Preliminary field observations in our maize breeding nurseries indicated that breeding for improved resistance to gibberella ear rot (Fusarium graminearum) in maize may indirectly select for resistance to another ear disease, common smut (Ustilago zeae). To investigate this, we compared the disease severity ratings obtained on 189 maize inbreds, eight of which included our inbreds developed with selection for gibberella ear rot resistance after field inoculation and breeding for 8-10 years. No correlation was found between disease severities for the 189 inbreds but the eight gibberella-resistant lines were consistently more resistant to smut. To further examine this relationship and to determine if these eight inbreds would be useful for developing inbreds with either common smut or fusarium ear rot (F. verticilliodes) resistance, we conducted a Griffing's diallel analysis on six inbreds of maize, four with high levels of gibberella ear rot resistance representing all of the pedigree groups in our eight gibberella lines, and two with very low levels. Our most gibberella ear rot resistant inbreds, CO433 and CO441, had the lowest disease ratings for all three diseases, the consistently largest general combining ability effects and several significant specific combining ability effects. It was concluded that some inbreds bred specifically for gibberella ear rot would also be useful in breeding for resistance to common smut and fusarium ear rot.
T. 2003. CO441 corn inbred line. Can. J. Plant Sci. 83: 79-80. CO441 is a short-season corn inbred line with improved resistance to silk infection by Fusarium graminearum. Resistance to infection via wounded kernels is also high in CO441. This inbred exhibits excellent combining ability and average to superior lodging resistance in hybrids.
R. I. 2001. CO388 and CO389 corn inbred lines. Can. J. Plant Sci. 81: 457-459. CO388 and CO389 are short-season corn inbred lines with improved resistance to silk infection by Fusarium graminearum. These inbreds are the first to be released from a public breeding program with improved resistance to ear rot; they can be used by maize breeders as a source of resistance. Both inbreds exhibit good combining ability and average to superior lodging resistance in hybrids.
Breeding Methods and Pedigree CO430, CO431 and CO432 were developed by the Eastern Cereal and Oilseed Research Centre, Agriculture and AgriFood Canada, Ottawa, ON, and are all lines derived from a synthetic population made up from five commercial hybrids (Pride K127, Funks G4106, Renk RK21, Northrup King NK9060, and First Line FL1656), which were found, during a routine screening of commercial hybrids in 1989, to possess moderate to high levels of resistance to ear rot. CO430 to CO432 were derived from individual ears of the second cycle of selection of the synthetic by continual inbreeding with selection for silk resistance to F. graminearum at the S 2 , S 3 , S 4 and S 7 generations using the silk channel screening protocol outlined by Reid et al. (1996). Only those lines in which greater than 50% of the fusarium-inoculated plants exhibited no visual symptoms of infection were advanced to the next generation. During development, lines were also selected on the basis of combining ability and adaptation with testing at the S 3 , S 4 and S 7 generations to testers of different heterotic groups. Subsequent studies on the original five hybrids of the synthetic indicate that Pride K127 and Funks G4106 (now known as Enerfeast) were the major sources of resistance. PerformanceIn 1997, the final yield performance evaluation of CO430, CO431 and CO432 was conducted (Table 1) at Ottawa, ON (2750-2800 CHUs) in trials consisting of two-row plots with four replications. Three commercial hybrids (Pioneer 3905, Pioneer 3893 and NK 0565) were used as checks. The testers were all single-cross hybrids: CO328 × CO309 is hybrid of two inbreds derived from Pride 5; CO390 × 99N19 is a Lancaster type tester; and, A641Ht × CM105 is a Reid, B14 type tester. CO432 has slightly better combining ability than the other two inbreds.All three inbreds were rated as possessing excellent emergence and seedling vigour in Ottawa, ON.Other Characteristics CO430, CO431 and CO432 all have wedge-shaped kernels and red cobs. CO430 kernels are red-orange in colour and intermediate between dent and flint. CO431's kernels are also red-orange but are flint-like. CO432's kernels are yellow-orange and flint-like. CO431 is suitable for use as a female or male parent with a seed parent ear yield of approximately 82 g while CO430 and CO432 are best suited as a male parent with a seed parent ear yields of approximately 71 g and 65 g, respectively. All three inbreds take 71-79 d for both 50% tasselling and silking, compared with CO255 which takes 67-68 d and B73 with 83 d. The ears of CO430 are cylindrical, 13 cm in length, 3.8 cm in diameter, have 16 kernel rows, and have up to 6 cm of husk covering the tip of the ear. CO430 is 151-163 cm in height with 14-16 leaves,
. 2006. CO443 corn inbred line. Can. J. Plant Sci. 86: 1157-1160. CO443 is a short season corn (Zea mays L.) inbred line with excellent combining ability and average to superior lodging resistance in hybrids. This stiff stalk type inbred performed best as a parent with non-stiff stalk inbreds. Excellent yields were achieved with the commercial inbred LH176.
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