Technicians perform visual scoring of select rice breeding lines that are resistant and susceptible to the hoja blanca virus.
Photo: © FLAR

Drone-assisted breeding can help stop rice hoja blanca disease

In Latin America rice is seriously threatened by the rice hoja blanca virus (RHBV). Now scientists of the International Center for Tropical Agriculture (CIAT) are applying drones to evaluate rice breeding lines in the field that are resistant to the virus.

It’s a sight no rice farmer in Colombia or elsewhere in Latin America would like to see: stunted rice plants with bleached white leaves. These are classic symptoms of a disease arising from the devastating rice hoja blanca virus (RHBV).

If left unchecked, the disease can wipe out up to 70 per cent of rice production. Pesticides have proven ineffective to stop it; thus, the only effective way to control the disease is to plant an RHBV-resistant variety. Currently, there is only one variety that is highly resistant to the virus and that is available on the market — Fedearroz 2000.

The Latin American Fund for Irrigated Rice (FLAR) has been working to breed more RHBV-resistant rice, in collaboration with the Rice Programme of the International Center for Tropical Agriculture (CIAT), Cali/Colombia.

The process entails screening breeding lines to discard the ones that are susceptible to the virus. FLAR organises screenings twice a year, in April and in October, with each involving an average of 10,000 to 12,000 breeding lines.

Previously, FLAR would need to deploy two people to score the rice breeding lines in the field. The assessment would take place each morning over ten days. Such a method, FLAR Plant Breeder Maribel Cruz acknowledges, is highly subjective as it relies on what the field evaluators see. The condition of their eyesight and the intensity of sunlight can affect their vision and therefore their scoring, she concedes.

Drone images provide objective screening of the rice breeding lines

For the next screening period, FLAR will begin using analysis of images from drones operated by the CIAT Phenomics Platform, led by Michael Gomez Selvaraj, to evaluate the breeding lines. Using drones can standardise screening of rice breeding lines. Images taken by drones can indicate which lines would have symptoms of the virus. These lines are lighter in colour, nearly white. RHBV-resistant breeding lines, meanwhile, would be vivid green.

“This is a breakthrough for rice breeding here in Latin America,” says Cruz. “Using drones will ensure objectivity in our screening.” In addition, screening time would be shorter.

The drone operated by the CIAT Phenomics Platform can take an image of 10,000 breeding lines within minutes. Analysing such image to identify plots with RHBV-susceptible crops is also quick, usually taking a day. Plans to enhance high-throughput image analysis to screen rice breeding lines are now underway.
According to Selvaraj, CIAT’s team are now working on multispectral image assessment. This involves using drones and software that will assign one spectrum for RHBV susceptibility, another for nitrogen deficiency, and another for water stress, among other traits.


For more information:
Visit the website of The Latin American Fund for Irrigated Rice (FLAR)

Visit the CIAT website

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