Influence of Seedling Age and Duration of Vernalization on Flowering of Cicer Milkvetch1

Abstract

Although most plants of cicer milkvetch (Astragalus cicer L.) require vernalization before flower induction, information is lacking on the influence that seedling age and duration of the chilling period have on receptivity to the vernalization stimulus. Therefore, treatments involving these two factors were evaluated to determine their effect on the flowering process. The influence of date of transplanting to the field in the spring on subsequent flowering also was investigated. In all studies the seedlings were from six polycross progenies that represented a wide range for date of flowering during the seedling year. Five to 6 weeks of exposure to 5 C night/20 C day temperatures in an environmental chamber provided excellent vernalization for seedlings in the 9th‐leaf stage of development. Six to 8 weeks of chilling provided good to excellent vernalization for seedlings in the 5th‐leaf stage of growth. However, flowering following 3 weeks of vernalization at the 5th‐leaf stage was poor. Flowering following 7 weeks of vernalization at the primary‐leaf stage and at the 3rd‐leaf stage was relatively poor, also. Flowering in the greenhouse without vernalization was exceptionally poor in the autumn, but was somewhat better in the spring. Flowering of seedlings in the 9th‐leaf stage was much better when the vernalization treatment included a dark period than when the vernalization treatment had continuous light. Progenies differed significantly in their response to the vernalization treatments. Their chilling requirements ranged from slight to considerable. Percentage of plants flowering and date of flowering in the seedling year were significantly correlated with date of transplanting to the field in the spring.