RA 00048.pdf - OAR@ICRISAT

egion after a careful study of factors which
contribute to contamination such as wind velocity
and direction of wind at flowering, natural barriers,
insect activity, size of seed field, pollen shedding
capacity of the male parent, etc. There is a real
need to conduct experiments and come to some
definite conclusion for each seed class and for
each climatic zone.
Roguing
Although it is expected that the basic seed lots
supplied for certified commercial seed production
are field tested for genetic purity, off-type plants
do appear. They may be delayed segregates, outcrosses,
mutant or volunteer plants. The originating
breeders should describe in detail the distinguishing
morphological characteristics of a newly
released variety or parents in the case of a new
hybrid. During the process of multiplication from
breeders through commercial seed, they help
producers and certification inspectors to identify
and remove off-types and thus maintain genetic
purity of the variety or hybrid. The seed producing
agency specialists should train the seed farmers
to identify and remove all off-type plants at the
vegetative, flowering and seed ripening stages.
Maintainer line plants from female parent rows
should also be removed daily during flowering.
Seed Harvesting and Processing
The procedure for harvesting the seed parent is
more or less the same for all seed classes.
Harvesting should begin only after the final
(preharvest) inspection has been undertaken to
remove leftover off-type and diseased earheads.
Although sorghum seed is highest in quality when
it attains physiological maturity, i.e.. about 3 0 %
seed moisture, harvesting at this stage is possible
only if the facilities for artificial drying and
threshing are available. Seeds harvested at this
stage have a better appearance, are vigorous,
have greater resistance to mechanical injury
during drying-processing, and give increased
yields.
Harvesting can be done with a combine or by
hand. In the case of varietal multiplication, combine
harvesting and threshing can be fast and
economical but is possible only on large-size plots
and is usually recommended only for the commercial
seed class. The combine should be thoroughly
cleaned before use. In most developing countries,
including India, harvesting is done by hand at
about 15% seed moisture. Panicles are sun dried
for 2 - 3 days and threshed under bullock or tractor
wheels. This does reflect on the physical quality of
the seed and reduces its germination and storability
but these are the cheapest, most readily
available and most widely used methods.
Regardless of the class of seed, specific procedures
have to be followed when two parents are
involved (multiplication of A-line or hybrid seed).
The restorer or maintainer rows are harvested
first, threshed, stored, or sold. The technical staff
of the producing agency and/or seed certification
agency inspect the field for lodged or broken male
panicles or plants of diseased panicles in the
female parent rows and then give permission to
harvest the seed parent.
The breeder's seed should be threshed with a
small-size seed thresher at 12% seed moisture.
These threshers can be easily cleaned thus
avoiding chances of mechanical mixtures. The
breeder or his associate can also examine each
head before putting it through the thresher. Since
the breeder's seed will usually be multiplied once
in 4 years, mechanical injury to seed, which can
reduce viability and vigor in storage, should be
avoided.
The threshing of basic seed should be done on
medium-size, power-operated threshers. The
identity of each lot should be separately maintained
through proper labeling and the seed may
be stored in bulk or in new gunny bags until
further processing.
After harvest the seed contains various admixtures
which have to be eliminated before sowing.
The seed is cleaned and graded to remove inert
matter, undersized, broken or shrivelled seed,
treated with an insecticide to provide protection
against stored grain pests and a fungicide to
protect against soil fungi on planting, then
weighed, bagged, and stored until sale.
Seed Distribution
The channels of seed distribution for a private
seed company are often different than the ones
available to the public or government-run company.
The efforts of the former are directed to
establishing its brand image—the brand being a
guarantee of its quality. The seed company slowly
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