Investigating Links Between Minerals In Rice Grain And Straighthead

Abstract

Straighthead or “Parrot Beaking” is a “physiological” disorder causing distortion and a high proportion of missing grains on the rice panicle. Crop losses range from 10 to 30% in medium grains and as high as 90% in short and long grains. Straighthead has been recorded in NSW rice crops since 1960s. It occurs in both the Murrumbidgee and Murray Valleys and the Coleambally Irrigation Area. Straighthead also occurs in Arkansas, Lousiana and Texas in the USA and in other countries who use other words to describe it. There is no known cause of Straighthead although it can be induced in the glass house by addition of arsenic based compounds and straw or sugar to the soil. In Arkansas Straighthead is associated with the use of arsenic based herbicides used in cotton during rotation. Straighthead is thought to be a relatively minor problem in the NSW rice area as a whole but can be devastating to individual growers who have the problem. However, its true extent is unknown because it is often confused with cold weather sterility and may occur at low levels unnoticed in many crops. Straighthead is thought to be related to soil conditions and is not seed borne or transmitted around the farm. The symptoms of Straighthead are upright panicles, with misshapen hulls of affected grains – often called “Parrot Beaking”. This effect is most pronounced in long grain. Medium grains tend to have some misshapen grain but not all “parrot beak”.