Weedy rice (Oryza sativa L.): (English Name: Weedy rice; Malay Name: Padi angin)

Weedy rice (Oryza sativa L.) is an important biotic constraint contributing to low rice production in Malaysia. This notorious weed is commonly known as "padi angin" in Malaysia. Weedy rice is made up of the undesirable agronomic traits which are damaging to both yield and grain quality of cultivated rice. The morphological and physiological characteristics of weedy rice are almost the same as those of cultivated rice varieties (Azmi & Johnson, 2009). However, weedy rice possesses considerable morphological diversity, which can often mimic rice varieties in response to selection pressures resulting from commercial rice farming. In general, weedy rice is usually taller than the commercial varieties, has less tillers, higher leaf area index per hill and easy plus early grain shattering characteristics. Taller plant in combination with higher leaf area index competes with the cultivated rice for space, lights and nutrients and ultimately reduces yield (Azmi et al., 2005). One of the main reasons for the distribution of weedy rice in Peninsular Malaysia is the shifting of rice establishment method from transplanting to direct seeding (DSR) in the 1980s (Azmi & Johnson, 2009).