Enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies (Mabs) enabled to classify Potato virus Y (PVY) strains into two main serological groups: PVY^O,C serotype (O serotype) and PVY^N serotype (N serotype). This test is being used in seed potato certification programs and research laboratories involved in PVY characterization. However, Mabs are not always able to discriminate PVY strains due to the cross-reactivity of the Mabs, and the presence of recombination events in the capsid protein (CP) of some PVY isolates. Moreover, it is difficult to obtain these Mabs in some cases. In the present study, based upon specific nucleotide motifs in the CP gene of the serotypes O and N of PVY, we designed specific primers that can be used in multiplex PCR form for the simultaneous detection and identification of these serotypes. This assay can be performed during the molecular characterization of PVY isolates, hence eliminating the need for a separate ELISA test to identify PVY serotypes O and N. The reliability of this method was evaluated by comparing the results with the results of ELISA using well-documented Mabs for more than 80 PVY infected samples.

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The postharvest characteristics of the banana cultivar ‘Williams’ grown in Ecuador under two production systems namely low chemical production system (LCPS) and conventional production system (CPS) during two seasons (wet versus dry season) were investigated. To elucidate the differences in the postharvest behavior of bananas between the two production systems, physicochemical changes occurring after ethylene treatment and storage under ambient room conditions were evaluated. LCPS bananas tended to ripen faster than the CPS bananas, regardless of the growing season, as evidenced by the lower peel firmness and hue angle during the shelf-life period. The LCPS bananas also showed relatively higher respiration and cumulative weight loss rates. The breakdown of starch to soluble sugars began earlier in the LCPS than in the CPS bananas. Sucrose was the dominant sugar throughout the ripening period, followed by glucose, then fructose, but their relative proportions varied at the different stages of ripening. Ripening was accompanied by a gradual increase in the moisture content of the pulp and the pulp: peel ratio.

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Seed yield of cowpea {Vigna unguiculata (L.) Walp.} is much lower than the potential in the farmer fields of the Sahelian zone and dissemination of improved cowpea varieties is limited in the zone. Yield performance, nitrogen and phosphorus acquisition of around 140 cowpea germplasm including IITA (International Institute of Tropical Agriculture) and INRAN (Institute National de la Recherche Agronomique du Niger) breeding lines/varieties were evaluated in sandy soils with low fertility level (hereafter referred to as “low-fertile sandy soils”) in the Sahelian zone in 2004 and 2005. Vegetative dry matter production was affected by time of flowering and thus was higher for late-flowering varieties. Meanwhile, seed production was affected by both the flowering date and rainfall in the late growing season. Early discontinuation of rainfall in the 2004 season significantly depressed the seed yield of the varieties which flowered later than 60 days after sowing. Varieties with higher biomass production were estimated to exhibit a higher ability of nitrogen and phosphorus acquisition and symbiotic nitrogen fixation. Three dual-purpose varieties were selected based on the results of the 2004 and 2005 evaluation. These varieties produced a larger amount of seeds but slightly less fodder than the local varieties from the dry savanna and Sahelian zone. The selected varieties did not display higher phosphorus use efficiency or higher dependence on nitrogen fixation than the local varieties. Therefore, genetic improvement of symbiotic nitrogen fixation and phosphorus use efficiency of varieties with a higher seed yield should be a priority for sustainable cowpea production in the Sahelian zone.

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The influence of direct sowing and transplanting on the yielding ability and agronomic traits of finger millet (Eleusine coracana Gartner) was examined. Twenty plants per square meter of nine accessions (3 Japanese and 6 Nepalese strains) were cultivated without the use of fertilizer. Significant differences between cultivation methods and strains were found in the yields. The yield of Japanese strains was not significantly influenced by the cultivation method, while the direct sowing increased the yield of Nepalese strains. The number of grains per ear was significantly greater in direct-sown plots than in transplanted plots. The plant height was significantly shorter in transplanted plots than in direct-sown plots. Principal component analysis (PCA) was performed to clarify the agronomic traits that cause the differences of yielding ability. The first principal component (PC) was considered to be the factor related to either ear-weight type or ear-number. The second PC was considered to be the factor related to the yielding ability and tillering activity. Transplanting tended to give lower yield, tillering, and ear-number. These results suggest that the transplanting culture of finger millet reduces the yield, although Japanese genotypes are hardly affected by transplanting. A change of plant type from ear-weight to ear-number was also found after transplanting.

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