Recent Progress in Breeding for Improved Performance in Programmed Cropping Systems

This study investigated the inheritance of traits related to performance in programmed cropping systems, known as 60-day production. Five lines that showed different performance in a 60-day trial were inter-crossed and progeny raised to establish a second 60-day trial. There were significant differences between families for all the traits measured and the value of the parental combining abilities was calculated. For all traits except crown diameter, only the additive genetic variance (GCA) was significant. The number of flowers per inflorescence and the number of inflorescence per crown were the strongest additive traits, with 97 and 78% of the genetic variation being additive for these traits respectively. These results support earlier findings which suggested that the number of inflorescences per crown and flowers per inflorescence are the key traits in breeding for improved 60-day performance. The strong additive component should allow parents to be chosen on their phenotypic performance in field trials. A further investigation was performed to assess the effect of two planting dates on the 60-day performance of 15 lines that had shown either an extended or a short 60-day season. The number of inflorescences and the timing of their emergence were recorded. The planting date had no effect on the mean number of inflorescences produced after 60 or 90 days, but after 30 days there were significantly more inflorescences from the second planting. This indicates that the later planting accelerated the emergence of inflorescences but had no effect on the total number.