Submitted to: Maize Genetics Conference Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 13, 1997
Publication Date: N/A
Technical Abstract: Multiple inoculations by inoculative Graminella nigrifrons were used to identify tolerant germplasm and develop highly tolerant inbred lines from the Virgin Island (V.I.), Dominican Republic, and Compuesto Cuba 551 populations which were crossed to a susceptible inbred, Va35. F2 populations were produced and 76 F2 individuals from each population were evaluated for their response to MCD. Veinbanding, chlorosis, and leaf twist and tear were used to evaluate disease severity. Plants were rated on a 1-5 scale (1= no symptoms, 5= severe) for each symptom type at 7, 11, 14, 18, and 21 days after the first of three inoculations. Individual plant AUDPC scores were calculated for each symptom. The V.I. x Va35 population was selected for mapping based on the level of tolerance and normality of the progeny distribution. An additional 240 F2 progenies of this cross were evaluated for disease reaction. Eighty-seven F2 progenies were selected from the tolerant and susceptible tails of the V.I. x Va35 population and genotyped with 107 RFLP markers. MAPMAKER and a single factor ANOVA were used to locate QTLs controlling host response to each of the three symptom types. The log 10 of the odds ratio (LOD) scores and chromosomal locations of two major QTLs for chlorosis and leaf twist and tear were similar to the QTLs previously reported for veinbanding. Major QTLs were found within a 99 cM region of chromosome three with peaks at asg24 (veinbanding, LOD 8.0) and php20508 (veinbanding, LOD 11.2); within a 126 cM region on chromosome ten, peaks were found at umc259 (veinbanding, LOD 3.4) and umc44 (veinbanding, LOD 6.0). Possible minor QTLs were identified on chromosome five at bnl5.40 (leaf twist and tear, LOD 3.1) and on chromosome seven at bnl8.39 (ANOVA, p=0.023).