Abstract
Recent progress in rice genomics has promoted the identification of quantitative trait loci (QTLs) associated with yield and its related traits. SPIKE, a QTL controlling spikelet number per panicle, and GPS, a QTL controlling leaf photosynthesis rate, were identical to NAL1. To assess the effect of SPIKE/GPS on yield potential, we compared DNA sequences of these alleles and conducted yield experiments in the field of Japan using the near-isogenic lines NIL-SPIKE (allele from Daringan in IR 64 genetic background), NIL-GPS (allele from Koshihikari in Takanari genetic background), and a chromosome segment substitution line, SL2115 (allele from Koshihikari in IR 64 genetic background). Despite the two SNPs in the promoter regions between Koshihikari and Daringan, both alleles were effective to increase the number of spikelets per panicle both in Takanari and IR 64 backgrounds. However, the extent of the increase was smaller and unstable in Takanari background than that in IR 64 background. In addition, SPIKE/GPS improved percentage of filled spikelets only in the IR 64 background. These results suggest that the effects of SPIKE/GPS alleles are similar but are affected by the difference of the genetic backgrounds. Because the increasing effect of spikelets number per panicle was canceled by the decrease of the number of panicles, which seems to be affected by environmental factors, none of NIL-SPIKE, SL2115, or NIL-GPS significantly out-yielded their parental cultivars. These results indicate the importance to consider genetic backgrounds and QTL-environment interaction toward the future use of SPIKE/GPS.
Highlights
Plant breeding is a continuous process of crossing and selection to produce new cultivars with desirable characteristics
Our results suggest that the effects of SPIKE/GREEN FOR PHOTOSYNTHESIS (GPS) may be influenced by the difference in genetic backgrounds
Our results indicate that the Daringan SPIKE allele and the Koshihikari GPS allele may not play a role in increasing yield potential at least under the present field conditions, and that other genetic factors that increase sink capacity or biomass production are necessary to improve yield potential in Takanari and IR 64
Summary
Plant breeding is a continuous process of crossing and selection to produce new cultivars with desirable characteristics. When the average yield of unhulled grain in tropical Asia was 1.4 t ha−1, IR 8, the first high-yielding indica cultivar (developed by IRRI in the Philippines) in tropics, produced nearly 10 t ha−1 through a high N response and high lodging resistance conferred by sd (De Datta et al, 1968). Continuing global population growth will require a further 60–70% increase in rice production in the limited area of arable land by 2050 (Tester & Langridge, 2010). This increase will require improvement of rice’s yield potential through the accumulation of favorable alleles of valuable genes (The 3000 rice genomes project, 2014)
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