Characterization, Conservation and Improvement of Common Bean Germplasm : USDA ARS

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Characterization, Conservation and Improvement of Common Bean Germplasm

Objectives

Objective 1: Acquisition, characterization and conversion of common bean genetic resources.
Objective 2: Genetic improvement for abiotic and biotic stress tolerance.
- Subobjective 2A: Genetic improvement of heat tolerance in beans and the investigation of the response to high temperature trough candidate gene analyis, genetic studies and marker development.
- Subobjective 2B: Development of bean germplasm with enhanced resistance to common bacterial blight.

Introduction

At a time when more of the world's population is relying on beans to satisfy its basic nutritional needs (protein, fiber, vitamins, minerals, and calories), per capita bean consumption has decreased in some countries due to a lack of supply. Under-developed countries face an increase likelihood of malnutrition as bean consumption decreases. In contrast, per capita consumption in the United States has increased due to a desire to improve the quality of diet and to satisfy the increasing popularity for ethnic foods. Although the demand for beans is high, yield per acre in the United States has plateaued. Increased yields can be accomplished by increasing the genetic diversity of the current narrow US germplasm base and by the incorporation of genetic resistance to common biotic (root rots, common bacterial blight, bean golden mosaic virus) and abiotic (high heat and aluminum toxicity) stresses encountered in many bean production areas.

SCREENING FOR TOLERANCE TO COMMON BACTERIAL BLIGHT

Above: Highly susceptible reaction of bean leaves two weeks following their inoculation with common bacterial blight. Bellow: susceptible and resistant reactions of bean leaves after two weeks following inoculation with common bacterial blight.

Genetic diversity outside of the US germplasm base likely contains genes for yield and resistance that are not in the current narrow gene pool. This project is a component of National Program 301, Plant, Microbial, and Insect Genetic Resources, Genomics and Genetic Improvement.

Materials and Methods

Survey, acquire, and increase common bean germplasm; evaluate for multiple disease and insect resistance; enhance superior germplasm through breeding and molecular genetic techniques; identify and select superior lines, field test, develop and release germplasm lines or cultivars.

Research Geneticist Tim Porch is in charge of this project.

Differentially limed plots at Corozal, Puerto Rico are used to screen bean germplasm for acid soil tolerance.

Accomplishments

The project has a long history of releasing disease-resistant germplasm and in publishing new research findings. Since 1996, the project has participated in the development and release of approximately 35 new germplasms.

These releases have featured resistance to common bacterial blight, white mold, bean common mosaic virus, bean common mosaic necrosis virus, ashy stem blight, rust, and anthracnose. There have been high-protein releases, releases adapted to Caribbean growing conditions, releases from crosses with other species, and releases of improved germplasm of other species. The project has impacted the bean industry by providing novel sources of resistance to important bean diseases and by developing the use of molecular markers for bean improvement. The current project is continuing to impact the US bean industry by introducing new "yield" and "resistance" genes into better and more usable germplasms. US breeders should be able to readily use this material in their programs to improve beans for their specific geographical areas. Some releases from this project are immediately usable by farmers.

U.S. DEPARTMENT OF AGRICULTURE

Tropical Crops and Germplasm Research: Mayaguez, PR