Abstract
Tainung82 (TNG82) is one of the most popular japonica varieties in Taiwan due to its relatively high yield and grain quality, however, TNG82 is susceptible to bacterial blight (BB) disease. The most economical and eco-friendly way to control BB disease in japonica is through the utilization of varieties that are resistant to the disease. In order to improve TNG82’s resistance to BB disease, five bacterial blight resistance genes (Xa4, xa5, Xa7, xa13 and Xa21) were derived from a donor parent, IRBB66 and transferred into TNG82 via marker-assisted backcrossing breeding. Five BB-resistant gene-linked markers were integrated into the backcross breeding program in order to identify individuals possessing the five identified BB-resistant genes (Xa4, xa5, Xa7, xa13 and Xa21). The polymorphic markers between the donor and recurrent parent were used for background selection. Plants having maximum contribution from the recurrent parent genome were selected in each generation and crossed with the recipient parent. Selected BC3F1 plants were selfed in order to generate homozygous BC3F2 plants. Nine pyramided plants, possessing all five BB-resistant genes, were obtained. These individuals displayed a high level of resistance against the BB strain, XF89-b. Different BB gene pyramiding lines were also inoculated against the BB pathogen, resulting in more than three gene pyramided lines that exhibited high levels of resistance. The five identified BB gene pyramided lines exhibited yield levels and other desirable agronomic traits, including grain quality and palatability, consistent with TNG82. Bacterial blight-resistant lines possessing the five identified BB genes exhibited not only higher levels of resistance to the disease, but also greater yield levels and grain quality. Pyramiding multiple genes with potential characteristics into a single genotype through marker-assisted selection can improve the efficiency of generating new crop varieties exhibiting disease resistance, as well as other desirable traits.
Highlights
As a carbohydrate-rich staple of more than half the world’s diet, rice (Oryza sativa L.) is one of the most important food crops on the planet
Bacterial blight (BB) can be managed through the use of fungicides, enhancing the genetic resistance in rice is the most effective and ecological method of overcoming the threat posed by the disease
Due to the relatively large amount of work involved with the marker-assisted selection (MAS) process, the conventional backcross breeding approach has been widely adopted in breeding programs designed to breed for BB resistance [10,26,27,28]
Summary
As a carbohydrate-rich staple of more than half the world’s diet, rice (Oryza sativa L.) is one of the most important food crops on the planet. The Food and Agriculture Organization of the United Nations (FAO) estimates that by 2050, overall global agricultural production may need to be increased by up to 70% to meet the dietary requirements of the world’s projected population of nine billion [1]. In order to satisfy the demand corresponding to the FAO’s projected population in 2050, global rice production would have to increase by nearly 42% over present-day levels [2]. Oryzae (Xoo) is a disease that poses one of the greatest threats to rice production worldwide. BB can be managed through the use of fungicides, enhancing the genetic resistance in rice is the most effective and ecological method of overcoming the threat posed by the disease
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