BACTERIAL LEAF-BLIGHT ON SHRUNKEN-2 SWEET CORN

Severity of bacterial leaf blight (BLB, caused by Acidovorax avenae su bsp. avenae) on shrunken-2 (sh2) sweet corn hybrids grown in BLB-condu cive environments and sporadic outbreaks of BLB in recent years warran ted evaluations of the potential for this disease to cause economic lo sses. BLB symptoms on 122 sh2 hybrids, 30 sh2 inbred lines, and 29 cro sses of the inbreds and the effects of BLB on yield (ear weight and ma rketable ears) were evaluated in 1994 and 1996. BLB severity ratings f or 122 hybrids averaged 3.3 and 3.7 (on a scale of 1 to 9) in 1994 and 1996, respectively. Hybrid means ranged from 1.8 to 5.5 in 1994 and f rom 1.9 to 5.7 in 1996, with Bayesian LSD values of 1.20 and 1.22, res pectively. There were no differences in BLB ratings among hybrids with yellow, white, or bicolored kernels. Severity of symptoms on 30 sh2 i nbreds ranged from 1.5 to 5.7, whereas the reactions of 29 crosses of the inbreds ranged from 1.9 to 5. The slope coefficient of the regress ion of crosses on mid-parent values was not different from 1. Thus, mi d-parent values gave a good indication of severity of BLB symptoms on crosses, with the exception of a few crosses that tended to be more se verely infected than expected based on mid-parent values. Ear weights and number of marketable ears differed among hybrids in the 1994 trial , but there was no significant effect of BLB treatments on either of t hese measures of yield. In 1996, ear weights in inoculated plots were 10 and 15% lower than those from noninoculated plots for 2 of 12 hybri ds. Despite moderately severe foliar symptoms, BLB did not affect yiel d substantially in these trials even among hybrids with the most susce ptible reactions.