MSc

Ageing of seeds is an inevitable natural deteriorative phenomenon, eventually
resulting in loss of vigour and viability. Adopting appropriate storage, ensuring
optimum storage environment have been advocated to slow down the pace of the
deteriorative process during storage, maintain the seed quality and prolonging seed
longevity. Considering the above, a study to elucidate the effect of different storage
structure on seed longevity and quality of short duration rice varieties (Experiment 1)
and medium rice varieties (Experiment 2) was conducted at College of Horticulture,
Vellanikkara, Thrissur, during 2019 - 2020.
The storage experiments were conducted following a completely randomized
design with four varieties replicated thrice under five storage conditions (SC1 to SC5),
each varying from the other with respect to the type of roofing and provision of
ventilation. The short duration varieties used in Experiment 1 were Harsha, Matta
Triveni, Manurathna and Kanchana, while, the medium durations varieties in
Experiment 2 were, Aiswarya, Sreyas, Jyothi and Uma. The quality parameters of seeds
stored in SC1 (Asbestos + ventilation), SC2 (Asbestos + without ventilation), SC3
(R.C.C. + ventilation), SC4 (R.C.C. + without ventilation) and SC5 (Asbestos + forced
ventilation) were recorded at the start of storage and subsequently at monthly intervals
for a period of nine months. The temperature and relative humidity in each storage
condition were recorded at weekly intervals.
Varieties, storage conditions, the period of storage and their interactions were
found to exert significant influence on seed quality and longevity in both short duration
and medium duration varieties. Irrespective of the varieties and the storage conditions,
the seed quality parameters viz., germination (%), vigour indices (VI-I and VI-II) and
field establishment (%), declined over the storage period, whereas an increase in seed
moisture content (%), electrical conductivity of seed leachate (dSm-1) and seed
microflora, was observed.
Germination and longevity of varieties Matta Triveni and Harsha was higher
than that of varieties Manurathna and Kanchana. Seed longevity was higher (8 months
each) in varieties Harsha and Matta Triveni compared to varieties Manurathna and
Kanchana (7 months each).
The seed vigour indices (VI-I and VI-II), field establishment (%) of Matta
Triveni were significantly high, while the estimates of seed moisture (%) and EC of
seed leachate were significantly low in Kanchana. In case of medium duration varieties,
although germination was higher in varieties Aiswarya and Shreyas compared to Jyothi
and Uma, the longevity of seeds in all varieties was retained for eight months.
Germination, vigour (VI-II) and field establishment (%) was significantly high in
Aiswarya, while the seed moisture and EC of seed leachate was found to be
significantly low in Sreyas. Variety Uma registered significant low seed quality
parameters.
In both short and medium duration varieties, the quality of seeds stored under
ventilated conditions (SC1, SC3 and SC5) was found to be the significantly superior to
those stored in non-ventilated structures (SC2 and SC4). Irrespective of the type of
roofing (Asbestos or R.C.C), seed longevity in ventilated godowns were found to be
retained above IMSCS, one month longer (8 MAS) than when stored under nonventilated
environment (7 MAS).
The interaction between varieties, storage condition and the period of storage,
indicated that seed longevity in all medium duration varieties stored under ventilated
storage and non-ventilated storages was eight and seven months respectively. Unlike
in the medium duration group, the longevity of all the longevity of short duration
varieties Matta Triveni and Harsha was higher by a period one month i.e., 8 MAS,
when stored under ventilated environments conditions viz., R.C.C. + ventilation
(SC3), Asbestos + ventilation (SC1) and Asbestos + forced ventilation (SC5) as
against 7 MAS under non-ventilated storage [Asbestos + without ventilation (SC2),
R.C.C. + without ventilation (SC4)]
High temperature and relative humidity within the storage environment strongly
influenced germination and seed longevity. The decline in germination was found to
be more pronounced when the seed was exposed to high temperatures in the early
period of storage i.e., between 1 and 13th week, while high RH during the 2nd half of
the storage period (i.e., between 24th and 36th week), proved to be detrimental to seed
longevity. Among the storage structures, the temperature and RH inside ventilated
storage (SC3, SC1 and SC5) was relatively lower than that in non-ventilated structure
(SC4 and SC4). Marginal variations in temperature and RH was evident between the
ventilated stores, with the least estimate in Asbestos + forced ventilation (SC5).
However, most quality parameters and longevity of seeds in these conditions were on
par with each other.
From the above results, it can be summarized that storing seeds in ventilated
storage structures, was clearly advantageous over storing them under non-ventilated
conditions. Only marginal variations in seed quality parameters was observed between
the ventilated conditions. Neither did storing seed in godowns with provision for forced
ventilation improve the longevity of stored seeds over those with provision for natural
ventilation. Incurring additional expenditure on installation, maintenance and operation
of forced ventilation system did not to confer any additional benefits. Considering all
the above, it would be more advantageous to store seeds under ventilated conditions
with provision for natural ventilation.