Delta summer–autumn rice planted too early, threatened by diseases
Delta rice yields fall on diseases 

Prof Dr Nguyen Hong Son, director of the Viet Nam Academy of Agricultural Sciences, speaks at the two-day International Conference on Bacterial Blight of Rice that ended on Tuesday in Can Tho. VNA/VNS Photo Ngoc Thien

Prof Dr Nguyen Hong Son, director of the Viet Nam Academy of Agricultural Sciences, told the sixth International Conference on Bacterial Blight of Rice and Bacterial Leaf Streak that the disease is one of the most serious production constraints world-wide, causing losses of up to 74 per cent of production.

For bacterial diseases that show no initial symptoms and are difficult to detect, prevention by only using antibiotics is not very effective, he said.

“The most effective solution in Vietnam and the world is to create disease-resistant rice varieties.”

Many countries have been successful in creating resistant rice varieties, but bacteria mutate into new strains quickly, requiring more than one resistance gene in each rice variety, he added.

Dr. Nguyen Thi Phong Lan, head of the plant protection department at the Mekong Delta Rice Institute, said rice blight disease had worsened in the delta, and now affected 50,000-60,000ha each crop.

“There are no measures to control the disease completely.”

According to the International Rice Research Institute, bacterial blight could reduce rice yields by 30-70 per cent depending on the stage of the infection, environmental conditions and which rice season it is.

Experts recommended that farmers should apply integrated measures to manage pests such as using rice varieties with good resistance, resilience and suitability to local conditions.

They should also apply appropriate rice cultivation techniques such as moderate density of sowing with balanced fertilisation and good drainage.

The institute is currently cooperating with Germany’s Bayer Company to test two transgenic hybrid rice varieties resistant to leaf blight.

They have been tested for nearly two months and remain free of blight.

Dr Tran Ngoc Thach, director of the institute, said Vietnam should “learn from Germany and the US” to research into this disease.

The conference acted as a forum for exchanging information and fostering collaboration between scientists from around the globe for the effective control and management of the disease, he said.

It helped make significant progress in understanding the disease through analyses of the interactions between the pathogen and rice at many levels, including studies focused on the epidemiology, population biology, physiology, cell biology, bio-chemistry, molecular genetics, and effectors involved in the interactions, he added.

According to experts, bacterial blight and bacterial leaf streak of rice are major diseases due to their high epidemic potential, especially when there is extreme climate variation, and its destructiveness on high-yielding but susceptible cultivars.

Despite attempts to control the diseases by incorporating genetic resistance into high-yielding cultivars, both remain a major constraint on production in both favourable and unfavourable rice environments throughout Asia.

The pathogen causes yellowing and drying of leaves, wilting of seedlings and blight lesions (in case of severe strains), which may also affect panicles. Various saprophytic fungi could invade the lesions, contributing to the damage.

The favourable factors for bacterial leaf blight are rain, high levels of fertiliser, high humidity, standing pools of water, and warm temperatures.

The two-day event, organised by the institute, discussed the current assessment of the diseases and their epidemiology and population biology.

VNS