Characterization of Colletotrichum Species Causing Anthracnose of Pomegranate in the Southeastern United States

Anthracnose fruit rot and leaf blight caused by Colletotrichum species are important diseases of pomegranate in the southeastern United States. In this study, 26 isolates from pomegranate were identified based on pathological and molecular characterization. Isolates were identified to species based on multilocus sequence analysis with the internal transcribed spacer region, glyceraldehyde-3-phosphate dehydrogenase, β-tubulin, and chitin synthase genomic genes. Pomegranate isolates grouped within the C. acutatum and C. gloeosporioides species complexes, with more than 73% belonging to the latter group. Three species were identified within the C. acutatum species complex (C. nymphaeae [n = 5], C. fioriniae [n = 1], and C. simmondsii [n = 1]), and three other species were identified within the C. gloeosporioides species complex (C. theobromicola [n = 11], C. siamense [n = 6], and C. gloeosporioides [n = 2]). Inoculations of pomegranate fruit showed that isolates from the C. acutatum species complex were more aggressive than isolates from the C. gloeosporioides species complex. Interestingly, opposite results were observed when leaves of rooted pomegranate cuttings were inoculated. In addition, Colletotrichum isolates from pomegranate, strawberry, blueberry, mango, and citrus were cross-pathogenic when inoculated to fruit. This is the first study identifying six different species of Colletotrichum causing pomegranate leaf blight and fruit anthracnose in the southeastern United States and the potential cross-pathogenic capability of pomegranate isolates to other commercially important crops.

Cohnella endophytica sp. nov., a novel endophytic bacterium isolated from bark of Sonneratia apetala

A Gram-stain-positive, aerobic, rod-shaped, endospore-forming bacterium, designated strain M2MS4P-1^T, was isolated from surface-sterilized bark of Sonneratiaapetala sampled in Guangxi, China. The bacterium was characterized by a polyphasic approach to determine its taxonomic position. 16S rRNA gene sequence comparisons revealed that strain M2MS4P-1^T belonged to the genus Cohnella and was most closely to Cohnella luojiensis HY-22R^T (98.4 % similarity). The average nucleotide identity value and estimated DDH value between strain M2MS4P-1^T and the type strain of C. luojiensis HY-22R^T were 79.2 and 20.1 %, respectively. Neither substrate nor aerial mycelia were formed, and no diffusible pigments were observed on the media tested. Strain M2MS4P-1^T grew in the pH range 6.0-9.0 (optimum, pH 7.0-8.0), at temperatures between 10-37 °C (30 °C) and in 0-1 % (w/v) NaCl (0 %). The predominant isoprenoid quinone in strain M2MS4P-1^T was menaquinone-7. The major fatty acids were anteiso-C15 : 0 and iso-C16 : 0. The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, lysyl-phosphatidylglycerol, four unidentified aminophospholipids and two unidentified phospholipids. The DNA G+C content was 51.5 mol%. According to the phylogenetic, phenotypic and chemotaxonomic evidence, strain M2MS4P-1^T was clearly distinguishable from other species with validly published names in the genus Cohnella and should therefore be classified as a novel species, for which we suggest the name Cohnellaendophytica sp. nov. The type strain is M2MS4P-1^T (=KCTC 43011^T=CGMCC 1.13745^T).

Factors Affecting the Response of Pomegranate Fruit to Alternaria alternata, the Causal Agent of Heart Rot

Heart rot, caused by Alternaria alternata, is a major pomegranate disease that impacts production worldwide; most fruits in orchards are colonized by A. alternata but, nevertheless, symptoms are apparent on only a small proportion of the colonized fruits. During the years of our previous research it was noticed that within individual orchards, the incidence of pomegranate fruits exhibiting heart rot symptoms was related to the visual appearance of the trees: trees that appeared visually frail bore more diseased fruits than robust trees. Furthermore, it was noticed that the disease responses of different pomegranate accessions and possibly of different variants of the same cultivar varied markedly. The specific objectives of the present study were: (i) to characterize the relationship between the visual appearance of pomegranate plants or individual stems and the incidence of heart rot and their vulnerability to heart rot; and (ii) to elucidate factors affecting the response of pomegranate fruit to A. alternata. Analysis of heart rot incidence in four orchards in 2014 revealed large differences in heart rot incidence among trees growing side by side in the same orchard; these differences were related to the visual appearance of the pomegranate trees. There were significant differences among germination rates of A. alternata spores in juice prepared from asymptomatic fruits originating from these trees, and comparable differences were found among the acidity levels (pH) of the juices. These differences may reflect differences among the physiological responses of pomegranate trees to heart rot. Fruits collected from the pomegranate collection located in Newe Ya'ar, which comprised 95 accessions in 2015 and 110 accessions in 2016, were also examined. There were differences among the acidity levels (pH) of the juices produced from these fruits and among the germination rates of A. alternata spores in the juices. These differences may reflect variances among the genetic responses of pomegranate accessions to heart rot. Results of studying the relationship between the acidity levels of pomegranate juice and the germination rates of A. alternata spores supported the hypothesis that, apart from pH, a compound(s) present in the juice regulates the germination of A. alternata spores in the juice.

Effects of fludioxonil, propolis and black seed oil application on the postharvest quality of "Wonderful" pomegranate

Pomegranate fruit consumption has increased rapidly throughout the world, mainly because of its medical and nutritive attributes. Thus, considerable commercial and scientific interest exists in prolonging its postharvest life with non-chemical applications as much as possible to meet the year-round demand for this fruit. The present work aimed to study the effects of black seed oil (0.1% and 0.5%), propolis (0.01% and 0.1%) and fludioxonil (0.06%), with and without modified atmosphere packaging (MAP), on the postharvest quality of pomegranate cv. Wonderful. Treated fruits were stored at 6.5±1 °C and 90-95% relative humidity for 150 days. The results indicated that both black seed oil and propolis treatments significantly influenced the maintenance of fruit weight and quality. At 150 days after storage, the fruit weight loss of the samples treated with MAP + 0.5% black seed oil, MAP + 0.1% propolis and MAP alone were found to be 5.5%, 6.3%, and 9.1%, respectively, whereas the weight loss of the untreated control fruits was 19.8%. Application of either 0.5% black seed oil or 0.1% propolis, especially when combined with MAP, was also effective in controlling gray mold development and slowing the occurrence of chilling injury.

Xanthomonas axonopodis pv. punicae uses XopL effector to suppress pomegranate immunity

Xanthomonas axonopodis pv. punicae (Xap) causing bacterial blight is an important pathogen that incurs significant losses to the exportability of pomegranate. Xap uses the Xop TTSS-effector, via the type three secretion system, to suppress pomegranate immunity. Here, we investigate the role of XopL during blight pathogenesis. We observed that XopL is essential for its in planta growth and full virulence. Leaves inoculated with Xap ΔxopL produced restricted water-soaked lesions compared to those inoculated with wild-type Xap. XopL supports Xap for its sustained multiplication in pomegranate by suppressing the plant cell death (PCD) event. We further demonstrated that XopL suppresses immune responses, such as callose deposition and production of reactive oxygen species (ROS). RT-qPCR analysis revealed that immune responsive genes were upregulated when challenged with Xap ΔxopL, whereas upregulation of such genes was compromised in the complemented strain containing the xopL gene. The transiently expressed XopL::EYFP fusion protein was localized to the plasma membrane, indicating the possible site of its action. Altogether, this study highlights that XopL is an important TTSS-effector of Xap that suppresses plant immune responses, including PCD, presumably to support the multiplication of Xap for a sufficient time-period during blight disease development.

Influence of Fermentation with Different Lactic Acid Bacteria and in Vitro Digestion on the Biotransformation of Phenolic Compounds in Fermented Pomegranate Juices

This study describes the effect of fermentation and the impact of simulated gastrointestinal digestion (SGD) of four fermented pomegranate juices with different lactic acid bacteria (LAB) on the biotransformation of phenolic compounds. The changes of the antioxidant capacity (AOC) and of LAB growth and survival in different fermented juices were also studied. Two new phenolic derivatives (catechin and α-punicalagin) were identified only in fermented juices. During SGD, the AOC increased together with the phenolic derivatives concentration mainly in the juices fermented with Lactobacillus. These derivatives were formed due to the LAB metabolism of the ellagitannins, epicatechin, and catechin after fermentation and during SGD. The FRAP assay performance might be associated with the degradation and biotransformation of catechin. The fermented pomegranate juices with these LAB increased the bioaccessibility of phenolic compounds, ensuring the survival of LAB after SGD, suggesting a possible prebiotic effect of phenolic compounds on LAB.

Development of a nested-PCR assay for the rapid detection of Pilidiella granati in pomegranate fruit

Pilidiella granati, a causal agent of twig blight and crown rot of pomegranate, is an emerging threat that may cause severe risk to the pomegranate industry in the future. Development of a rapid assay for the timely and accurate detection of P. granati will be helpful in the active surveillance and management of the disease caused by this pathogen. In this study, a nested PCR method was established for the detection of P. granati. Comparative analysis of genetic diversity within 5.8S rDNA internal transcribed spacer (ITS) sequences of P. granati and 21 other selected fungal species was performed to design species-specific primers (S1 and S2). This primer pair successfully amplified a 450 bp product exclusively from the genomic DNA of P. granati. The developed method can detect 10 pg genomic DNA of the pathogen in about 6 h. This technique was successfully applied to detect the natural infection of P. granati in the pomegranate fruit. The designed protocol is rapid and precise with a high degree of sensitivity.

Polyketides with Immunosuppressive Activities from Mangrove Endophytic Fungus Penicillium sp. ZJ-SY₂

Nine polyketides, including two new benzophenone derivatives, peniphenone (1) and methyl peniphenone (2), along with seven known xanthones (3-9) were obtained from mangrove endophytic fungus Penicillium sp. ZJ-SY₂ isolated from the leaves of Sonneratia apetala. Their structures were elucidated on the basis of MS, 1D, and 2D NMR data. Compounds 1, 3, 5, and 7 showed potent immunosuppressive activity with IC₅₀ values ranging from 5.9 to 9.3 μg/mL.

[Diversity and cytotoxic activity of endophytic bacteria isolated from Sonneratia apetala of Maowei Sea]

OBJECTIVE

The purpose of this study was to study the distribution, diversity and cytotoxic activity of endophytic bacteria of Sonneratia apetala collected from Maowei Sea, Qinzhou city.

METHODS

The 16S rRNA gene sequencing and MTT were used to explore the diversity and cytotoxic activity of endophytic bacteria isolated from different organs and tissues of Sonneratia apetala.

RESULTS

Total of 38 isolates were obtained. The result of diversity analysis showed that these isolates could be phylogenetically classified into 21 genera and 12 families, based on their 16S rRNA gene sequencing. Of them 5 were potential new genera or new genus. Five strains (R74, R71, S92, S85 and S84) had cytotoxic activity against human liver carcinoma Hep G2 cell line.

CONCLUSION

Endophytic bacteria of Sonneratia apetala are genetically diverse and most of them have abundant new bioactivities.

Quality changes of fresh-cut pomegranate arils during shelf life as affected by deficit irrigation and postharvest vapour treatments

BACKGROUND

The effect of two sustained deficit irrigation (SDI) strategies, compared to a control, on postharvest physicochemical, microbial, sensory quality attributes and anthocyanin content of fresh-cut pomegranates arils throughout 18 days at 5 °C was studied. Furthermore, the effect of vapour treatments (4, 7 and 10 s) compared to a conventional sanitizing treatment with NaClO on such quality parameters in combination with the preharvest treatments was also studied.

RESULTS

According to sensory analyses, the shelf life of arils from control and SDI-irrigated fruit was established in 14 and 18 days at 5 °C, respectively, showing 4 and 7 s vapour treatment time the best sensory quality. No significant change was observed in physicochemical quality attributes, across all treatments during storage, while low microbial loads were registered (<3 log CFU g(-1)) after shelf life. Postharvest treatments that had least effect on anthocyanin content on processing day were 7 and 10 s.

CONCLUSION

Vapour treatments of 7-10 s applied to pomegranate arils led to an extended shelf life up to 18 days at 5 °C with better results in SDI-irrigated samples with a water saving of 6-11%.

Swarm motility of Salmonella enterica serovar Typhimurium is inhibited by compounds from fruit peel extracts

Controlling spread of human pathogens on fresh produce is a top priority for public health reasons. Isolation of compounds from agricultural waste that would control spread of human pathogens was explored using Salmonella enterica serovar Typhimurium as a model organism. In the environment, micro-organisms migrate as a 'community' especially when they move on moist surfaces. This type of motility is characterized as swarming motility. We examined extracts from agricultural waste such as soya bean husk, peels of orange, pineapple, avocado and pomegranate for antiswarming activity. Avocado and pineapple peels showed moderate (~40%) inhibition of swarming motility while pomegranate peel extract had high antiswarming activity (~85% inhibition) and was examined in further detail. Although the pomegranate peel extract was acidic, swarm-inhibitory activity was not due to low pH and the peel extract did not inhibit growth of Salmonella. Among the key swarm motility regulatory genes, class II (fliF, fliA, fliT and fliZ) and class III (fliC and fliM) regulators were downregulated upon exposure to pomegranate peel extract. Pomegranate peels offer great potential as a bioactive repellent for pathogenic micro-organisms on moist surfaces.

SIGNIFICANCE AND IMPACT OF THE STUDY

Controlling the spread of food-borne pathogens in moist environments is an important microbial food safety issue. Isolation of compounds from agricultural waste (such as fruit peels) that would control spread of human pathogens was explored using Salmonella enterica serovar Typhimurium as a model organism. Pomegranate peels offer great potential as a bioactive repellent for pathogenic micro-organisms.

Hot water, UV-C and superatmospheric oxygen packaging as hurdle techniques for maintaining overall quality of fresh-cut pomegranate arils

BACKGROUND

In recent years there has been increasing consumer pressure to avoid the use of agrochemicals such as chlorine on fresh plant products for extending their shelf life. The combined use of eco-sustainable techniques may be an alternative. The effect of hot water (HW), ultraviolet-C (UV-C) light and high oxygen packaging (HO) on the overall quality of fresh-cut pomegranate arils stored under modified atmosphere packaging (MAP) for up to 14 days at 5 °C was studied.

RESULTS

Arils extracted manually, washed with chlorine (100 µL L⁻¹ NaClO, pH 6.5, 5 °C water), rinsed and drained were exposed to single or combined (double and triple) hurdle techniques. The HW treatment consisted of a 30 s immersion in water at 55 °C followed by air surface drying. A 4.54 kJ m⁻² dose was used for the UV-C treatment before packaging. Active MAP with initial 90 kPa O₂ was used in the HO treatment. The respiration rate remained relatively constant throughout shelf life, with no differences among treatments. CO₂ accumulation was higher within HO packages. HW induced a slight reduction in total soluble solids, while no changes in titratable acidity were found. HO-treated arils had the highest phenolic content, while the lowest was found in HW-treated arils. The lowest antioxidant activity was found in HW + UV-C + HO and the highest in UV-C + HO and HO treatments. HW alone or in combination with UV-C and HO inhibited mesophile, mould and yeast growth, while UV-C + HO was most effective for controlling yeast and mould growth.

CONCLUSION

UV-C and HO either alone or in combination are promising techniques to preserve the quality of pomegranate arils for up to 14 days at 5 °C.

Effect of chitosan coating on maintenance of aril quality, microbial population and PPO activity of pomegranate (Punica granatum L. cv. Tarom) at cold storage temperature

BACKGROUND

Chitosan edible coating was used in an attempt to extend the storage life of pomegranate arils during 12 days at 4 °C. Prior to storage, treated arils were dipped in 0.25, 0.5 and 1% (w/v) chitosan aqueous solutions and 1% (v/v) acetic acid for 1 min, while control arils were dipped in distilled water with 1% (v/v) acetic acid.

RESULTS

Chitosan coating inhibited bacterial and fungal growth on the surface of arils. The water content of arils coated with 0.5 and 1% chitosan was maintained during 12 days of storage. Chitosan reduced the increase in total soluble solids (TSS) and titratable acidity (TA) of arils during storage. The lowest TSS and TA were detected in arils coated with 0.5 and 1% chitosan, which maintained the highest TSS/TA ratio after 12 days of storage. In contrast, application of chitosan delayed the decrease in total phenolics, total anthocyanins and antioxidant capacity during storage. The results also showed that chitosan coating suppressed the monophenolase activity of polyphenol oxidase (PPO) with pyrogallol substrate and the diphenolase activity of PPO with dopamine hydrochloride substrate, but the diphenolase activity of PPO with pyrocatechol substrate increased during storage.

CONCLUSION

The results suggest that chitosan coating has the potential to extend the storage life of pomegranate arils by reducing the microbial population on their surface.

[Isolation of Cryptococcus neoformans from living tree trunk hollows in Denizli City Center, Turkey]

Cryptococcus neoformans is a basidiomycetous yeast leading to life-threatening infections in human and animals. It has been isolated from decaying hollows and fissures from various tree species in different parts of the world. The isolation of the yeast from the environment is less in the eastern part of Mediterranean area. Only one C. neoformans strain from debris of Eucalyptus camaldulensis in the blossoming period, has been reported by consecutive studies done in suspected areas since the last 10 years. In this study, 300 tree including trunk hollows and fissures have been screened for colonization of C. neoformans in Denizli city (located on Aegean part of Turkey) center during july 2008. All samples has been collected by swabbing technique and cultured on minimal Staib agar medium (without creatinine and potassium dihydroden phosphate). Two (0.6%) strains of C. neoformans have been isolated from the total of 300 screened trees. One of these isolates was from Platanus orientalis (plane tree; n = 92) and one from Punica granatum (pomegranate tree; n = 2). Six and three colonies per plate have been isolated from P. orientalis and P. granatum samples, respectively. C. neoformans has not been isolated in the repeat cultures done in the following two months. Although C. neoformans was isolated from previously unac-complished niches in this study, our results suggested that C. neoformans colonization of trees trunk hollows and fissures was not common in Denizli city center.

Penicillium Implicatum Causes a Destructive Rot of Pomegranate Fruits

In this study Penicillium implicatum Biourge was found to be the cause of a destructive rot of stored pomegranate (Punica granata) fruits. This species has not previously been reported to cause disease of the fruit. The ability of the strain to decay pomegranates as well as some varieties of apples (Jonagold, Selena and Vanda) under laboratory conditions after inoculation with conidia into the subcutaneous layer of healthy fruits was demonstrated. The fungus was also found on mouldy stamens of pomegranates.