1.1 Requirements of plant breeders
The aim of plant breeding is to develop genetically superior cultivars that are adapted to specific environmental conditions and suitable for economic production in a commercial cropping system. These new, and more productive cultivars, are increasingly necessary to fulfil humankind's escalating needs for food, fibre and fuels.
The basic concept of varietal development is rather simple and involves three distinct operations:
produce or identify genetically diverse germplasm from which segregating breeding populations are developed;
carry out selection procedures on phenotypes or genotypes from within this germplasm to identify superior genotypes with specific improved characteristics;
stabilize and multiply these superior genotypes and release cultivars for commercial production.
The general philosophy underlying any breeding scheme is to maximize the probability of creating, and identifying, superior genotypes which will make successful new cultivars; in other words, genotypes that will contain all the desirable characteristics/traits necessary for use in a given production system, or at least offer a beneficial trade-off between key advantageous characteristics compared with undesirable ones.
Plant breeders can be categorized into two types. One group of plant breeders is employed within private companies, while the other group works in the public sector (e.g. government-funded research institutes or universities). Private sector and public sector breeders often have different approaches to the breeding process. Many of the differences that exist between public and private breeding programmes are related to the time available for variety release, types of cultivar developed, and priorities for traits in the selection process.
Plant breeders within the public sector are likely to have a number of responsibilities related to academic activities or extension services, in addition to those solely directed towards producing new varieties. Public sector breeders also play an additional, often unappreciated yet critical role: the attraction, training and development of a younger generation of men and women interested in plant breeding. As plant breeding is a combination of science and art, the personal component of training plant breeders at the graduate level is generally recognized as more relevant and significant than in most other areas of science.
Private sector plant breeders tend to have a more clearly defined goal: developing new cultivars and doing it as quickly as possible. In addition, many private breeding organizations are, or are associated with, biotechnology and/or agrochemical companies. As a result, varietal development may be designed to produce cultivars suitable for integration within a specific production system. In many countries, including the US, the ratio of private to public breeders has increased over time, particularly in those highest acreage crops such as maize, soybeans and canola, to mention just a few, as well as in crops with a high profit, such as tomato, pepper and lettuce, where private companies can gain greatest financial returns from seed or chemical sales.
Despite the apparently simple description of the breeding process given above, in reality plant breeding involves a multidisciplinary and long-term approach. Regardless of whether a breeding scheme is publicly or privately managed, a successful plant breeder will require knowledge in many (if not all) of the following subjects:
Evolution It is necessary to have knowledge of the origins and past progress in adaptation of crop species if additional advances are to continue into the future. When dealing with a crop species, a plant breeder benefits from knowledge of the timescale of events that have modelled the giv