A postharvest fruit rot of apple caused by Lambertella corni-maris in Washington State

Authors: WISEMAN, M - Washington State University; Dugan, Frank; KIM, Y - Pace International, Llc - Usa; Xiao, Chang-Lin

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2014
Publication Date: 2/1/2015
Citation: Wiseman, M.S., Dugan, F.M., Kim, Y.K., Xiao, C. 2015. A postharvest fruit rot of apple caused by Lambertella corni-maris in Washington State. Plant Disease. 99:201-206.

Interpretive Summary: During surveys for postharvest diseases of apple in Washington State, an unknown fruit rot disease was observed on stored apples collected from commercial fruit packinghouses. This disease was observed in 66 of the 179 grower lots sampled, but disease incidence was relatively low. The disease appeared to originate from infection of wounds on the fruit skin. A fungus was consistently isolated from the decayed fruit and identified as Lambertella corni-maris based on its morphological and molecular characteristics. In laboratory tests, the fungus was able to cause decay at 0ºC on apple fruit inoculated with the fungus and reisolated from decayed fruit, proving that L. corni-maris is a postharvest fruit-rotting pathogen of apple. This is the first report of a fruit rot in stored apple caused by L. corni-maris in the United States. We propose Lambertella rot as the name of this disease.

Technical Abstract: During surveys for postharvest diseases of apples conducted in Washington State from 2003 to 2005, an unknown fruit rot was observed on stored apples collected from commercial fruit packinghouses. This disease was present in 66 of the 179 grower lots sampled, accounting for an average 1 to 3% of the total decayed fruit sampled. The disease appeared to originate from infection of wounds on the fruit skin. Lesions were brown and decayed tissues were spongy. Lambertella sp. was consistently isolated from the decayed fruit. Sequences of the fungus and Lambertella corni-maris sequences in GenBank differed by 0-4 base pairs across the combined SSU+ITS+LSU regions with a maximum identity ranging from 99 to 100%. The fungus grew at 0 to 20°C and formed apothecia on artificial media after 8-24 weeks. On potato dextrose agar under a 12 h photoperiod, apothecial dimensions were variable, ranging from 1-6 mm in diameter with stipes of 1-4 × 0.5 mm. Asci were 76-125 × 3.5-5.5 µm, inoperculate, eight-spored, clavate, and narrowed at the base. Ascospores were aseptate, 7-10 × 2.5-4.5 µm, uniseriate to biseriate and orange-brown at maturity in the ascus. Colony characteristics included: little/no aerial mycelium, dark-yellow to gray-black mycelium, gray-black pseudosclerotia, and yellow pigmentation in the agar. Morphological characteristics of the fungus overlapped with the description of L. corni-maris. ‘Fuji’ apple fruit that were wounded, inoculated with representative isolates, and incubated at 0°C yielded the same symptoms as seen in packinghouses, and the fungus was re-isolated from the diseased fruit. This is the first report of a fruit rot in stored apple caused by L. corni-maris in the United States. We propose Lambertella rot as the name of this disease.