Abstract
Brown planthopper, blast, and bacterial blight are the main biotic stressors of rice and can cause a massive loss in rice production. Aroma is an important character of rice quality. It is of far-reaching significance to breed resistant and high-quality varieties using germplasms with objective genes. In this study, the introgression and pyramiding of brown planthopper (BPH), blast, and bacterial leaf blight (BLB) resistance genes and aroma genes into elite rice maintainers and restorers were conducted through conventional cross-breeding coupled with the marker-assisted selection (MAS) breeding method. Single-plant selection was performed from F2 onwards to select desirable recombinants possessing alleles of interest with suitable phenotypes. Respective linked markers were used in each generation from intercrossing to the F7 generation for tracking the presence of targeted genes. A total of 74 improved lines (ILs) have been developed which possess a combination of 1 to 4 genes for BPH, blast, and BLB resistance and aroma. These ILs showed moderate to high resistance to multiple biotic stresses (BPH, blast and BLB) or aromatic fragrance without obvious negative effects on agronomic traits. As multiple resistance and aromatic traits have become significant objectives in rice breeding, these resistance and/or aroma gene introgressed or pyramided lines have important application prospects. Core ideas: (1) marker-assisted breeding was used to pyramid multiple genes for an elite breeding line; (2) improved lines with the introgression of 1–4 genes were developed to achieve high resistance against various biotic stresses and aroma; (3) new lines were used as donor parents to introgress multiple genes in other genetic backgrounds.
Highlights
Rice is one of the main food crops in the world
A breeding strategy involving foreground selection coupled with phenotypic selection in each generation was implemented in assembling the nine targeted genes from different donors in different genetic backgrounds of recipients
The crossing program was initiated during the spring of 2017 to combine two genes for brown planthopper (BPH) resistance (BPH3 and BPH24), five genes for blast resistance (Pi2, Pi9, Pita, Pib and Pimh), one gene for bacterial leaf blight (BLB) resistance (Xa23) and one gene for aroma (Figure 1, Table 2)
Summary
Rice is one of the main food crops in the world. The prevalence of diseases and insect pests often causes serious losses in rice production [2,3]. Rice grain yield is significantly affected by multiple stresses. The major biotic stresses which result in yield penalty are BPH, blast, and BLB. Chemical pesticides, bactericides and fungicides are still widely applied in controlling BPH, blast and BLB. In addition to extra high costs in rice production, they are not environmentally friendly and lead to food contamination. The long-term abuse of pesticides could stimulate the tolerance and evolution of pests and pathogens, which becomes a greater threat to the safety of rice production [4]
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