Stem canker and dieback are important factors that limit the longevity and reduce the yield of blueberry (Vaccinium spp.) in Chile. In this study, species of Diaporthe associated with blueberry were isolated and identified. The internal transcribed spacer (ITS) regions of ribosomal DNA of 30 isolates and the translation elongation factor 1-α (EF1-α) of 14 isolates were sequenced, analyzed, and compared with their morphological and pathological characteristics. The molecular analysis of ITS sequences by alignment with those of ex-type strains deposited in GenBank and morphological characteristics allowed the identification of Diaporthe ambigua, D. australafricana, D. neotheicola, D. passiflorae, and Diaporthe sp. 1. However, morphology alone was insufficient to identify these species. The combined analysis of ITS and EF1-α gene sequences grouped the Chilean blueberry isolates in the same five groups obtained in the ITS analysis. Pathogenicity tests conducted with attached and detached blueberry shoots (<1 year old) and stems (1 to 2 years old) confirmed that isolates of these Diaporthe spp. were pathogenic. The symptoms were reproducible and consisted of necrotic reddish-brown cankers on blueberry shoots and stems. These isolates were capable of infecting blueberry fruit, causing a soft decay, suggesting that they were tissue nonspecific and were also pathogenic on shoots of apple, grapevine, and pear. D. australafricana was the most frequently isolated species and D. ambigua, D. australafricana, and D. passiflorae were highly virulent in shoots, stems, and fruit of blueberry. This study showed that at least four species of Diaporthe are primary pathogens, capable of causing stem canker symptoms on blueberry, and this is the first report of D. ambigua, D. neotheicola, and D. passiflorae attacking this host.

by Botrytis cinerea is a major disease of grapes (Vitis vinifera) that substantially reduces the yield and quality of grape production in temperate and humid regions of the world. B. cinerea is a necrotrophic fungus that attacks the non-lignified aerial organs of grapes; in particular, berries are highly susceptible during ripening. The polycyclic nature and exponential progress exhibited by GM at the beginning of the its epidemic, as well as the abundant inoculum production, the high dissemination efficiency, the wide host range and the high genetic variability of B. cinerea, explain the difficulties encountered in attempting to control GM. At present, integrated disease management, including cultural and chemical control, is the main control strategy. These control measures can be used to reduce the initial inoculum or to lower the disease infection rate. However, control measures that reduce the infection rate are the most effective means of controlling GM. Important progress toward understanding the complexity of the biology and epidemiology of this pathogen has occurred in recent decades. This has allowed the improvement and development of more effective and sustainable control strategies against B. cinerea. This review article provides a recent update regarding grape GM, with special emphasis on Chilean production conditions.

Moldy core (MC) of apple is an important disease in Chile, with prevalence observed between 4 and 46% in Fuji, Oregon Spur Red Chief, and Scarlet apple in the 2014-15 and 2015-16 growing seasons. However, there is no information on the identity of the causal agents associated with MC in Chile. The analysis of 653 MC fruit revealed the presence of several genera of filamentous fungi. However, species of Alternaria (67.7%) were by far the most frequently fungi isolated. In total, 41 Alternaria isolates were characterized morphologically and molecularly using Alternaria major allergen Alt a1, calmodulin, and plasma membrane ATPase gene regions. Six small-spored Alternaria spp. were identified; namely, in order of importance, Alternaria tenuissima, A. arborescens, A. alternata, and A. dumosa in sect. Alternaria; A. frumenti in sect. Infectoriae; and A. kordkuyana in sect. Pseudoalternaria. MC symptoms were reproducible and consisted of a light gray to dark olive-green mycelium over the carpel and seed of immature and mature fruit, confirming that the isolates of these Alternaria spp. were pathogenic. These isolates caused brown necrotic lesions with concentric rings on wounded detached apple leaves. This study demonstrated that at least six Alternaria spp. are the cause of MC of apple in Chile. These Alternaria spp. were isolated alone, or with two or more species coexisting in the same fruit. This is the first report of A. tenuissima, A. arborescens, A. frumenti, A. dumosa, and A. kordkuyana associated with MC of apple in Chile and the first report of A. frumenti, A. kordkuyana, and A. dumosa causing MC of apple worldwide.

Grapevine trunk diseases (GTDs) are caused by multiple unrelated fungal pathogens, and their management remains difficult worldwide. Biocontrol is an attractive and sustainable strategy given the current need for a cleaner viticulture. In this study, twenty commercial vineyards were sampled across California to isolate endophytic and rhizospheric bacteria from different grapevine cultivars with the presence and absence of GTD symptoms. A collection of 1344 bacterial isolates were challenged in vitro against Neofusicoccum parvum and Diplodia seriata, from which a subset of 172 isolates exerted inhibition levels of mycelial growth over 40%. Bacterial isolates were identified as Bacillus velezensis (n = 154), Pseudomonas spp. (n = 12), Serratia plymuthica (n = 2) and others that were later excluded (n = 4). Representative isolates of B. velezensis, P. chlororaphis, and S. plymuthica were challenged against six other fungal pathogens responsible for GTDs. Mycelial inhibition levels were consistent across bacterial species, being slightly higher against slow-growing fungi than against Botryosphaeriaceae. Moreover, agar-diffusible metabolites of B. velezensis strongly inhibited the growth of N. parvum and Eutypa lata, at 1, 15, and 30% v/v. The agar-diffusible metabolites of P. chlororaphis and S. plymuthica, however, caused lower inhibition levels against both pathogens, but their volatile organic compounds showed antifungal activity against both pathogens. These results suggest that B. velezensis, P. chlororaphis and S. plymuthica constitute potential biocontrol agents (BCAs) against GTDs and their application in field conditions should be further evaluated.

From 2018 to 2021 a decline was detected in young vineyards of both wine and table grape (Vitis vinifera L.) in seven counties across California (Kern, Monterey, Napa, Sonoma, Tulare, Yolo, and Yuba). Affected vines showed poor or no growth throughout the season, dieback, sap exudation and internal cankers around the graft union. Lack of feeder roots was detected, indicating weak root development. In some cases, graft failure was associated with the symptomatology in recently established vineyards (<3 years old). A prevalence from 5 to 50% was estimated in 10 vineyards. Affected vines (n=34) were collected by farm advisors and submitted to the laboratory. Symptomatic vines were surface disinfected with 70% ethanol for 1 minute and air dried under sterile conditions. Vascular discoloration around the graft union was observed and inspected by removing the bark using a sterile knife. Isolations were performed from the margin of lesions by placing five wood sections (1×1 mm) per vine onto potato dextrose agar acidified with 0.5 mL/L of 85% lactic acid (APDA) and incubated for 7 days at 25°C in the dark. Even though other fungi associated with young vine decline were isolated and identified as Phaeoacremonium, Ilyonectria, and Botryosphaeriaceae species, Fusarium colonies (Leslie and Summerell, 2006) were the most prevalent among all the symptomatic vines. Pure cultures were obtained by transferring single hyphal tips onto fresh PDA. After 5 days of incubation, colonies formed white aerial mycelium with orange to purple colors on the bottom. Colonies in Spezieller Nährstoffarmer agar (SNA) produced abundant microconidia that were hyaline and ovoid to elliptical, ranging from 5.4 to 10.6 (7.4) × 1.4 to 3.3 (2.4) µm in size (n=50). Straight and slightly curved macroconidia varied from 15.5 to 42.3 (23.7) × 2.6 to 5.0 (3.6) µm in size (n=50). Upon DNA extraction, the translation elongation factor 1α (tef1) and the RNA polymerase II second largest subunit (rpb2) partial gene regions were amplified and sequenced using the EF1/EF2, 5F2/7cR and 7cF/11aR pair primers, respectively (O’Donnell et al. 1998, O’Donnell et al. 2007, Liu et al. 1999). Consensus sequences were compared to the NCBI database using BLAST, showing over 99% similarity with the ex-type sequence of F. annulatum CBS 258.54 (MT010994 and MT010983). A maximum likelihood multi-locus phylogenetic analysis confirmed that all the Californian isolates cluster with F. annulatum strains. Sequences were deposited in GenBank (nos. OK888534 to OK888537). Two representative isolates (UCD9188 and UCD9416) were used for pathogenicity tests. One-year-old ‘Chardonnay’ vines were inoculated between the second and third node by removing a 5-mm diameter disk of the bark using a sterile cork borer and placing a 5-mm agar plug with actively growing mycelium. Five replicates per isolate including controls with sterile agar plugs were incubated under greenhouse conditions for 2 months. The experiment was performed twice. Symptoms expressed as vascular linear necrotic lesions that ranged from 25.6 to 62.8 mm and the same pathogen was recovered, thus fulfilling Koch’s postulates. Fusarium annulatum Bugnic. is a morphologically and genetically diverse species that has been widely known as F. proliferatum and known to be pathogenic in more than 200 plant hosts (Yilmaz et al. 2021). Fusarium spp. have been previously reported to cause young vine decline in Australia and British Columbia, Canada (Highet and Nair, 1995; Úrbez-Torres et al. 2017). To the best of our knowledge, this is the first report of F. annulatum associated with young vine decline complex in California.