Chromosome constitution of some Indian tea clones

Abstract

Resultant of large-scale spontaneous hybridization between Camellia taxa, the present day commercial tea clones are highly variable and heterozygous. It is in this context that thirty two UPASl and other tea clones were investigated with regard to comparative karyomorphology and meiotic pairing properties so as to ascertain the nature and extent of intra - and interclonal differentiation. Barring one clone (UPASI 3), all other investigated clones were diploid (2n = 2x = 30) in constitution. UPASl3 was triploid (2n = 3x = 45) in constitution. The chromosome complements in the diploid tea clones, wherever investigated, resolved into 15 median and submedian homomorphic pairs. Between clones, minor variation in the proportion of median and submedian chromosomes and (or) number and location of secondary constrictions was observed. lnspite of the fact that tea clones are considered to be highly heterozygous, the male meiosis in the diploid clones was perfectly normal resulting in regular 15 bivalents at diakinesislmetaphase I, and equal (1 5:15) distribution of chromosomes at anaphase I. The only feature which could indicate degree of cryptic hybridity was the occurrence of bivalents with localized chiasmata. The predominant occurrence of trivalents in the triploid UPASI 3 indicated either autopolyploid or segmental allopolyploid origin. The genomic constitution of tea clones is discussed in the light of present results.