Study of Fitness, Virulence, and Fungicide Sensitivity of Lambertella corni-maris Causing Yellow Rot on Apple.

Very little is known about the biology, epidemiology, and best practices to manage Lambertella rot, a newly identified postharvest disease caused by Lambertella corni-maris on apples in the United States. In this study, we investigated the prevalence of L. corni-maris in 92 grower lots throughout Washington State in 2016, evaluated the effect of nutrient availability on L. corni-maris growth, and L. corni-maris sensitivity to pH, osmotic stress, and fungicides in vitro. We assessed pathogen aggressiveness on major apple cultivars and the efficacy of pre- and postharvest fungicides to control L. corni-maris on detached fruit. L. corni-maris was widespread and was found in 40% of the growers lots surveyed at frequencies ranging from 2 to 40% of the total decay. The fungus grew faster on acidic media such as apple juice agar and V8 agar media and was able to grow equally at pH values ranging from 3 to 7. L. corni-maris isolates showed relatively low sensitivity to osmotic stress and grew evenly at 1M KCl. All nine apple cultivars tested were susceptible to L. corni-maris, but the disease severity was significantly higher on some cultivars such as Honeycrisp, Piñata, and Gala. The baseline sensitivity of 100 L. corni-maris isolates was determined based on the effective concentration necessary to inhibit 50% mycelial growth (EC50) for fludioxonil, boscalid, pyraclostrobin + SHAM, pyrimethanil, and thiabendazole. The respective mean EC50 values were 0.07, 0.84, 1.32, 2.45, and 3.68 µg/ml. Fludioxonil and pyrimethanil applied at label rates were the only fungicides able to control L. corni-maris effectively on detached apple fruit. This study is a first step toward understanding the eco-physiological requirements for L. corni-maris to survive and cause decay on apple, assessing potential shifts in fungicide sensitivity, and enhancing Lambertella rot management. We suggest "yellow rot" as the new common name for Lambertella rot.

[1]  F. Dugan,et al.  A Postharvest Fruit Rot of Apple Caused by Lambertella corni-maris in Washington State. , 2015, Plant disease.

[2]  C. Xiao,et al.  Sources and Availability of Inoculum and Seasonal Survival of Sphaeropsis pyriputrescens in Apple Orchards. , 2014, Plant disease.

[3]  Kazuaki Tanaka,et al.  Lambertellin system, the mechanism for fungal replacement of Monilinia fructigena with Lambertella corni-maris without competitive inhibition on agar media. , 2014, Bioorganic & medicinal chemistry.

[4]  N. Peres,et al.  Resistance to Fluopyram, Fluxapyroxad, and Penthiopyrad in Botrytis cinerea from Strawberry. , 2014, Plant disease.

[5]  G. Schnabel,et al.  Selection of a Suitable Medium to Determine Sensitivity of Monilinia fructicola Mycelium to SDHI Fungicides: SDHIs Sensitivity Assay with Monilinia fructicola Mycelium , 2011 .

[6]  C. Xiao,et al.  A new canker disease of crabapple trees caused by Phacidiopycnis washingtonensis in Washington State. , 2009 .

[7]  C. Xiao,et al.  Distribution and Incidence of Sphaeropsis Rot in Apple in Washington State. , 2008, Plant disease.

[8]  G. Chilosi,et al.  Modulation of host pH during the wheat-Fusarium culmorum interaction and its influence on the production and activity of pectolytic enzymes , 2007 .

[9]  Y. Harada,et al.  Stimulation of the Biosynthesis of the Antibiotics Lambertellols by the Mycoparasitic Fungus Lambertella corni-maris under the Acidic Conditions Produced by Its Host Fungus in Vitro , 2007, Bioscience, biotechnology, and biochemistry.

[10]  C. Xiao,et al.  A Postharvest Fruit Rot in Apple Caused by Phacidiopycnis washingtonensis. , 2006, Plant disease.

[11]  J. Rogers,et al.  Phacidiopycnis washingtonensis--a new species associated with pome fruits from Washington State. , 2005, Mycologia.

[12]  G. Bompeix,et al.  Diversity and population dynamics of Penicillium spp. on apples in pre‐ and postharvest environments: consequences for decay development , 2005 .

[13]  J. Rogers,et al.  A Postharvest Fruit Rot in d'Anjou Pears Caused by Sphaeropsis pyriputrescens sp. nov. , 2004, Plant disease.

[14]  Y. Harada,et al.  Lambertellols A and B, novel 3,4-dihydronaphthalen-1(2H)-ones with spiro-butenolide produced by Lambertella sp.1346. , 2004, Organic letters.

[15]  S. Abouna,et al.  Differential regulation by ambient pH of putative virulence factor secretion by the phytopathogenic fungus Botrytis cinerea. , 2003, FEMS microbiology ecology.

[16]  H. Schüepp,et al.  A Reliable Method for Testing the Sensitivity of Botryotinia fuckeliana to Anilinopyrimidines In Vitro , 1996 .

[17]  R. Spotts,et al.  Postharvest decay of winter pear and apple fruit caused by species of Penicillium , 1995 .

[18]  T. Michailides,et al.  Postharvest diseases of pome and stone fruits caused by Mucor piriformis in the Pacific Northwest and California. , 1990 .

[19]  W. Turner,et al.  1110. The structure of lambertellin , 1965 .

[20]  R. Wood.  The antagonism of Lambertella cornimaris to fungi and bacteria , 1953 .

[21]  A. El-Helaly,et al.  On Lambertella Corni-maris von Höhnel, a brown-spored parasitic discomycete , 1935 .