Bayer CropScience’s hybrid rice is known for its especially high yield potential. A new variety has an additional characteristic: Arize® Dhani is resistant to bacterial leaf blight. It was brought onto the market in five Indian States in 2008. Caused by the bacterial pathogen Xanthomonas oryzae, bacterial leaf blight is a major problem. Depending on the severity and timing of infection, harvest losses of between 20 and 60 percent can occur. Bactericidal agents are available but none of them has proven effective enough to date. Arize® Dhani is the world’s first hybrid rice with greater than 95% resistance against all known races of bacterial leaf blight. In developing it, Bayer CropScience has taken advantage of the fact that nature already presents us with rice varieties that are partially resistant to bacterial leaf blight. Breeders brought the resistance genes from the naturally-occurring varieties together. They did this through advanced breeding, using molecular markers. The comprehensive resistance thus achieved was then brought together with a strong yield potential using well-proven hybridization technology. „When the disease hits, farmers who use Arize Dhani can produce up to 80 percent more yield than their neighbours using classical varieties“, says Arun Mittal, rice product manager at Bayer CropScience.
World leaders in hybrid rice
Bayer CropScience plans to continue to bring further second-generation hybrid rice varieties onto the market. These deliver a double benefit: high yield potential combined with, for example, resistance to a particular pest or to other types of stress. However, hybrid rice currently accounts for only two percent of the Indian rice cultivated area. Increasing this proportion would be a way of increasing the productivity of Indian rice cultivation, which is clearly lower than in other countries. Productivity in the People’s Republic of China for instance equated to more than six tonnes of rice a hectare, compared with just over three tonnes a hectare in India.
Increasing demand for rice
In an article early in 2008, researcher Dr. Sushil Pandey predicted that the demand for rice will continue to rise. In fact, an additional 50 million tonnes will be needed by 2015. For comparison: the total global rice harvest in 2006 was around 635 million tones, according to FAO-figures. The main reason is strong population growth and particularly so in Asia. Because there is no capacity for extending the area under cultivation, most of the required increase in production must come from higher yields per hectare. Among the technical solutions to achieve this will be new possibilities for crop protection. But also, there will be seed with improved yield potential. In order to bring forward this type of development, Bayer CropScience is investing five million Euros in its new Rice Research Laboratory in Singapore. The Institute began its work in June 2008, and it will contribute a significant extension in breeding capacity for hybrid rice, among other things. Here, the use of modern biochemical methodology will accelerate the otherwise prolonged process of developing new varieties.
Bayer CropScience’s hybrid rice is now on the market in six Asian countries. Further market introductions are planned in several other countries, including Thailand and the USA. The product portfolio will continue to expand, too.
What is hybrid rice?
Hybrids are produced by crossing two different parental plant lines. Under this approach, one of the lines is deliberately sterilized to prevent the usual process of self-pollination. The plants then receive pollen exclusively from plants of the second parental line. In this way, the genetic material of the two lines is combined. Targeted choice of the two parental lines allows for producing hybrids with specific, desirable properties. Thanks to modern molecular biology techniques, Bayer CropScience is able to accelerate the development of new hybrid varieties. The company is a world leader in hybrid technology. Besides rice, Bayer CropScience also develops oilseed rape and cotton seed using the hybrid approach.
Bacterial leaf blight
The most characteristic symptoms of bacterial leaf blight are light-coloured, longitudinal stripes on the leaf lamina. Badly-infected plants first wilt, then quickly dry out. Diagnosis of the disease can be confirmed by cutting off the leaf at the lower end of a lesion and dipping the cut end into water: masses of bacteria can be seen against the light, streaming into the water, which eventually becomes cloudy.
Warm temperatures and high humidity favour the development of bacterial leaf blight. Damp areas, strong winds that damage the rice plants, and over-fertilising are further factors that encourage the disease. The presence of weeds or infected rice stubble ensures the survival of the pathogen between crops, such that a new outbreak of the disease can occur as soon as the following crop is sown.
The younger the plants are at the time of infection, the greater the resulting harvest loss. Asian countries are particularly badly affected.
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