Shifts in Pest Resistance, Fall Dormancy, and Yield in 12‐, 24‐, and 120‐Parent Grazing Tolerant Synthetics Derived from CUF 101 Alfalfa

Abstract

Selection for grazing tolerance has been reported to be accompanied by changes in resistance to blue alfalfa aphid (Acyrthosiphon kondoi Shinji) and fall dormancy in alfalfa (Medicago sativa L.). This study was conducted to determine changes in pest resistance, fall dormancy, grazing tolerance, and yield between ‘CUF 101’ alfalfa and three experimental, grazing tolerant synthetics. A 120 parent experimental synthetic was derived from CUF 101 after two cycles of selection for grazing tolerance. Two synthetics composed of 12 and 24 parents were selected from the 120 grazing tolerant parents on the basis of the genetic dissimilarity of amplified fragment length polymorphism (AFLP) markers. There were no significant differences between the three experimental synthetics for grazing tolerance; however, all experimental synthetics were more grazing tolerant than CUF 101. All experimental synthetics had lower levels of resistance to blue alfalfa aphid, but generally higher levels of resistance to five other diseases in comparison to CUF 101. All experimental synthetics were more fall dormant than CUF 101. No consistent differences in yield were documented among the synthetics at testing locations in Georgia or California. In conclusion, this study underscores the need for further evaluation, after selection for grazing tolerance, to document fall dormancy and blue alfalfa aphid resistance ratings and to practice reselection for these traits if necessary.