Genomic regions controlling stalk-rot resistance
--Giorgio Binelli, Luca Gianfranceschi, Renato Tarchini, Raffaella Greco, Graziana Taramino and M. Enrico Pè

The F3 families obtained by selfing the F2 plants used for the production of the genetic map described in the companion report have been analysed for resistance to infection of Fusarium graminearum, the conidial form of Gibberella zeae, one of the agents of stalk-rot. 112 F3 families were grown according to a Randomized Block Design: fifteen plants per plot were injected with the spore suspension one week after anthesis and 40 days later harvested and split longitudinally. The character measured was the infected area/total area ratio in the inoculated internode (INF). Both regression analysis between each RFLP and RAPD locus and the INF character and interval mapping (using MAPMAKER/QTL) were used to localize genomic regions involved in resistance to Gibberella zeae. The results are indicated in Figure 1 where each marker is represented by its R2 value while the likelihood surface obtained by interval mapping is shown limited to the significant regions. The concordance between the two methods is remarkable, with the exception of clone pio100033b (chromosome 2) significant by regression but not by interval mapping and of the region between umc42 and pio200802 (the opposite). The results obtained show that at least four genomic regions exist in the maize genome involved in the determination of resistance to stalk-rot.

Figure 1. Localisation of putative QTLs controlling resistance to Gibberella zeae in maize. Horizontal bars indicate degree of correlation between RFLP loci and the character in terms of R2. *=p<0.05; **=p<0.01. The continuous line represents the likelihood surface as obtained by interval mapping of QTLs.  1&2, 3&4, 5&6, 7&8, 9&10.

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