CHAPTER 6
Participatory Rice Breeding,
Using Population Improvement:
A New Methodology
Adapted to the Needs
of Small Farmers
in Central America
and the Caribbean

Gilles Trouche

Gilles Trouche

CIRAD/CIAT Rice Project, CIAT, LM 172, Managua, Nicaragua.
E-mail: [email protected]

Abstract

Participatory plant breeding (PPB) is a new approach in genetic improvement. In contrast to conventional breeding, it aims to fully integrate farmers and other stakeholders of the production chain into the whole process of variety development. It also aims to decentralize, towards farm fields, the most important steps of selection and evaluation. PPB intends mainly to answer the needs of small farmers living in poor and marginal areas for whom conventional breeding cannot offer suitable varieties. Within the framework of a new research project, CIAT and CIRAD began, in April 2002, an upland rice PPB programme, using population improvement methods. Although currently implemented in Nicaragua and Honduras, plans are to extend the programme to other Central American and Caribbean countries. This chapter presents the strategies proposed for this work, emphasizing initial diagnosis and participatory varietal selection of available materials. The paper also describes stages of population improvement and extraction of improved lines to respond to the specific demands of each production zone. Finally, the expectations for the use of this methodology in the region are indicated.

Resumen

El fitomejoramiento participativo (FMP) es un nuevo enfoque del mejoramiento genético. En contraste con el mejoramiento convencional, busca integrar completamente a los productores y los otros grupos de interesados de la cadena de producción en todo el proceso de desarrollo de variedades. El también busca descentralizar hacia los campos de los agricultores los más importantes pasos de la selección y de la evaluación. Este enfoque también busca descentralizar, hacia los campos de los agricultores, los pasos más importantes de selección y evaluación. El FMP pretende principalmente responder a las necesidades de los pequeños campesinos de las zonas pobres y marginales a quienes el mejoramiento convencional no pudo ofrecer variedades. Dentro del marco de un nuevo proyecto de investigación entre el CIAT y el CIRAD, se propone desarrollar un programa de MP del arroz de secano para América Central y el Caribe con los métodos del mejoramiento poblacional. Este proyecto se inició en abril del 2002 en Nicaragua y Honduras. El objetivo de este capítulo es presentar las estrategias propuestas en ese trabajo enfatizando las etapas iniciales de diagnóstico y de selección participativa con materiales ya disponibles; y presentar las etapas de mejoramiento poblacional y de extracción de líneas mejoradas para responder a las demandas específicas de cada zona de producción. Al final se incluyen las expectativas en cuanto a la utilización de esta metodología en la región.

Introduction

Rice is a major ingredient in the diet of urban and rural populations in Central America (CA) and the Caribbean, where it is considered as a staple grain. Rice production in CA and the Caribbean (Cuba, Haiti and Dominican Republic) is almost 2.4 million tonnes from a total area of 630,000 ha (FAO, 2002). Although such production does not meet demand in these countries, it does constitute a strong component of food security. Small and medium-scale farmers play an important part in that production, especially upland rice growers.

Population improvement of rice through recurrent selection is a method of genetic improvement that produces results over the medium and long term. Through the use of a broad genetic base and a male-sterility gene that facilitates crossing, the method allows increasing the frequency of favourable alleles and, hence, of desired combinations. This method is justified where simultaneous selection is to be conducted for various traits with complex genetic determinism such as adaptation to a specific environment, resistance to diseases and insect pests, and grain yield and quality (Châtel and Guimarães, 1997).

Population improvement is also justified when the preservation of genetic resources is an objective per se, simultaneously with genetic gain for agronomic traits. An interesting application is to preserve and enhance the genetic diversity of landraces in a region of diversification of this crop, when such diversity is threatened by climatic, biological or socio-economic factors (Almekinders and Elings, 2001; Trouche et al., 2004).

Participatory crop improvement (PCI) is a new approach in genetic improvement, first developed to respond to the demands for improved varieties from small farmers situated in poor or marginal areas, for whom conventional breeding had generally failed. The approach aims to deepen the involvement of farmers and other actors (in the crop’s production chain) in the different stages of variety development (Ashby et al., 1996). Moreover, the method has a decentralized approach; it takes into account the specific environmental conditions of targeted sites such as climate, soils and farming practices to better control the genotype-by-environment interactions that are frequently very strong in traditional, low-intensity, production systems (Ceccarelli et al., 1996).

Participatory crop improvement usually has four objectives:

• Gains in productivity, including increases in quality and product value

• More effective breeding made through closer consideration of the demands and preferences of farmers and other stakeholders, and of environmental conditions

• Dynamic conservation of biodiversity

• Strengthening the capacities of farmer groups and organizations (Sperling et al., 2001).

Participatory crop improvement involves farmers in different stages of selection and evaluation of future varieties, and proposes several levels of involving farmers in decision making (Sperling et al., 2001). Generally speaking, PCI is differentiated into:

(1) participatory varietal selection (PVS), which consists of evaluating and selecting, with farmers, advanced lines and/or varieties

(2) participatory plant breeding (PPB). The latter involves farmers in the selection of segregating generations (Witcombe et al., 1996).

It is based on the principle of sufficient knowledge of farmers’ specific production needs and of the advantages and disadvantages of the local varieties they use.

When farmers are involved from the first segregating generation (F₂ or F₃) and when selection is to be carried out in their own fields, PPB should necessarily be conducted with relatively few plants. That is, the number of either crosses or plants from the F₂ generation should be smaller than that used in a conventional programme on an experiment station. Considering this limitation, some authors consider that PPB should involve a strategy that makes only a few crosses, rigorously selects parental varieties and uses a large number of plants from the F₂ generation (Witcombe and Virk 2001).

Another PPB strategy comprises population improvement methods associated with recurrent selection, using a narrow genetic base and well-selected specific germplasm. It can be applied to autogamous crops when several traits are being selected and the proportion of desired recombinations is expected to increase, thus limiting the risks of a strategy of few crosses (Witcombe and Virk, 2001).

The PCI project for upland rice in CA and the Caribbean, carried out by CIRAD and CIAT, began in April 2002 in Nicaragua and Honduras. It is based in Managua, Nicaragua. This chapter aims to present the strategies followed by this project. It emphasizes the stages of population improvement and extraction of improved lines, and indicates expectations regarding the methodology’s use throughout the region.

Breeding objectives

The objectives and priorities of genetic improvement should be defined for each region and cropping system, using the outputs from a preliminary characterization of the systems (i.e. diagnosis) conducted in sites chosen as reference. The project, however, can be initiated, using four groups of well-established general objectives, whose classification can change according to area and production goals. These are:

• Adaptation to environmental conditions
• Increased productivity
• Grain quality as required by the market and/or household consumption
• A high level of stable resistance to insect pests and diseases, particularly rice blast caused by Pyricularia grisea Sacc.

To start the project, adaptation to environmental conditions and crop management will be regarded as the most important objectives to ensure future adoption of new varieties. Increase in yield is always a priority for farmers. Moreover, grain characteristics must satisfy local requirements for household consumption and for sale of harvest surpluses. Finally, resistance to major insect pests and diseases is often a priority for varietal improvement, especially where small farmers cannot access, or have difficulties in accessing, credit to buy pesticides.

Diagnosing production problems and farmers’ demands

The project’s implementation began with a participatory diagnosis, carried out through informative meetings and workshops with groups of organized farmers, and conducted in collaboration with relevant local actors such as research institutions, nongovernmental organizations (NGOs) and farmers’ organizations. Further information was then obtained on cropping systems (e.g. environment, practices, varieties used and sources of seed) and socio-economic and institutional contexts. The tools used included semi-structured individual interviews, interviews with key informants and meetings with focus groups. Thus, the principal problems of production, and/or marketing and use were identified. Finally, the diagnosis allowed defining, together with the farmers, the objectives of varietal improvement (Weltzien et al., 1996).

As part of that diagnosis, in situ PVS trials with phenotypically diversified lines and varieties were also carried out. We used certain tools of participatory rural appraisal (PRA) such as discussions with focus groups and exercises of preference matrix ranking and scoring (Subedi et al., 2000). These enabled us to better understand how farmers appreciate a variety. For example, we could see the traits they considered as the most important, the criteria they used for selecting or discarding a variety, and their priorities and preferences when choosing a new variety. This step can also reveal new demands from the farmers with respect to new traits that they did not know their own varieties had. Moreover, this step may highlight the essential traits for local adaptation or grain quality of local varieties that would justify their incorporation into the diversity of future populations.

Finally, diagnosis will also identify expert and well-motivated farmers, with whom the future work of participatory breeding of new varieties can be developed.

Sources of genetic materials for participatory breeding

To start this research project, different types of genetic materials of rice, developed from collaborative efforts between CIRAD, CIAT and Embrapa Arroz e Feijão, were used. These were:

Composite populations

• Populations with broad genetic bases- PCT-4, PCT-11 and PCT-13- developed by the CIRAD/CIAT Rice Project in Cali, Colombia, for the acid soils of the savannah ecosystem; and population CNA-7, produced for the cerrados by Embrapa Arroz e Feijão, Goiânia, Brazil

• Populations with narrow genetic bases from the CIRAD/CIAT Rice Project such as PCT-17 for high-altitude hillsides with problems of cold; and PCT-18 for savannahs and low-altitude hillsides.

Advanced lines and varieties

• Advanced lines derived from the improved PCT-4 population and inter-specific crosses, and developed for unfavourable upland conditions. The lines possess early and medium cycles, high yield potential and adequate grain quality

• Varieties with adaptability to diverse upland conditions and stable resistance to blast such as CIRAD 361, CIRAD 364, CIRAD 366, CIRAD 367 and CIRAD 409.

Population improvement and line development

Population development

To start this work in the project’s targeted areas, we chose several populations with broad or narrow genetic bases still available in the CIRAD/CIAT Rice Project. However, the possibility of incorporating well-adapted local varieties into these populations was considered in terms of contributing, for example, to adaptation to specific environmental conditions, stable resistance to diseases, or a specific grain quality for household consumption. These choices were based on the results of the diagnosis and the preliminary in situ PVS trials of diverse lines and varieties. The incorporation of local varieties as contributors of local adaptation genes into the exotic populations may be carried out in two ways, according to the type of population and the time needed to develop new varieties:

• Enhancement of populations with broad genetic bases for population improvement and varietal development over the medium and long term

• Development of new populations with narrow genetic bases focused more on specific objectives for more rapid improvement and extraction of lines.

In fact, for populations with broad genetic bases, population improvement and amplification of the genetic base should coexist permanently.

It should be emphasized that, when seeking a specific adaptation or insect pest resistance, the direct incorporation of new germplasm, whether landrace or exotic, into an existing improved population could induce a setback in genetic progress in productivity, plant height, earliness or grain quality, thus moving away from the objectives as defined by Chaves (1997). Hence, new materials should first be incorporated through intermediate populations and then, after several crosses between these materials and the improved population, introduced into the principal population (Gallais, 1990). Morais et al., (2000) presented the alternative of crossing each new parent with the population and evaluating the individual crosses, before mixing the seeds of all individual combinations. Châtel et al., (1997) describe an example this strategy being used to develop PCT-4\0\0\0.

Figure 1. Outline of a strategy for rice population improvement and line extraction.

Population improvement

Starting with different existing populations, the purpose is to improve them through recurrent selection for adaptation to local conditions, yield, grain quality and other traits identified during the participatory diagnosis and PVS.

As Gallais notes (1990), because of the succession of several short selection cycles, followed by crosses, recurrent selection should result in genetic gain for the traits under selection. Simultaneously, it should also permit the conservation of important genetic diversity. The strategy proposed for this work is described in Figure 1.

The farmers involved in the participatory population improvement schemes may intervene from the first phases of selection (S₀ plants). For this, however, the farmer-breeders need training in several topics like reproduction biology, genetics and plant improvement. They should be taught, for example, how to perform crosses, what to expect from these and the levels of heritability for the different traits under selection. With this knowledge, the farmers can become involved in the in situ selection of fertile S₀ plants from the base population, focusing on the most heritable traits such as earliness, plant morphology and grain size.

Table 1. Schemes that include the participation of farmers and researchers at different stages of population improvement for rice.

For the following generation, the S_0:1 progeny can be evaluated ex situ during the dry or off-season and/or the next rainy season for resistance to major diseases, particularly blast, using a methodology already applied in Colombia by CIAT (Vales et al., 2002). During the second year, early trials for yield evaluation can be carried out during the rainy season under conditions of inter-plant competition on farm plots, using S_0:2 lines proceeding from families previously evaluated as the most resistant. Farmers can participate in evaluating these families for yield, diverse agronomic traits and grain quality, and, jointly with the breeders, they can carry out the final selection from the best-performing lines (Table 1).

This does not mean that, in the same trials, plant breeders cannot also do their own selections for more general or diversified objectives. In each cycle, the best-performing families (using remnant seed from plants of the S₀ and S_0:1 generations), proceeding from the triple selection (adaptation to production constraints, yield and resistances) are recombined to give rise to a new and improved population (Figure 1).

Extracting lines from populations

Because the main interest of the farmers who participate in this process is to obtain new varieties, not to improve breeders’ populations, the strategy to use is to evaluate the best S_0:1 families selected by farmers for varietal development. These families will be advanced, using the pedigree method, over 3 years, and then evaluated for yield carried out on farms at various sites of the targeted area during the rainy season.

The verification of resistance to blast and other diseases and insect pests will be conducted in greenhouses or irrigation plots during the off-season. This means that varietal development programmes will be achieving results in 3 or 4 years. Similarly to what is proposed for the population improvement strategy, farmers and plant breeders will jointly conduct the final selection of lines for the following stage in each generation.

Participatory selection of lines

As mentioned above, this activity first complements the participatory diagnosis of production constraints and farmers’ variety needs. It should be done before population improvement, and should start with a workshop to explain the objectives and methods of the research, and to plan activities. Another workshop is then organized during the cropping cycle to define, with the farmers, the main criteria for evaluating and selecting varieties and, on the same day, carry out the first evaluation.

Three dates are appropriate for these activities:

• The end of the vegetative period or beginning of the reproductive phase (facultative)
• At grain maturity
• After harvest, for culinary trials, if a production objective is for household consumption.

To facilitate the process, evaluation is carried out with small groups of 5 to 10 farmers, who have been grouped according to criteria such as social level, gender or geographic location. At crop maturity and after harvest, each group is asked to select from 5 to 10 lines or varieties that they most preferred (bringing together the greatest number of desired traits). These are evaluated again in the following year either at the same site on larger plots with more replications, or if the area has agroecological stratification, at several representative sites. Good PVS experiments found in the literature with good descriptions of the methodology used include Weltzien et al., (1996) with millet in Rajasthan, and Sthapit et al., (1996) with rice in Nepal.

In our work so far, we expect to identify materials able to respond to farmers’ immediate needs. The project’s partners will help evaluate and validate these materials on a larger scale, and will also provide support with seed production. This phase is also expected to highlight the limitations or defects of those materials, thus giving needed orientation for developing the framework of participatory breeding, using population improvement.

Participatory selection will also be applied to the advanced lines derived from participatory breeding schemes to identify the farmers’ most-preferred lines, so that these may be validated and released in the targeted areas.

Prospects for the project in the region

The project has started activities in Nicaragua, where upland rice production is important and encompasses diverse production conditions involving small and medium-scale farmers. Since then, the project has collaborated with other CA countries such as Honduras, Costa Rica, and Cuba. This last country has already experimented with population improvement (Pérez-Polanco et al., 2000; Chapter 11, this volume) and has started PCI schemes on ‘popular’ rice. These collaborative activities aim to diffuse the idea of participatory population improvement as a tool for PCI and to exchange experiences.

Expected results

The research focus of participatory and decentralized crop improvement should permit the development of a diversified range of new populations and improved lines. Such diversity will, hopefully, respond to the diversity of production constraints in each targeted area, and the area’s respective objectives (Figure 2).

Through closer collaboration between plant breeders and farmers, the project will also facilitate exchange of knowledge and experiences that will be useful as much for conventional improvement as for PCI. The project should also help strengthen the capacity and group dynamics of farmers for agronomic experimentation in general, and for the evaluation and selection of plants and varieties in particular. A major result of this project would be improved rice populations that satisfy farmer group demands at targeted sites, as they will be involved in all stages, from start to finish. The result of such improvement would be an increase in the possibilities of developing enhanced varieties for the small farmers of CA and the Caribbean.

Figure 2. General scheme of participatory and decentralized selection.

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