The nature of Solanum × chaucha Juz. et Buk., a triploid cultivated potato of the South American Andes

Summary The variation in Solanum × chaucha Juz. et Buk. (2n=3x=36) was studied using 114 accessions from the Potato Collection maintained by the International Potato Center. These accession represented less than 5% of the collection originally screened for ploidy. Twenty morphological characters of the tubers, inflorescences and leaves were scored. The accessions were grouped into 20 morphotypes on the basis of the tuber characters. Two-qualitative characters, red-anther tip and sky-blue flowers were diagnostic of 4 morphotypes, but the variation of the quantitative characters overlapped among morphotypes, and were of limited value. Electrophoretic separation of tuber proteins in 7.5% polyacrylamide gels generally confirmed the morphotype groupings. It is concluded that each of the morphotypes represents a single genotype, and these are named according to the International Code of Nomenclature for Cultivated Plants. The variation within S. × chaucha apparently has been restricted by its hybrid origin.     

Symbiotic variability in Vicia faba. 1. Genetic variation in the Rhizobium leguminosarum population

Summary Twenty isolates taken at random from indigenous populations of Rhizobium leguminosarum sampled near Aberystwyth were each inoculated into plants of a standard Vicia faba variety grown aseptically under conditions free of combined nitrogen. Plants in association with the individual rhizobium isolates exhibited large differences in dry matter yield, nitrogen content, efficiency of nitrogen utilization and date of first flower. The implications of these differences to the productivity and reliability of varieties of field beans are discussed.     

Phylogenetic studies in Citrus reticulata and related types

Summary Sixteen types of mandarins were screened for their leaf flavonoid patterns with the help of cellulose thin-layer chromatography. In general, Tanaka's classification of mandarins into 36 species is untenable, as was already concluded by Swingle (1948), Hodgson (1965) and Singh (1967). It is likely that a fine loose skinned mandarin was first evolved. Later, it hybridized with wild mandarin to give rise to numerous types and forms.Contribution No. 474 of Indian Institute of Horticultural Research, Bangalore-6, India.