Bacterial blight is a serious disease of rice that easily spreads to large
areas, causing around 30 percent loss in yield, affecting incomes for
smallholder farmers in Asia. Scientists at the International Rice Research
Institute (IRRI) led a study that looked into genes that will help bacterial
blight disease in rice.

Major genes for resistance to bacterial blight called Xa genes (e.g., Xa4,
Xa5, Xa21), have already been used in rice breeding programs, but the
bacteria adapted to resistant varieties making them susceptible again. In a
paper published in PLOS One, scientists discovered variations of SWEET genes
that make rice plant resistance to Xanthomonas oryzae pv. Oryzae which
causes bacterial blight. In normal conditions, the pathogen promotes the
leakage of sugars by activating SWEET genes in the plant cell. However, the
new SWEET gene variants prevent the release of sugar, which stops the
bacteria from getting nutrition from the host plant. "The bacteria
eventually dies," explains IRRI senior scientist on plant pathology Dr.
Ricardo Oliva.



According to Oliva, the genes naturally occur in rice. They were able to
identify potential variations in the SWEET gene to be used in breeding new
blight-resistant varieties using IRRI's germplasm collection. Oliva adds,
"The variations appear to have emerged from at least three rice subspecies.
This opens up the gates to use similar techniques to fight other pathogens
in rice as well as in other crops such as corn, wheat, and cassava."



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