Euphytica (2007) 153:329–337 DOI 10.1007/s10681-006-9171-y Fusarium ear rot and how to screen for resistance in open pollinated maize in the Andean regions E. Silva · E. A. Mora · A. Medina · J. Vasquez · D. Valdez · D. L. Danial · J. E. Parlevliet Received: 22 April 2005 / Accepted: 6 April 2006 / Published online: 13 October 2006 C  Springer Science + Business Media B.V. 2006 Abstract Ears infected with ear rot were collected from five provinces in Ecuador. Of the 44 samples anal- ysed 26 carried Fusarium verticillioides, 11 F. subgluti- nans, two F. graminearum and five carried fungi differ- ent from Fusarium. The pathogenicity of ten isolates, seven of F. verticillioides and three of F. subglutinans, were tested. Per isolate 30 ears of the susceptible cul- tivar Mishca were inoculated by pricking a steel pin, dipped into a spore suspension, through the husks in the central part of the ear 14 days after mid-silk. Ears inoculated with sterile water and ears without any treat- ment, natural infection, served as controls. The disease severity (DS) of the ears ranged from 14 to 58% ear rot, the range being similar for both species. The DS of the water control, 19%, was much higher than that of the natural control of 2%. Five strains gave a DS of E. Silva · E. A. Mora · J. Vasquez E.E. Santa Catalina, INIAP, Km 1, Panamericana Sur, Quito, Ecuador A. Medina E.E. Banos del Inca, INIA, A. Postal 169, Cajamarca, Peru D. Valdez Programma Maiz, Las Barrancas Km2, Casilla 1158, Tarija, Bolivia D. L. Danial · J. E. Parlevliet Lab. Plant Breeding, Dept. Plant Science, Wageningen University, P.O. Box 386, 6700 AJ Wageningen, The Netherlands over 40%, significantly higher than the water control. The DS of the others were similar to the water control. In a series of experiments the effect of various meth- ods of applying Fusarium spores through the husks into young ears were compared. All tested methods resulted in DSs significantly higher than those of the two con- trols. Inoculation with tooth picks and steel pins dipped in a spore suspension gave similar ear rot percentages. Inoculations at 7 to 14 days after mid-silk produced the highest DS’s. There was no significant effect of spore concentration on the DS. Cultivars differed consider- ably, the range being from around 20% to over 50%. Surprisingly, only wounding the husks, the sterile wa- ter control, resulted in a fairly high DS, much higher than that of the natural control. As the ranking order of the cultivars after wounding only and after inoculation did not seem to be different from the ranking order of the natural control it is suggested to use in areas with high inoculum pressures like the Andes only wounding by means of a steel pin for screening for resistance to maize ear rot. Keywords Ear rot . Fusarium . Inoculation methods . Isolate . Maize . Pathogenicity . Resistance . Strain Introduction Ear rot in maize occurs world wide and is caused by several Fusarium species. F. verticillioides, formely F. moniliforme (Summerell et al., 2003), teleomoroph Springer INIAP - Estación Experimental Santa Catalina