Feasibilty of zein proteins, simple sequence repeats and phenotypic traits for background selection in quality protein maize breeding

Abstract

Widespread adoption of quality protein maize (QPM), especially among tropical farming systems has been slow mainly due to the slow process of generating varieties with acceptable kernel quality and adaptability to different agroecological contexts. A molecular based foreground selection system for opaque 2 (o2), the cause of enhanced lysine content in maize exists. Background selection systems albeit, are poorly developed in spite of the mapping of putative loci associated with kernel modification and knowledge on causes of modification. The aim of this study was to develop background selection systems for o2 introgression into locally adapted genotypes. Experiments were conducted at Makerere University Agricultural Research Institute, Kabanyolo (MUARIK), in Uganda on backcross progeny (BC1F1) and BC2F2), derived from a locally adapted line 136R and a QPM donor CML176. We tested the use of zein proteins known to influence modification as well as DNA markers and phenotypic descriptors as tools for background selection for recurrent parent genome and modifier loci in locally adapted maize genotypes. Simply inherited traits such as maize streak virus disease resistance were suitable for background selection. Other traits include plant and ear heights. The simple sequence repeats markers mapped to chromosomes 3, 5, 7, respectively and associated with quantitative trait loci (QTL) conditioning resistance in maize to grey leaf spot and anthesis to silking interval were suitable for assay of recurrent parent genome. The 27-kDa g zein protein levels was suitable for background selection for kernel modification. It should, however, be used along with other zeins such as the 22 kDa and 19 kDa zein proteins.L'adoption du ma\uefs de prot\ue9ne de qualit\ue9 (QPM), sp\ue9cialement parmi les syst\ue8mes culturaux tropicaux a \ue9t\ue9 lente principalement due au processus lent de g\ue9n\ue9ration de vari\ue9t\ue9s avec de grains acceptables de qualit\ue9 et d'adaptabilit\ue9 \ue0 diff\ue9rents contextes agro\ue9cologiques. Il existe une cause du contenu am\ue9lior\ue9 de la lysine dans le ma\uefs, un syst\ue8me bas\ue9 sur la s\ue9lection mol\ue9culaire opaque 2 (o2). Malgr\ue9 les syst\ue8mes de s\ue9lection de fond, ceux-ci sont pauvrement d\ue9velopp\ue9s en d\ue9pit du "mapping" du loci associ\ue9 avec la modification du grain et la connaissance sur les causes de modification. L'objet de cette \ue9tude \ue9tait de d\ue9velopper les syst\ue8mes de s\ue9lection de fond pour l'introgression o2 dans les g\ue9notypes localement adapt\ue9s. Des essais \ue9taient conduits sur la prog\ue9nie de "backcross" (BC1F1) et BC2F2), d\ue9riv\ue9s de lign\ue9es adapt\ue9es 136R et un QPM doneur CML176. Nous avons test\ue9 l'usage des prot\ue9ines z\ue9ines capables d'influencer de modifications des marqueurs d'ADN et descripteurs ph\ue9notypiques comme mat\ue9riel de s\ue9lection de fond pour parent de g\ue9nome recurrent et modifiant de loci dans les g\ue9notypes de ma\ubfs localement adapt\ue9s. Des traits simplement h\ue9rit\ue9s dont la r\ue9sistance \ue0 la maladie de virus de m\ue8che \ue9taient appropri\ue9s pour la s\ue9lection de fond. D'autres traits incluaient la hauteur de plants et la taille de l'\ue9pis. Les marqueurs SSR repr\ue9sent\ue9s sur les chromosomes 3,5,7, respectivement et associ\ue9s aux traits quantitatifs loci (QTL) conditionnant la r\ue9sistance dans le ma\ubfs \ue0 la maladie de t\ue2che grise de feuilles ansi que l'intervalle de l'anthesis jusqu'\ue0 la s\ue9cr\ue9tion du "silk" \ue9taient appropri\ue9s pour \ue9valuation du g\ue9nome parent recurrent. Les niveaux de prot\ue9ines z\ue9ines 27-kDa g \ue9taient appropri\ue9s pour la s\ue9lection de fond pour la modification de grains. Ceci pourra \ueatre utilis\ue9 \ue0 c\uf4t\ue9 d'autres z\ue9ines telles que les prot\ue9ines z\ue9ines 22 kDa et 19 kDa