Secondary associations in ‘Himalayan pink’ (Dianthus angulatus Royle ex Benth., Caryophyllaceae) from cold deserts of Lahaul-Spiti

In current investigation we studied the male meiosis and details of secondary chromosomal associations or pairing recorded for the first time in Dianthus angulatus Royle ex Benth., from the cold deserts of Lahaul-Spiti (Himachal Pradesh, India). All the presently studied individuals of the species existed at 2x level (x = 15). The present chromosome count of n = 15 in the species is in conformity with the previous counts from India and outside of India. Secondary associations are defined as the affinity of bivalents to be positioned in pairs having gentle connections. The secondary chromosomal associations in the species existed among bivalents/chromosomes were observed in the meiocytes at metaphase-I and continued till the metaphase-II. The bivalents positioned side by side and end to end to form secondary pairing. The difference in the number of bivalents/chromosomes involved in the secondary associations has also been witnessed. A secondary association between bivalents is considered to be of immense importance as it is being taken as a gauge of ploidy in plants. The incidence of such secondary associations of bivalents/chromosomes in D. angulatus which existed at 2x level indicated the secondary polyploid nature of the species.

CHROMOSOME ASSOCIATIONS AT DIAKINESIS IN THE CULTIVATED STRAWBERRY

The analysis of chromosome pairing in the cultivated strawberry revealed that multivalent formation occurs in each of the nine cultivars examined. Secondary pairing and a loose association of bivalents were also observed. The cytological evidence suggests that tetrasomic inheritance should be considered in the interpretation of genetic data.

III.—Cytological Studies in the Genus Solanum. I. Wild and Native Cultivated “Diploid” Potatoes

Previous studies on the cytology of the wild and less highly developed “diploid” forms of potatoes have been mainly concerned with the number of chromosomes. Rybin (1933) in his cytological investigation on the South American cultivated and wild potatoes has recorded 12 as the haploid number of chromosomes in seven species including S. Rybinii. Ratera (1938) reported the same number of haploid chromosomes in S. Parodii and six other species indigenous to Argentine.The present study is concerned primarily with the secondary pairing of chromosomes at meiosis in six “diploid” species with a view to determining the basic number in potatoes and to ascertaining the exact “status” of these species.