Morphological characterisation of Italian weedy rice (Oryza sativa) populations

Weedy rice (Oryza sativa) is one of the most widespread and problematic weeds in rice cultivation; it spans the globe and can cause high yield losses. In 2008, seeds of 149 weedy rice populations were collected from the major Italian rice cultivation area. In 2009, these populations were sown in a single field to determine their morphological characteristics, including plant height, flag leaf attitude and length, panicle attitude and length, auricle and node colour, seed weight and size, awn length and germination rates at 0, 10 and 30 days of after-ripening (DAR). Of the collected populations, c. 56% were awned, 17% mucronate and 27% awnless. The morphological characteristics among the awned populations varied widely and displayed the highest average lengths of flag leaf (27.6 cm) and seed (8 mm). Mucronate populations were mainly characterised by small seeds and low germination rates. Awnless populations showed higher germination rates at 30 DAR (20%) and wider seeds (3.7 mm). Awn length and distribution, seed length, 1000 seed weight and germination rates were the most important traits influencing the variability among populations. Awned populations are expected to adapt better to differing environmental and cropping conditions, because of their larger variability.