Disease Resistance in Five Cycles of 'BS9' Corn Synthetic Selected for Resistance to Two Generations of European Corn Borer

Publisher Website
Google Scholar
Abstract
A corn (Zea mays) synthetic, BS9, was evaluated to determine if Si recurrent selection for resistance To European corn borer, Ostrinia nubilalis, resulted in correlated changes in resistance to Exserohilum turcicum, causal organism of northern corn leaf blight, or resistance to Diplodia maydis, causal organism of Diplodia stalk rot. On a 1-to-9 scale (1 = highly resistant and 9 = highly susceptible), first-generation borer damage ratings dereased from 3.6 to 2.4, and second-generation damage ratings decreased from 6.5 to 4.3 in the populations BS9C0 and BS9(CB)C4, respectively. Percentage of leaf area infected with leaf blight was rated in six times after inoculation with E. turcicum; ratings were transformed to the natural logarithm (lnNLB), and dates of ratings were transformed to the natural logarithm of days after first inoculation (lnDAY). Linear and quadratic components of the regression of lnNLB on cycles of selection were significant, resulting in a significant increase in leaf blight infection from the C0 to C4 population of BS9. Ratings expressed as percentage of leaf area blighted, in terms of the linear regression, increased from 4.6 and 5.8% at day 16 to 38.9 and 41.7% at day 71 for BS9C0 and BS9(CB)C4, respectively. Selection for borer resistance did not affect Diplodia stalk-rot ratings. Selection for resistance to one pest, therefore, cannot be expected to increase the resistance to other pests, although DIMBOA (2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one) content in a corn plant has been correlated with resistance to a wide range of pests.