1 CfE Higher Biology 3.2(a,b,c) Plant and animal breeding

2 Key areas: 3.2 a) Plant and animal breeding by manipulation of heredity: for improved plant crops, improved animal stock, to support sustainable food production. Breeders develop improved crops and animals with higher food yields, higher nutritional values, pest and disease resistance and ability to thrive in particular environmental conditions. b) Plant field trials are carried out in a range of environments to compare the performance of different cultivars or treatments and to evaluate GM crops. In designing field trials account has to be taken of the selection of treatments, the number of replicates and the randomisation of treatments. (c) Selecting and breeding. Animals and cross- pollinating plants are naturally outbreeding.

3 Quick revision An increasing human population requires an increased food yield. GM crops may be an alternative to mitigate the effects of intensive farming on the environment. Alleles are different forms of a gene. Homozygous means having the same allele for a particular gene. Heterozygous means having different alleles for a particular gene.

4 Some examples of desirable characteristics PlantAnimal 1.Higher yield 2.Higher nutritional values 3.Pest resistance 4.Disease resistance 5.Wider environmental range 6.Shorter/longer time of flowering/fruiting Higher yield of products produced by animal Body composition (ratio of meat to fat) Disease resistance Clutch size (number produced) Environmental tolerance e.g. to cold Size of animal

5 Breeding programmes Developing new varieties of crops and livestock breeds could be one way of meeting the challenge of food security. These programmes encourage 'desirable features' to be developed and new and improved organisms to provide sustainable food sources. Inbreeding involves selecting individuals to breed who are close relatives. It aims to ensure homozygous genes that will continue to breed for many generations to come. Natural selection is important to ensure that the recessive unwanted genes are eliminated.

6 Cauliflower – sterility of flowers Broccoli – suppression of flower development Cabbage – suppression of internode development Kale – enlargement of leaves Kohirabi – enhancement of lateral meristems

7 Livestock example Carry out your own research to show an example of livestock breeding. Set your findings out in the same way as the wild cabbage example on the previous slide.

8 Field trials The aim of plant breeding is to produce 'cultivars'. These are plots of different varieties of crops that will have a good yield in the growth conditions typical for that plant. Final crop growth is a result of both genetic and environmental factors ‒ the field trials make sure a crop that grows well in a lab will still do as well in the 'outside‘. Field trials can also be used to evaluate GM crops and the use of fertilisers/growth treatments on crop growth.

9 Field trials ‒ definitions Write down a definition and an example of each of the words below. 1. Valid 2. Accurate 3. Reliable

10 Field trials ‒ definitions Valid Correct measurements have been taken to allow a conclusion to be drawn. Water fluctuation accounted for; range of genders. Does the trial give results that allow an appropriate conclusion to be drawn? Accurate The measurements taken are meaningful- rounded up or down numbers when counting organisms is more accurate that working to 1 or 2 decimal places.... There are no ‘half’ or ‘0.2’s’ of an organisms for example! Is the measurement tool appropriate? How should the results look as an end producvt in a table/graph? Does the measurement you are recording allow this? Reliable How robust and trustworthy the result is. If your results were compared to a similar study, would they match well? Have you carried out enough replicas to make sure there are no anomalies? Is the sample size appropriate?

11 Plant field trials care used to compare the performance of different cultivars or GM crops. Explain how each of the following are involved in the design of the trial 1. Selection of treatments 2. Number of replicates 3. Randomisation of treatments

12 1. Selection of treatments: These must be carried out to allow a fair comparison. Each field plot for example, should be sprayed with the same concentration of fertiliser and same volume of fertiliser if DIFFERENT fertilisers were being compared. 2. Number of replicates: If only one treatment of fertiliser was being carried out on plots of crops, then anomalies could occur and possible experimental errors. The reliability of the results would be questioned. Replicas are repeat experiments that allow meaningful statistical analysis and validity. 3. Randomisation of treatments: To ensure bias or observational errors don’t occur, patterns of replica treatments are designed.

13 Selecting and breeding Outbreeding: Fusing two gametes from unrelated members of the same species. Cross pollinating plants are a good example. Inbreeding: Fusing two gametes from members of the same species/ related family members. Some plants are naturally self-fertile which allows them to self pollinate.

14 Test crosses Sometimes animals or plants need to be identified that carry unwanted recessive alleles. The unknown genotype will be crossed with a homozygous recessive genotype and the phenotype of the offspring will be examined.

15 Inbreeding depression

16 Questions. F1 hybrids are often used in plant breeding. Describe what is meant by hybrid vigour. Why is the F2 generation not as useful as the F1?

17 F1 hybrids are often used in plant breeding. Describe what is meant by hybrid vigour. The first generation has characteristics of both parents and often this means they are more ‘vigorous’ and have a higher yield. Why is the F2 generation not as useful as the F1? The F1 will be a uniform group of heterozygotes, breeding to the F2 will produce a wide genetic variation, so less controlled production.