Pathogenicity and symptom expression of seventeen described isolates of bean common mosaic virus (BCMV) and five previously unreported isolates were compared on many bean cultivars (Phaseolus vulgaris L.). From these cultivars, a standard set of differentials were assigned to nine groups with different disease reactions. The twenty-two virus isolates comprised seven strain (pathotype) groups, three of which were divided into two subgroups each. To promote international standardization in BCMV research, recommendations are given for test conditions and procedures, criteria for strain differentiation, and maintenance of differential cultivars and virus strains.
Introduction and literature review
String formation was analysed in F1, F2 and F3 generations of crosses between cultivars without string, with incomplete string and with complete string, and in B1 and B2 generations of the hybrid between a stringless and a stringy cultivar back crossed to the stringless parent. F1 plants were maintained at constant temperatures of 17 and 23 deg C, and the remaining plants were maintained at 23 deg C, to promote string formation. Segregation ratios suggested that two genes were involved in string development, stringlessness and complete string formation being controlled by the dominant and recessive alleles respectively of St, and incomplete string development, at high temperature and in genotypes with the dominant St allele, being controlled by the dominant allele of the second gene (Ts). (Abstract retrieved from CAB Abstracts by CABI’s permission)
Phaseolus acutifolius, tepary bean, Xanthomonas campestris pvphaseoli, common blight, inheritance of resistance.
SUMMARYThe Fl, F2 and F3 from two crosses within Phaseolus acutifolius were exposed to Xanthomonas campestris pvphaseoli to analyse the inheritance of resistance. The resistant parent, PI 319.443, gave a hypersensitive reaction in leaves and pods with small necrotic lesions. Based on the resistance of Fl, the segregation in F2 and the reaction of F3 plants and lines, it is concluded that resistance in leaves and pods is governed by one dominant gene. Comparisons are made with the resistance to X. campetris in P. vulgaris.
Two sap-transmissible virus isolates from bean (Phaseolus vulgaris L.) were identified as bean common mosaic virus (BCMV) on the basis of particle size and morphology, serology, non-persistent aphid transmission, very limited host range, and symptoms and seed transmission in bean.In bean varietal reaction both isolates differed from each other and all six Dutch BCMV strains described before. From literature data it may be concluded that they also differ from thirteen other strains described elsewhere. The isolate from Peruvian seed may be related to strains reported from Costa Rica and Peru, but these have been described incompletely.The two isolates obtained at Wageningen are therefore described as new strains and designated BCMV-NL7 and BCMV-NL8. The latter seems unusual in its extremely high dilution end point, in its serological affinity to both BCMV and BYMV, and in not being infectious to Chenopodium amaranticolor and C. quinoa.Tetragonia expansa proved to be a new local lesion host of BCMV. There is an urgent need for international standardization of strains of BCMV.
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