Introduction

A main goal of plant breeders is to develop lines improved for particular traits, for example larger fruits, quick maturing, etc. Genetic diversity is the basis for all crop improvement; therefore it is crucial to be able to assess and understand the diversity available for a crop before developing a breeding strategy. Using molecular analysis techniques it has been demonstrated that not all genotypes are reflected in a phenotype (important alleles may be masked by other alleles) and therefore molecular level analysis is a better tool to assess and measure genetic diversity. The diversity available in genebanks as well as wild relatives can be an important resource in increasing crop diversity.

This eLesson is written for plant breeders and professionals working with plant breeders.  Participants who have little to no knowledge of genetic diversity issues within a plant breeding program will find this eLesson module useful for understanding the role genetic diversity plays in crop improvement. This module is not intended to be comprehensive for genetic diversity analyses but rather to help those in the field of plant breeding understand why genetic diversity is crucial, how it is assessed and evaluated, and how it can be useful to a plant breeding program.

This module is organized into three parts:

Part 1: Genetic Diversity

• Importance of diversity in plant breeding
• Importance of diversity for molecular marker work
• Polymorphism

Part 2: Selecting for desired characteristics and effects on diversity

• Crop domestication and consequences
• Artificial selection and germplasm banks
• Phenotypes and genotypes
• Phenotype Selection

Part 3: Preserving and Improving Genetic Diversity

• Assessing genetic diversity
• Measuring genetic diversity
• Selecting parents to create desired traits

This module ends with a listing of selected software resources for genetic diversity assessment, a summary of the eLesson, introduction to the next module, and a quiz which randomly pulls questions from a quiz bank.  If you correctly answer 80% of the quiz, you will earn an electronic badge of completion which will be emailed to you directly.  You may retake the quiz as many times as you wish.  On average, it will take participants approximately 20-45 mins to complete this eLesson, including the quiz.

Goals and Objectives

The overall goals of this lesson/module are that you will have an increased understanding of the following:

• The importance of genetic diversity and the consequences of domestication
• Artificial (human) selection and the role of genebanks and wild relatives
• Assessing and measuring genetic diversity derived from selected parents

After completing this lesson/module, you will be able to:

Part 1: Genetic Diversity

1.  Explain why diversity is important in crop improvement, both for plant breeding in general and marker assisted breeding in particular.
2. Define what is meant by polymorphism.

Part 2: Selecting for desired characteristics and effects on diversity

1. Define domestication
2. Explain the consequences of the loss of genetic diversity
3. Give examples of traits selected by humans

Part 3: Measuring and Improving Genetic Diversity

1. Describe how genetic diversity can be measured
2. Explain what is meant by a germplasm bank and what might be stored here
3. Explain how a plant may contain alleles for traits not directly observed
4. Explain how the results of a genetic diversity study, such as a dendogram, can help in selecting crossing parents