1. Genetics of Resistance to Pink Stem Borer Attack in Flint Maize Populations A. Butrón, P. Soengas, P. Revilla, A. Ordás, and R.A. Malvar Misión Biológica de Galicia

2. Introduction Pink stem borer is the main pest in northwestern Spain Average yield losses = 15% Ear damage Stem damage Plant Breeding is one of the means that can be used in a pest integrated control system

3. Introduction Life cycle of Sesamia nonagrioides Lef. Larva Eggs Pupa Moth

4. Introduction Previous studies have identified sources of resistance and determined the genetics involved Nevertheless, resistance of flint maize populations has not been fully prospected  Objective: to test the variability for resistance to pink stem borer attack among flint maize populations and to determine the genetics involved

5. Introduction Local flint maize varieties supply: –Early vigor –Early flowering –Lower stem lodging –Relative resistance to drough stress –High quality flours

6. Material and methods Diallel among 10 flint maize populations PopulationOrigin GallegoNorth Gallego/Hembrillla norteñoNorth NorteñoNorth Norteño largoNorth Basto/Enano levantinoEast FinoCenter TremesinoSouth Relámpago 8 hilerasArgent. Amarillo precoz de SimoneArgent. LongfellowUSA

7. Material and methods Diallel was tested in 1998 and 1999 Randomized complete block designs Ten plants/plot were infested with Sesamia nonagrioides eggs Tunnel length to estimate stem damage General appearance of the ear to estimate ear damage (1-9) Analysis II of Gardner and Eberhart (1966)

8. Material and methods Analysis II (Gardner and Eberhart, 1966) –Y ij = µ v + 1/2(v i + v j ) + h ij »Y ij = observed mean of the cross of varieties i and j »µ v = mean of all varieties »v i and v j = variety effects »h ij = observed heterosis –hij =  (h +h i + h j + s ij )

9. Results Analysis of variance of the diallel Source of variation TLGA Population** Variety** HeterosisNSNS P x YearNSNS * Significant at the 0.05 probability level.

10. Results Variety effects = difference between a paticular variety mean and the mean of all varieties Population TL GA Gallego -5.7-0.95 Gallego/Hn -5.6-0.33 Norteño 1.5-0.50 Norteño largo 2.2-0.50 Fino 10.5 0.75 Basto/El-23.6-0.12 Tremesino -6.3 0.97 Longfellow 0.5 0.15 Relámpago 10.0 0.42 Simone 16.6-0.03 LSD 16.5 1.12

11. Conclusions  Additive gene effects were the most important effects  Variability for stem resistance was larger than variability for ear resistance  Basto/Enano levantino could be the base material in a recurrent selection program