Phenotypic variation in floral development and pyrethrin content in genetically different clones of pyrethrum chrysanthemum cinerariefolium vis

Abstract

Pyrethrum, Chrysanthemum cinerariae folium vis, is an important insecticide producing plant propagated vegetatively by splits and shoot cuttings. The objectives of the study were to determine the pattern of pyrethrins and dry weight net accumulation during the entire flowering cycle, the duration of transition in days from one stage to the other during the flowering cycle and to determine the optimum picking time for six recommended pyrethrum clones (Ma/70/1013, Ma/71/423, 4331, SB/ 66/107, Ks/71/6 and Ks/70/64. The experiment was laid out in split-plot block design with three replicates. During the 1985/86 growing season three plants from each fully establi~hed clone were randomly selected and labelled. From each plant three flower heads were randomly selected and labelled at bud stage. The date when the selected bud had just started to open was noted and the number of days from there on to reach each of the eight stages of development were counted in each clone. Sampling for dry weight and pyrethrins content was done January, June and September There were highly significant differences arnon gs L t.h o cLon os in pyre t hr Lns CUll Len Land 100 flower dry weight at different stages of flower development. Lack of interaction between clones and developmental stages in both pyrethrins content and 100 flower dry weight suggested the pattern of dry weight and pyrethrins net accumulation was similar in all pyrethrum clones. The 100 flower dry weight increased from closed bud (Stage I) and reached a maximum at the late overblown stage (Stage VII) in all the clones. The pyrethrins in the flower head generally increased from closed bud (Stage I) to a maximum when nearly all disc florets were open (Stage V) in all the clones except clone Ma/71/423 which had a maximum pyrethrins content at Stage IV. The pyrethrins yield increased from a closed bud (Stage I) to u maximum at Stage VI in clones Ks/70/64 and Mu/71/423 while clones SB/66/107, Ks/71/6 and Ma/70/1013 had a maximum pyrethrins yield in Stage VII. Clone 4331 showed slight changes in pyrethrins yield from Stage V to VII. The time lapsed from closed bud (Stage I) to nearly all disc florets open (Stage V) when most of the clones had maximum pyrcthrins content varied from 18 to 21.2 days except for clone 4331 which varied from 11 to 19.5 days. Results suggested that the optimum picking stage for clones SO/66/107, Ma/70/101~Ks/71/6 should be in Stage" VI, while clones Ks/70/64 and Ma/71/423 in Stage V. Clone 4331 can be picked in Stage IV to VII as it showed very slight changes during these stages.