Breeding in Vanda

In nature Vanda occurs in two vegetative forms -terete- leaved and strap-leaved . The first recognised Vanda hybrid x Vanda Miss Joaquim, which flowered in the garden of Miss Agnes Joaquim of Singapore in 1893, was a cross between two terete -leaved species , V. hookeriana and V. teres. This is a very floriferous from and is still very popular as the ' lei orchid' in South East Asiatic countries.

Breeding in the Sarcanthoid group started in earnest at a much later date than in other orchid groups. This was first initiated in Singapore during the nineteen twenties by the combined efforts of Dr. R.E. Holttum,who succeeded Dr. Ridley as the Director of the Singapore Botanical Gardens and John Laycock , a resident of Singapore who was greatly interested in growing unusual plants .

The most spectacular of our Vanda hybrids come from the semi-terete group,which are products of hybridisation between the terete- leaved and the strap-leaved species . These hybrids were, however, found to be quite sterile and for a time it appeared as though this would be a dead end to Vanda breeding . But these semiteretes ,when crossed with natural diploid , strapleaved Vandas, sometimes produced progeny of outstanding merit and which turned out to be far more fertile than the hybrid parent. Storey (1952, 1953, 1956)was the first to clarify the cytological situation in these hybrid plants and explain their unusual behaviour on the basis of his findings . He and later Kamemoto (1956, 1959) found out that the sterility of the first generation semi-terete hybrids is due to the incompatibility between the genomes of the strap-leaved and the terete -leaved species . There is no pairing of chomosomes during meiosis and distribution at anaphase is at random, resulting in a high degree of sterility . But polyploid gametes also result from this random distribution and consequent restitution , giving rise to diads, triads and tetrads. These on fusing with haploid gametes from the other parent , produce tripoids and tetraploids. A diploid gamete fusing with a triploid one produces a pentaploid.

The circumvention of the sterility barrier in the first generation semiterete hybrids by the production of polyploid gametes , gave the necessary impetus to further breeding of Vanda hybrids like Vanda Clara Shipman Fischer , Vanda Tan Chay Yan etc. The blue Vanda coerulea has figured prominently in the breeding of the much-priced blue Vanda hybrids like x Vana rothschildiana.

In no other group of orchid hybrids have such exhaustive cytological investigations been carried out as in the Vanda Group by the team of orchidologists at the University of Hawaii . As a result of their investigations, the peculiar breeding behaviour of terete and strap -leaved species and their hybrids could be explained and the breeding programmes could be planned with a certain amout of certainty as to the results to be expected .