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Jojoba (Simmondsia chinensis L.) is a dioecious desert shrub that produces highly valued oil for cosmetics and
lubrication. Most of the existing plantations have low yields due to high ratio 1:1 of the males compared to the
females. However, there is no existing morphological trait method for distinguishing sex at an early age in
Jojoba. Use of morphological traits for identifying sex at the juvenile stage is economical and more practicable
for field workers hence more preferred than the molecular marker technique. To overcome this problem, two
experiments were carried out with an objective of identifying sex of young Jojoba plants using morphological
traits. The first experiment was set up using nursery seedlings whereas the second used rooted cuttings. The
experimental design was a Randomized Complete Block Design (RCBD) consisting of 8 treatments replicated 3
times. The treatments consisted of 4 males and 4 females per replicate which were selected using stratified
random sampling. Foliage morphological data was collected from both the seedlings and rooted cuttings
according to a modified Jojoba descriptors procedure. The nursery seedlings were raised in an open nursery
whereas those of the rooted cuttings were carried out in a polythene sheet tunnel. These experiments were
carried out from February to August 2012. Data was analyzed using SAS statistical package whereas means were
separated by Least Significant Difference (LSD). The results for seedlings showed that foliage morphological
traits for single leaf area in male seedlings (4.4 cm 2 ) were significantly higher (p< 0.05) compared to the female
seedlings (3.2 cm 2 ). However, all the other foliage variables did not show any significant difference although
male seedlings were greater in leaf length, leaf width, number of leaves, total leaf area and leaf area/0.3m
relative to the female seedlings by 13%, 14%, 19%, 63% and 69% respectively. The females were superior in
only leaf shape index by 1.4% compared with the males. On the other hand, rooted cuttings showed a similar
pattern with those of seedlings although there was no significant difference in all the morphological traits
measured. However, males showed higher foliage growth compared with the females in leaf length, leaf width,
single leaf area, number of leaves and total leaf area by 37%, 43%, 95%, 155% and 458% respectively. The
results indicate that single leaf area can be used for sex differentiation in juvenile Jojoba plants hence
recommended at the nursery stage in order to determine the right planting ratio of male to female of 1: 10
respectively in the field for maximum stand production. Further research is recommended for a longer period to
identify other foliage traits useful for sexing of Jojoba nursery plants. |
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