IDENTIFYING THE LEVELS AND SOURCES OF THE RESISTANCE TO CORN STUNT
RICARDO GONÇALVES SILVA | JOÃO CARLOS CARDOSO GALVÃO | GLAUCO VIEIRA MIRANDA | ELIZABETH DE OLIVIERA
Aiming to identify the levels and sources of the resistance to corn stunt, two experiments were set up on March 2001 in Coimbra, MG and Sete Lagoas, MG. Each experiment consisted of 30 treatments, from which 10 were represented by the maize hybrids and their selfings. The other ones consisted of the hybrid combinations and their reciprocal ones. The randomized block experimental design was used with 3 replicates. The experimental plot was integrally used, and consisted of two 5 m rows with 25 plants per row at a 0.9 m spacing, so representing a population around 55,000 plants ha-1. At the time of kernel fulfillment, the evaluations were performed for incidence and severity of the corn stunt. The incidence was determined based on the percentile of plants per plot presenting the corn stunt symptoms. The severity was determined by ascribing the scores to the averages of the symptoms in plants at each plot. These scores ranged from 1 (absence of symptoms) to 6 (plants presenting early death caused by corn stunt). The disease index was also used. In both places, evaluation was performed for productivity of the maize kernels in each plot. The method based on percentage of symptomatic plants per plot (incidence) showed to be the most efficient in discriminating the levels of resistance to corn stunt under field conditions. This method would be useful for discriminating the genotypes that are resistant to corn stunt. The hybrids P 3041 and C 333B have high frequency of distinct alleles giving resistance to corn stunt.
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