A hybrid rice field. R. Toledo, IRRI.

A hybrid rice field. R. Toledo, IRRI.

Plant breeding is the process of selecting plants with the most desirable qualities to produce offspring that inherit these desired traits.  It aims to develop improved crop cultivars – crops selected for desirable characteristics that can be reproduced – to satisfy a variety of needs and overcome a multitude of challenges. Different cultivars are needed for different growing environments, such as rain-fed versus irrigated farming or upland versus paddy rice production. Insect and disease resistant cultivars are often highly desirable, if not essential, especially where pesticides are ineffective or restricted. Breeders also seek to produce crop varieties that appeal to consumer taste, satisfy cooking preferences, adhere to food safety regulations, enhance nutritional quality or behave best when used for industrial applications.

The application of genetics in crop improvement has yielded many successes leading to unprecedented growth in agricultural productivity, spurred by government commitments to agricultural research and development and supporting sectors. The Green Revolution was the spread of short-strawed, fertiliser-responsive varieties of wheat and rice that led to ’quantum leaps’ in food supplies in many Asian countries. Rice yields grew by 32% and wheat by 51%. Without these advances, it is largely recognised that there would be enormous food deficits in the world today.[1]  Successes in breeding new varieties of staple crops in sub-Saharan Africa were smaller in magnitude but no less important in addressing food insecurity in the region. In East and Southern Africa, improved varieties led to growth in both maize production and yields primarily for small-scale, resource-poor farmers.

Improved wheat variety being grown for seed in farmer's field. Credit, X. Fonseca, CIMMYT.

Improved wheat variety being grown for seed in farmer’s field. Credit, X. Fonseca, CIMMYT.

Despite these successes, the performance of local varieties of maize, cassava, millet, and other African food staples lags far behind the rest of the world. Harvests per hectare for major crops like maize can be as much as 80% below their potential.[2] Poorly functioning and developed seed systems across Africa are a major reason for this yield gap. Improving food security will therefore require responsive plant breeding programmes and effective seed delivery systems that develop high quality and well-adapted improved seed varieties that meet the needs and preferences of smallholder farmers.[3]

In sub-Saharan Africa, a rapidly growing population is increasing food demand whilst resources such as good quality land, water and soil are becoming scarcer. As fertilisers such as phosphorous and nitrogen become increasingly scarce and expensive, developing plant varieties that can withstand climate variability, lower rainfalls, warmer temperatures, fewer inputs and pest and disease outbreaks is increasingly vital. Plants that use resources more efficiently or require fewer resources altogether improve the sustainability of agricultural as well as urban and forest ecosystems.  New crop cultivars must also be bred that improve both soil and human health.

Breeding provitamin A-enriched orange maize, Zambia. Credit, CIMMYT.

Breeding provitamin A-enriched orange maize, Zambia. Credit, CIMMYT.

Conventional plant breeding can occur through a variety of approaches and for a number of objectives, including participatory plant breeding, improving seeds through hybridisation or enhancing their nutritional properties with biofortification.  Rather than employing a ‘top-down’ model whereby seed varieties are improved by professional breeders and then made available to farmers, participatory plant breeding involves farmers in the various stages and decision-making milestones during the breeding process. Hybridisation, the deliberate cross of two genetically different plants from two separate plant populations, tends to create varieties that mature earlier, produce higher yields and greater uniformity.  Micronutrient deficiencies, a health problem affecting more than 2 billion people worldwide, can be addressed in part by breeding more nutritive varieties of crops through the process of biofortification.

     
References
  1. [1] Evenson, R & Gollin, D 2003, Crop variety improvement and its effect on productivity: the impact of international agricultural research. Cabi publishing, Wallingford.
  2. [2] Alliance for a Green Revolution in Africa (AGRA) 2014, Planting the Seeds of a Green Revolution in Africa, Available from <http://agra-alliance.org/silo/files/pass-report-launched-at-wef.pdf> [1 July 2015].
  3. [3] Alliance for a Green Revolution in Africa (AGRA) 2014, Africa Agriculture Status Report: Climate Change and Smallholder Agriculture in Sub-Saharan Africa. AGRA, Nairobi.