Abstract:
Weedy Rice (Oryza sativa complex) becomes the most dominant and competitive weed in Sri Lanka. Seed shattering
and seed dormancy have enriched the soil seed bank. Weedy rice seeds remain longer period in soils at different depths
and that contribute to the success of weedy rice as a "weed." Hence study about the level of longevity, dormancy and
germination behavior of weedy rice under the conditions similar to those of field conditions is important to implement
efficient control measures. In this study, weedy rice seeds were collected from 6 infested locations from Matara district
and two widely grown improved varieties (At 362 and Bg 379-2) were included as check lines. Thirty panicles were
randomly collected from each location and 5 seeds from each panicle were taken and mixed thoroughly. From that 100
seeds were randomly selected for each test with 3 replicates for viability and germination testing. Seeds of the weedy
and cultivated rice were placed separately in nylon bags and buried at 15 and 30 cm depths (in soil). Seed germination
and viability were tested before burial and in two week intervals after burial. Both weedy rice and improved rice
varieties showed more than 85% viability before burying. Weedy rice seeds could remain viable under soil for more
than 24 weeks compared with the improved rice varieties, which did not remain viable beyond 16 weeks after burial in
both depths tested. Viability and germination ability were always higher in seeds buried at 30 cm depth when
compared with those buried at 15 cm depth for both weedy and improved rice. These results help to understand the
persistent nature of weedy rice and it will help to adopt efficient control measures for weedy rice.
