GREEN SEED COAT COLOUR RETENTION IN LENTIL - University ...

2.6 Cotyledon chlorophyll degradation in Brassica spp.
It is currently not known in lentil seed coats which factors play major or minor
roles in chlorophyll degradation and if it is possible to minimize the degradation.
The Brassica genus includes species which are very important to the world’s
vegetable oil supply. To be of maximum value the sample must have few green
cotyledons, or few seeds that are still green, because it causes the oil to be green due
to elevated levels of chlorophyll. The chlorophyll reduces the shelf life of the oil
and thus expensive industrial processes have to be employed to remove it. It has
been a major objective of plant breeders to reduce the incidence of green cotyledons
in canola samples. The goal of green lentil is to have a seed coat that appears more
green while in Brassica sp. the goal is to have a cotyledon that appears less green.
It is unknown if similar mechanisms that prevent green cotyledon loss in Brassica
sp. are similar to increased green colour desirability in lentil.
The green colour that is observed in seeds of canola and rapeseed is due to
the cotyledon retaining a high level of chlorophyll or pheophytins, which are the
initial chlorophyll breakdown product (Daun, 1982). As the plant ripens,
chlorophyll degradation in the cotyledon was related to the moisture content of the
seed (Figure 2.2). If environmental conditions are ‘normal’ during ripening there is
little chlorophyll left in the seed. The ripening period occurs between physiological
maturity and harvest maturity (Elias and Copeland, 2001). There is minor genotype
× environment interaction that affects the amount of chlorophyll that is present in
the seed at harvest. The production of ethylene, which is known as a ripening
hormone in many plant species, has no effect on chlorophyll loss from canola or
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