Effect of isolation distances on varietal seed purity for open pollinated varieties of pearl millet [pennisetum glaucum (l.) r. br.] at farmers’ level in Northern Ghana
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Date
August 2015
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Abstract
Pearl millet seed supply in West Africa is dominated by the informal system in which
small scale farmers produce and supply local seeds of landraces or open pollinated
varieties mostly without any quality control during production. Standards for quality
control are mostly designed for the formal and commercially oriented system which fails
to supply adequate quantity of seeds. To increase agricultural productivity through the
use quality planting materials more attention is required on small seed producers to
ensure that seed of acceptable quality are produced and used by large scale millet
producers.
This study aimed at assessing the level of varietal seed purity at farmer‟s level. Two
open pollinated varieties of Pearl millet were used, one variety as pollen source
characterized by yellow coloured seeds and the other seed parent with grey coloured
seeds. After cross pollination, it was expected to produce hybrid of yellow coloured
seeds on the seed parents due to xenia effect. The results showed significant differences
(p<0.001) in varietal seed purity with regard to the interaction between distance and
direction of seed parents from the pollen parents. Closer pollen parents (from 0.4 to 30
m) showed higher significant differences in varietal seed purity compared to distant seed
parents (from 40 to 60 m). Seed parents located to the direction of wind from pollen
parents produced seeds with significantly lower seed quality compared to those located
in the opposite direction. Varietal purity was positively and strongly correlated (p<0.01)
with distances from pollen parents.
Wind speed and direction showed significant direct effect on varietal seed purity while
other climatic parameters such as temperatures, relative humidity and rainfall may have
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some indirect effects. Although it was possible to produce pure seed on some points of
the experimental field at 60 m to the South East and to the West, 45 m and above to the
South East, 50 m and above to the South, 55 m and above to the South West and North
West, it is very challenging for farmers to produce seeds that meet standards. However,
some measures can be taken by farmers in order to produce seed with an acceptable
level of seed purity. These measures include: plotting the seed field by considering the
prevailing wind direction in the area, planting at least 3 weeks after the source pollen is
planted, choosing seed parents that are „‟taller‟‟ than the pollen parents, adopt a
communal seed grower system where a cluster of farmers grow the same variety. These
could not prevent cross-contamination from neighbouring farms with different varieties
but rather can minimize the flow of pollen grains in the seed production filed.
Description
A Thesis Submitted to the Department of Horticulture, Kwame Nkrumah University of Science and Technology in Partial Fulfilment of the Requirement for the Degree of Master of Philosophy (Seed Science and Technology), 2015