Sunday, 27 June 2021

How to breed new barley varieties

Finally, years after learning how new hop varieties are bred I learnt about barley breeding and how the seeds breed true. I don't think I've been as happy to hear anything since I learnt the invisible etchings of Salvador Dali were safe. 

With hops each new seed is a unique individual and so in effect a new variety, established hop varieties essentially being clones made by taking cuttings from a single female plant. Barley though is clearly grown from seed so how does that work? Read on and see:

Various methods can be used for developing new varieties of plants:

  • Cross breeding
  • Hybridisation
  • Mutation
  • Genetic Modification

We were told that breeding is easy, but the punch line is that making new varieties might be easy but making new varieties better than the old ones is a lot more difficult. 

The registration system is important because unless your variety can get official approval (Agiculture and Horticulture Development Board and Malting Barley Committee) it is unlikely to go far. 

Plants are selected for a number of criteria, but particularly harvest yield. 

Non-GN (glycosidic nitrile) is important for malts used in distilling because of concerns it can produced the carcinogenic ethyl carbamate during distillation.

Barley plants have male and female parts. The first stage of making a cross is to cut the male parts off a plant to prevent it self pollinating. 

Then pollen is taken from the other plant involved in the cross and used to fertilise the first one. 

As Confucius says, in breeding filial generations of offspring are numbered F1, F2, F3 for first, second and third generations, etc. 

Each cross will make 500-1000 sibling seeds, with the same parents but different combinations of genes, 

These will be crossed again, giving move diverse gene combinations but also fixing diversity by inbreeding to get homozygous plants which will breed true due to having the same alleles for each gene.

The best plants will be chose to proceed with for further breding trials.

Seeds will be sent to New Zealand to speed up the process, rather than waiting another year to plant. 

By this stage only plants breeding true will be moved forward in the trials.

One quick test if the plant will be a good variety is if it makes 25g of seeds. Laboratory and genetic tests will also be used to look for desired traits in the plant. 

Larger scale trails will be carried out:

100kg of seed will be obtained from these. From these further tests, including micromalting will be carried out. 

The breeding and selection of new barley varieties is in many ways similar to how new hop varieties are made, except for the self pollinated inbreeding to get homozygous plants that will breed true from seed. Tissue culture can also be used instead of self pollination as haploid pollen can be used to make homozygous diploid plants. 

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