Contents - Faperta

Physico-Chemical and Molecular Markers for Resistance to Insect Pests 175
previously mapped to the distal part of the short arm of wheat chromosome group 7. The
selection accuracy when the RFLP markers Xhcd98, Xpsrll9, or XZnfp and Pr1b fl anking
Gby are used together to tag Gby is 99.78%, suggesting that they can be used successfully
in MAS (Boyko, Starkey, and Smith, 2004).
In barley, resistance to cereal aphids, Rhopalosiphum padi (L.) and R. maidis (Fitch.)
(Moharramipour et al., 1997), and the Russian wheat aphid, D. noxia (Nieto-Lopez and
Blake, 1994) has also been mapped.
Maize
A linkage map with 932 ESTs has been developed in maize (Davis et al., 1999). A small
number of QTLs have been found to account for 50% of the genetic variation for resistance
to sugarcane borer, Diatraea saccharalis Fab. and southwestern corn borer, Diatraea grandiosella
(Dyar) (Khairallah et al., 1997). Several chromosomal regions were involved in the
resistance to stem borers, and some QTLs were common to both the species. Genetic diversity
decreased in a maize population during selection for resistance to pink stem borer,
Sesamia nonagrioides LeFevbre (as expected since random genetic drift as well as selection
could reduce genetic variability), but not signifi cantly (Butron et al., 2005). Changes in the
frequency of fi ve alleles were signifi cantly greater than expected. Linear trend of the
departure from the random genetic drift model was signifi cant for some allelic versions
of two SSR markers, umc1329 and phi076, indicating that directional selection was acting
on these loci. The signifi cant effect of directional selection on those markers suggested
the presence of QTLs for tunnel length and/or for yield under artifi cial infestation with
S. nonagrioides on the long arm of chromosome 4.
Genes controlling the synthesis of DlMBOA, the maize leaf organic acid with antibiotic
effects on European corn borer, Ostrinia nubilalis (Hubner) leaf feeding, occur on maize
chromosome 4. Resistance to stem boring by O. nubilalis in temperate maize and to Diatraea
species in tropical maize appears to be controlled by QTLs on chromosomes 2, 3, 5, 7, and
9 (Cardinal et al., 2001). Of the 12 QTL for neutral detergent fi ber (NDF) and acid detergent
fi ber (ADF) in leaf-sheaths, fi ve for each trait were at or near QTL for European corn borer
tunneling (Cardinal and Lee, 2005). Four of the eight leaf-sheath acid detergent lignin
(ADL) QTL were detected in the same genomic regions as ECB QTL. Resistance to European
corn borer may be associated with a subset of the QTLs observed for cell wall components
and ADF and starch concentration in the stalk (Krakowsky, Lee, and Holland, 2007). QTLs
affecting resistance to O. nubilalis have been identifi ed in genomic regions of maize chromosomes
2, 3, 5, and 9 (Shon et al., 1993; Cardinal et al., 2001; Jampatong et al., 2002;
Krakowsky et al., 2002). Comparison of QTLs linked to stem boring and leaf feeding
resistance have shown that there are few common elements in the genetic control of the
two types of resistances ( Jampatong et al., 2002). However, QTL alleles on maize
chromosomes 2, 5, 7, and 9 play a major role in resistance to stem boring by O. nubilalis,
southwestern corn borer, D. grandiosella and the sugarcane borer, D. saccharalis (McMullen
and Simcox, 1995; Bohn et al., 1996, 1997; Groh et al., 1998a, 1998b; Khairallah et al., 1998;
Cardinal et al., 2001). The major QTLs for production of silk maysin and apimaysin, which
control resistance to H. zea, occur on chromosomes 5 and 9. The relationship between the
QTLs for different types of resistance on chromosomes 5 and 9 is not fully understood
(Cardinal et al., 2001). Selection in maize for rind penetrometer resistance (RPR), linked to
stalk resistance to European corn borer, has been found to be useful in enhancing germplasm
for stalk strength, and therefore, improving stalk lodging resistance. Multilocus
models, including single-effect QTLs and epistatic interactions, accounted for 33.4, 44.7,