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REGISTRATIONS OF GERMPLASMS

Registration of 16 Extra-Early Maturing Striga Resistant Tropical Maize Inbred Lines

IITA, c/o L.W. Lambourn & Co., Carolyn House, 26 Dingwall Road, Croydon CR9 3EE, UK

^* Corresponding author (b.badu-apraku{at}cgiar.org)

Sixteen extra-early maturing maize (Zea mays L.) inbred lines TZEEI 1 to TZEEI 16 (Reg. no. GP-473 to GP-485, PI 641251 to PI 641266) with moderate levels of resistance to the parasitic witchweed, Striga hermonthica (Del.) Benth were developed at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria (Table 1). Extra-early maize is particularly suitable for cultivation in areas with short growing periods, such as the northern fringes of the Guinea savanna and the Sudan savanna of West and Central Africa (WCA). These zones are characterized by terminal drought and infestation by S. hermonthica, which are major constraints to increased maize production and productivity. Losses caused by the parasitic weed in farmers' fields can be up to 100% (Lagoke et al., 1991). The inbred lines also have good levels of resistance to Maize streak virus (MSV), tropical lowland rust (incited by Puccinia polysora Underw.) and blight [caused by Bipolaris maydis (Nisikado & Miyake) Shoemaker]. The lines, which are at the S₆ or S₇ stages of inbreeding, have white or yellow endosperm, silk in about 56 d after planting and grow to a height of about 1 m. In 2001, they were released to national maize programs in WCA as source germplasm for broadening the genetic base of tropical extra-early populations and as parents for the development of Striga resistant synthetic varieties for the savanna ecologies.

At the S₄ stage, 250 to 300 lines derived from each population were crossed to the corresponding base population as the tester. The S₄ lines per se and the testcrosses were evaluated at Sinematialli under Striga-free conditions and at Ferkessedougou under artificial infestation with S. hermonthica seeds collected from sorghum [Sorghum bicolor (L.) Moench] fields near each testing site. About 5000 germinable Striga seeds per maize hill were used for the artificial infestation. The yield performance of the lines per se, their combining abilities for grain yield, Striga damage rating, Striga emergence count, and ear number and other desirable agronomic characters across the two locations were used as criteria for selecting 90 to 100 S₄ lines, which were advanced to S₆.

Eighty-one lines selected from all source populations were evaluated during the dry and rainy seasons of 2001 under artificial infestation with S. hermonthica and under noninfested conditions at Ferkessedougou. In the dry season trial, the maize inbred lines were irrigated up to physiological maturity using an overhead sprinkler irrigation system, which applied 12 mm of water per week. Irrigation water was withdrawn thereafter till harvest. Thirty-six of the 81 lines, were further evaluated under artificial Striga-infested and noninfested conditions at Mokwa (9°18'N, 5°04'E) and Abuja (9°16'N, 7°20'E) during the planting season of 2004. Apart from Striga seed infestation, all management practices for both Striga-infested and noninfested plots were the same.

The inbred lines being registered were selected based on mean performance across all trials. Grain yield of the 16 lines ranged from 520 to 3966 Mg ha^–1 under Striga-free conditions while grain yield under Striga infestation ranged from 254 to 3112 Mg ha^–1. Under Striga infestation, the inbred lines silked between 52 and 64 d, with plant height ranging from 84 to 123 cm. The mean number of emerged Striga plants per plot of the inbreds under artificial Striga infestation ranged from 3 to 56 plants while the Striga syndrome rating ranged between 4 and 5 on a scale of 1 to 9, where 1 = little or no damage and 9 = severe damage.

Small quantities of seed (40 kernels) could be made available to crop researchers on request to the WECAMAN Coordinator, the Maize Breeding Unit, IITA, PMB 5320, Ibadan, Nigeria. In the USA, small quantities of seed may be obtained from the National Plant Germplasm System (NPGS). We request that appropriate recognition of the source be given when the inbred lines contribute to an improved cultivar or germplasm.

ACKNOWLEDGMENTS

The authors are grateful to the United States International Development Agency for financial support, and the support staff of the IITA Maize Program for technical support. Appreciation also goes to Prof. M.A.B. Fakorede of Obafemi Awolowo Univesity, Ile-Ife, Nigeria for critical review of the manuscript.

NOTES

Research supported by grants from USAID. IITA Manuscript no. IITA/05/JA/06. Registration by CSSA.

Received for publication June 14, 2005.

REFERENCES

• Kling, J.G., J.M. Fajemisin, B. Badu-Apraku, A.O. Diallo, A. Menkir, and A. Melake-Berhan. 2000. Striga resistance breeding in maize. p. 103–118. In B.I.G. Haussmann, D.E. Hess, M.L. Koyama, L. Grivet, H.F.W. Rattunde, and H.H. Geiger (ed.) Breeding for Striga resistance in cereals. Proc. of a workshop held at IITA, Ibadan, Nigeria. 18–20 Aug. 1999. Margraf Verlag, Weikersheim, Germany.
• Lagoke, S.T.O., V. Parkinson, and R.M. Agunbiade. 1991. Parasitic weed control methods in Africa. p. 3–14. In S.K. Kim (ed.) Combating Striga in Africa. Proc. Int. Workshop (IITA, ICRISAT, and IDRC), Ibadan, Nigeria. 22–24 Aug. 1988. IITA, Ibadan, Nigeria.

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