EARLYTROP: A PROGRAM TO ADAPT 100% TROPICAL MAIZE GERMPLASM TO SHORT-SEASON ENVIRONMENTS
Tropical maize germplasm can contribute useful and unique genes. It can provide greater resistance to pests and diseases, better quality crops, and trait genes and combinations not often present in commercially available northern U.S. temperate hybrids. Uniform farmer fields with genetically identical hybrids have a high risk of genetic vulnerabilities due to disease epidemics and abiotic stresses, especially after the recent major industry mergers. The EarlyTROP program was created with the long-term goal to increase the genetic diversity of short-season maize carrying 100% tropical germplasm. Five tropical maize populations were assessed for adaptation to ND short-season environments: NDSHLC (an improved composite from highland Mexico), BS16 (an improved strain of ETO from Colombia), BS28 (an improved strain of Tuxpeño from Mexico), BS29 (an improved strain of Suwan-1 from Thailand), and BS39 (an improved strain of Tusón mainly from Brazil and Cuba). The program conducted three cycles of stratified mass selection for days to silking near Casselton and Prosper, ND for all varieties except for NDSHLC, which had six selection cycles of stratified mass selection. Selected populations (NDHighland, NDEto, NDTuxpeño, NDSuwan-1, and NDTusón), and 31 checks including standard known and commercialized population and single-cross hybrids were evaluated across 12 short-season environmend. Stratified mass selection was a cost-effective and successful breeding procedure for adapting tropical populations to short-season environments without exceptions. NDTuxpeño is ready to be used in very short-season areas. It has shown to be the driest population of the experiment with 17.6% grain moisture at harvest time, statistically lower than 18 checks. Thus, confirming its adaptation to short-season environments. NDHighland, NDEto, NDSuwan-1, and NDTusón also showed evidence of adaptation. Adapted varieties represent unique new options for maize breeders to expand the genetic base of their current breeding programs. This gene pool, not present in current U.S. genome sequences or short-season areas, will offer unique early maturing competitive genes and products not available in the northern U.S. industry.