Success

The term "seedless" is a little misleading. It is internationally accepted that less than one seed per hop is classed as seedless. So, if in a batch of 100 hops, 86 seeds were found, that variety of hop would be called seedless. In New Zealand plants there are about 15 seeds to one hop. Other countries grow seedless hops, why not New Zealand?

New Zealand, Australia and Great Britian, the only three countries still growing seeded hops, interplant females with males. All other countries grow hops without interplanting males and produce seedless hops.

The answer seemed simple: Grow hops without male plants. Pollen from male plants was abundant in the Motueka-Riwaka area so Dr Roborgh established a trial plot of 50 plants in Collingwood in Golden Bay. This experiment continued for three years and a seedless hop was grown. However, the hop did not fill out and even when mature was small. Pollen was needed to increase the size.

Varieties of seedless hops imported from Germany, Czech-oslavakia, Yugoslavia and America were not suited to New Zealand conditions.

Dr Roborgh then applied a technique which had been used to develop the navel orange which has no pips.

The drug Colchicine was applied to the hop shoot and this doubled the chromosomes in the hop from 20 to 40. The hop with the chromosome count of 40 is called a tetraploid and this was pollinated by a diploid (male). The result was a triploid which was seedless - that is, sterile.

The triploid hop can be surrounded by males whose pollen increases the size of the hop, which was lacking in those grown in the Collingwood experiment, but does not produce seed in the hops.

This seedless variety was developed in 1965 and there are now three types - 65-1-31, 65-3-82 and 65-3-95.

This year the triploid varieties were released to 25 growers. And next year it will be known if they can be grown commercially. Dr Roborgh is confident of success.