THE EFFECT OF ENVIRONMENTAL CONDITIONS UPON PYRETHRUM (CHRYSANTHEMUM CINERARIAEFOLIUM). I.

Abstract

Summary. The effect of soil fertility upon the insecticidal value of the flowers has been studied in a series of pot experiments. On heavy soil the pyrethrin I content of the flowers was not increased by the application of fertilisers. The plants produced good yields of flowers, rich in pyre‐thrins, when grown in soil of low fertility. Under conditions of normal growth and vitality, the extent of production of the pyrethrins in the flowers was characteristic of the individual plant and was dependent upon some factor which appeared to be genetical in character. A plant initially producing flowers of high or low percentage poison content continued to give flowers of the corresponding degree of richness in succeeding years, independently of the application of manures, or apparently of the number of heads produced. Plants derived from rooted shoots produced flowers corresponding in quality with those initially yielded by the parent plant. The insecticidal value of pyrethrum flowers may be improved by plant selection, followed by vegetative propagation. In the fully open flowers, the complete disc florets contained 90 per cent. of the total pyrethrins present in the flowers, and of this the greater part was found to be located in the ovaries.

Rapid generation cycling transforms pyrethrum (Chrysanthemum cinerariifolium) into an annualized perennial

“…Both seed lots were significantly earlier than Seed Lots C (42.8 wk) and G (42.7 wk), whereas the other lots overlapped (Table 5). This is the first report of pyrethrum seedlings flowering in <1 yr from sowing, particularly without the requisite cold treatment (winter) to remove dormancy, mobilize gibberellins, and induce flowering (Martin & Tattersfield, 1934). In all pyrethrum breeding populations, flowering occurs only in Year 2 after an intervening cold (vernalization) period (Bhat & Menary, 1984;Bhat et al, 1985;Glover, 1955).…”

“…This phenomenon is also known as RGC, which has been successfully instituted in both monocots (Gladiolus, Lilium) and dicots (Chrysanthemum ×grandiflorum) to reduce the generation time and enhance the rate of breeding and selection for desired traits (Anderson, 2019;Anderson et al, 2015). For instance, selection of early-flowering pyrethrum genotypes in Year 1 is novel and unprecedented since previous studies have used a 2-to-3-yr model for selection of initial traits (Bhat, 1995b;Gnadinger, 1936;Gullickson, 1995;Martin & Tattersfield, 1934;Parlevliet, 1969;Singh et al, 1987;Singh et al, 1988aSingh et al, , 1988b. Thus, our breeding program poses a revision of the pyrethrum ideotype (Bhat, 1995b;Parlevliet, 1974Parlevliet, , 1975 to develop an annualized, early-flowering plants with high floral and %Py production capability, including annualization components of germination week, numbers of weeks to VBD and flowering within the first year.…”

“…Recurrent and mass selection were then used in a breeding program started in Tasmania which continues to the present time (Bhat et al, 1985). Pyrethrum breeding also occurs in Japan, Kenya, Tanzania, the United States, Croatia, and Russia (Bhat & Menary, 1987;Martin & Tattersfield, 1934;McDaniel, 1991;Pandita & Bhat, 1978). Historically, pyrethrum has been bred in a perennial cropping cycle…”

“…Industrial Development Organization, 1995). Other countries currently producing pyrethrum include Tasmania, Tanzania, and Ecuador (Martin and Tattersfield, 1934;Gnadinger, 1945).…”

“…Recurrent and mass selection were then used in a breeding program started in Tasmania which continues to the present time (Bhat et al, 1985). Pyrethrum breeding also occurs in Japan, Kenya, Tanzania, the United States, Croatia, and Russia (Bhat & Menary, 1987;Martin & Tattersfield, 1934;McDaniel, 1991;Pandita & Bhat, 1978). Historically, pyrethrum has been bred in a perennial cropping cycle Crop Science wherein synchronous or asynchronous flowering (McLaughlin, 1973) occurred in Years 2-3 after seed sowing or rooting of cuttings (splits) with one or two intervening cold periods (winter) (Bhat et al, 1985;Martin & Tattersfield, 1934).…”