Yellow leaf curl disease of tomato caused by tomato yellow leaf curl virus (TYLCV: a begomovirus) causes severe damage. In general, the virus is transmitted by the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) and has been assumed not to be mechanically transmissible. Because mechanical inoculation has great practical uses, e.g., screening for resistant tomato varieties, here we developed a method using a toothbrush to inoculate plants of susceptible tomato cv. House-Momotaro with TYLCV. The inoculum solution (buffer ingredients, molarity, pH, dilution of viruliferous leaf sap) were optimized to achieve the highest infection rates. After 35 days, characteristic symptoms appeared on the inoculated tomato plants, and infection of TYLCV was confirmed in non-inoculated upper leaves by polymerase chain reaction. The highest infection rate (73.3%) was obtained using 100 mM potassium phosphate buffer (pH 7.0) containing 0.1% (v/v) 2-mercaptoethanol at a 1000-fold volume of macerated infected leaf tissue. TYLCV was transmitted mechanically at 73.3 % infectivity in proportion of plants inoculated.
Tomato chlorosis virus (ToCV) is an emerging virus that causes a yellowing disease of tomato worldwide. Lower leaves of infected plants develop interveinal chlorosis, which gradually advances toward the upper leaves. ToCV is mainly transmitted by the whiteflies Bemisia tabaci or Trialeurodes vaporariorum in a semipersistent manner. Because little is known about the effects of ToCV on fresh tomato fruit production in Japan, we investigated the impacts of ToCV on commercial cv. Reiyo. Typical symptoms were first observed on leaves about 2 months after ToCV inoculation of plants using B. tabaci, and mean fruit mass was reduced by 24.6% to 31.7% compared with healthy plants.
A stem blight of Bupleurum falcatum, characterized by blackish lesions, stem folding, wilt and blight of upper parts and lesions that bore acervuli with setae and pale-orange conidial masses, was found in Ibaraki Prefecture, Japan in 2020. The isolated fungus was identified as Colletotrichum chrysanthemi based on morphology and rDNA-ITS and β-tubulin-2 sequences and reproduced the original symptoms after inoculation of B. falcatum. We named the disease anthracnose (tanso-byo in Japanese).