ‘Fuerte’ and ‘Hass’ avocados: physical and chemical characteristics, damages and control of diseases

Doença pós-colheita é considerada uma importante causa de desvalorização do abacate por ocasião da comercialização. Este trabalho objetivou avaliar os danos pós-colheita e as características físicas e químicas de abacates ‘Fuerte’ e ‘Hass’, beneficiados em packinghouse, e o efeito de produtos no controle pós-colheita das podridões. As características cor da casca, firmeza, acidez titulável e sólidos solúveis e a incidência dos danos pós-colheita foram avaliadas periodicamente, em abacates amostrados em três etapas do beneficiamento (chegada, beneficiados no palete e beneficiados após armazenamento a 5ºC por 30 dias). Para o controle das doenças testou-se por imersão os seguintes produtos: azoxistrobina, cloreto de benzalcônio, dióxido de cloro, Ecolife®, hipoclorito de sódio, imazalil, procloraz e tiabendazol. Em geral, as maiores alterações físicas e químicas foram observadas nos frutos amostrados na chegada ao packinghouse e nos frutos beneficiados, armazenados por 30 dias. A ocorrência de podridões foi de 56,7% em abacate ‘Fuerte’ e de 75,7% em ‘Hass’ aos 15 dias de armazenamento a 25ºC. Menor incidência de podridões foi observada nos frutos do palete e uma maior incidência nos frutos beneficiados, após armazenamento refrigerado. A antracnose foi a principal doença nas duas cultivares. As injúrias mecânicas foram crescentes com o beneficiamento, entretanto, não influenciaram no aparecimento das podridões. Os fungicidas procloraz e imazalil foram os mais eficientes em reduzir a incidência das podridões.  Postharvest disease is considered an important cause of avocado depreciation during its commercialization. This work aimed to evaluate the postharvest damages and the physical chemical characteristics of avocados ‘Fuerte’ and ‘Hass’, processed at the packinghouse, and to evaluate the effect of products for postharvest disease control. The characteristics skin color, firmness, titratable acidity and soluble solids content and the incidence of the postharvest damages were evaluated periodically in avocados sampled in three different stages in a packinghouse (arrival, pallet and processed fruits after storage for 30 days at 5ºC). For diseases control, ‘Hass’ avocado were treated by immersion with the following products: azoxystrobin, benzalkonium chloride, chlorine dioxide, Ecolife®, sodium hypochlorite, imazalil, prochloraz and thiabendazole. In general, the highest physical chemical changes were observed in fruits collected at their arrival to the packinghouse and in processed fruits after stored for 30 days at 15 days of storage at 25°C. The rots incidence was 56,7% in ‘Fuerte’ and 75,7% in ‘Hass’. Lower incidence of rots was observed in fruits sampled at the pallet and a higher incidence in the processed fruits, after refrigerated storage. Anthracnose was the most important disease in both cultivars. The mechanical injuries increased with the processing stages; however, they did not influence the incidence of the rots. Procloraz and imazalil were the most efficient fungicides in reducing the incidence of rots

Etiology and pathogenicity of two different isolates of Colletotrichum spp. obtained from physic nut seeds

The species known as physic nut (Jatropha curcas L.) has become important as one of main sources of feedstock for biodiesel production. The aims of this study were characterizing two different isolates of Colletotrichum spp. obtained from seeds of this species, through morphological, cultural, and molecular analyses; as well as assessing pathogenicity of both isolates on leaves and fruit of this plant species. For morphological analysis, length and width of 30 spores of each isolate, produced on medium Malt Extract-Agar (MEA), at 25 ± 1 ºC, and under constant light, were measured. Cultural analysis was performed by the fungus growth on PDA medium, through daily measurements of the mycelial growth, and the color of colonies after seven days incubation. DNA of the isolates was extracted and specific oligonucleotides primers (region ITS4) were identified by PCR and used to identify C. capsici (CcInt) and C. gloeosporioides (CgInt). Pathogenicity of isolates was assessed on plants aged 10, 20, 30, 40, 50, and 60 days after sowing and fruits at six maturation stages. Based on these analyses, isolates were identified as C. gloeosporioides and C. capsici. Young plants and the older fruits were more susceptible to infection by the two fungus species

Comportamento de Ceratocystis sp. in vitro sob diferentes temperaturas, meios de cultura e pH

The genus Ceratocystis fungus is a cosmopolitan and in Brazil the main species is C. fimbriata, which causes disease in many plants of great economic importance. The study aimed to evaluate the mycelial growth in the media: Oats, BDA, MEA, AA, CE, CEA, and V8-A. For this we used 14 isolates of Ceratocystis from different hosts. The colonies were incubated at 30 ° C under a photoperiod alternating, 25oC, 20oC and 15oC. As for the study on the effect of pH on the mycelial growth of Ceratocystis isolates were used 6. The colonies were incubated in alternating photoperiod (12h) at 25 ° C ± 2. The tests were performed on MEA medium (malt, yeast extract and agar) with different pH ranges: 5, 7 and 9. In all experiments each treatment consisted of four replicates in a randomized design. Evaluations were performed daily until the first contact one of the colonies with the edge of the board, through measurements of diameters of each colony. The means were the CE and CEA that provided better growth to the fungus at all temperatures, since the middle of oats and AA were the fungus had lower growth. The fastest growth was observed in the temperature of 25oC. Most of the isolates did not produce sexual structures through AA. The best growth for isolated eucalyptus and teak was observed in medium with pH 7, while for the isolated cocoa showed no significant difference between the different pH ranges worked.O gênero Ceratocystis é um fungo cosmopolita sendo que no Brasil a principal espécie é C. fimbriata, causadora de doenças em muitas plantas de grande importância econômica. O trabalho objetivou avaliar o crescimento micelial nos meios: Aveia, BDA, MEA, AA, CE, CEA e V8-A. Para isso foram utilizados 14 isolados de Ceratocystis de diferentes hospedeiros. As colônias foram incubadas sob fotoperíodo alternado a 30oC, 25oC, 20oC e 15oC. Já para o estudo referente ao efeito do pH sobre o crescimento micelial de Ceratocystis foram usados 6 isolados. As colônias foram incubadas em fotoperíodo alternado (12h) a 25oC±2. Os testes foram realizados em meio MEA (Malte, extrato de levedura e Agar) com diferentes faixas de pH: 5, 7 e 9. Em todos os experimentos cada tratamento foi constituído de quatro repetições, em delineamento inteiramente casualizado. Realizaram-se avaliações diárias até o primeiro contato de uma das colônias com a borda da placa, através de mensurações de diâmetros de cada colônia. Os meios CE e CEA foram os que propiciaram melhor crescimento ao fungo em todas as temperaturas, já meio de aveia e AA foram os que o fungo teve menor crescimento. A maior velocidade de crescimento foi observada na temperatura de 25oC. A maioria dos isolados não produziu estruturas sexuais em meio AA. O melhor crescimento para isolados de eucalipto e teca foi observado em meio com pH 7, já para o isolado de cacau não apresentou diferença significativa entre as diferentes faixas de pH trabalhadas

Characterization of Ceratocystis fimbriata from passion fruits

ABSTRACT: Passion fruits (Passiflora edulis ) were found with symptoms of rot in the field, in the city of Tanhaçu, Bahia. After isolating the pathogen associated with this rot, in the present study we aimed to characterize the Ceratocystis isolate from passion fruit for better understanding this pathosystem. Molecular characterization was done based on the region ITS-5.8S rDNA. Pathogenic characterization was carried out for seedlings and fruits of passionflower. Passion fruit colonization was monitored by means of scanning electron microscopy techniques (SEM). DNA analysis of the Ceratocystis isolate from passionflower pointed out that this species belongs to Ceratocystis fimbriata . The inoculated passionflower seedlings showed injury at 30 days post-inoculation, but no inoculated plant showed wilt or died. Considering fruits, no differences were found for lesions caused by this fungus among cultivars, and lesions had average diameters of 1.0 and 2.2 cm at 7 and 11 days, respectively. The analysis using SEM indicated fungus spore germination and penetration in the fruit between 2 and 6 hours post-inoculation. At 12 and 24 hours post-inoculation, fruit colonization was noted both externally and internally, while fruit wall degradation started at 48 hours post-inoculation. At 90 hours post-inoculation, formation of new perithecia was observed inside and outside the fruit. This study complements the available information about the interaction of this fungus with passion fruit