Contents - Faperta

Evaluation of Transgenic Plants and Mapping Populations for Resistance to Insect Pests 69
weight per day (consumption index, CI) or leaf area consumed, larval growth rates (GR),
approximate digestibility (AD), effi ciency of conversion of ingested food (ECI) into body
matter, and the effi ciency of conversion of digested food (ECD) into body matter. The CI is
calculated as: CI F/TA. Where F weight of food ingested, T duration (in days) of
feeding period, and A mean weight of the insect during the feeding period. Mean larval
weight is determined by averaging the initial and fi nal weights of the larvae (Soo Hoo and
Fraenkel, 1966). The approximate digestibility (AD) of food is calculated as:
Weight of food ingested weight of feces
AD ______________________________________ 100
Weight of food ingested
Growth rate (GR) is calculated as percentage increase in larval weight per unit of time.
GR Weight gain/Initial weight of larva 100
Larval effi ciency in converting the ingested food into body matter (ECI) is calculated as:
Weight gained by the larva
ECI ________________________ 100
Weight of food ingested
The effi ciency with which the larvae convert the digested food into body matter
(ECD) is calculated as:
Weight gained by the larvae
ECD ______________________________________ 100
Weight of food ingested Weight of feces
Measurements of Insect Behavior
Several techniques have been developed for studying insect behavior inside plant tissue
or to quantify the effects of allomones and kairomones on insect behavior (Table 3.8).
TABLE 3.8
Physical Methods for Detecting and Monitoring Insect Behavior and Measuring Plant
Resistance to Insects
Crop Insect Species Remarks References
Rice Rice bloodworm,
Chironomus tepperi
Skuse
Computer-based image analysis can be used
to assess rice cultivars for resistance.
Maize Leaf feeding insects Pulsed x-ray can be used to examine silica
deposition in the leaf blades.
Sorghum Sorghum midge,
Stenodiplosis sorghicola
Sugarcane African sugarcane
borer, Eldana
saccharina
Cowpea Bruchid,
Callosobruchus
maculatus (Fab.)
Lettuce Lettuce root aphid,
Pemphigus bursarius
X-ray monitoring of the diapausing midge larvae
can be used as an indicator for midge infestation.
Sorghum midge females show differential responses
to odors from wild relatives of sorghum.
Use NIR in screening the material for resistance.
Stalk surface wax (alcohols and carbonyls)
contributed towards resistance.
Use biomonitor to measure activity of internally
feeding insects. The activity of larvae can be
recorded for 24 h starting 14 days after oviposition.
Feeding behavior monitored on resistant and
susceptible varieties.
Stevens et al. (2000)
Cheng and Kim
(1989)
Harris (1971)
Sharma and
Franzmann (2001)
Rutherford and
Van Staden (1996)
Devereau et al. (2003)
Cole, Riggall, and
Morgan (1993)