[Mating system and causes of low fructification rate by self-pollination of Codonopsis pilosula]

To study four kinds of germplasm resources of Codonopsis pilosula and provide the basal mating systems data for the breeding and cultivation of C. pilosula.

0.5% TTC (2,3,5-triphenyl tetrazolium chloride) solution was used for the pollen viability test and benzidineand-H2O2 [1% benzidine in 60% ethanol,hydrogen peroxide (3%), and water, 4:11:22] was used for estimation of the stigma receptivity. The mating systems were tested by out crossing index (OC1), pollen-ovule ratio (P/O) and pollination by bagged and emasculated in the field.

The pollen viability of C. pilosula reached highly about 80% when the pollen staying in the anther, 2-3 days before the petals opening. The anther began scattering pollen before the day of the petals opening, the pollen viability was the highest about 95%, the pollen stick thickly aroud the stigma and quickliy lost in the next day. The stigma life-span was about 4-5 days, the optimal time for pollination was the first day of the petals opening, when the stigma was highly sticky and yellow. The value of out crossing index (OC1) was 4, pollen-ovule ratio was between 104.84-185.75. The natural fructification rate of cross-pollination by emasculated-treatment was 25.6% 42.4%. The fructification rate and compatible index of self-pollination by bagged- treatment were about 3.3%-6.7% and 3.0-21.8.

The mating system of C. pilosula is mixed with self-pollination and cross-pollination, prone to cross-pollination. The compatibility of self-pollination is high. The difference of maturing period of pistil and stamen and the lack of polen amount cause low fructification rate of self-pollination.