Abstract
BackgroundThe development of hybrid rice is a practical approach for increasing rice production. However, the brown planthopper (BPH), Nilaparvata lugens Stål, causes severe yield loss of rice (Oryza sativa L.) and can threaten food security. Therefore, breeding hybrid rice resistant to BPH is the most effective and economical strategy to maintain high and stable production. Fortunately, numerous BPH resistance genes have been identified, and abundant linkage markers are available for molecular marker-assisted selection (MAS) in breeding programs. Hence, we pyramided two BPH resistance genes, Bph14 and Bph15, into a susceptive CMS restorer line Huahui938 and its derived hybrids using MAS to improve the BPH resistance of hybrid rice.ResultsThree near-isogenic lines (NILs) with pyramided Bph14 and Bph15 were obtained by molecular marker-assisted backcross (MAB) and phenotypic selection. The genomic components of these NILs were detected using the whole-genome SNP (Single nucleotide polymorphism) array, RICE6K, suggesting that the recurrent parent genome (RPG) recovery of the NILs was 87.88, 87.70 and 86.62 %, respectively. BPH bioassays showed that the improved NILs and their derived hybrids carrying homozygous Bph14 and Bph15 were resistant to BPH. However, the hybrids with heterozygous Bph14 and Bph15 remained susceptible to BPH. The developed NILs showed no significant differences in major agronomic traits and rice qualities compared with the recurrent parent. Moreover, the improved hybrids derived from the NILs exhibited better agronomic performance and rice quality compared with the controls under natural field conditions.ConclusionsThis study demonstrates that it is essential to stack Bph14 and Bph15 into both the maternal and paternal parents for developing BPH-resistant hybrid rice varieties. The SNP array with abundant DNA markers is an efficient tool for analyzing the RPG recovery of progenies and can be used to monitor the donor segments in NILs, thus being extremely important for rice molecular breeding.
Highlights
The development of hybrid rice is a practical approach for increasing rice production
Among 100 BC2F1 plants, two individuals containing Bph14 and Bph15 and with a phenotype similar to Huahui938 were used for subsequent backcrossing
Eight BC3F3 family lines were obtained and further confirmed by Polymerase chain reaction (PCR) analysis of the target loci, which suggested that both Bph14 and Bph15 were homozygous in all family lines (Fig. 1b)
Summary
The development of hybrid rice is a practical approach for increasing rice production. The brown planthopper (BPH), Nilaparvata lugens Stål, causes severe yield loss of rice (Oryza sativa L.) and can threaten food security. Breeding hybrid rice resistant to BPH is the most effective and economical strategy to maintain high and stable production. Rice (Oryza Sativa L.) is one of the most important food sources for more than half of the world population. The brown planthopper (BPH, Nilaparvata lugens Stål), which sucks the phloem sap of the rice leaf sheath and transmits viral diseases such as rice grassy stunt virus (RGSV), rice ragged stunt virus (RRSV) and rice wilted stunt virus (RWSV), often leads to severe yield losses in the agricultural industry (Fujita et al 2013). China is the largest rice-producing country in the world, the planting area is less than that in India.
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