Nucleus and Breeders seed production
initial handful of seeds obtained from selected individual plants of a particular variety,
for the purposes purifying and maintaining that variety, for the purposes and purifying
and maintaining that variety, by the originating plant breeder and its further
multiplication under his own supervision, or the supervision of a qualified plant breeder,
to provide Breeders Seed constitutes the basis for all further seed production. The
varietal purity of subsequently multiplied foundation, registered and certified seed
largely depend upon the quality of the nucleus/breeders seed. Unless the nucleus/
breeders seed is of highest purity and quality the seed multiplied from it cannot be
regarded as of satisfactory genetic purity. Unsatisfactory genetic purity, especially in
cross pollinated crops, could ultimately severely affect the performance of a variety. It
is therefore, of utmost importance that the nucleus/breeders seed is produced in
such a manner that satisfactory genetic purity, identity and the other good qualities of
seed are maintained.
Methods of maintence of nucleus and breeders seed in self fertilised crops
of maintaining nucleus seed/breeders can be conveniently divided into the following
- Maintenance of newly released
- Maintenance of established varieties
of Nucleus Seed of Pre-released or Newly Released Varieties
procedure outlined by Harrington (1952) for the maintenance of nucleus seed of
pre-released or newly released varieties is described below:
of the variety to obtain nucleus seed. New numbers, lines or selection which are highly
promising, on the basis of performance in breeding nurseries and yield trials, should be
sampled for seed purification. These samples provide a beginning for purifying new
varieties and for possible increase and distribution to farmers. Not more than fifteen new
varieties in any one crop at a station should be sampled in one year.
examination of samples: The two hundred plants of each sample should be threshed
separately and the seed should be examined in piles on the table. Discard any pile
appearing obviously off type, diseased or otherwise unacceptable. The seeds of each two
hundred plant samples or less is now ready to be sown in a variety purification nursery
called as nucleus.
and seeding of nucleus: Each nucleus seed should be grown on clean fertile land at an
experiment station in the region or in area in which this new variety could be grown, in
the event of its release. The land must not have had a crop of the same kind in the
of nucleus two-row plots and removal of off types: Throughout the season of growth, from
the seedling stage until maturity, the nucleus plot should be examined critically.
Differences in the habit of early plant growth, leaf colour, rate of growth, time of
heading, height head characteristics and diseases reactions should be looked for. If a
plot differs distinctly from the average in the preheading stages of growth, it should be
removed before heading.
and threshing of nucleus; Each remaining plot, of which there should be at least 180 out
of the original 200. should be harvested individually with a sickle and tied in a bundle.
The total bundles of each nucleus should be labelled and stored until the current years
yield rests for trials are obtained. The nucleus bundles of any new variety should be
discarded, if it is found unworthy of being continued.
the seed should be cleaned in a fanning mill or by hand methods, the grain from each
nucleus plot being placed in a pile on the seed table. The 180 or more piles of seed of
one nucleus must be examined for approximate uniformity of seed appearance, and any pile,
which appears to be off type discarded. All the remaining piles of the of seed should be
masked together in one lot. This should treated with fungicide and insecticide, bagged,
labelled and stored as "Breeders Stock Seed" for use in the next year.
Breeders stock seed is the original purified seed stock of a new variety in the
hands of the plant breeders.
of Breeders Seed of Pre-released or Newly Released Varieties
following steps are involved in the maintenance of breeders seed.
stock seed from the nucleus should be sown on the clean, fertile land, which did not grow
a crop of the same kind in the previous year. The space required for the seeding the
breeders stock is about 1.2 ha in the case of wheat and as much as 3 ha in the case
of transplanted rice.
field should properly isolated.
best farm procedures should be used in the sowing, raising and harvesting of
should be produced at the experiment station in the area in which the new variety has been
seeding should be done in such a way as to make the best use of the limited amount of seed
available and to facilitate roguing. The row spacing should be sufficient to permit
examination of plants in rows for possible mixture or off types.
All plants not typical of the variety should be pulled and removed. There should be very
few plants to rogue out if the previous years nucleus breeders stock seed was well
protected from natural crossing and careful roguing was done and there were no impurities
during cleaning etc. The rouging should be done before flowering, as was done for the
nucleus/breeders stock seed.
the breeders stock: In the breeders stock is harvested and threshed, the
equipment used must be scrupulously clean and free from seeds of any other varieties. This
cleanliness should be extended to cards and bags as well as threshing machine it self. The
seed should now be about 99.9 per cent pure as to variety. These breeders seed is
ready now for increase of foundation seed. A portion of this breeders seed should be
retained by the breeders to sown a continuation breeders seed of the variety.
of breeders seed of established varieties: The breeders seed of established
varieties could be maintained satisfactorily by any one of the following methods)
raising the crop in isolation. The breeders seed of local varieties could be
maintained by growing them in isolated plots and by very rigorous roguing during various
stages of crop growth, where the various plant characters are observable. The method of
handling the breeder seed crop is the same as described earlier for breeders seed of
newly released varieties.
bulk selection. The genetic purity of established varieties could be satisfactorily
improved by bulk selection. In this method 2,000 to 2,500 plants typical of the variety
are selected, harvested ,and threshed separately. The seeds from each plant are examined
and any pile which shows any obvious off-types, or otherwise appears dissimilar, are
discarded. The remaining piles of seed are bulked to constitute the breeders seed.
The other practices of handling remains the same.
breeder must carry-over at least enough seed to safeguard against, the loss of variety if
there is a complete failure during the foundation seed multiplication phase. In
addition,the breeder should further safeguard variety by arranging to have a portion of
the seed originally released stored under the ideal conditions.