Figure 1. Map of Mexico with agricultural regions (after Arroyo, 1990); numbers identify states in the following order: 1= Baja California, 2= Baja California Sur, 3= Sonora, 4= Sinaloa, 5= Nayarit, 6= Chihuahua, 7= Coahuila, 8= Durango, 9= Zacatecas, 10= Nuevo León, 11= Tamaulipas, 12= San Luis Potosí, 13= Aguascalientes, 14= Guanajuato, 15= Jalisco, 16= Querétaro, 17= Michoacán, 18= Hidalgo, 19= México, 20= Morelos, 21= Tlaxcala, 22= Puebla, 23= Colima, 24= Guerrero, 25= Oaxaca, 26= Chiapas, 27= Veracruz, 28= Tabasco, 29= Campeche, 30= Yucatán, 31= Quintana Roo.