First Report of Leaf Rust of Blueberry Caused by Pucciniastrum vaccinii in Hawaii

Abstract

Blueberries (Vaccinium corymbosum L.) are a potential high-value, niche market crop for Hawaii. In May of 2007, rust-like symptoms were observed on multiple blueberry plants in a private nursery in Waimea, HI. In September of 2007, a similar leaf rust was observed on one bush of V. corymbosum cv. Sharpblue in the corner of a 36.6 × 9.1-m experimental plot at Mealani Research Station in Waimea. Within a month, rust was observed throughout the plot on ‘Biloxi’, ‘Emerald’, ‘Jewel’, ‘Misty’, ‘Sapphire’, and ‘Sharpblue’. Preliminary field observations suggest that ‘Sharpblue’ and ‘Sapphire’ are highly susceptible to the rust and ‘Biloxi’ shows some tolerance. Leaf lesions began as approximately 1-mm2 chlorotic flecks that expanded and developed into reddish brown, necrotic spots with a chlorotic halo. New lesions and uredinia kept appearing over the course of 4 months. Defoliation occurred on plants where infection was severe. Yellowish orange pustules containing urediniospores first appeared on the abaxial side of older leaves and later appeared on new leaves. Urediniospores were elliptical to obovate (19.4 to 24.8 × 15.2 to 19.8 μm) with a thick, slightly roughened wall and a well-developed pore. Urediniospore morphology and dimensions were consistent with the description of Pucciniastrum vaccinii (G. Wint.) (1). A pathogenicity test was conducted with two 18-month-old ‘Sharpblue’ plants. Fully expanded leaves were sprayed with freshly collected urediniospores (3.8 × 105 spores per ml) suspended in a 0.05% solution of Tween 20 in water. The control plant was sprayed with sterile distilled water (SDW). Plants were covered with plastic bags for 48 h and held in a growth chamber at 20 to 22°C under continuous fluorescent lighting. The plastic bags were then removed and the plants were maintained in the growth chamber. Yellowish orange pustules that were identical to the original symptoms developed on 100% of inoculated leaves after 10 days. The plant inoculated with SDW remained symptomless. While leaf rust caused by P. vaccinii has been reported on Ohelo berry (V. reticulatum) (2), it has not been reported on V. corymbosum in Hawaii. To our knowledge, this is the first report of P. vaccinii on blueberry plants in Hawaii. This rust disease may pose a threat to the potential blueberry industry in Hawaii. References: (1) P. R. Bristow and A. W. Stretch. Page 20 in: Compendium of Blueberry and Cranberry Diseases. F. L. Caruso and D. C. Ramsdell, eds. The American Phytopathological Society, St. Paul, MN, 1995. (2) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory. Online publication. ARS, USDA, 2008.

Reaction of Different Vaccinium Species to the Blueberry Leaf Rust Pathogen Thekopsora minima

“…Urediniospores developed on the lower surface of older leaves as yellow-orange pustules within 10 to 14 d of infection and abundant sporulation across the lower leaf surface was observed. The disease symptoms displayed by these accessions were similar to the ones described in previous leaf rust reports (Barrau et al, 2002;Dal Bello and Perello, 1998;Keith et al, 2008;McTaggart et al, 2013;Mostert et al, 2010;Rebollar-Alviter et al, 2011;Shands et al, 2018;Wiseman et al, 2016;Zheng et al, 2017).…”

“…3 and 4). Spore sizes and morphology were congruent with T. minima described previously (Keith et al, 2008;Shands et al, 2018;Wiseman et al, 2016).…”

“…This may reduce plant vigor and lead to poor fruit production. The incidence of the disease has been increasing in the United States, where the pathogen has been reported in several states, including Delaware, New York, Michigan, Oregon, Hawaii, California, and Georgia (Keith et al, 2008;Sato et al, 1993;Shands et al, 2018;Wiseman et al, 2016). In addition, leaf rust has been reported in many countries, including South Africa, Mexico, Spain, Argentina, Australia, and China (Barrau et al, 2002;Dal Bello and Perello, 1998;McTaggart et al, 2013;Mostert et al, 2010;Rebollar-Alviter et al, 2011;Zheng et al, 2017).…”

Prospecting and management alternatives of fungal diseases associated in the blueberry crop (Vaccinium corymbosum L.)

“…Mctaggart et al (2013), informan que a medida que la enfermedad avanza como infecciones severas, las hojas se marchitan y caen, produciendo una defoliación de la planta. Estas observaciones concuerdan con lo descrito por Keith et al (2008). La penetración en el tejido del hongo Thekopsora minima, se produce a través de las estomas y dentro de las células parénquima del mesófilo de la hoja introduce una estructura denominada haustorio (Lorrain et al, 2019) para luego producir los síntomas.…”

Emerging Fruit Crops

“…A maintenance medium can be used for medium-term (5-year) storage of the plantlets under refrigerated conditions. Several disease symptoms have been observed on cultivated highbush blueberries, V. corymbosum , growing at the Mealiani Agricultural Research Station in Waimea, Hawai'i (Hummer and Zee 2007 ;Keith et al 2008 ) . The main disease pressure that may limit 'ōhelo berry production and ornamental qualities in Hawaii was determined to be powdery mildew (Keith Personal communication).…”