2. What are main activities of plant
(i) varietal development:- it makes use of various
plant breeding method(selection, hybridization, mutation
and genetic engineering) to develop new variety.
(ii) Seed multiplication:- it deal with multiplication of
successive generation of various categories of seed. It
regulated by seed certification agencies and breeders.
(iii) varietal maintenance:- It deals with continuous
fresh supply(annually) of breeder seed which used to start
another cycle of seed multiplication.
The initial handful of seeds obtained from selected
individual plants of a particular variety for the purpose of
purifying and maintaining this variety, under supervision of
The varietal purity of subsequently multiplied foundation,
registered and certified seed largely depend upon the quality
of the nucleus/breeder’s seed.
Unsatisfactory genetic purity, especially in cross pollinated
crops, could ultimately severely affect the performance of a
variety So it’s of very most importance to maintain the
genetic purity and identity of n/s or b/s.
4. what’s maintenance breeding?
A branch of plant breeding which deals with principles and
method of breeder seed production and maintenance is
called maintenance breeding.
It’s a breeding procedure followed to maintain the genetic
purity of the variety or parents of hybrid.
it deals with principles and methods of breeder seed or
nucleus seed production.
It deal with ways and means of maintaining genetic and
physical purity of released and notified variety.
It’s also known as varietal maintenance technology.
5. Feature of maintenance breeding
Continuous breeder seed production of released variety
means fresh breeder seed production.
It also undertake breeder seed production of parental line of
Genetic purity, physical purity and germination are main
point taken into account.
Seed health also taken.
Breeder and foundation seed is use as base material for
It prevents varietal deterioration(mutation , cross
6. MAINTENANCE OF NUCLEUS AND
Methods of maintaining n/s or b/s can be divided into
Maintenance of newly released varieties.
Maintenance of established varieties.
7. MAINTENANCE OF NUCLEUS SEED
OF NEWLY RELEASED VARIETIES
1.Selection and Sampling of the variety.
Newly released variety are selected for nucleus seed
production. These variety used as base material.
These samples provide a beginning for purifying new
varieties and for possible increase and distribution to
Not more than fifteen new varieties in any one crop at a
station should be sampled in one year.
2.Table examination of samples.
Minimum 200 plants should be threshed separately.
And examined in piles on the table. discard the off types.
Left over seeds are now ready to be sown in a variety
purification nursery called as nucleus.
8. 3.Locating and seeding of nucleus seed:
Each nucleus seed should be grown 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
4.Inspection of nucleus seed plots and removal of off types:
The nucleus plot should be examined critically from the
seedling stage until maturity,
Differences in the habit of early plant growth, other traits,
diseases reactions should be critically examined..
If a plot differs distinctly from the average in the pre-
heading stages of growth, it should be removed before
9. 5.Harvesting and threshing of nucleus seed
Each remaining plot, of which there should be at least
180 plant progeny 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 test for trials are
Discard if found unworthy
After threshing seed should cleaned in fanning mill and
placed in pile on seed table. Examine it for uniformity of
seed appearance. Discard off type. Remain are bulk
together and stored as breeder seed stock.
10. MAINTENANCE OF BREEDER’S
NEWLY RELEASED VARIETIES
1.Selection of field:-
Breeder’s 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. Space required for seeding breeder stock is
about 1.2 ha in wheat and 3 ha in transplanted rice.
2.The field should properly isolated.
The best farm procedures should be used in the sowing, raising
and harvesting of breeder’s stock.
4.It should be produced at the experiment station in the area in
which the new variety has been bred.
5.Sowing:- Seeding done in such a way :
1.Best use of the limited amount of seed available .
2.Row spacing should be sufficient for examination of plant.
11. 6. Roguing: All unworthy plants of the variety should be
pulled and removed like diseased, mechanical mixture,
etc..The roguing should be done before flowering as well as
after flowering for the nucleus/breeder’s stock seed.
7.Harvesting the breeder’s stock: The equipment used must
be 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. A portion of this breeder’s seed should be retained
by the breeders for next cycle. Remaining distributed for
12. MAINTENANCE OF BREEDER SEED
OF ESTABLISHED VARIETIES.
A) By raising the crop in isolation:
The breeder’s seed of local varieties could be maintained by
growing them in isolated plots and by rouging during various
stages of crop growth.
Method of handling of the breeder seed crop is same as
breeder’s seed of newly released varieties.
B) 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 off-type are discarded,
The remaining piles of seed are bulked to constitute the breeder’s
seed. The other practices of handling remains the same.
13. Carry-over Seed
The 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
In addition, the breeder should further safeguard
variety by arranging, to have a portion of the seed
originally released stored under the ideal conditions.
14. Advantage of maintenance
It helps in purification of improved cultivars and
parental line of hybrids.
It prevent cultivars from genetic deterioration and
so it prolong life of variety.
It is useful in studying the efficiency of various
It help in quality seed production which in turn lead
to higher crop yield.
15. limitation of maintenance breeding
Some maintenance procedure requires lot of experimental
material of evolution.
Large number of single plant have to be evaluated in term of
agronomic performance hence Only limited number of
cultivars can be handled at a time.
Progeny row method require more time(2-3 season) for
evolution of purity of a variety.
Most of testing procedures are based on phenotypic
Maintenance procedure are used for varietal purification.
Hence chance of evolve new variety through MB are rare.