CRUZ, I.

GUIMARAES, P. E. O.

SANTOS, J. P.

VIANA, P. A.

WAQUIL, J. M.

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RESISTANCE TO THE MAIZE WEEVIL, SITOPHILUS ZEAMAIS,AMONG ENTRIES FROM THE NATIONAL AGRONOMICPERFORMANCE TRIAL FOR QPM CORN GENOTYPES. Jamilton PereiraSantos(1), Paulo Evaristo Oliveira Guimaraes(1), Jose Magid. Waquil(1), Paulo Afonso Viana(1) &Ivan Cruz(1); (1) Embrapa Milho e Sorgo, Cx. Postal-151, 35701-970, Sete Lagoas, MG, Brazil.KEY WORDS Maize weevil, Sitophilus zeamais, stored grain pest, QPM corn, resistance toinsects.Corn is the most widely grown grain crop in Brazil, occupying more than 12 million hectares.Grain storage remains a problem. The maize weevil, Sitophilus zeamais, has long been consideredone of the most important pests of stored corn grain in Brazil (Santos and Fontes 1990).  Mertz etal. (1964) reported the discovery of a corn type with the Opaque-2 (O2), a mutant gene thatchanges the protein composition and increases the content of lysine and tryptophan, in the maizeendosperm. However, the endosperm of the O2 gene corn was found to be light and soft (Dimler1966). The softness of the endosperm caused the O2 maize to be very attractive to the stored grainpest (Ortega 1974). To solve this problem, researchers in CYMMIT, Mexico, transferred the O2gene to corn with normal kernels. This new type of maize was called Quality Protein Maize(QPM). Additional breeding selections made at Embrapa Maize and Sorghum Research Center inBrazil produced some white and yellow color QPM lines and/or hybrids. Many differentapproaches have been used to evaluate grain for resistance to insects. One technique which seemsto be very appropriate for measuring susceptibility was reported and named by Dobie (1974) asIndex of Susceptibility (IS). This method is based on the number of progeny from the firstgeneration of insects emerged after a set of females were allowed to oviposit for a fixed number ofdays on test material and on the developmental period (egg to adult) of this progeny. Theobjective of this research was to evaluate a selected group of QPM experimental genotypes inrelation to the susceptible check, IAC- I O2 IV, from the germplasm bank and BR-106 acommercial variety for genetic resistance to the maize weevil.This research was conducted at the Embrapa Maize and Sorghum Research Center, Sete Lagoas,MG, Brazil. The seed samples, which had never been treated with insecticide, were placed in thefreezer (-15C) for five days to eliminate any insect infestation. The insects used came from a S.zeamais laboratory culture maintained in controlled environment (70% R.H. and 27±0.5C).Neonate to 5-day-old insects were placed in a small sample of each tested entry to allow them toadjust to the new food source and oviposition site on the experimental materials. The parameterderived from the procedure referred above is the IS and defined as:              (x, y)                                                      log e  xMDP  =             ,                      and            I S =  ________     X 100                x                                                           MDPWhere:MDP   = Mean of the Developmental Periodx  = Number of insects emerged daily from the F1 generation       y  = Number of days from initial infestation to emergence of insects       IS = Index of SusceptibilityThe Index of Susceptibility (IS) has been described in detail and found to be correlated withimportant genetic resistant factors like grain weight loss number of F1 progeny grain hardness andrate of insect increase (Classen et al.1990). The antibiosis and nonpreference were observed actingtogether as mechanisms of resistance to the maize weevil in corn grain (Santos and Foster 1983),and they would possibly be responsible for the variation of the IS value.In Table 1 it is possible to see the IS to maize weevil for all genotypes tested. The higher the ISthe more susceptible is the genotype. Entries followed by the same letter are not different fromone another at the =0.05 level of significance. The IS value ranked from 7.78 for the CMS 456to 10.78 for the CMS 28, with the IS for the susceptible check being 9.98. Nine QPM genotypeshad the IS lower than the BR 106, the normal endosperm resistant check but other three QPMshad IS higher than the susceptible check. The fact that some QPM genotypes had IS very similarto the normal endosperm resistant check is a very significant result. It is one indication that someof the QPM corn tested, in addition to carrying genes for enhanced protein quality, also carrygenes for resistance to maize weevil. This observation opens the possibility to increase theresistance to insect attack by means of specific selection for resistance, since this trait was notincluded in the breeding process of the QPM hybrids tested. Also, it indicates the possibility todevelop QPM commercial hybrids with resistance to stored grain insects in levels compatible withthose of the normal endosperm commercial hybrids. It should also be mentioned here that some ofthese QPM hybrids have yielded as much grain as some of the commercial hybrids tested(EMBRAPA-CNPMS, 1994). Many authors have attempted to explain the genetic resistance incorn grain to maize weevil based on the chemical composition of the grain (Singh andMacCain,1963. Whitney (1973) observed that vitreum endosperm contributed to resistance incorn.  Some more recent research on resistance to maize weevil in corn grain (Serratos et al. 1987,1993; Classen et al. 1990) have discovered that 90% of phenolic acid compounds, mainly in theform of (E)-ferulic acid were found concentrated in the pericarp, testa, and aleurone layer of theseeds, which play a very important role in suppressing weevil development, most possibly due toantibiosis effect. The results observed in this research agree with those reported by Arnason et al.(1992) when they studied one group of QPM genotypes in relation to maize weevil resistance. Theultimate conclusion possible to draw from this research is the discovery of a group of QPM cornthat carry genes for resistance to the maize weevil, S. zeamais. It can also be said that the QPMcorn is not necessarily, or not always, more susceptible to weevil damage than is the normalendosperm type of corn.ReferencesArnason, J.T., J.D.H. Lambert, J. Gale, J. Mihm, M. Bjarnason, D. Jewell, J. A. Serratos,J. Fregeau-Reid and L. Pietrzak. 1993. Is quality protein maize more susceptible than thenormal lines to attack by the maize weevil Sitophilus zeamais? Postharvest Biology andTechnology, 2:349-358.Classen, D., J. T. Arnason, J.A. Serratos, J.D.H. Lambert, C. Nozzolillo and B.J.R.Philogene. 1990. Correlation of phenolic acid content of maize to resistance to Sitophiluszeamais, the maize weevil, in COMMIT’s collections. J. Chemical. Ecol., 16:301-315.Dimler, R.J. 1966. Report on kernel structure and wet milling of high lysine corn. Proc. HighLysine Corn conf. Purdue Univ. U.S.A., pp. 121-127.Dobie, P. 1974. Laboratory assessment of the inherent susceptibility of maize lines to post-harvestinfestation by Sitophilus zeamais Motschulsky. (Coleoptera: Curculionidae). Jour. StoredProd. Res. 10:183-197.Embrapa Milho e Sorgo. 1994. Relatorio Tecnico Anual do Centro Nacional de Pesquisa deMilho e Sorgo. 1992-1993. S ete Lagoas: EMBRAPA-CNPMS, 1994. 342 p.Mertz, E.T., L.S. Bates, and O.E. Nelson. 1964. Mutant gene that changes protein compositionand increases lysine content of maize endosperm. Science, 145:279-280.Ortega A. G. de Leon, G. Grandos ans S. K. Vasal. 1974. Disease - insect interaction in qualityprotein maize. IN: High Quality Protein Maize, Hutchinson Ross Publishing Co.,Strondsburg, PA. pp 173-192.Santos, J.P. and J.E. Foster. 1983. Mecanismos de resistência do grao de milho ao gorgulho.Pesq. Agropec. Bras., Brasilia, 18:1059-1063.Santos, J.P. and R.A. Fontes. 1990. Armazenamento e Controle de insetos no milho estocado napropriedade agricola. Informe Agropecuária. Belo Horizonte, 14:40-45.Serratos J.A., J.T. Arnason, C. Nozzolillo, J.D.H. Lambert, B.J.R. Philogene, K. Davidson,L.  Peacock, J. Atkinson and P. Morand. 1987. Contributions of phenolics antefeedants toresistance of maize to the maize weevil, Sitophilus zeamais. J. Chem. Ecol., 13:751-761.Serratos J.A., A. Blanco-Labra, J. A. Mihm, L. Pietrzak and J.T. Arnason. 1993. Generationmean analysis of compounds in maize grain and susceptibility to maize weevil Sitophiluszeamais  infestation. Can.J. Bot. 71:1176-1181.Singh, S.R., and F.S. McCain. 1963. Relationship of some nutritional properties of the cornkernel to weevil infestation. Crop. Sci. 3:259-61.Whitney, W.K. 1973. Control of insects by non-chemical methods. Tropical Stored ProductsInformation. London. No. 25 pp. 20-21.Table 01 - Index of Susceptibility (IS) of some Quality Protein Maize (QPM ) from the NationalAgronomic Performance Trial, tested for genetic resistance to maize weevil. SeteLagoas, MG, Brazil. 1998.ORDER GENOTYPE NAME INDEX OFSUSCEPTIBILITY (IS)101020304050607080910111213CMS-28CMS-50IAC I O2 IV2BR 106**3BR 473CMS- 454CMS-455 CECMS-52CMS-452CMS-474CMS-476CMS-59CMS-45610.78 A10.54 A  9.98 A  9.33 A  9.23 A  9.15 A  9.08 A  9.05 A  8.64 A  8.56 A  8.26 A  8.10 A  7.78 A1 Mean followed by the same letter are not significantly different from one another at 0.05 level,according to the Duncan`s  Tesst.2 Opaque-2 (O2) genotype maize3 Normal endosperm open pollinated maize variety

Resistance to the maize weevil, Sitophilus zeamais, among entries from the national agronomic performance trial, for QPM corn genotypes.

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