Inheritance of stem borer resistance in maize (Zea Mays L.)

[摘要] English: The stem borer Busseala fusca (Lepidoptera: Noctuidae) is animportant pest in maize production in South Africa and many othercountries South of the Sahara.The mean goal of the present study was to gather information aboutthe genetic and phenotypic characteristics of B. fusca resistance inmaize as a help to understand the nature of the resistance in order toovercome the difficulties standing in the way of transfer of theresistance from available sources to the local and adapted cultivars.The inheritance was studied through assessment of the resistance onbasis of phenotypic expression after artificial infestation with first instarlarvae of B. fusca of 36 crosses of 18 susceptible inbred lines with twosources of resistance, CML 139 and Mp706. Plants were evaluated forcharacters like leaf feeding, larval mass gain, internal damage andyield losses. A scaling test was used to analyse the data. Resultsindicated that additive, dominant and non-heritable parameters wereall important for B. fusca resistance. GCA and SCA values indicatedgood performance of the crosses for additive and dominant geneeffects (heterosis). The correlation coefficient was used to evaluate therelatedness of three parameters of assessment of the resistance andthe result indicated that there are significant correlations between leaffeeding, larval mass gain and internal damages caused by the insect.Different levels of inheritance from the two sources were seen in eachcross indicating that the resistance is inherited differently, dependingon the source used.F2:3 lines were obtained from selected crosses (CML 139 xP608) and(Mp706 xP608) for AFLP analysis. The analysis of the 10 categories ofphenotypic assessment evaluated for the fragment segregationindicated that additive gene contribution from the parents was presentat several loci. This was in agreement with negligible one locus nonallelic interaction found by the scaling test for absence of epistasis.Different fragments were found to be specific for resistant parents andthe progeny, which indicated that dominance was again present in theinheritance of the resistance.In this study we have concluded that despite attempts to improve thevarieties' resistance by transfer of the resistance from resistantsources to more adapted varieties, the polygenic nature of theresistance and the presence of high levels of non-inherited parametersare still the most important cause of ineffective use of conventionalmethods of breeding.The use of markers to tag the genetic information about the inheritanceof the resistance in cross progenies of resistant and susceptiblevarieties is seen as one of the ways to overcome this barrier.Unfortunately the use of this important tool is still not perfected for usein this particular area of science. Until the perfection of molecularmarker technology, the recurrent selection approach will have to beused for insect resistance improvement in maize cultivars.

[发布机构] University of the Free State