Morphology, Yield and Breeding Behavior of Diploid Dendrobium Species Hybrids and Their Corresponding Amphidiploids

Abstract

Morphology, yield and breeding behavior of eleven diploid Dendrobium species hybrids and their corresponding colchicine-induced amphidiploids from intersectional combinations of Ceratobium x Eleutheroalossum. Phalaenanthe x Ceratobium and Phalaenanthe x Eleutheroalossum were compared. Increased flower width and broader petals and sepals resulted in increased flower size of the amphidiploids. The amphidiploids were less floriferous and produced fewer and shorter racemes than their corresponding diploids, although statistical significance varied from selection to selection. Irregular sporad formation was observed in two Ceratobium-Eleutheroalossum amphidiploid selections, while a preponderance of tetrads was produced by the Phalaenanthe-Ceratobium amphidiploid selections. The Phalaenanthe-Eleutheroalossum diploid selection produced more tetrads than its amphidiploid counterpart. Fertility was evaluated by crossing the diploids and the amphidiploids with D. rumphianum and D. stratiotes. Cross combinations with the diploid selections resulted in low fruit set and low embryo viability. Male sterility was observed in the majority of the crosses, although female fertility increased with chromosome doubling. D. xJaquelyn Thomas ' K 3 3 3 - 2 2 ' , D. xMemoria Edward Trevor 'D251', D. superbiens 'D184' and D. xAutumn Lace 'K432-2' were evaluated for their potential use as parents for seed-propagated cultivars. Offspring of the amphidiploids D. xJaquelyn Thomas 'K333-22', D. xMemoria Edward Trevor 'D251' and D. xAutumn Lace 'K432-2' were variable, and were therefore not desirable parents for the production of seed propagated potted plant cultivars. Amphidiploid D. superbiens 'D184' crossed with Dj. phalaenopsis produced uniform D. xLouis Bleriot progeny which can be used for lei flower production. Eleven crosses were made in 1985 using three clones of D. xLouis Bleriot as female parents and three clones of amphidiploid D. xJaquelyn Thomas and one clone of D. xNeo-Hawaii as male parents to substantiate the occurrence of androgenesis. Chromosome numbers of the majority of hybrid offspring were aneuploid ranging between the triploid and tetraploid levels, which is expected of 3N x 4N crosses. Some diploids which strongly resembled the male parents were recovered in 10 out of the 11 crosses and were presumed to be androgenetic. Although the parent amphidiploids were heavily infected with Cymbidium Mosaic Virus, the virus was not detected in most of the androgenetic diploids.