Revisiting rice breeding methods – evaluating the use of rapid generation advance (RGA) for routine rice breeding

Figures & data

Table 1. Rice varieties developed by RGA.

Country	Name of variety	Alias	Designation*	Distinguishing features	Year of release	Reference
Philippines	IRRI142	MS11, NSIC Rc170	IR68333-R-R-B-22	Grain quality	2008	Ha et al. (2011)
	IRRI165	NSIC Rc296, Salinas 9	IR71896-3R-8-3-1	Salinity tolerance	2011	Gregorio et al. (2013)
Bangladesh	BINA dhan8	FL449	IR66946-3R-149-1-1	Salinity tolerance	2010	Gregorio et al. (2013)
	BRRI dhan61		BR7105-4R-2	Salinity tolerance	2013	BRRI (2013, 2015, 2017); http://www.brri.gov.bd/
	BRRI dhan62		BR7517-2R-27-3	First zinc-enriched variety	2013
	BRRI dhan67		BR7100-R-6-6	Salinity tolerance	2014
	BRRI dhan72		BR7527-2R-19-HR10	Zinc enriched variety	2015
India	Luna Sankhi	CR Dhan 405	IR72046-B-R-3-3-3-1	Salinity tolerance	2012	Gregorio et al. (2013)

^* The letter ‘R’ in the designation indicates 1 generation advance using RGA in the selection history. The number preceding the ‘R’ indicates the number of cycles.

Figure 1. Countries using RGA in rice breeding (based on 2015 survey).

Figure 2. RGA system used in irrigated breeding programme at IRRI. (a) seeding (b) seedling stage (c) vegetative stage (d) flowering stage (e) glasshouse set-up (f) showing tillering (g) showing panicles (h) harvesting stage with inset showing harvested panicles (i) inside view of screenhouse (CS-08B).

Figure 3. Field RGA system piloted at IRRI. (a) initial seeding (b) seedling stage (c) vegetative stage resembling seedling nurseries (d) booting stage (e) harvesting mature plants (f) harvesting in the field.

Figure 4. Photos of field RGA implemented at BRRI. (a) An F_3:4 generation is grown under FRGA conditions at BRRI Farm, Gazipur, 2017. (b) F₂ generation with >3000 plants grown under FRGA conditions at BRRI Farm, Gazipur, 2017.

Figure 5. Histograms of yield and flowering time for 3 different RGA populations evaluated in the 2015 dry season OYT. IR98492: yield (a), flowering time (b). IR98590: yield (c), flowering time (d). IR96915: yield (e), flowering time (f). Means of parents and IRRI154 check variety are indicated by arrows.

Table 2. Performance of selected RGA lines in 2015 DS OYT and 2015 WS PYT. (a) RGA lines tested in group 1 (early/medium maturity) of the PYT (2015 WS) sorted by yield performance.

(a) RGA lines tested in group 1 (early/medium maturity) of the PYT (2015 WS) sorted by yield performance
Fixed line	Designation	Parentage	MAT GP 2015 DS OYT	Mean plot yield (g)	SE (g)	SMY (%)	RANK	FLW (days)	PH (cm)	2015 WS PYT Gp1 Plot yield (g)	SE (g)	SMY (%)	RANK	FLW (days)	PH (cm)
IR15A1163	IR98590-2R-119	NSICRC158/IR09F437	1	3991	279	111	9	84	92	2724	174	115	16	81	115
IR15A1771	IR98594-2R-11	IRRI154/IR09F436	2	3880	228	107	95	84	95	2633	216	112	33	85	124
IR15A1716	IR97367-3R-75	IRRI119/IR02A127//IR10F379	2	4175	228	115	4	85	106	2610	171	111	40	79	130
IR15A1053	IR97367-3R-67	IRRI119/IR02A127//IR10F379	1	3837	279	107	73	81	114	2582	215	109	47	81	136
IR15A1225	IR98590-2R-100	NSICRC158/IR09F437	1	3542	279	98	461	86	85	2566	215	109	54	81	113
IR15A1800	IR97367-3R-40	IRRI119/IR02A127//IR10F379	2	3939	228	108	52	82	107	2554	216	108	59	80	127
IR15A1029	IR98492-B-2R-51	IR03A568/IR05F102	1	3922	279	109	21	86	108	2515	215	107	73	81	127
IRRI156	IRRI156	IR72870-102-2-2-1-3/IR72870-19-2-2-3	1	3672	194	102	272	86	100	2424	133	103	103	89	128
IRRI123	IRRI123	IR47761-27-1-3-6/PSBRC28(IR56381-139-2-2)	1	3371	194	94	619	82	94	2421	134	103	105	85	127
IR15A1042	IR96915-3R-1	IR09F436/IR10F365	1	3879	280	108	45	84	111	2416	216	102	110	79	129
IR15A1893	IR98590-2R-61	NSICRC158/IR09F437	2	3888	228	107	88	83	95	2360	216	100	126	86	120
IR15A1557	IR96922-3R-16	IR09F437/IR10F365	2	3851	228	106	130	86	106	2355	215	100	129	85	132
IR15A1695	IR96915-3R-25	IR09F436/IR10F365	2	4001	230	110	29	81	100	2334	171	99	144	84	128
IR15A1796	IR96915-3R-31	IR09F436/IR10F365	2	4212	228	116	3	85	105	2302	171	98	156	80	120
IR15A1926	IR97367-3R-109	IRRI119/IR02A127//IR10F379	2	3896	228	107	78	84	110	2282	216	97	164	81	129
IR15A1714	IR98492-B-2R-82	IR03A568/IR05F102	2	3904	228	107	72	83	102	2217	215	94	183	81	118
IR15A1405	IR96922-3R-49	IR09F437/IR10F365	1	3811	279	106	88	85	107	2215	215	94	184	85	140
IRRI154	IRRI154	IR73012-137-2-2-2/PSBRC10(IR50404-57-2-2-3)	1	3858	194	107	58	87	98	2158	131	91	196	87	126
IR15A1769	IR98590-2R-10	NSICRC158/IR09F437	2	3887	227	107	89	81	122	2134	216	90	200	76	140
IR15A1168	IR98590-2R-99	NSICRC158/IR09F437	1	3934	278	109	18	81	116	2073	215	88	208	79	131
IR15A1031	IR98590-2R-40	NSICRC158/IR09F437	1	3791	280	105	109	83	128	1985	216	84	222	77	136
IRRI104	IRRI104	IR33021-39-2-2/IR50404	1	3109	194	86	697	79	77	1246	133	53	239	71	93

(b) RGA lines tested in group 2 (medium/late maturity) of the PYT (2015 WS) sorted by yield performance
Fixed line	Designation	Parentage	MAT GP 2015 DS OYT	Mean plot yield (g)	SE (g)	SMY (%)	RANK	FLW (days)	PH (cm)	2015 WS PYT Gp1 Plot yield	SE (g)	SMY (%)	RANK	FLW	PH (cm)
IR15A1614	IR97367-3R-65	IRRI119/IR02A127//IR10F379	2	3860	228	106	113	90	105	2537	215	118	14	86	128
IR15A1045	IR98492-B-2R-81	IR03A568/IR05F102	1	3795	280	105	104	92	112	2516	215	117	18	97	140
IRRI105	IRRI105	IR24594-204-1-3-2-6-2/IR28222-9-2-2-2-2	2	3186	145	88	681	91	96	2447	131	114	28	101	123
IRRI146	IRRI146	IR73885-1-4-3-2-1-6(MATATAG9)/IR70479-45-2-3//IR64680-81-2-2-1-3	2	3534	144	97	496	89	88	2276	131	106	79	89	124
IR15A1668	IR96915-3R-14	IR09F436/IR10F365	2	3937	228	108	54	85	94	2230	215	104	104	84	130
IR15A1684	IR98492-B-2R-95	IR03A568/IR05F102	2	3821	228	105	157	87	115	2209	215	103	110	99	147
IRRI154	IRRI154	IR73012-137-2-2-2/PSBRC10(IR50404-57-2-2-3)	2	3560	146	98	465	88	96	2194	131	102	116	87	129
IR15A1515	IR96915-3R-51	IR09F436/IR10F365	2	3882	228	107	94	98	100	2098	214	98	150	93	129
IR15A1030	IR98492-B-2R-68	IR03A568/IR05F102	1	4012	279	111	7	93	105	2055	173	96	162	99	138
IR15A1362	IR96915-3R-26	IR09F436/IR10F365	1	3925	279	109	20	91	119	2050	215	95	168	86	141
IR15A1523	IR96915-3R-104	IR09F436/IR10F365	2	4037	228	111	25	87	104	2015	171	94	178	81	129
IR15A1856	IR96915-3R-3	IR09F436/IR10F365	2	3927	227	108	58	87	97	1981	215	92	189	81	117
IR15A1813	IR96915-3R-53	IR09F436/IR10F365	2	4170	228	115	5	92	105	1901	173	88	205	87	135
IR15A1530	IR98492-B-2R-119	IR03A568/IR05F102	2	3926	230	108	59	89	108	1831	215	85	213	98	146

Notes: MAT GP = maturity group; SE = standard error; SMY = site mean yield, expressed as a percentage of the trial mean; FLW = flowering time; PH = plant height.

‘R’ indicates 1 cycle or RGA, ‘2R’ indicates 2 cycles of RGA etc. In IRRI’s current ‘Breeding for Rice database’, ‘R’ is equivalent to ‘BRGA’ following the methods described in this paper.

Figure 6. Histograms of yield for RGA and pedigree lines from population IR97367 evaluated in the 2015 dry season OYT. (a) RGA lines. (b) pedigree lines (from the same cross). Means of parents and IRRI154 check variety are indicated by arrows.

Table 3. Operational and investment costs for the RGA and pedigree method.

Type of cost	Resource cost*
	Pedigree 2012	RGA 2015
Yearly operational costs
Land use	$ 94,694	$ 7425
Seasonal labour	$ 32,725	$ 7673
Maintenance greenhouse/screenhouse	–	$ 10,752
Investment costs
Construction screenhouse	–	$ 73,199
Construction greenhouse	–	$ 428,316

* Calculations are based on IRRI’s internal cost structure.

Table 4. Measures of project value for RGA.

	NPV*	Benefit-cost ratio*
Screenhouse (n = 10)	$ 494,258	4.16
Greenhouse (n = 20)	$ 487,511	1.87
Greenhouse (n = 50)	$ 913,282	2.46

Note: n = expected lifetime (in years).

* Results were calculated for a discount rate of 5%.

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