Control of anthracnose in papaya fruits by acetylsalicylic acid and 1-methylcyclopropene / Controle da antracnose em mamão por ácido acetil salicílico e 1-metilciclopropeno

This study assessed the effect of acetylsalicylic acid (ASA) and 1-methylcyclopropene (1-MCP) to control anthracnose in papaya (cultivar Golden). Disinfested-surface fruits were inoculated with Colletotrichum gloeosporioides and then the compounds were applied. The lesion diameters and the physical-chemical properties were analyzed. Assays were carried out with ASA and 1-MCP targeting the control of anthracnose and maintenance of the fruit's physical-chemical properties. The effect of ASA (20 mM; 20 min) on reducing lesion diameter occurred when applied before inoculation. Fruits treated with 1-MCP (300ppb) for 12 h showed a smaller lesion diameter than control. For the physical-chemical analysis, fruit treated with 1-MCP (200; 300 ppb; 12h) maintained fruit firmness, delayed fruit ripening and fruit fresh weight loss.

Neste trabalho avaliou-se o efeito do ácido acetilsalicílico (ASA) e 1-metilciclopropeno (1-MCP) no controle da antracnose do mamão (cv Golden). Para isso o Colletotrichum gloeosporioides foi inoculado em frutos superfícialmente desinfestados para depois aplicar-se os compostos. O diâmetro das lesões e as características físico-químicas foram determinadas. Os ensaios foram conduzidos com ASA e 1-MCP visando o controle da antracnose e a manutenção das características físico-químicas do fruto. O efeito do AAS (20 mM; 20 min) na redução do diâmetro da lesão ocorreu quando aplicado antes da inoculação. Frutos tratados com 1-MCP (300 ppb) por 12 horas apresentaram menor diâmetro de lesão que controle. Para a análise físico-química, frutos tratados com 1-MCP (200; 300 ppb; 12h) mantiveram a firmeza, o amadurecimento tardio e a perda de massa fresca dos frutos.

Correction to: Evaluation of microbial communities in peels of Brazilian tropical fruits by amplicon sequence analysis.

The original version of this article unfortunately contained two mistakes in the "Materials and methods" section, subsection "DNA extraction and PCR" of the article. The correct information is given below.

Evaluation of microbial communities in peels of Brazilian tropical fruits by amplicon sequence analysis.

Elucidation of the distinctive microbial taxonomic profiles of tropical fruit peels is the indispensable component of investigations aimed at the detection of microorganisms responsible for the post-harvest loss. The objective of the present work was to dissect the bacterial and fungal community of five tropical fruit peels (banana, guava, mango, papaya, and passion fruit) in wild (non-cultivated) and conventionally produced samples from Brazil. To that end, 16S rRNA-encoding gene and ITS rDNA amplicon analysis of the five tropical fruit peels were performed to discriminate the bacterial and fungal communities, respectively. The result showed that bacterial communities of the five types of fruit peels were by far more diversified than that of fungal communities, independent of the type of production system involved. Among the investigated fruits, non-cultivated papaya peels hosted the most diversified bacterial community while the least bacterial community diversity was found in the conventionally produced papaya fruit peels. The gene amplicon analysis clearly discriminated the bacterial community into their respective classes, while fungal communities were better classified in their phyla, yet with clearer component discrimination of fungal community based on the type of cultivation system practiced. Conventionally produced banana and non-cultivated passion fruit peels were characteristically dominated by fungal and bacterial groups, respectively. Overall, in conventionally produced fruit peels, bacterial community was mainly composed of Proteobacteria, Actinobacteria, and Bacilli. The result provided a broad microbial diversity profile that could be used as an important input for seeking alternative fruit spoilage control and post-harvest treatments.

Seasonal Variation of Plant Mineral Nutrition in Fruit Trees

Abstract This research evaluated the monthly variation of plant mineral nutrition in six species of fruit trees over a year. Leaf samples were taken from the fruit trees and nutritional status (N, P, K, Ca, Mg, Fe, Zn, Cu, Mn, and Mo) was determined in the leaves in a month basis from April until November for apple, persimmon and peach. Mandarin mineral nutrition was monitored for one year, and grape and fig from May to November. Using this data, the Diagnosis Recommendation Integrated System (DRIS) was also calculated to evaluate the nutrient balance in the plants. The concentration of N and P had seasonal differences, especially in apple and peach, which reached the peak during the summer. Apple, fig, and grape trees had large ranging on their mineral contents over the year, especially with the P and K levels reaching the minimum during the harvesting season. However, the seasonal changes in leaf micronutrient concentrations were not uniform and not affected by phenological stage. The DRIS data demonstrated that mandarin had the best nutrient balance compared to others and that K was the most limiting element among the fruit trees. In summary, the current data suggest the occurrence of a significant seasonality in mineral nutrition in these six fruit trees, especially in temperate ones.

Arbuscular mycorrhizal fungal spores host bacteria that affect nutrient biodynamics and biocontrol of soil-borne plant pathogens.

The aim of this research was to isolate and characterize bacteria from spores of arbuscular mycorrhizal fungi (AMF). We designated these bacteria 'probable endobacteria' (PE). Three bacterial strains were isolated from approximately 500 spores of Gigaspora margarita (Becker and Hall) using a hypodermic needle (diameter, 200 µm). The bacteria were identified by morphological methods and on the basis of ribosomal gene sequences as Bacillus sp. (KTCIGM01), Bacillus thuringiensis (KTCIGM02), and Paenibacillus rhizospherae (KTCIGM03). We evaluated the effect of these probable endobacteria on antagonistic activity to the soil-borne plant pathogens (SBPPs) Fusarium oxysporum f. sp. lactucae MAFF 744088, Rosellinia necatrix, Rhizoctonia solani MAFF 237426, and Pythium ultimum NBRC 100123. We also tested whether these probable endobacteria affected phosphorus solubilization, ethylene production, nitrogenase activity (NA), and stimulation of AMF hyphal growth. In addition, fresh samples of spores and hyphae were photographed using an in situ scanning electron microscope (SEM) (Quanta 250FEG; FEI Co., Japan). Bacterial aggregates (BAs), structures similar to biofilms, could be detected on the surface of hyphae and spores. We demonstrate that using extraction with an ultrathin needle, it is possible to isolate AMF-associated bacterial species that are likely derived from inside the fungal spores.

Evaluation of the mycelial network formed by arbuscular mycorrhizal hyphae in the rhizosphere of papaya and other plants under intercropping system

An experiment was carried out under greenhouse conditions to observe the distribution of arbuscular mycorrhizal (AM) hyphae in the rhizosphere of papaya and other plants under intercropping system. Special acrylic root boxes with three compartments, separated by nylon mesh screens, were constructed. One outer compartment contained seedlings of papaya (Carica papaya L.) and other contained seedlings of bahiagrass (Paspalum notatum Flügge) or millet (Pennisetum glaucum L. R. Br.). The central compartment was inoculated with an AM fungus (Gigaspora margarita). In another experiment, the outer compartments were treated with 25 percent MeOH eluates of bahiagrass (BRE) and millet (MRE) root extracts. A control box, containning only papaya seedlings was also prepared. Hyphal density, root infection levels and spore numbers were higher in the bahiagrass and millet compartments than in the papaya compartment. Similar results were found for the percentage of AM infection and the number of AM spores. In the compartments treated with BRE and MRE the density of AM hyphae was around 20 percent, and a few spores were found in those compartments. Few AM hyphae and spores were observed in the control compartment.