Genetics of Resistance to Pink Stem Borer Attack in Flint Maize Populations A. Butrón, P. Soengas,...

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