Yield response of corn hybrids and inbred lines to phylloplane treatment with mycopathogenic fungi

This study was part of a larger investigation on the biological control of stalk rot of corn (Zea mays L.) through application of mycopathogenic fungi on above-ground surface (phylloplane) of the corn plant conducted at Iowa State University, Ames, IA. The objectives were to determine if grain yield is an effective trait for testing the interaction of selected mycopathogenic fungi with corn genotypes and whether the application of mycopathogens to the corn phylloplane had an effect on yield. Seven corn hybrids and nine inbred lines were planted in a Spillville clay loam (fine-loamy, mixed mesic Cumulic Hapludoll) with three cultural histories: oat (Avena sativa L.)-corn-soybean [Glycine max (L.) Merr.] rotation, continuous corn cultivation, and fumigation. Plants were treated in the phylloplane with aqueous spore suspension of mycopathogens Gliocladium roseum (Link) Bainier, Gonatobotrys simplex Corda, and Sphaeronaemella helvellae (Karsten) Seeler, and water as control. Hybrid yields were not affected by the treatments, whereas inbred yields differed significantly. Fumigation of the soil with methyl isothiocyanate resulted in a significant response by inbreds to treatment with mycopathogens, which was primarily due to G. roseum. Differences in the yields of the inbreds planted in corn-soybean-oat rotation were nonsignificant. Variation in the yield of the inbreds indicated that there was a highly significant interaction between inbred genotypes and mycopathogens in continuous corn culture and in fumigated soils. Inbreds B73 and Va26 had the most varied responses to the mycopathogens, whereas B85 and W629A had the least. Selection and breeding of inbreds with high yield response to mycopathogens could result in genotypes, that, in the presence of a compatiable mycopathogen, would suppress stalk rot development and have greater yield potentials.