Abstract:
This study was conducted in the laboratory of the Seed
Administration, Federal Ministry of Agriculture and Forestry,
Khartoum Sudan, to show the effect of normal and accelerated
ageing (AA) on onion seed quality. Seed samples were drawn
according to the International Seed Testing Association (ISTA,
1999) from four seed lots produced in four consecutive seasons
(2004, 2005, 2006 and 2007) and stored in a normal store room
under normal storage conditions. According to their production
season, they are considered to be of four ages (one, two, three
and four years old, respectively).The seed samples were tested
in two experiments. The first one was for testing the effect of
normal aging and the second one for testing the effect of AA, on
seed quality. The AA treatment were done according to
Matthew and Powell,(1981) where the seed moisture content
(SMC) was increased from the initial moisture content (5%
SMC) to 10, 12.5 and 15 %, and dried again to 5% at 45oC for
48, 72 and 96 hours (accelerated aging durations (AAD),
respectively. Both germination and emergence (vigour) and their
attributes (germination percentage, mean germination time,
germination homogeneity, emergence percentage, mean
emergence time and emergence homogeneity, respectively) were
evaluated. For both experiments the germination and its
attributes were evaluated after growing the seeds on filter paper
in Petri dishes under controlled conditions, where as the
IV
emergence and its attributes were evaluated after growing the
seeds in sand in plastic pots under room conditions.
The experimental units of both experiments were distributed in a
complete randomized design (CRD) with four and three
replications, respectively.
The results showed that ageing has significant effect on
both germination and emergence (vigour) and their attributes) of
onion, especially if the seeds were above two years old. The
interactions between normal and AA were significant, especially
at 12.5 % SMC and 72 hours AD at 45oC. Seeds more than two
years old had almost lost their vigour at this AA treatment. The
highest AA (15% SMC and 96 hours AD) led to a complete seed
deterioration.
It could be concluded that onion seeds quality decreased
significantly after two years age and above three years age
would lose vigour and may be of no commercial value as seed .
AA treatment of 12.5%SMC and 72 hours AD may be suitable
as vigour test of onion seed lots of two years age and the
relatively lower AA treatment (10% SMC and 48 hours AAD)
for older seed lots (above two years old) because a higher SMC
and a longer AA (12.5 % and 72 hours, respectively) may
increase the effect of temperature and may be conducive to
fungal growth and so accelerated seed deterioration.
