1. Specialty Maize (Brewbaker)|.Increasing attention is given to specialty corn types (mainly vegetable maize), in the markets of the world, because of the high net returns to farmers. Surprisingly, there is little interest in public research centers, notably CIMMYT, to invest in research.|.Many primitive maize races are good as vegetables; major civilizations such as Caribbean Arawak used corn only for vegetable purposes.|.In the tropics, the brittle gene is preferred over the sh2, and these two genes, are preferred over the su gene and su + se gene combination because of better tolerance to kernel rot. Waxy is still common in SE Asia, but use of supersweets is increasing rapidly. A $40 million|market already exists in Thailand.|.Specialty starches; the waxy gene (100% amylopectin) has an expanding market for food supplements and adhesives: amylose -extender (ae) doubles amylose levels to over 50%, has unusual properties with a wide range of potential applications. Several other modifier loci are under study, some patented, including combinations of the genes Q!!, 11 and ~ with ~ and wx.|.High-oil: Pure lines can be bred to very high levels of oil content, but with major yield losses (large embryo, small endosperm). Exploitation of xenia effect is underway, mixed seed of male-sterile Sx and a high oil inbred as male brings oil to 6- 7% and above (normal is 4.5% ), with premium prices of 10-15%. Important in Asia where fatty feed supplements are expensive.|.Quality protein maize; see summary at Zhang presentation below.|.Popcorn : Modern popcorn is derived from tropical germplasm. Therefore, many perform well in tropics and have high disease resistance. Special processing requires careful drying between 13.5% land 14.5% moisture. Breeding for pericarps that explode into flakes is achieved through recurrent selection.|2. High Quality Protein Maize (Zhang Shihuang)|.Hard -endosperm versions of opaque -2 now increasing use in China, Africa.|.Yield evidently comparable to normal endosperm, but no isogenic comparisons currently|feasible.|.All are based on CIMMYT populations and hybrids.|.The question of enhanced susceptibility to kernel diseases and insects is under debate.|3. Forage Maize (P. Faylon)|.Chopped green corn excellent for ruminants and best silage, but challenging in tropics.|.Silage is very difficult in tropics, with problems of aerobic fermentation (spoilage) after anaerobic phase sweetens silage. It needs, immediate use once silo is opened.|.Half of Australia corn goes into pit silos, usually concrete lined and plastic covered using tires for weights.|4. Hybrid Maize (L. Empig)|.Hybrids rapidly dominating Asian markets, due to improved yields and appearance.|.Stability is best measured by the durability of a hybrid in the market; while stability regressions (Eberhart) are helpful, variance due to deviations from regression are most important.|.Probable over-emphasis on the maintenance of a very broad germplasm by breeders; Locally-adapted elite hybrids often exploit just one heterotic group and recycled / converted inbreds.|.Use of hybrids changes from 4x to 2x and later to 3x and modified singles. Identification of high-yielding female parents is a major challenge for 2x breeding; few tropicals are superior.|5. Heterosis in Maize (Saxena)|.Many heterotic gorups identified in India, differing from one state to another; many pools exist for RRS improvement and line extraction.|.Nonetheless, a favorite heterotic group identified in 1950's still is excellent, that of CM202 (=CI21E, George Sprague's inbred from Southern dents) times CM111 (Indian inbred from Cuban Flint).|.Open-ended pools recommended, with additions based on GCA of lines with opposite member of the heterotic group.|.Many heterotic groups still reflect those identified by Welhausen for CIMMYT, involving Tuxpeno with ETO, coastal Tropical Flint, Cuban Flint, etc.|.The classic Reid x Lancaster heterotic group can also be used in North India and in highland Africa, although it is useless and of limited value in most of tropics.|.Heterosis increases with genetic diversity; Moll ' s theory that heterosis drops off if diversity is too great is questioned, as the day length sensitivity of tropical inbreds he used, as "highly diverse", make his temperate data suspicious.|6. Diseases and Pests in Indonesia (D. Baco)|.Many pests occur, including pigs and rats.|.IPM is stressed, and should be based on farmer and environmenta1- friendly procedures.

English

0208|AGRIS 0201|AL-Maize Program|R01PROCE

Juan Carlos Mendieta

CIMMYT Publications Collection