engleski

Response of maize inbreds and hybrids to stalk rot naturally and artificially infested with Fusarium spp.

Due to considerable yield and quality reduction, stalk rot in maize is a very inportant issue in a resistance breeding program. The most frequent pathogens of stalk rot in maize in the region of Eastern Croatia are fungi from the genus Fusarium (F. graminearum, F. moniliforme, F. subglutinans). The selection of resistant material naturally infected is not reliable because the disease severity depends on environmental factors and differs between years and locations. Some of the investigations proved high correlation between maize inbreds and resistance to stalk rot on artificially and naturally infected, and some did not. The objective of the study was to test the resistance of 36 maize inbreds and 72 hybrids for stalk rot and to determine relationship between natural and artificial infection with a mixture of spores of F. graminearum, F. moniliforme and F. subglutinans.The trials were conducted in 1998 and 1999 acording to a lattice design with three replications. Inbreds and hybrids were set in separate and adjacent trials. Each entry was planted in two rows, the first row for the artificial infection and the second row for the natural infection. Artificial infection was perfomed by injecting 1 ml inoculum, of spore concentration cca. 60000 per ml, at the first elongated internode. Degree of stalk rot was estimated using a 1-5 scale for artificial infection and FAO 1-9 scale for natural infection. Inbred differed in their resistance to stalk rot significantly: from 1.0 to 4.8 for artificial and from 1.0 to 7.8 for natural infection. Correlation coefficients between inbreds resistance in natural and artificial infections were highly significant (r=0.87 and r=0.80, in 1998 and 1999, respectively). There were significant differences between hybrids in several years and types of infections. Generally, scores for hybrids were lower than these in inbreds: for artificial infection between 1.0 and 3.0 and for natural infection between 1.0 and 2.4. Natural and artificial infections in hybrids were weaker associated then in inbreds, with highly significant correlation coefficients (r=0.45 and r=0.55, in 1998 and 1999, respectively). Our results suggest that artificial infection with Fusarium spp. can provide a satisfactory method of evaluating maize genotypes, particulary inbred lines, to insure a satisfactory level of stalk rot presence.

fusarium; maize; resistance

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