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

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 meansthat can be used in a pest integrated control system

Introduction

Life cycle of Sesamia nonagrioides Lef.

Larva

EggsPupa

Moth

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

Introduction

• Local flint maize varieties supply:– Early vigor– Early flowering– Lower stem lodging– Relative resistance to

drough stress– High quality flours

Material and methods

Diallel among 10 flint maize populations

Population Origin• Gallego North• Gallego/Hembrillla norteño North• Norteño North• Norteño largo North• Basto/Enano levantino East• Fino Center• Tremesino South• Relámpago 8 hileras Argent.• Amarillo precoz de Simone Argent.• Longfellow USA

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)

Material and methods

Analysis II (Gardner and Eberhart, 1966)

– Yij = µv + 1/2(vi + vj) + hij

»Yij = observed mean of the cross of varieties i and j

»µv = mean of all varieties

»vi and vj = variety effects

»hij = observed heterosis

– hij = (h +hi + hj + sij)

Results

Analysis of variance of the diallel

Source of variation TL GA

Population * *Variety * *Heterosis NS NS

P x Year NS NS

* Significant at the 0.05 probability level.

Results

Variety effects = difference between a paticular variety mean and the mean of

all varietiesPopulation TL GA

Gallego -5.7 -0.95Gallego/Hn -5.6 -0.33Norteño 1.5 -0.50Norteño largo 2.2 -0.50Fino 10.5 0.75Basto/El -23.6 -0.12Tremesino -6.3 0.97Longfellow 0.5 0.15Relámpago 10.0 0.42Simone 16.6 -0.03LSD 16.5 1.12

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