'NuMex Chaco' Onion

Abstract

Additional index words. Allium cepa, vegetable breeding, Phoma terrestris tion of yellow and white bulbs. Six families that produced only yellow bulbs were selected and recombined in 1989. In 1991, 1993, 1995, and 1997, selections were made using recurrent selection and each year’s selections were intercrossed to form the next generation. The selection criteria were the same as mentioned previously except that the last three generations were also selected for the production of single growing points per bulb (single center). Selection for bolting resistance was done from field plantings that possessed 70% or more plants with seedstalks. Seeds were planted on an early planting date (around 1 Sept.) to induce seedstalk production. This date is three to four weeks earlier than the earliest recommended planting date for fall-planted onions in southern New Mexico. Selection for pink root resistance was accomplished by planting selections in fields that were severely infested with P. terrestris. At bulb maturity, bulbs were rated for the incidence of pink root on their root system. Only bulbs that possessed a healthy root system with minimal symptoms of pink root were selected. Selection for bulb shape was for a medium depth grano shape, and for a bulb that was more rounded, with less pronounced shoulders and taper than a typical grano shape. Selection for bulb shape uniformity was for