Participatory varietal selection with improved pearl millet in West Africa

A reconnaissance survey and participatory varietal selection trials (PVS) were conducted in four major pearl millet-growing countries of the Sahel between 2001 and 2003. The studies aimed to identify farmers' preferences in improved pearl millet varieties, increase awareness, test new varieties and enhance farmers' access to the improved varieties. Farmers selected five out of 10 tested varieties, with preferred characteristics, namely, maturity cycles of 80-90 d in the Sahel and 90-100 d in the Sudanian agro-ecozones, acceptable grain yield, compact and long (30-100 cm) panicles, a large number of tillers with panicles, adaptation and an acceptable taste. Farmers indicated that their local varieties were of superior adaptation and taste. They mentioned that hindrances to uptake and sustained use of improved varieties were due to lack of awareness, traditional values, seed unavailability, early maturity, bird damage and lack of fertilizer. The strong genotype × environment interactions in the Sahel suggests that breeding should be directed towards producing varieties adapted to specific zones rather than for wide adaptation. Notably, since farmers often cultivate pearl millet without any soil amendments, it may be advisable to disseminate varieties as a package (with fertilizer and agronomic instructions) rather than as varieties alone in a PVS programme, in order to achieve the full potential of improved varieties. The PVS trials are synergistic to plant breeding in identifying varieties suitable for harsh environments, which are difficult to duplicate in the research station. However, in the absence of formal distribution seed systems in the trial countries, village- or community-based seed production of varieties selected by farmers appears critical to the sustainable adoption of selected varieties

Major and minor genes for stimulation of striga hermonthica seed germination in sorghum, and interaction with different striga populations

The parasitic angiosperms Striga hermonthica (Del.) Benth. and S. asiatica (L.) Kuntze severely constrain cereal production in sub-Saharan Africa. A resistance mechanism to these root parasites in sorghum [Sorghum bicolor (L.) Moench] is low exudation of striga seed germination stimulants. The trait is controlled by a single recessive gene in the sorghum x S. asiatica interaction, but information is lacking for S. hermonthica. Objectives of this investigation were to study the inheritance of stimulation of S. hermonthica seed germination in three F2 and two F3:5 recombinant inbred populations of sorghum, and to determine the effects of striga populations from Mali, Niger, and Kenya on the effectiveness of the low-stimulant character. An agar-gel assay was employed for this purpose. In this laboratory assay, the maximal distance between sorghum rootlets and germinated striga seed ("maximal germination distance") reflects the magnitude of germination stimulation. Bimodal frequency distributions supported the hypothesis of one recessive gene with a major effect for low maximal germination distance in progenies from crosses of low-stimulant lines (Framida, IS 9830) with a high-stimulant line (E 36-1), tested with striga from Mali or Niger. However, low- versus high-stimulant classes were not always clearly distinct, indicating that additional minor genes modified maximal germination distance in the progenies. The Kenyan striga population led to higher maximal germination distances and larger overlap of low- and high-stimulant classes than striga from Mali or Niger. Minor genes seemed therefore more important with Kenyan striga seed. The general involvement of minor genes in stimulating S. hermonthica seed germination was also evident from the heritable, quantitative variation observed in F3:5 lines derived from a cross of the high-stimulant lines N 13 and E 36-1. Because of the higher sensitivity of Kenyan striga to germination stimulation, the low-stimulant character may be less effective in Kenyan fields

Utility of indirect and direct selection traits for improving Striga resistance in two sorghum recombinant inbred populations

Breeding of sorghum (Sorghum bicolor L. Moench) for resistance to the parasitic weed Striga hermonthica (Del.) Benth. has been hampered by the difficulty of evaluating host resistance in the field and lack of reliable screening techniques. Therefore, we investigated the value of various indirect and direct measures of Striga resistance as selection traits. Two sorghum recombinant inbred populations of 226 F3:5 lines each were developed from the crosses (1) IS 9830 × E 36-1 and (2) N 13 × E 36-1. Striga-resistant line IS 9830 is characterized by low stimulation of Striga seed germination, whereas Striga-susceptible line E 36-1 produces germination stimulants in abundance. Line N 13 possesses "mechanical" resistance and probably also an antibiosis mechanism. Resistance was assessed in 1997 and 1998 using in vitro agar-gel assays with Striga seeds from Kenya, Mali, and Niger, pot trials in the respective three countries, and field experiments in Kenya and Mali. The agar-gel assay proved to be a useful, precise and fast indirect selection method to screen for sorghum entries with the low-stimulant character. However, correlation analysis showed that this resistance mechanism was ineffective in some environments, especially in Kenya, pointing to the necessity of field evaluation. Because of low heritability estimates and moderate to low correlations to Striga resistance under field conditions, pot screening appeared to be of limited use in breeding programs. The field trials confirmed the effectiveness of several direct measures of Striga resistance in sorghum: emerged Striga counts, Striga severity index, and area under the Striga number or severity progress curves. A two-row plot field layout with an empty row between plots, coupled with artificial infestation of test rows, lattice design and six replications offered an improved screening procedure that achieved high heritability. Significant genotype × environment interactions in the field experiments stress the importance of multi-locational trials to achieve stable Striga resistance