Plant damage and grain yield reduction by fall armyworm and stem borers on certain maize hybrids containing resistance genes from varying sources under experimental and farmers field conditions

The fall armyworm (FAW), Spodoptera frugiperda (J,E. Smith) is an important pest of maize in central, south and north America. The objective of this study was to examine certain hybrids with resistance to FAW and compare these hybrids with agronomically good (CML-AG) lines developed at the International Maize and Wheat Improvement Center (CIMMYT). The insect-resistant lines (CML-IR) used belonged to two categories: CML-IR with high inbreeding and CML-IR lines with low inbreeding derived from population 390. The following three categories of hybrids were examined in three different experiments: (1) CML-AG x CML-AG; (2) CML-AG x CML-IR (high inbreeding); (3) CML-AG x CML-IR (low inbreeding). The hybrids were grown along with CML67 x CML135 (resistant check), Ki3 x CML69 (susceptible check) and Criollo (local check). Resistance among CML-IR lines belonging to the first category (high inbreeding) was much more effective than that of second category in inhibiting FAW damage on the 24 hybrids tested. FAW caused much damage on the hybrids (CML-AG x CML-AG) but they still produced the highest yield. Leaf feeding resistance in the CML-AG x CML-IR hybrids did not cause any significant reduction of yield losses. Leaf feeding damage by FAW also did not cause any reduction in the growth of the CML-AG x CML-AG hybrids. In farmers fields, CML-AG x CML-IR hybrids were less damaged by FAW than CML-AG x CML-AG hybrids, but grain yield of the latter was significantly higher. Hybrids grown with a mulch suffered more stalk rot than those grown in the absence of mulch. Sources of resistance can be used therefore to reduce damage and less of yield caused by FAW provided that the grain yield is not the primary consideration. It is suggested that through conventional backcrossing procedures, inbred lines with desired levels of resistance and agronomic traits can be developed for utilization in breeding program to produce FAW resistant hybrids with high yields. (C) 2002 Published by Elsevier Science Ltd.