Abstract
BackgroundBroad-spectrum resistance gene pyramiding helps the development of varieties with broad-spectrum and durable resistance to M. oryzae. However, detailed information about how these different sources of broad-spectrum resistance genes act together or what are the best combinations to achieve broad-spectrum and durable resistance is limited.ResultsHere a set of fifteen different polygene pyramiding lines (PPLs) were constructed using marker-assisted selection (MAS). Using artificial inoculation assays at seedling and heading stage, combined with natural induction identification under multiple field environments, we evaluated systematically the resistance effects of different alleles of Piz locus (Pigm, Pi40, Pi9, Pi2 and Piz) combined with Pi1, Pi33 and Pi54, respectively, and the interaction effects between different R genes. The results showed that the seedling blast and panicle blast resistance levels of PPLs were significantly higher than that of monogenic lines. The main reason was that most of the gene combinations produced transgressive heterosis, and the transgressive heterosis for panicle blast resistance produced by most of PPLs was higher than that of seedling blast resistance. Different gene pyramiding with broad-spectrum R gene produced different interaction effects, among them, the overlapping effect (OE) between R genes could significantly improve the seedling blast resistance level of PPLs, while the panicle blast resistance of PPLs were remarkably correlated with OE and complementary effect (CE). In addition, we found that gene combinations, Pigm/Pi1, Pigm/Pi54 and Pigm/Pi33 displayed broad-spectrum resistance in artificial inoculation at seedling and heading stage, and displayed stable broad-spectrum resistance under different disease nursery. Besides, agronomic traits evaluation also showed PPLs with these three gene combinations were at par to the recurrent parent. Therefore, it would provide elite gene combination model and germplasms for rice blast resistance breeding program.ConclusionsThe development of PPLs and interaction effect analysis in this study provides valuable theoretical foundation and innovative resources for breeding broad-spectrum and durable resistant varieties.
Highlights
Broad-spectrum resistance gene pyramiding helps the development of varieties with broad-spectrum and durable resistance to M. oryzae
Development of polygene pyramiding lines (PPLs) in the genetic background of Yangdao 6 (YD6) Two set of near-isogenic lines (NILs) which harbored different broad-spectrum resistance genes were used for the development of PPLs in this study
The second set consisted of three NILs with YD6 as genetic background carried the broad-spectrum resistance gene Pi1, Pi33 and Pi54, respectively
Summary
Broad-spectrum resistance gene pyramiding helps the development of varieties with broad-spectrum and durable resistance to M. oryzae. Approximately 100 R genes and 350 quantitative trait loci (QTL) associated with blast resistance have been identified (Tanweer et al 2015), of which 28 R genes have been cloned and functionally validated (Ashkani et al 2016; Deng et al 2017) Most of these cloned and characterized R genes only confer resistance to one or a few isolates of M. oryzae follow the model of gene-for-gene interaction (Jia et al 2000), and their resistance tend to retain an effective level for only a short time, especially when the varieties with R genes grown in large areas (Qu et al 2006). R genes showed broad-spectrum resistance to a number of isolates or races from one or different countries seem to be more reliable and sustainable in breeding programs (Skamnioti and Gurr 2009)
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