Contents - Faperta

Evaluation of Transgenic Plants and Mapping Populations for Resistance to Insect Pests 63
pests based on damage to bolls or pods. To overcome these problems, the test material can
be evaluated on a visual damage rating scale of 1 to 9, taking into consideration the extent
of leaf damage or recovery from insect feeding during the vegetative stage (on seedlings
and leaves), numbers of fruiting bodies and their distribution on the plant, and the proportion
of fruiting bodies or grain damaged by insects.
Data can also be recorded on insect numbers, survival and development, fecundity,
consumption and utilization of food, host selection and feeding behavior, numbers of the
diapausing insects, etc. The following methods can be used to assess insect damage to
evaluate the germplasm, segregating breeding material, mapping populations, and transgenic
plants for resistance to insects.
Visual Damage Rating
1. Plants with little damage during the vegetative stage and damaged plants that
show good recovery from insect damage, and/or fruiting bodies uniformly distributed
throughout the plant canopy, and 10% of the fruiting bodies with insect
damage.
2. Plants with 10 to 20% damage during the vegetative stage and showing good recovery
from insect damage, and/or large number of fruiting bodies retained on the plant
with uniform distribution, and 10 to 20% of the fruiting bodies with insect damage.
3. Plants with 20 to 30% damage during the vegetative stage, and showing good
recovery from insect damage, and/or a large number of fruiting bodies retained
on the plant and 20 to 30% of the fruiting bodies with insect damage.
4. Plants with 30 to 40% damage during the vegetative stage with moderate recovery
from insect damage, and/or moderate number of fruiting bodies retained on the
plant, and 30 to 40% of the fruiting bodies with insect damage.
5. Plants with 40 to 50% damage during the vegetative stage with moderate recovery,
and/or nearly 50% of the fruiting bodies retained on the plant, and 40 to 50% of the
fruiting bodies with insect damage.
6. Plants with 50 to 60% damage during the vegetative stage, with low to moderate
recovery, and/or nearly 40% of the fruiting bodies retained on the plant, and
50 to 60% of the fruiting bodies with insect damage.
7. Plants with 60 to 70% damage during the vegetative stage, with poor recovery
from insect damage, and/or nearly 30% of the fruiting bodies retained on the
plant, and 60 to 70% of the fruiting bodies with insect damage.
8. Plants with 70 to 80% damage during the vegetative stage with very poor recovery
from insect damage, and/or nearly 20% of the fruiting bodies retained on the
plant, and 70 to 80% of the fruiting bodies with insect damage.
9. Plants with 80% damage during the vegetative stage with little recovery from
insect damage, and/or 20% of the fruiting bodies retained on the plant, and
80% of the fruiting bodies with insect damage.
Indirect Feeding Injury
Measurements of insect damage to plants are more useful than insect numbers, insect
growth, or development. Plant damage and the resulting reduction in yield or quality are
important while establishing the goals of a crop improvement program. Measurements of