Book Description

CIMMYT's program for developing resistance to the sugarcane borer has based primarily on screening under natural infestation in an unreplicated insect nursery. To test the effectiveness of that system, the 10 least damaged and 10 most damaged fmilies (based on insect nursery data from 1975 to 1976) from each of 10 CIMMYT population were grown from remnant seed and tested for resistance in 1977 at Poza Rica, Veracruz. Six populations were artificially infested at silking with newly hatched sugarcane borer larvae; the others received only natural infestation. For eight of the 10 populations, the gropu of 10 families selected as most resistent had a lower mean percent damaged internodes than the susceptile group.These means were significatntly different (5% level) for only two of the populations. artificial infestation was effective in increasing dmage as compared to natural infestation only ofr three of the six infested population (mean increase of 7.7% damaged internodes). This was apparently due to low levels of only about 10 to 15 larvae infested per plant. The variation among population for percent damaged internodes was relatively small, with a range of only 24.1% for Cogollero to 33,4% for Antigua X Veracruz 181 (Pedigree selections.) Genetic varation among families was to a large degree masked by a high environmental variability. For three populations additional damage evaluations were made, including number of tunnels per plant, tunnel length per plant, number of tunnels per damaged internode (...).