Morphology and biological characteristics of some popular weedy rices in the Mekong delta of Vietnam

Abstract

The growing trend of cropping intensification, mechanisation, the use of poor-quality rice seeds, and the shift in rice cultivation methods from transplanting to direct sowing to meet food security and export demand are causes of the emergence and spread of weedy rice (Oryza sativa f. spontanea) in the Mekong delta in recent years. Therefore, it is necessary to study the agronomic, morphological, and physiological characteristics of collected weedy rice lines to help identify, analyse, and distinguish weedy rice in the rice field. Out of a total of 28 weedy rice lines planted, selected, and observed from 248 weedy rice samples collected in the main rice production areas in the Mekong delta, there are 12 weedy rice lines with one or more morphological and biological characteristics that can distinguish among them and with cultivated rice varieties, such as growing duration, plant height, leaf colour and shape, stem colour and shape, awn or without awn, husk colour, seed length, grain colour. These key characteristics can be used to distinguish and identify weedy rice lines from rice varieties grown at different growth stages in the field. However, some weedy rice lines are sharing major morphological features with the cultivated rice variety such as short or similar growing duration, shorter or similar height, similar husk colour, seed shape. Those weedy rice lines are not easy to identify and eliminate on the rice field, leading to the possibility of becoming widespread and difficult to control in rice production in the Mekong delta.