Zimbabwe Absurdity

Rob Jarvis, then the manager of ART farm, gave me some cobs of ornamental maize (sometimes known as Indian corn to the Americans) some years ago. I was fascinated by all the colours and saw photographic potential. I grew a small plot of them in our garden two years ago and got the photos I wanted. The cobs were harvested, seeds sorted by colour and stored in an airtight container. There must have been weevils on the seed because they quickly got stuck into the seed. A spell in the freezer sorted them out and left the seed none the worse for wear and another plot was planted this year. The seeds were planted in rows of the same colour for what is called a “look see” experiment i.e. to see if a properly designed experiment is warranted. I have not the space for an experiment of this magnitude but was curious to see what would transpire.

Initially I was hoping to run a comparative taste test of the immature cobs but I soon realized that this would not be feasible due to the lack of uniformity in their maturity. Sorting them by colour whilst on the plant was also a non-starter. So I settled for harvesting at near full maturity before the rats caused too much damage and seeing what colour patterns I could identify.

I am no geneticist and my semester’s course at university on fundamental genetics was a very long time ago so I will share my observations and musings. After all, Barbara McClintock, who spent a lifetime studying the genetics of maize kernel colours and won numerous awards culminating in a Nobel Prize, ascertained that maize genetics is vastly complicated.

Some nomenclature:
tassel – the male flower on top of the plant that sheds the pollen. Each pollen granule carries a single set of chromosomes that must combine with a single set of chromosomes carried by the ovule which will result in a kernel/seed developing.
silk – the structures in the ear (female) that will collect pollen from the tassel and cause a seed/kernel to develop. There is one per ovule.
cob/ear – the female flower that bears the seeds/kernels
gene – a gene is a section of DNA that contains a specific instruction for an organism. This instruction provides information about it will develop, function or grow.
recessive gene – a recessive gene requires 2 copies to be present in order to be expressed. If a recessive gene is inherited alongside a dominant gene, the recessive gene will be ‘masked’, but if it is inherited with another recessive copy, it will be expressed. e.g. A blue eyed person must have 2 blue genes present (one from each parent).
dominant gene – if a gene is dominant, there only has to be one copy present in the pair for it to be expressed e.g. if a brown eyed human passes on a brown eye gene to a child it will override any blue eye gene present and the child will have brown eyes.
monoecious – only one plant is necessary to set seed/fruit as in maize – a plant carries both male and female flowers. They can self-pollinate or cross-pollinate with another plant.
imperfect flowers – as in maize which has both male and female flowers (separate) that need to pollinate.
perfect flowers – have both male and female reproductive structures in one flower.

Bedtime reading – to understand the biology of maize and some fundamental genomics

Commercial maize plants are much more uniform in their yields for obvious reasons and inevitably bear two cobs. Sometimes there are three but the third is too small to be significant. In this trial most plants did not even produce two cobs but where they did there were interesting characteristics. Colours from any pair of cobs from a plant were very similar, even so far as distribution on the cob – see the pair of cobs in the bottom right row above that have mainly yellow and white seeds at their tips. This may even have extended to the number of seeds set (top left) but could just mean that the silks that weren’t pollinated due to mistiming with pollen shedding. Most cobs were not reasonably full i.e. had few seeds to the end of the cob. Commercially produced maize looks more like the cobs on the bottom right pair.

To me this suggests that somehow the colours of the cobs on a single plant can be linked. Having searched the internet this is suggested as being indicative of plants self-pollinating i.e. the cob is pollinated by the tassel on the same plant. So far as I have observed silks don’t emerge at the same time so self-pollination is unlikely to be the cause.

Interestingly, commercial maize is either yellow or white. In this part of the world white maize is favoured for human consumption and yellow for livestock. Yellow maize has higher carotenoid content which gives it the yellow colour and higher vitamin A precursor (beta carotene) than white and it causes yellower eggs and poultry skin. I think yellow has more flavour than the white which is often consumed here in the refined form as a staple carbohydrate. Corn on the cob is a popular snack in this part of the world and is sold by the roadside in the early summer. This often comes from illegal plantations in the areas close to streams in the suburbs and vacant plots.

Does this imply that plants grown from grey seed are more homogenous than others or that they are more likely to self-pollinate or that the grey gene is dominant over other colours? This was also observed in cobs sown from red seed – there were a large number of red kernel cobs which were often entirely shades of red (as in the top right pair in the top picture). To me this suggests that the red gene is dominant.

Other peole have milled the coloured maize and eaten it. While most commented that it was tasty, the thicker seed coat (pericarp) than commercial maize make it a niche crop and it will mostly remain what it is – ornamental.

I have yet to decide what to do with the wheelbarrow of cobs that were harvested. I don’t have the means to mill the kernels and try a few internet recipes. It was an interesting little experiment but that’s about it and they will likely be consigned to the compost heap. Or just maybe I’ll try sowing a single coloured seed, say red, and see what happens…