Plant & Animal Breeding Higher Biology Plant & Animal Breeding Mr G R Davidson

Genetic Selection Genetics can be used to improve plants and animals in order to increase productivity. Characteristics which breeders would like to see improved include those in the table below: Saturday, 10 November 2018 G R Davidson

Desirable Characteristic Genetic Selection Desirable Characteristic Organism Disease resistance Potato Frost resistance Strawberries Increase in grain yield Wheat Increase in milk yield Dairy cattle Increase in nutrition Soya bean Ability to thrive in certain environments Maize can be grown in cold, damp climates Saturday, 10 November 2018 G R Davidson

Genetic Selection Plant breeders have discovered that some dwarf varieties of cereal put a lot more energy into seed creation than actual growth. This increases the yield and improves food security. It also makes them easier to harvest. Saturday, 10 November 2018 G R Davidson

Genetic Selection Cultivars are plants which have been created or selected for desirable characteristics. They are maintained by cultivation. Food crops are almost all cultivars. Saturday, 10 November 2018 G R Davidson

Genetic Selection Breeders try to cross individuals with the most desirable characteristics, e.g. high grain yield, high meat yield, etc. The offspring will then be used as the parents of the next generation. It is hoped that the most desirable alleles of each parent will be passed on each time. Saturday, 10 November 2018 G R Davidson

Inbreeding Inbreeding involves the crossing of close relatives. The most intense form of this is found in self-pollinating plants such as peas and wheat. Saturday, 10 November 2018 G R Davidson

Inbreeding The result of this is that eventually the stock will be homozygous for the desired characteristics and will therefore produce plants with the desired trait over multiple generations. Saturday, 10 November 2018 G R Davidson

Inbreeding The disadvantage of inbreeding can be that recessive alleles can also become homozygous and inbreeding depression occurs. Inbreeding depression can result in a loss of vigour, reduced size, poor health, etc. Saturday, 10 November 2018 G R Davidson

Outbreeding Outbreeding is the crossing of 2 individuals which are unrelated. Cross-pollinating plants and animals are the natural out-breeders. Outbreeding keeps the alleles heterozygous and the main disadvantage of this is that the offspring are not guaranteed to show the desirable traits. Saturday, 10 November 2018 G R Davidson

Crossbreeding In order to prevent things like inbreeding depression, breeders will carry out crossbreeding. Crossbreeding involves the introduction of new alleles by introducing individuals with a different genotype, but one which will also be desirable. The F1 produced usually perform well and show hybrid vigour because they combine the best qualities of both parents. Saturday, 10 November 2018 G R Davidson

Test Crossing A test cross is used to identify the genotype of an individual to see if it is homo- or heterozygous. E.g. in cattle H =hornless and h=horns. How can we work out the genotype of a cow with no horns? We would carry out a test cross. Saturday, 10 November 2018 G R Davidson

Test crossing If the cow was crossed with a horned bull we would get one of the following: Hh x hh HH x hh All Hh Either Hh or hh All hornless 50% hornless, 50% horned If they are all hornless, we now know that the original cow was HH. If half are hornless and the other half horned, we now know that the original cow was Hh. Saturday, 10 November 2018 G R Davidson

Gene Technology Genetic transformation is the process of inserting a gene from one organism into another. It is normally carried out by a bacterial plasmid being used as a vector. The organism which has been transformed is then used in a breeding programme. Saturday, 10 November 2018 G R Davidson

Gene Technology These genetically transformed crops can be used to: Increase yield Increase drought tolerance Protect from insects, fungi, etc. Reduce the use of fertilisers Increase nutritional value Saturday, 10 November 2018 G R Davidson

Gene Technology Genomic sequencing is the process used to determine the DNA sequence of an organism. This allows genes to be identified which can then allow these organisms to be used in breeding programmes. This will hopefully introduce the new gene into a new cultivar. Saturday, 10 November 2018 G R Davidson

Field Trials Field trials are used to establish the best conditions under which certain plants will grow. They are experiments which are very carefully controlled. They take place in fields which are divided up into smaller areas called plots. Saturday, 10 November 2018 G R Davidson

Field Trials Field trials can be used to: Find out if different environmental conditions has an effect of the growth of plants. Find out which plants grow better under the same conditions. Find out how well genetically modified plants perform. Saturday, 10 November 2018 G R Davidson

Field Trials In any field trial there has to be a fair comparison between the plots or between the treatments. Replicates have to be carried out to improve the reliability of the results. The plots have to be scattered randomly to ensure that no other conditions can bias the experiments. Saturday, 10 November 2018 G R Davidson

Field Trial Plot A 10kg seed plus 5kg fertiliser Plot B Plot C 15kg fertiliser Plot D 20kg fertiliser Saturday, 10 November 2018 G R Davidson