Leguminous Vegetable Cultivation and Seed Production S ...

SEED PRODUCTION AND MANAGEMENT OF MUNGBEAN AND SOYBEAN 363
Mungbean and soybean are self-pollinated, annual species reproduced by
normal fertilization. In mungbean, natural outcrossing varies from 0.0 to 13%
(Shanmugasundaram and Poehlman 1988). A high level of outcrossing can cause
considerable variation in the seed produced. In India, when rnungbean seed was
produced, a 1.5-m border was left unharvested between adjacent varieties (Kernick
1961). Considering the large extent of outcrossing in some genotypes, the isolation
requirement has been increased to 3 m.
Usually, a plant breeder maintains a variety by planting single plant progeny
and checking characteristics against the variety's official description. If the rows are
uniform, they are bulked. In soybean, 30-50 kg of pedigree seed normally is reserved.
In rnungbean, .10-15 kg of pedigree seed is reserved. In temperate and tropical
countries, seed production rates vary because of the length of growing seasons and
the yield potential of varieties. Pedigree seed is planted on 0.5-1.5 ha to produce 1-3 t
soybean and 0.3-1 t rnungbean basic seed.
Basic seed is used to produce the subsequent categories of seeds (Shanrnugasundaram
1982). At each stage, care is exercised to remove variants. In countries
with official seed certification programs, designated agencies supervise and regulate
seed certification.
In India, a parastatal national seed corporation coordinates the production of
certified seed through a series. of state seed farms that are profit-responsible. They
were set up and funded by World Bank (Walker 1980). The All-India Coordinated
Research Project on Soybean, in its annual meeting, allocates to each breeder the
quantity of seed to be produced. For example, in 1985-86 breeders produced about
92 t of basic seed of 20 new soybean varieties (P. S. Bhatnagar, pers. comm.).
Factors to consider in seed production
Seed production is a specialized activity. Preharvest and postharvest factors must be
considered (Nangju et al 1978): field environment, cultural practices, genetic
influence, and harvest time (Tekrony et al 1978) and biotic and abiotic factors
(Roberts 1972b, Sinclair and Jackobs 1982).
Basic constraints in seed production can be varietal (genetic characteristics),
environmental, biological, and socioeconomic, alone or in combination. Vagaries of
climate and soils must not be used as excuses for deficiencies in plant genetics,
selection procedures, isolation distances, good crop management, and quality
control (Walker 1980).
Constraints such as photoperiod, temperature, soil properties, and rainfall
cannot be controlled by the seed producer (Shanmugasundaram and Tsou 1987).
Land preparation, organic or inorganic fertilizer applications, pest and disease
control, and weed control and management are factors that can be regulated. A
sufficient knowledge pool is available (for a review see Morton et al 1982, Nangju et
al 1978, Scott and Aldrich 1970, Shanmugasundaram 1982, Shanmugasundaram
and Tsou 1987, Sinclair and Jackobs 1982, Tekrony et al 1978). Although obtaining
a high yield is a consideration, the most important criterion is producing good