Real‐time PCR quantification of Bemisia tabaci (Homoptera: Aleyrodidae) B‐biotype remains in predator guts

The cotton whitefly, Bemisia tabaci (Gennadius) B‐biotype, is fed on by a wide variety of generalist predators, but there is little information on these predator–prey interactions, especially under field conditions. In this study, a real‐time polymerase chain reaction (PCR) assay was developed to quantify B. tabaci B‐biotype remains in predator gut. The B. tabaci B‐biotype genomic DNA copy number was referred to the actual amount of BT1 isolate, the B. tabaci B‐biotype specific DNA fragment. The numbers of BT1 isolate in one B. tabaci B‐biotype egg, individual adult and a single red‐eyed nymph were 2.56 × 10³, 2.56 × 10⁴, and 1.29 × 10⁴ copies, respectively. When Propylaea japonica adults fed on one, two, four, eight or 16 red‐eyed nymphs, the detected numbers of BT1 isolate ranged from 2.77 × 10⁴ to 4.05 × 10⁵ copies, forming a strong linear relationship (R² = 0.9899). Following the consumption of two red‐eyed nymphs, prey DNA was detectable in 100% of P. japonica at t = 0, decreasing to 80.0% and 60.0% after 1–4 h and 8 h of digestion, respectively, with 3.36 × 10⁴–1.25 × 10³ BT1 isolate copies. The predation by field‐collected predators, 26 larvae of P. japonica, and of Harmonia axyridis each, Chrysopa spp. larvae (Chrysopa pallens and C. formosa, 18 individuals in total), and a single adult of Scymnus hoffmanni, 19 adults of Orius sauteri and nine adult spiders (Erigonnidium graminicolum and Neoscona doenitzi), on B. tabaci B‐biotype were quantified. Of the 99 analysed predator individuals, 3.65 × 10²–4.60 × 10⁵ copies of BT1 isolate, equivalent to 0.8–18.8 red‐eyed nymphs were detected. These results suggest that TaqMan real‐time PCR technology may provide a rapid and sensitive method for quantifying B. tabaci B‐biotype remains in predator guts and will be invaluable in assessing the food web relationship between prey and arthropod predators.