Distinctiveness in chromosomal behaviour in interspecific hybrid genotypes of cotton

Cytological studies in interspecific hybrid derivatives of cotton viz., IS-244/4/1 and IS-181/7/1 obtained in BC₁F₈ generation of trispecies cross of [(G. hirsutum x G. barbadanse) x G. arboreum] was carried out to find out the chromosome behaviour. During the meiosis variation in chromosome no. from 26 to 31 in IS-181/7/1 and 19 to 49 in IS 244/4/1 was observed against the normal choromosomal behaviour of G. arboretum (2n == 26)and G. hirsutum (2n= 4x=52). Chromosome pairing revealed the presence of univalent, bivalent, trivalent and qudrivalents. Chromosome association of 5.19 I + 8.33 II +1.14 III + 1.09 IV and 6.0 I+ 7.7 II +0.7 III + 1.25 IV was observed in genotypes IS-244/4/1 and IS-181/7/1 respectively. Cytomixix resulted in haploids, anueploids and binucleated cells. Laggards at anaphase, chromosome stickiness and interbivalent connection were also observed due to chromatin transfer. Inspite of variation in chromosome number at dihaploid level and high degree of abnormalities at meiosis, these lines were showing normal boll setting, viable seed and (65–70%) pollen fertility. This is certainly due to parthenogenetic nature of these lines. These lines are of great importance as they have potential for heterosis as well as for evolving aneulpoides and homozygous lines by doubling the chromosomes in haploids. Morphologically these lines were distinct as plant height, leaf size, staminal column, number of anthers/flower, 100 seed weight and number of seeds per boll were found drastically reduced.