Polyploid Induction in ‘kram phak troung’ indigo (Indigofera tinctoria L.)

Abstract

Kram Phak Troung or Indigofera tinctoria L. is Sakon Nakhon’s indigenous plant. It has small leaves and is categorized as a species of self-pollinated breeding plant. Two species of Indigofera tinctoria L. have been grown at present. Thus, there is an attempt to develop the new kind of Indigofera tinctoria L. which contains more chromosomes becoming polyploidy indigo plant. This polyploidy indigo is expected to grow taller bearing bigger leaves than the indigenous plant. With higher stem and wider leaves, the polyploidy indigo can produce higher amount of its essence. Polyploid in Indigofera tinctoria L. is induced by immersing the germinated seed in colchicines of different concentrations (0.1%, 0.2% and 0.4%) and for a period of 6 and 12 hours. It was found that different concentrations of colchicines resulted differently and significantly in the death, height and leaflet number of the fifteen-days old Indigofera tinctoria L. (P<0.01). That is the more colchicines was concentrated the more Indigofera tinctoria L. plants survived while their height and leaflet number decreased. However, the immersion period of the Indigofera tinctoria L. seedlings did not affect the survival percentage, height and leaflet number of these Indigofera tinctoria L. plants. Furthermore, all plants that survived demonstrated abnormal trait of swollen hypocotyls. In contrast, the seedlings which were not treated by colchicines immersion could grow normally. When using flow cytometry to inspect the abnormal plants whose hypocotyls swelled, it was revealed that 0.2% colchicine solution produced 75% tetraploid Indigofera tinctoria L. seedlings when they were immersed for 6 hours; it produced 66% tetraploid Indigofera tinctoria L. seedlings if immersed for 12 hours. The seeds immersed in 0.1% colchicine solution obtained more diploids and mixoploids than immersed in 0.2% colchicine solution. With the 0.4% colchicine solution for 6 hours’ treatment, all polyploids were gained (33.33 mixoploids and 66.66 tetraploids). Nevertheless, if the seeds were immersed in 0.4% colchicine solution for a period of 12 hours, the seedlings could live less than a month and their polyploidy traits could not be examined; only the diploids of these seedlings survived.