Fusarium ear rot and how to screen for resistance in open pollinated maize in the Andean regions

Abstract

Ears infected with ear rot were collected from five provinces in Ecuador. Of the 44 samples analysed 26 carried Fusarium verticillioides, 11 F. subglutinans, two F. graminearum and five carried fungi different 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 cultivar 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 treatment, 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 In a series of experiments the effect of various methods 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 controls. 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 considerably, the range being from around 20% to over 50%. Surprisingly, only wounding the husks, the sterile water 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.

Breeding for resistance to ear rots caused by Fusarium spp. in maize – a review

“…2002). Silva et al. (2007) used 14 days in regular tests; later inoculations (19, 21 and 23 days after mid‐silking) resulted in significantly less disease severity.…”

“…Genotype differences are normally much larger for artificial inoculation regimes than for natural ones (Oberforster and Felder 2010). Silva et al. (2007) compared natural and artificial inoculation results and concluded that when only the husks were wounded, the sterile water control resulted in higher disease severity than the natural control.…”

Effects of artificial inoculation on trait correlations with resistance to Fusarium ear rot and fumonisin contamination in maize

“…The hybrid × inoculation treatment interaction was significant for FUM and TW, indicating that the relative performance of genotypes for these traits differs under artificial and natural inoculation (Table 1). Hybrid × treatment interaction was not significant for FER, however, congruent with Silva et al (2007) and Eller et al (2010), who found no significant difference in the ranking of genotypes with and without inoculation. The entry mean-basis heritabilities for FER and FUM were 0.57 and 0.67 under artificial inoculation but reduced close to zero under natural conditions (Table 1).…”

Gene action and reciprocal effects for ear rot resistance in crosses derived from five tropical maize populations

“…n 6 9 63 ? n 7 9 88)/ P N, where n 1 -n 7 are the number of ears with scale values 1-7 which are multiplied with the mean percentage of the scale (Silva et al 2007). The diallel analysis of the 10 full-sib families were performed using Griffing's (1956) Method 1 fixed model, using the Diallel SAS-05 program (Zhang et al 2005) in the SAS computer package.…”