Straighthead is a ‘physiological’ disorder of rice which causes floret sterility and reduced grain yield. The symptoms are only obvious at panicle emergence and it is often confused with cold induced sterility, particularly in less severe cases.
Although there is no known cause of straighthead it is thought to be related to soil conditions induced by permanent flooding. It is not seed borne or transmitted around the farm.
Pseudomonas fuscovaginae is a bacterial pathogen of rice that causes sheath brown rot, grain discolouration and panicle sterility. It is slowly gaining recognition as a yield constraint of rice in many regions of the world. Although, P. fuscovaginae was first reported in Australia in 2009, there is little information available on the relative pathogenicity and aggressiveness of the Australian strains when compared to world strains. In this thesis its pathogenicity and aggressiveness, as well as prevalence in the rice growing areas of the Riverina region in New South Wales Australia were presented. Australian strains were more pathogenic and aggressive than world strains. The DAR 77138 strain from Australia was the most pathogenic and aggressive. A further survey of bacteria associated with discolouration of the panicle and sheath in the rice growing areas of the Riverina region in NSW Australia in 2010, failed to find any P. fuscovaginae.Read More
Episodes of high temperature at anthesis, which in rice is the most sensitive stage to temperature, are expected to occur more frequently in future climates. The morphology of the reproductive organs and pollen number, and changes in anther protein expression, were studied in response to high temperature at anthesis in three rice (Oryza sativa L.) genotypes. Plants were exposed to 6 h of high (38 degrees C) and control (29 degrees C) temperature at anthesis and spikelets collected for morphological and proteomic analysis. Moroberekan was the most heat-sensitive genotype (18% spikelet fertility at 38 degrees C), while IR64 (48%) and N22 (71%) were moderately and highly heat tolerant, respectively. There were significant differences among the genotypes in anther length and width, apical and basal pore lengths, apical pore area, and stigma and pistil length. Temperature also affected some of these traits, increasing anther pore size and reducing stigma length.Read More
Sucrose is the main form in which assimilate, produced by photosynthetic source tissues such as the flag leaf blade, is transported via the long-distance vascular pathway to sink tissues. In sink tissue, sucrose may be used directly for metabolism or may be temporarily stored prior to remobilization for use at a later stage of the plant’s development. The primary sink tissue in cereal species is the filling grain of the panicle, in which the carbohydrate accumulates as starch in the endosperm and embryo.
Cell biology of chilling damage in rice anthersRead More
The benefits of understanding these processes will eventually be realised in rice breeding through the identification of varieties likely to have the desired attributes that confer improved grain quality and will be important for farm management through establishment of appropriate fertiliser regimes that address not only productivity but also processing quality.Read More
Cold physiology at the plant levelRead More
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, Louisiana 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.Read More
Perceptions of rice cold damageRead More
This IREC Farmer Newsletter report present results of a RIRDC project undertaken on increasing farm yields based on physiology research. The aim of the project was to investigate increasing yield potential of new rice varieties with the outcome to help farmers to manage N fertilizer. District nitrogen trials were undertaken, investigations of PI nitrogen uptake and understanding rice yield potential. MaNage rice version 5.0 was released to growers in December in December 2000. Version 5.0 included a new slide, which predicts crop development. The high yield potential of the short season variety Jarrah at high N rates was found to be due to extended period of grain filling, ie from flowering to maturity.Read More
The project reviews and updates the publication Rice Growing in New South Wales, which was produced in 1984, bringing together all the current understanding and knowledge behind rice growing practices and recommendations. The publication does not attempt to provide information on 1tow to' but rather 'why' recommendations are given.Read More
Reproductive cold damage is the main environmental limitation to yields in the NSW rice industry, causing an average loss of approximately 2 t/ha over the last 10 years. In extreme years, this can cost the rice industry over $60 million. The mechanisms by which cold temperatures cause pollen sterility are poorly understood. This lack of knowledge needed to be addressed to accelerate the rate at which resistance to cold-temperature sterility can be introduced into current commercial cultivars. Past research has been unable to identify the causes of the sterility. Recent technological advances in proteomics offer the ability to discover what causes sterility and provide the breeding program with an understanding of what traits to incorporate for resistance to cold-temperature sterility.Read More
This pilot project suggests a strong possibility of increasing seedling establishment and midseason cold tolerance by using polyamines and/or glycinebetaine. These compounds should be tested under field conditions to confirm the agronomic use. A thorough understanding of their mode of action and existence of varietal differences (for polyamines) would lead to the application of molecular biology tools for rice crop improvement. These aspects are being studied in the second phase of RIRDC Project UQ- 91A.Read More