Karyological and isozyme variation in West Indian and allied American mainland races of maize

The maize races (Zea mays L.) of the West Indies have considerable historic and economic importance. The present study reports the isozyme variation in these races and selected collections of related South and Central American races. These data were subjected to cluster and principal component analyses in conjunction with isozyme data previously collected for other mainland races. Karyological descriptions from more than 200 accessions of West Indian and related races were taken from previous studies by McClintock and co-workers and were analyzed with the same statistical techniques used for the isozyme data. Viewed together, isozyme and karyological evidence revealed that the evolutionary history and systematic relationships of these races were complicated. The West Indian races formed a distinct supraracial group with affinities especially to races from the Caribbean coast of South America and the Central American lowlands. Geographic variation in the chromosome morphology of West Indian races seemed strongly associated with colonial history. Two races, Early Caribbean and St. Croix, were not very closely related to other West Indian races. Haitian Yellow was more distantly related (especially karyologically) to other West Indian races than its morphology would suggest. It is suggested that Cuban Flint is an indigenous Cuban race rather than simply a South American Cateto recently introduced to Cuba. Chandelle was highly variable and had affinities to coastal South American races, Cuban Flint, and Coastal Tropical Flint. The latter race was more closely related to Cuban Flint and Chandelle than to Tus6n, which karyologically strongly resembled lowland Central American races but isozymatically resembled coastal South American races. MAIZE (Zea mays L.) of the West Indies has been classified into seven races (Fig. 1) that have considerable historic and economic importance (Brown, 1960). Columbus probably carried maize from the West Indies back to Europe on his first voyage (Hatheway, 1957), and soon afterwards other European explorers transported it from the West Indies to many parts of the world, leading to maize's international importance as a crop (Finan, 1950; Brown, 1960). The West Indian races have been judged to be "probably one of the world's most important sources of maize breeding material" (Brown, 1960, 2). The results of breeding studies (Goodman, 1965; Eberhart, 1971; Hallauer, 1978) have supported Brown's judgement. Among the more prominent and widely distributed indigenous West Indian races are Tu' Received for publication 26 September 1986; revision accepted 10 February 1987. Paper No. 10733 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC. This work was supported in part by NIH Research Grant No. GM1 1546 and by a grant from Pioneer Hi-Bred International. PKB was supported by USDA-SCA No. 58-7B303-573. We thank Drs. W. L. Brown, J. F. Doebley, and J. F. Wendel for their helpful critiques of this manuscript, and D. Beattie, J. Poole, and E. Terrell for their technical assistance. son and Coastal Tropical Flint [the latter including Hatheway's (1957) Maiz Criollo of Cuba] which, together with Haitian Yellow, form a complex of morphologically similar races (Brown and Goodman, 1977). Tuson and Coastal Tropical Flint are also found in South and Central America. Tuson is particularly valuable agronomically because of its vigor and high yield, which Brown attributes to its possible hybrid origin. Brown and Goodman (1977) also consider Haitian Yellow (known only from a small region of Haiti) to be descended from a hybrid, probably from a cross of Coastal Tropical Flint. Based upon their morphologies, Haitian Yellow, Tuson, and Coastal Tropical Flint are considered to be related to races of lowland South America such as Costefio or Comiun (Grant et al., 1963; Brown and Goodman, 1977) and possibly Puya (Roberts et al., 1957; Goodman and Bird, 1977). Chandelle [includes Hatheway's (1957) Canilla] is readily distinguished from other West Indian races by its thin cob. This race is most commonly found in the Greater Antilles and Venezuela (Brown, 1960) and is morphologically most similar to Canilla and Puya from the Caribbean coast of South America (Roberts et al., 1957; Grant et al., 1963; Brown and Goodman, 1977; Goodman and Bird, 1977).