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Field trials were conducted in the dry (Experiment I) and wet (Experiment II) seasons of 1997 at Samaru (11°11' N, 7°38' E, 686 m above sea level) in the northern Guinea Savanna ecological zone of Nigeria to study the effects of nitrogen rates on the reaction of upland rice (Oryza sativa L.) varieties to Striga hermonthica (Del.) Benth. The results indicate that FARO 48, a variety normally susceptible to Striga hermonthica, exhibited resistance. FARO 11 exhibited tolerance, while FARO 38, FARO 46 and FARO 45 exhibited susceptibility. The application of 90 and 120 kg N/ha delayed and reduced Striga emergence on the crop, induced a low crop reaction score and produced grain yields that were the maximum or significantly higher than the least. No significant differences in Striga infestation were observed between nitrogen rates of 30-120 kg N/ha. The significant interaction between upland rice varieties and nitrogen rates indicates that the susceptible varieties require higher rates of nitrogen to ameliorate the effect of Striga compared with the resistant varieties.

, for use of controlled-atmosphere facilities; to K. A. Kimble and Curt Waters for technical assistance; and to Jeff Hall for preparation of illustrations.

A factorial field experiment was conducted on the demonstration plot of the Plateau Agricultural Development Project (PADP), Jos Plateau State in 1996 with three variables, nitrogen (0 or 80 kg/ha), growth regulator (none, ethephon or chlormequat) and inoculation (none, inoculation with macroconidia of Fusarium graminearum at anthesis or inoculation 1 week after anthesis). No head blight symptoms developed on plants in the field that year because of the dry conditions. Grain infection by Fusarium graminearum was assessed on a Fusarium selective medium. Nitrogen and growth regulators had no effect on grain infection. In 1997 and 1998, a 3 × 3 factorial experiment was conducted on the same site using the same growth regulator treatments and three inoculation treatments (no inoculation, heads inoculated with macroconidia or rows infested with Fusariumcolonized corn kernels that produced ascospores). The incidence of spikelet infection ranged from 2-4% in non-inoculated treatments to 7-25% in inoculated treatments. The incidence of seed infection ranged from 12-31% in non-inoculated treatments to 74-85% in inoculated treatments. Both growth regulators and inoculation treatments had significant effects (P=0.05) on spikelet infection and interacted with each other. These data suggest that growth regulators and nitrogen do not change the inherent susceptibility of wheat heads to F. graminearum, but dwarfed plants may be subject to higher inoculum doses because they are closer to ejected ascospores.

Fonio (Digitaria spp), considered as one of the lost crops of Africa, remains an important food crop for millions of people in Africa. The intimidating challenge today is to produce enough fonio to meet the growing demand for its products. Research has an important role to play in enhancing fonio production in Africa. This paper discusses the innovative research techniques of agricultural biotechnology that are particularly relevant to facilitating the genetic improvement of fonio for higher productivity. The paper considers the potential role of biotechnology applications like DNA markers in understanding the evolution, origin, distribution and diversity of fonio in Africa; somaclonal variation in generating genetic variability in fonio; and genetic transformation in circumventing fonio breeding barriers to introduce alien genes of agronomic importance into fonio.

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