Diaporthe ambigua Associated with Post-Harvest Fruit Rot of Kiwifruit in Chile

Identification of the Pathogens and Laboratory Bioactivity Determination of the Rot Disease of Kiwifruit (Actinidia spp.)

Kiwifruit is an important economic crop in the world today with a high nutritional value. It can cause huge damage by causing kiwifruit rot disease; however, at present, the control methods for this disease are limited. In this study, the rotten fruits of kiwifruit (Cultivar “Jinyan”) were collected from Pujiang city (Sichuan province), Xixia city, (Henan province), Zhouzhi (Shaanxi province), Meixian city (Shaanxi province), and Bijie (Guizhou province), China, and the pathogenic fungi were identified by isolation and purification, pathogenicity test, morphological characteristics, and analysis of ribosomal DNA internal transcribed spacer (rDNA-ITS) sequences. The results showed that the pathogenic fungi of kiwifruit rot disease were Botryosphaeria dothidea and Dothiorella gregaria. Meanwhile, the in vitro antifungal activity of 11 kinds of fungicides and 5 kinds of plant essential oils against B. dothidea and D. gregaria were determined and the results showed that all the tested fungicides and plant essential oils had a certain inhibitory effect on B. dothidea and D. gregaria. Among them, propiconazole had the best inhibitory effect on B. dothidea with an EC50 value of 4.10 mg/L, and quinolinone had the best inhibitory effect on D. gregaria with the EC50 value of 10.05 mg/L. Moreover, the pesticides and essential oils have practical application values for prevention and treatment of fruit rot diseases pathogens.

Characterization of Botrytis cinerea and B. prunorum From Healthy Floral Structures and Decayed 'Hayward' Kiwifruit During Post-Harvest Storage

Gray mold is the primary postharvest disease of 'Hayward' kiwifruit (Actinidia deliciosa) in Chile, with a prevalence of 33.1% in 2016 and 7.1% in 2017. Gray mold develops during postharvest storage, which is characterized by a soft, light to brown watery decay that is caused by Botrytis cinerea and B. prunorum. However, there is no information on the role of B. prunorum during the development and storage of kiwifruit in Chile. For this purpose, asymptomatic flowers and receptacles were collected throughout fruit development and harvest from five orchards over two seasons in the Central Valley of Chile. Additionally, diseased kiwifruits were selected after storage for 100 days at 0°C and 2 days at 20°C. Colonies of Botrytis sp. with high and low conidial production were consistently obtained from apparently healthy petals, sepals, receptacles, and styles and diseased kiwifruit. Morphological and phylogenetic analysis of three partial gene sequences encoding glyceraldehyde-3-phosphate dehydrogenase, heat shock protein 60, and DNA-dependent RNA polymerase subunit II were able to identify and separate B. cinerea and B. prunorum species. Consistently, B. cinerea was predominantly isolated from all floral parts and fruit in apparently healthy tissue and diseased kiwifruit. During full bloom, the highest colonization by B. cinerea and B. prunorum was obtained from petals, followed by sepals. In storage, both Botrytis species were isolated from the diseased fruit (n = 644), of which 6.8% (n = 44) were identified as B. prunorum. All Botrytis isolates grew from 0°C to 30°C in vitro and were pathogenic on kiwifruit leaves and fruit. Notably, B. cinerea isolates were always more virulent than B. prunorum isolates. This study confirms the presence of B. cinerea and B. prunorum colonizing apparently healthy flowers and floral parts in fruit and causing gray mold during kiwifruit storage in Chile. Therefore, B. prunorum plays a secondary role in the epidemiology of gray mold developing in kiwifruit during cold storage.

Eco-friendly management of postharvest fungal decays in kiwifruit

Kiwifruit is purchased by consumers worldwide and is increasing in demand. Unfortunately, kiwifruit is susceptible to postharvest decay caused by a variety of fungal pathogens, including Botrytis cinerea, Penicillium expansum, Alternaria alternata, Botryosphaeria dothidea, and Diaporthe spp. Among these pathogens, B. cinerea is the most prevalent and devastating. Infections by these fungal pathogens result in a deterioration in fruit quality and a reduction in marketable yield. Eco-friendly methods to control kiwifruit postharvest decay have been explored as alternatives to the use of synthetic fungicides. In this review, we provide an overview and discuss the virulence and pathogenesis of fungi that are causal agents of kiwifruit decay, especially B. cinerea, including recent molecular and genomic studies. Advances in pre- and postharvest measures for postharvest decay management, including biological control, physical applications, the use of natural compounds and plant hormones, and the use of combined methods, are also reviewed. Eco-friendly control measures are a critical component of an integrated management approach for sustainable production of kiwifruit. The need for further research on the use of microbial consortia for the management of postharvest diseases of kiwifruit is also discussed.

High-Quality Genome Resource of the Pathogen of Diaporthe (Phomopsis) phragmitis Causing Kiwifruit Soft Rot

Diaporthe spp. are critical plant pathogens that cause wood cankers, wilt, dieback, and fruit rot in a wide variety of economic plant hosts and are regarded as one of the most acute threats faced by the kiwifruit industry worldwide. Diaporthe phragmitis NJD1 is a highly pathogenic isolate of soft rot of kiwifruit. Here, we present a high-quality genome-wide sequence of D. phragmitis NJD1 that was assembled into 28 contigs containing a total size of 58.33 Mb and N₅₀ length of 3.55 Mb. These results lay a solid foundation for understanding host-pathogen interaction and improving disease management strategies.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Identification and Characterization of Diaporthe ambigua, D. australafricana, D. novem, and D. rudis Causing a Postharvest Fruit Rot in Kiwifruit

Diaporthe spp. are important plant pathogens causing wood cankers, blight, dieback, and fruit rot in a wide range of hosts. During surveys conducted during the 2013 and 2014 seasons, a postharvest rot in Hayward kiwifruit (Actinidia deliciosa) was observed in Chile. In order to identify the species of Diaporthe associated with this fruit rot, symptomatic fruit were collected from seven kiwifruit packinghouses located between San Francisco de Mostazal and Curicó (central Chile). Twenty-four isolates of Diaporthe spp. were identified from infected fruit based on morphological and cultural characters and analyses of nucleotides sequences of three loci, including the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2), a partial sequences of the β-tubulin, and translation elongation factor 1-α genes. The Diaporthe spp. identified were Diaporthe ambigua, D. australafricana, D. novem, and D. rudis. Multilocus phylogenetic analysis revealed that Chilean isolates were grouped in separate clades with their correspondent ex-types species. All species of Diaporthe were pathogenic on wounded kiwifruit after 30 days at 0°C under normal and controlled-atmosphere (2% O₂ and 5% CO₂) storage and they were sensitive to benomyl, pyraclostrobin, and tebuconazole fungicides. D. ambigua isolates were the most virulent based on the lesion length measured in inoculated Hayward and Jintao kiwifruit. These findings confirm D. ambigua, D. australafricana, D. novem, and D. rudis as the causal agents of kiwifruit rot during cold storage in Chile. The specie D. actinidiae, a common of Diaporthe sp. found associated with kiwifruit rot, was not identified in the present study.