T100 thermal cycler instrument

In brief, 500 ng of total RNA was reverse transcribed to cDNA using the PrimeScript RT Reagent Kit (Takara, Tokyo, Japan) on a T100 Thermal Cycler instrument (BIO-RAD, Hercules, California, USA). Next, the cDNA was amplified by the TB Green Premix Ex Taq (Takara) on a Roche LightCycler® 480II PCR instrument (Basel, Switzerland). GAPDH and U6 were used as the internal standard controls. The relative RNA expression was estimated by the 2–ΔΔCT method. The primers used in the study are described in the Table S3.

The Las populations in whole or dissected mealybugs (n = 50) and psyllids (n = 50) were studied by conventional PCR using primer pairs LJ799/858, LJ868/864 and LJ860/863 specific for Type A, B and D, respectively [24] . In brief, genomic DNA was extracted using the DNeasy Blood and Tissue Kit (QIAGEN, Valencia, CA). Ferrisia virgata and D. citri dissected tissues or whole bodies were homogenized in tubes containing glass beads using Fast Prep®-24 homogenizer (MP Bio., Solon, OH) at speed 4.0 m/s for 30 seconds. After mixing, 20 µl of proteinase K were added to each tube, and then followed the manufacturer’s protocol. The DNA was eluted in nuclease-free water and analyzed by Nanodrop for DNA concentration and quality. Leaf discs were collected and analyzed for Las bacterial titers. All the leaf discs or insect DNA samples were subjected to Las titer estimation by qPCR using 16S rDNA-based primers and probe [27] (link) prior to typing analysis. Conventional PCR was performed on the T100 thermal cycler instrument (Biorad, Hercules, CA, USA) following the protocol as described previously [24] .