PLANT FIBER COMPOSITION AND RESISTANCE TO EUROPEAN CORN-BORER IN 4 MAIZE POPULATIONS

Feeding activities of herbivorous insects are influenced by physical a nd nutritive characteristics of host plants. Improved resistance to in sects resulting from either natural or artificial selection may be acc ompanied by changes in composition of plant fiber. The objectives of t his study were to 1) determine heritabilities in each of four maize (Z en mays L.) populations (WFISIHI, WFISILO, BS9 cycle 2, and B73 x DE81 1) for fiber components, and 2) determine the relationship between sec ond-generation European corn borer (ECB) [Ostrinia nubilalis (Hubner)] resistance and fiber composition within each population. One-hundred- fifty F-3 families from B73 x DE811 and 100 S-1 families from each of WFISIHI, WFISILO, and BS9 cycle 2 were evaluated for leaf-sheath and s talk concentrations of neutral and acid detergent fiber (NDF and ADF, respectively), and stalk concentrations of lignin. The same families f rom B73 x DE811 and subsets of 45, 49, and 49 S-1 families from WFISHI , WFISILO, and BS9, respectively, were also evaluated for resistance t o second-generation ECB in order to estimate generic variances and cov ariances for fiber components and ECB resistance. Significant phenotyp ic and genetic correlations were found between ECB tunneling and fiber components. Calculations of correlated response for fiber components predicted that with a selection intensity of 10% for increased second- generation ECB resistance, leaf-sheath NDF and ADF would increase by a n average of 8 and 5 g kg(-1) cycle-l, respectively, and stalk concent rations of NDF, ADF, and lignin would increase by 10, 8, and 2 g kg(-1 ) cycle(-1), respectively. These calculations are in approximate agree ment with empirical observations over five cycles of S-1 selection for ECB resistance in BS9.