)NS: Answer all questions 1. Discuss the history of plant breeding under the following subheadngs (6 marks) a. Pre-mendelian era b. Post-Mendelian Era 2. With the help of a schematic illustration , describe the "Mass Selection' Method of breeding self pollinated plants (10 marks) 3. While giving relevant examples distinguish between the following terms (6 marks) a. Clesitogamy and Chasmogamy b. Protogzymy and Protandry . Define 'Apomixis seeds' and the various categories (5 marks). Enumerate the various sources of male sterile cytoplasm (3 marks)

1. Discuss the history of plant breeding under the following subheadings:<br /><br />a. Pre-Mendelian era:<br />- In the pre-Mendelian era, plant breeding practices were primarily based on empirical observations and trial-and-error methods.<br />- Early plant breeders selected desirable traits in plants through natural selection, without any understanding of the underlying genetic principles.<br />- Techniques such as seed saving, selection of disease-resistant varieties, and hybridization were used to improve crop yields and quality.<br /><br />b. Post-Mendelian Era:<br />- The discovery of Mendel's laws of inheritance in the 19th century revolutionized plant breeding practices.<br />- Breeders began to understand the genetic basis of inheritance and started using controlled pollination and hybridization techniques to achieve specific desired traits.<br />- The development of molecular biology and biotechnology in the 20th century further advanced plant breeding methods, leading to the use of genetic markers, molecular markers, and genetic engineering techniques.<br /><br />2. With the help of a schematic illustration, describe the "Mass Selection" Method of breeding self-pollinated plants (10 marks):<br /><br />- Mass selection is a breeding method used for self-pollinated plants, where a large population of plants is grown, and the best-performing individuals are selected for further propagation.<br />- The process involves the following steps:<br /> 1. A large number of plants are grown in a field or plot.<br /> 2. The plants are allowed to self-pollinate.<br /> 3. The offspring are evaluated for the desired traits, such as yield, quality, and disease resistance.<br /> 4. The best-performing plants, typically the top 10-20%, are selected as parents for the next generation.<br /> 5. This process is repeated over several generations to improve the population for the desired traits.<br />- The schematic illustration would show a large field with self-pollinated plants, with the best-performing plants marked for selection and further propagation.<br /><br />3. While giving relevant examples, distinguish between the following terms:<br /><br />a. Cleistogamy and Chasmogamy:<br />- Cleistogamy: In cleistogamous flowers, the anthers and stigmas are enclosed within the same flower, preventing self-pollination. This ensures that the flower is only fertilized by pollen from another flower, promoting genetic diversity.<br />- Chasmogamy: In chasmogamous flowers, the anthers and stigmas are exposed and can potentially self-pollinate. This allows for both self-pollination and cross-pollination.<br /><br />b. Protogyny and Protandry:<br />- Protogyny: In protogynous flowers, the stigma becomes receptive before the anther dehisces (releases pollen). This ensures that the flower is fertilized by pollen from another flower, promoting genetic diversity.<br />- Protandry: In protandrous flowers, the anther dehisces before the stigma becomes receptive. This allows the flower to self-pollinate, as the pollen is released before the stigma becomes receptive.<br /><br />4. Define 'Apomixis seeds' and the various categories (5 marks):<br /><br />- Apomixis is a form of asexual reproduction in plants, where seeds are produced without fertilization. The offspring are genetically identical to the parent plant.<br />- Apomixis seeds can be categorized into two main types:<br /> 1. Apomixis: This is the most common type, where seeds are produced without fertilization, resulting in genetically identical offspring.<br /> 2. Apogamy: In this type, seeds are produced without the involvement of gametes, and the offspring are genetically identical to the parent plant.<br /><br />5. Enumerate the various sources of male sterile cytoplasm (3 marks):<br /><br />- Male sterile cytoplasm can be obtained from various sources, including:<br /> 1. Mutations: Inducing mutations in the genes responsible for male fertility can result in male sterility.<br /> 2. Genetic engineering: Modifying the genes involved in male fertility can lead to male sterility.<br /> 3. Radiation: Exposing plants to radiation can induce mutations that result in male sterility.