GENERATION OF HAPLOIDS IN MAIZE - A MODIFICATION OF THE INDETERMINATEGAMETOPHYTE (IG) SYSTEM

Haploids in maize, Zea mays L., are relatively infrequent, but have co ntinually been considered potential tools for the development of fixed inbred lines or as vehicles of cytoplasmic transfer. This study was u ndertaken to develop an efficient method for the production of androge netic haploids in maize. A novel modification of the indeterminate gam etophyte (ig) system was developed and the resulting frequency of andr ogenetic haploids investigated. The method combines the traditional ge netic behavior of the ig allele with a tertiary trisomic (3 3 B-3LA) s tock in a modified W23 background. Maintenance and generation of ig ho mozygotes are greatly simplified. The frequency of haploid generation has been elevated to as high as 8% utilizing inbreds of Lancaster heri tage. The C, S, SD, Vg, ME, MY, CA, L, and Q cytoplasmic male-sterile stocks, homozygous for ig and of similar background to the tertiary tr isomic stock, are also discussed. Development of a 3(ig) 3(ig) B-3Ld(I g) tertiary trisomic stock in an improved modified W23 background shou ld simplify the production of androgenetic haploids and facilitate the exchange of male-sterile cytoplasm into inbred lines of maize. This s tock has potential use in experiments involving wide hybridizations be tween maize, teosinte [Zea mays subsp. mexicana (Schrader) Iltis], and eastern gamagrass [Tripsacum dactyloides (L.) L.]