33

Rgn13

33. Identification of wide compatibility varieties (WCV's) and tagging of WC gene

with isozyme markers

S.S. malik and G.S. khush International Rice Research Institute, P.O.Box 933, 1099 Manila, Philippines.

The F1 hybrid sterility in indica/japonica crosses is the major handicap in developing F1 hybrids between these two adverse germplasm. Ikehashi and Araki (1986) have demonstrated that the sterility of hybrids between indica and japonica varieties is caused by an allelic interaction at a locus at which the indicas have S-5i allele, the japonicas have S-5j allele and some of the tropical japonicas from Indonesia have neutral allele, S-5n allele. The donors of S-5n are known as a wide compatibility varieties (WCV). These WCV's produce fertile F1 plants when crossed with indicas as well as with japonicas. To overcome sterility problem in japonica-indica hybrids, wide compatibility gene should be incorporated into either of the two parents.

To identify WCV germplasm, 85 tropical japonica varieties from Indonesia were crossed with indica (IR36) and japonica (T65) testers. f1's were planted in one row each along with their parents. Pollen as well as spikelet fertility of the F1's and their parents were analyzed. Ten panicles each from f1's and parents were analyzed for spikelet fertility.

The pollen fertility of parents varied from 71-93%. while pollen fertrility of f1's with indica tester varied from 35-91% and with japonica tester varied from 32-90%. The spikelet fertility of parents varied from 60-97%, while that of their F1's with indica tester varied from 41-92% and with japonica tester varied from 59-95%.

Varieties having average spikelet fertility of more than 70% with both the indica and japonica testers were rated as WCV. On this basis, 21 tropical japonica varieties were rated as WCV (Table 1 ). The data are presented in Table 1.

Several tropical japonica varieties from Indonesia were analyzed for allelic constitution at Amp-3. All the WCVs have allele 2 and all non-WCV have allele 1 of Amp-3. F2 population of a WCV (Azucena) and Non-WCV (IR36) consisting of 250 plants was analysed for allelic constitution at Amp-3, Est-2, Pgi-2 and Cat-1 loci which are located on chromosome 6. Co-segregation analysis of WC and isozyme loci in F2 showed tight linkage of WC with Amp-3 and Est-2. WC gene was found to be located at a distance of 4.1 cM from the Amp-3 and Est-2 loci. Such tight linkage is of great value for selecting wide compatible indviduals in a segregating population, based on allelic composition at Amp-3 and Est-2 loci. We are already using this information for marker-based selection program for developing breeding lines with wide compatibility. (Gene symbol: Old system)

122 Rice Genetics Newsletter Vol. 13

Table 1. Pollen and seed fertility of F1, hybrids of tropical japonica varieties with Indica (IR36)

and Japonica (T65) testers and allelic constitution at Amp-3 locus

Varieties	Pollen fertility of f1s		Seed Fertility of F1s		Allele of
	with IR36	with T65	with IR36	with T65	Amp-3
Azucena	81	59	85	78	2
Banda	70	45	69	83	2
Bomalsang	85	60	80	70	2
Buyugaw Daykat	75	65	78	78	2
Gendjah Gampol	35	52	85	78	2
Gendjah Wangkal	68	72	87	90	2
Gendjah Rante	73	68	81	90	2
Goak	35	65	85	83	2
Huma Pasir-1	75	76	91	86	2
Jimbrug	85	65	79	76	2
Leci Gogo	69	42	80	85	2
Loas Gendjah	63	48	74	83	2
P.B.B. Harum	85	65	83	75	2
Pae Umbala	55	66	70	90	2
Paedai Nodowatu-2	83	70	71	80	2
Pare Bogor	61	66	70	77	2
Pring	84	53	83	77	2
R.S.	65	54	84	78	2
Sarimahi	91	83	71	78	2
Sokoni	79	45	70	73	2
Zaitun	91	78	78	78	2
Ase Balong Kamandi	68	38	55	86	1
Abang Busur	82	78	49	92	1
Ase Bandong	80	67	56	74	1
Ase Lotang	80	73	61	81	1
Ase Mandi	64	72	51	80	1
Bali Ontjer	82	50	59	72	1
Beak Balok Loas	65	55	63	73	1
Benong-130	88	85	61	85	1
Beton berik	58	65	54	75	1
Bonjo	76	74	50	80	1
Bulu Gampolan	70	45	61	82	1
Cicih Beronol	75	70	63	91	1
Cicih Kaplik	71	55	60	68	1
Dangge	71	79	52	92	1
Dejawa Senit	75	70	66	76	1
Dendek Rebiaq	64	70	56	85	1
Djoro One	69	42	66	66	1
Genjah Urang	65	75	41	95	1
Gropak	76	73	51	71	1
Gundil Kuning	73	42	62	79	1
Jelean	72	75.	49	90	1
Hawarah Langgari	74	68	54	73	1

Research Notes 123

Table 1. (Continued)

Varieties	Pollen fertility of F1s		Seed Fertility of F1s Allele of
	with IR36	with T65	with IR36	1
Jokodolok	73	63	43	93	1
K. Rondo Marong	61	38	59	90	1
Kamandi Pance	73	50	67	60	1
Kaprit	68	40	62	74	1
Karang Sarang-55	90	71	55	84	1
Ketan Apel	68	66	53	92	1
Ketan Aram	89	38	59	78	1
Ketan Bandang	36	72	61	87	1
Ketan Geude	60	68	56	70	1
Ketan Gubat	62	61	59	92	1
Ketan Lombok	83	32	63	67	1
Ketan Lumbli	53	42	64	89	1
Ketan Menah	39	40	54	94	1
Ketan Montor	75	63	64	88	1
Ketan Slawi	71	60	56	90	1
Ketan Welut	71	57	62	95	1
Kopo	88	52	67	92	1
Lembang	68	40	55	73	1
Leri	65	72	68	94	1
Manong Tjinde	66	62	56	91	1
Mauni	65	64	57	90	1
Menco Manurum	78	63	59	91	1
Padi Buring Gogo	68	63	68	79	1
Paedai Nadimo	73	38	63	88	1
Palangan	65	74	54	94	1
Pare Minar	80	50	65	59	1
Pasak Jalan	74	78	51	96	1
Pulut Cenarana	73	75	55	92	1
Pulut Taddaga	73	73	53	87	1
Pulut Tembahan	70	58	52	92	1
Putus Tolo	77	70	54	95	1
Ribon	76	88	59	81	1
Rodjolele	80	62	68	83	1
Sampang Atal	78	83	62	69	1
Sengkeu	58	90	58	73	1
Serendeh	82	69	68	71	1
Soponjono	86	70	58	80	1
Sri Kuning	82	62	60	83	1
Tulak Bala	81	84	68	74	1
Tundus	68	81	63	78	1
Turpan-2	68	52	68	85	1
Gendjah Urang	65	75	41	95	1