During the September‐December season of 1990, severe symptoms of Fusarium wilt were for the first time observed on a popular climbing bean (Phaseolus vulgaris L.) cultivar. G 2333. introduced within the previous 5 years. Seventy‐three bean genotypes were screened for resistance lo the disease, using artificial inoculation. The effect of inoculation density on the reaction of four selected genotypes was also investigated. Of the 29 climbing bean genotypes evaluated, 19 were resistant, including 11 of the 15 pre‐release or released cultivars. Of the 44 bush bean cultivars evaluated, 28 were resistant, five were intermediate and 11 were susceptible. All susceptible cultivars showed vascular discoloration. In both susceptible and resistant genotypes, the fungus spread almost equally from the entry points in inoculated roots to the base of the plants, but colonization and vertical spread within the vascular system were markedly less in resistant than in susceptible cultivars. At 20 and 30 cm above soil level, the fungus was only recovered from susceptible cultivars. Increasing inoculum density from 102 to 107 conidia/ml did not affect the resistance of cultivars RWR 950 and G 685 but. in the susceptible cultivars G 2333 and MLB‐48‐89 A. it resulted in early appearance, high incidence and severity of the disease.
Samples of bitter seeds of local ecotypes and cultivars of lupin (Lupin mutabilis), white and yellow ecotypes of quinoa (Chenopodium quinoa Wild) and a local ecotype of amaranth (Amaranthus caudatus) grown in the Peruvian highlands were analysed for total saponin content and sapogenol composition. Sweet cultivars of L albus and L luteus cultivated in mild-rainy lowlands of Chile were also analysed for comparison. Fast atom bombardment-mass spectrometry (FAB-MS) of the saponin extracts and gas chromatography (GC) analysis of the sapogenols after acid hydrolysis of the crude extract were used for the identification and quantification of saponins. It was found that L albus and amaranth had undetectable levels of saponins making them attractive for human consumption. The cultivars and ecotypes of L mutabilis contained saponin levels in the range of 229.8-390.5 mg kg-'. FAB-MS showed the presence of soya saponins I and 11, whereas GC allowed the identification of soya sapogenols A and B. The same saponin composition was determined in L luteus whose total content was 55.3 mg kg-'. Saponin composition in quinoa seeds comprised oleanolic acid and three other sapogenols identified as hederagenin, phytolaccagenic acid and deoxyphytolaccagenic acid. Oleanolic acid saponins were found to be the main class of saponin in quinoa seeds sampled for this study. The yellow ecotype of quinoa presented a significantly higher content of saponins and of oleanolic acid as compared to white ecotypes. Since only one ecotype of amarinth was analysed, the nutritional significance of no detectable saponin needs further study. It was concluded that the environmental conditions in the Peruvian highlands are determinants of the amount and composition of saponins present in bitter lupin and quinoa.
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