Variability analysis of normal and opaque2 maize inbred lines

Abstract

Nutritional value of maize is poor due to deficiency of two essential amino acids - tryptophan and lysine. It was shown than opaque2 (o2) mutations can nearly double the lysine and tryptophan content of the endosperm compared with the normal type. Maize Research Institute Gene bank maintains a collection of opaque2 inbred lines developed in the seventies, primarily based on kernel hardness and analytical methods. In order to describe these lines in more detail they were analyzed for tryptophan content and subjected to SSR analysis with opaque2 markers, a marker for endosperm hardness modifier gene and the most significant amino acid modifier markers. Also, a pathogenicity test for inbred lines tolerance to Fusarium spp., which is one of the most important maize pathogens in our region and a causer of maize stalk, root and ear rot, was performed. Differences in tryptophan content between normal and opaque2 lines were significant. All primers used for distinguishing alleles between normal and opaqu2 inbred lines gave positive results. Each genotype gave a specific allelic pattern with amino acid modifier gene primers, without any obvious correspondence to the tryptophan content. Phythopathogenicity test showed on average higher susceptibility to Fusarium graminearum of opaque2 genotypes. These results gave an insight into the applicability of the methods in describing opaque2 lines to be converted into quality protein maize QPM - genotype in which opaque2 has been incorporated along with associated modifiers.

Kukuruz ima nisku hranjivu vrednost zbog nedostatka dve esencijalne amino kiseline - triptofana i lizina. Utvrđeno je da opaque2 (o2) mutacija može skoro udvostručiti sadržaj lizina i triptofana u endospermu kukuruza. Banka gena instituta za kukuruz 'Zemun Polje' poseduje kolekciju opaque2 inbred linija razvijenih tokom sedamdesetih godina, prvenstveno na osnovu tvrdoće zrna. Sa ciljem detaljnijeg opisa ovih linija urađena je analiza sadržaja triptofana i SSR analiza sa opaque2 markerima, markerom za gen modifikator tvrdoće endosperma i najsignifikantnijim markerima za gene modifikatore amino kiselina. Takođe je urađen test fitopatogenosti radi utvrđivanja osetljivosti opaque2 genotipova na Fusarium gramaenarum, jednog od najvažnijih prouzrokovača truleži stabla, korena i klipa kukuruza u našem regionu. Utvrđene su značajne razlike u sadržaju triptofana između normalnih i opaque2 linija kukuruza. Svi SSR prajmeri korišćeni za razlikovanje normalnih i opaque2 linija su dali pozitivne rezultate. Svaki od analiziranih genotipova je dao specifičnu alelnu sliku sa markerima za gene modifikatore amino kiselina, bez očigledne saglasnosti sa sadržajem triptofana. Test fitopatogenosti je, u proseku, pokazao veću osetljivost opaque2 linija na Fusarium graminearum. Ovi rezultati su dali uvid u primenjivost navedenih metoda za opisivanje opaque2 linija radi njihovog konvertovanja u kukuruz visokog kvaliteta proteina (QPM) - genotipa u koji se opaque2 inkorporira zajedno sa odgovarajućim genima modifikatorima.