A word about the science


A word about the science

This may seem a little obvious but it doesn’t hurt to revisit our basic precepts from time to time and it may be helpful for our new members.

The primary objective of The Guild of Ocabreeders is to discover a genetic variation of Oxalis tuberosa that permits the plants to tuberise in daylight longer than 12 hours – that is the sort of day lengths found in Northern European summers. Oca in its native range doesn’t have such a wide sweep of day lengths. Varieties in cultivation there have been selected for other qualities so few of them do well in the European environment. Without the ability to form tubers before the killing frosts oca will never be successful in Europe but other attributes are also necessary, good yields, a pleasant taste and attractiveness are all necessary for the crop to be widely appreciated and adopted.

There are various established and novel methods for plant breeding. The simplest is to identify plants that already have some of the characteristics needed and by selective breeding enhance them to the required degree.

A lot of work is done to move characteristics from one organism to another by means of direct genetic manipulations and editing but again, that requires finding the attributes needed and which genes are responsible for them before the transfer can be made.

seedlings2016

Tubers from 2016 seedlings waiting to be assigned numbers.

And what do you do if the desirable qualities are not immediately apparent? We have chosen the deceptively simple method of recurrent mass selection; starting from the widest possible diversity of parent materials seeds are created, grown out, assessed and discarded or retained depending on their fitness for the project. It’s a sort of accelerated mediated evolutionary process and although the odds are slim the more seedlings evaluated the better the chance of finding that genetic anomaly that will be key to bringing success with early tuberisation.

The best plants are chosen by observations of actual cropping so when we grow out the seedlings and trial tubers they must be grown with due diligence to their nurture. Ground should be well cleared, a little feeding should be provided, pests and weeds prevented and regular attention to the health of the plants given. In short, the same care as would be given to any garden vegetable crop. We want to give the plants the best opportunity to demonstrate how they develop in good conditions, it might be their only chance of fame. At this stage we are not testing for anything more than early tubers and a pleasing form.

The general assumption is made that a plant that has produced a heavy crop by the time it is killed by frost had started producing its tubers earlier than plants killed at the same time with few or small tubers. Therefore, plants which don’t crop well are discarded from the programme. In order to compensate for possible confounders like locally bad weather or poor cultivation each variety is grown out a number of times in different locations by different people. Anything that is consistently bad is definitely a dud, anything that does well under some conditions may be worth further consideration. It’s a very dramatic and powerful filter and only the strongest survive.

As well as this selection process we also take certain observations of plant characteristics and habits. The total weight of each crop is recorded but it’s also of use to know what sort of crop the plants produce. 1kg of 1cm marbles is much less useful in the kitchen than a 750g handful of good sized tubers, size matters to the gardener and the cook, so these attributes are recorded.

We record the basic physical attributes of the tubers and the plants they grow from. Each seedling is unique and so the characteristics form an identity that will help track them over time. Analysis may reveal that there are genetic links to certain forms that can indicate good prospects towards our aim or may just show that there are some very pretty plants out there. Either way the measurements document the individual traits for each of our seedlings.

Flower forms in Oxalis are complex and the result of evolutionary processes designed to prevent inbreeding. There are three forms and to date no information about what determines which flower type a seedling will have, all we know is that if we want to use natural methods of pollination to produce our seeds we need to keep our flower diversity to a maximum. Looking at the flower types will help us ensure we’re not breeding ourselves out of the insect cross-fertilisation market.

The taste test is unlikely to reveal the chocolate Turkish delight flavoured oca that we’re all secretly hoping for and indeed, is such a subjective exercise that opinions on sourness or blandness or flavour are not too significant but we do need to test for nasty. We don’t want to introduce or allow unpleasant eating characteristics into the gene pool because they could prove to be too difficult to breed out at a later date.

In addition to details of the plants we also record information on where the plants are growing, some general environmental conditions and certain details of the weather, oca is susceptible to drought as well as hard frost so cropping may be affected as strongly by the weather as the actual genetic make-up of the seedling being tested.

This season it’s intended to start some more structured experiments, still with the same aim of discovering our day-length neutral form and the best practice for oca cultivation. The protocols for the work will be extremely prescriptive because unless all the experimenters are working from the same basis the results will be invalid, unsupported anecdote at best. Plant breeding and research is an enormous subject, to get repeatable and usable results needs dedication and focus. The Guild of Ocabreeders is an alliance pursuing that goal.

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