New Perspectives in Bougainvillea Breeding

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Effect of certain plant growth regulations on the growth and the metabolism of isolated cotyledons and hypocotyls segments.

The present study aims at studying the effects of Gibberellins (GA3 and GA4+7) and of fusicoccin in addition to those of cytokinins (Kinetin and benzylaminipurine) on expansion growth and on certain aspects of metabolism in cucumber cotyledons. The effects have been studied both without and with 5mm pottassium (supplied as KCl) to find out-how far presence of potassium, which also includes expansion, can modify the effect their growth regulations

Cytogenetical studies on Bougainvillea. I. A case of interchange heterozygosity

A case of interchange heterozygosity has been found inB. peruviana cv "Princess Margaret Rose" in which there is a regular formation of 15 bivalents and an interchange multiple of 4 chromosomes. The multiple is always associated with the nucleolus at diakinesis, indicating that one of the chromosome involved is nucleolar. The nucleolar pair of chromosomes shows a slight heteromorphicity which may be due to an unequal interchange. Although 80% of interchange multiples orientate non-disjunctionally, yet 65% pollen is stainable. The pollen is ineffective in self pollination, but highly effective in crosses with 2x and 3x cultivars ofB. spectabilis. The higher pollen stainability indicates that the deficiencies and duplications caused by non-disjunction do not have serious physiological offects on pollen grains and that its genome can withstand rearrangements

Cytogenetics of cultivated Bougainvilleas. V. Induced tetraploidy and restoration of fertility in sterile cultivars

Induced tetraploidy restores fertility in sterile cultivars of Bougainvillea. However, like the fertile diploid cultivars induced tetraploids are self-incompatible, but set seeds readily on crossing. Diploid progenitors show irregular meiosis, while in tetraploid counterparts there is predominant bivalent pairing. Low frequency of quadrivalents at 4x level implies that pairing at diploid level is between chromosomes heterozygous for cryptic structural changes. This also accounts for lower number of chiasmata per chromosome in diploids in comparison with their tetraploid counterparts. Sterility at 2x level appears to be due to recombination of cryptic structural differences and/or unequal distribution or aberrant behaviour of univalents. Predominant bivalent pairing accompanted by high fertility is a strong pointer towards preferential pairing in induced tetraploids