Browsing by Author "Doi, Kazuyuki"
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Item Contribution of genes related to grain number (Gn1a and WFP) introgressed into NERICA 1 to grain yield under tropical highland conditions in central Kenya(2023) Kikuta, Mayumi; Menge, Daniel Makori; Gichuhi, Emily Waringa; Samejima, Hiroaki; Tomita, Rena; Kimani, John Munji; Musila, Ruth Nzisa; Doi, Kazuyuki; Ashikari, Motoyuki; Angeles-Shim, Rosalyn (TTU); Jena, Kshirod Kumar; Makihara, DaigoIn Kenya and many other African countries, improving rice productivity is vital for future food security. To improve rice productivity in Kenya, near-isogenic lines (NIL) were developed by introducing Gn1a and WFP, genes that function to increase grain number per panicle by increasing secondary and primary rachis-branches, into NERICA 1, a registered variety in Kenya. The aim of this study was to determine whether the introduction of these genes has the potential to improve rice productivity under tropical highland conditions in central Kenya. Field experiments were conducted in 2016 and 2017 at a lowland rice field in Mwea, Kenya, under different nitrogen fertilization conditions using three lines of NERICA 1 introgressed with Gn1a and/or WFP (NIL-Gn1a, NIL-WFP, and NIL-Gn1a+WFP) and their recurrent parents, NERICA 1. Two years of field experiments revealed that the introgression lines enhanced grain yield by increasing the number of primary and secondary rachis-branches and the number of grains per panicle. Gn1a and WFP showed additive effects and the introgression of both genes alleviated the negative effects on yield components observed in the introgressed lines, resulting in higher grain yield. Sufficient nitrogen fertilization was required to increase yield in the single-gene introgression lines. However, the line with both Gn1a and WFP achieved reasonable yields even under low fertilizer conditions in Mwea, Kenya. As these introgression lines have similar growing characteristics to their parent variety, they are expected to contribute to increased rice production in Kenya and similar environments in sub-Saharan Africa.Item Marker-assisted introgression and stacking of major qtls controlling grain number (Gn1a) and number of primary branching (wfp) to nerica cultivars(2021) Reyes, Vincent P.; Angeles-Shim, Rosalyn B. (TTU); Mendioro, Merlyn S.; Manuel, Ma Carmina C.; Lapis, Ruby S.; Shim, Junghyun (TTU); Sunohara, Hidehiko; Nishiuchi, Shunsaku; Kikuta, Mayumi; Makihara, Daigo; Jena, Kshirod K.; Ashikari, Motoyuki; Doi, KazuyukiThe era of the green revolution has significantly improved rice yield productivity. However, with the growing population and decreasing arable land, rice scientists must find new ways to improve rice productivity. Although hundreds of rice yield-related QTLs were already mapped and some of them were cloned, only a few were utilized for actual systematic introgression breeding programs. In this study, the major yield QTLs Grain Number 1a (Gn1a) and Wealthy Farmer’s Panicle (WFP) were introgressed and stacked in selected NERICA cultivars by marker-assisted backcross breeding (MABB). The DNA markers RM3360, RM3452, and RM5493 were used for foreground selection. At BC3 F4 and BC3 F5 generation, a combination of marker-assisted selection and phenotypic evaluation were carried out to select lines with target alleles and traits. Further, genotyping-by-sequencing (GBS) was conducted to validate the introgression and determine the recurrent parent genome recovery (RPGR) of the selected lines. The Gn1a and/or WFP introgression lines showed significantly higher numbers of spikelets per panicle and primary branching compared to the recurrent parents. In addition, lines with Gn1a and/or WFP alleles were comparatively similar to the recurrent parents (RP) in most yield-related traits. This study demonstrates the success of utilizing yield QTLs and marker-assisted selection to develop and improve rice cultivars.Item Marker-Assisted Introgression of Quantitative Resistance Gene pi21 Confers Broad Spectrum Resistance to Rice Blast(2020) Angeles-Shim, Rosalyn B. (TTU); Reyes, Vincent P.; del Valle, Marilyn M.; Lapis, Ruby S.; Shim, Junghyun (TTU); Sunohara, Hidehiko; Jena, Kshirod K.; Ashikari, Motoyuki; Doi, KazuyukiThe quantitative resistance gene pi21 from Sensho was introgressed to an indica breeding line IR63307-4B-13-2, a pyramiding line IRBB4/5/13/21, and a tropical japonica line Kinandang Patong by marker-assisted backcrossing. A total of 192 improved lines at the BC4F3 and BC4F4 generations were developed and confirmed to have the gene introgression via genotyping using a pi21-specific InDel marker. Thirteen randomly selected improved lines, representing all the three genetic backgrounds, demonstrated resistance against leaf blast composites in the field and a broader spectrum resistance against individual isolates compared to the recurrent parents in the glasshouse. Specifically, the tested lines exhibited pi21-acquired resistance against 11 leaf blast isolates that elicited susceptible reactions from the recurrent parents. All the tested lines maintained a comparative heading date, and similar or improved panicle length, number of primary branches per panicle and number of total grains per panicle relative to the recurrent parents. The physical grain characteristics of the recurrent parents were also maintained in the 13 lines tested, although variability in the amylose content and chalkiness degree was observed. The successful marker-assisted introgression of pi21 in diverse genetic backgrounds and the resulting broader spectrum resistance of improved lines against leaf blast indicate the potential of pi21 for deployment in cultivars grown across other rice growing regions in Asia.