Cytomorphological studies in F1 hybrids (Corchorus capsularis L. x Corchorus trilocularis L.) of jute (Tiliaceae)

Cytomorphological features of F-1 hybrids (12 sets were analyzed; F-1 plants raised from seeds of each crossed pod was considered as a single set) between Corchorus capsularis Linnaeus - 2n = 14 (male parent) and C. trilocularis Linnaeus - 2n 14 (female parent) were studied in relation to parents. The hybrid plants looked morphologically alike in 12 sets. The F-1's were intermediate to parents for few traits (stem colour, bud shape and flower colour); while, for other characters (pod colour, pod shape, seed colour and seed shape) they resembled the female parent. Average chromosome association per cell at diplotene and metaphase I (MI) of F-1 plants was 0.007 hexavalent (VI) + 0.007 quadrivalent (IV) + 6.74 bivalent (II) + 0.70 univalent (I) [parents: C capsularis - 6.98 II + 0.03 1 /cell, C trilocularis - 7II /cell] and it varied from 0.05 VI + 4.00 II + 2.00 1 to 8.86 11 + 0.00 1 among the sets. F1 plants formed bivalents (4.00 to 8.86 /cell, frequency - 0 to 14/cell) and univalents (0.00 to 2.00 /cell, frequency - 0 to 24/cell) mostly and very rarely quadrivalents (0.07/cell, set-7) and hexavalents (0.05/cell, set-5) in ring configurations. Predominant associations in F1 plants were 7 II (39.47% to 94.44%; average 70.17%) and 6 11 + 21 (0.00% to 30.77%, average 11.08%). PMC's (pollen mother cells) with aneuploidy (hypo - and hyperploids) and polyploidy (n=1, 2, 3, 4, 5, 8, 10, 12 and 14) were noted in some hybrid lines (set-1, 2, 5, 6, 7, 8 and 10) at diplotene and MI only, which was attributed to the consequence of cytomixis. Cytomixis was evident from all hybrid lines including the female parent C trilocularis L. Anaphase I showed equal (7/7) segregation of chromosomes in 100.0% cells of both parents and in 96.5% cells of hybrid plants. Pollen fertility was high (F-1, plants: 79.7% to 95.6%, average - 89.1%; parents: C capsularis L. - 91.2%, C trilocularis L. - 73.3%) in the plant types. Results indicated close genetic relationship between the parents.