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

Maity S., Datta A.K.

Abstract. Cytomorphological features of F1 hybrids (12 sets were analyzed; F1 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 F1’s were intermediate to parents for few traits (stem colour, bud shape and ?ower 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 F1 plants was 0.007 hexavalent (VI) + 0.007 quadrivalent (IV) + 6.74 bivalent (II) + 0.70 univa-lent (I) [parents: C. capsularis – 6.98 II + 0.03 I /cell, C. trilocularis – 7II /cell] and it varied from 0.05 VI + 4.00 II + 2.00 I to 8.86 II + 0.00 I 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 II + 2I (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 (F1 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.