Caterpillar relative growth rate (RGR) no-choice assay
To determine the resistance of tomato under different salt regimes
against H. zea , caterpillar relative growth rate (RGR) on plants
from different treatments was evaluated (Figure 1A ). Two types
of no-choice assays were conducted:
1. Detached-leaf agar cup-based caterpillar RGR assay: The fourth fully
expanded leaf from each salt-pre-treated plant was cut and placed in
individual plastic cups lined with 3% agar (to ensure the leaves
retained moisture). A single pre-weighed 2nd instarH. zea caterpillar was added to each cup. Caterpillars were
weighed after three days of feeding.
2. On-plant caterpillar RGR assay: Salt pre-treated plants were placed
in individual cages and a single pre-weighed 2ndinstar H. zea caterpillar was allowed to feed freely on the
plant. Caterpillars were weighed after three days of feeding.
Caterpillar relative growth rate (RGR) was calculated as:
RGR = (W2- W1)/(W1 *(T2-T1)), where W1 and W2 are caterpillar weights at
time T1 and T2 respectively.