ABSTRACT
Two field experiments were conducted in 2007 and 2008 cropping seasons at the Department
of Crop Science research farm, University of Nigeria, Nsukka, to characterize some Nigeria
cucurbita genotypes with respect to morphology, nutrient composition and the cytology. The
results obtained showed that Shannon diversity index (Hs) was 4.136 which suggests high
level of diversity among the Nigerian cucurbita species evaluated. Cucurbita moschata had
the highest Shannon diversity index of 1.559 followed by C. maxima (1.474) and C. pepo
(1.103) thereby revealing C. moschata as the most diverse. The mature fruit colour, seed
colour, immature fruit colour, leafiness, petiole colour recorded high Hs values vis-a-vis the
other qualitative descriptors. This is an indication that the above traits contributed
meaningfully to the observed diversity in the species. The evenness of C. pepo, C. Maxima
and C. moschata were 0.187, 0.250 and 0.265, respectively, suggesting uneven species
distribution in the Nigerian agro-ecologies. The genotypes differed significantly (P<0.05) in
all the agronomic and yield traits measured. The only exception was in weight of healthy
fruits. The planting season had significant effects (p<0.05) on all the floral and agronomic
traits measured with the exception of number of leaves per plant, girth size, vine length,
weight of healthy fruits and 100-seed weight. The interaction of genotype and planting
season also had significant effects on days to 50% emergence, number of healthy fruits,
number of damaged fruits, 100-seed weight and seed length. The principal component
analysis of the agronomic and yield traits showed that the first three components accounted
for 72.20% and 74.75% of the total variation in the 2007 and 2008 plantings, respectively.
The traits representing the genotypes along the first principal axis were 100-seed weight and
weight of healthy fruits for the 2007 planting and, number of damaged fruits, seed length and
100-seed weight in the 2008 planting. Genotypes were differentiated on the basis of days to
50% flowering, fruit diameter, girth size, number of damaged fruits, number of healthy fruits
and vine length in the 2007 planting and, days to 50% emergence, number of fruits per plant,
number of healthy fruits, number of leaves and weight of healthy fruits in the 2008 planting
along the second principal axis. The hierarchical cluster analysis and cluster plot revealed
that the 10 cucurbita genotypes were grouped into two clusters with Akwa-01 alienated from
the clusters in the 2007 and 2008 planting seasons. The coefficients of similarity between the
clusters were 0.86 and 0.89 for the 2007 and 2008 plantings, respectively. The members of
cluster I genotypes at both planting seasons are very promising in the production of male and
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female flowers, ability to sustain larger and healthier fruits. However, genotypes in cluster II
are prolific in terms of leaf production and are suceptible to fruit damage. The correlation
coefficient for weight of healthy fruits was highly significant and positive with number of
seeds per fruit (r = 0.339**) and days to 50% flowering (r = 0.494**) indicating that increase
in these traits will ultimately increase weight of healthy fruits. The number of male flowers
had significant positive relationships with seed length, number of seeds per fruit, fruit length,
fruit diameter, number of fruits per plant and number of female flowers indicating that the
above traits are influenced linearlly by the number of male flowers. However, days to 50%
emergence was negatively correlated with seed length (r = -0.560**), fruit length (r = –
0.557**), fruit diameter (r = -0.371**), number of fruits per plant (r = -0.430**), number of
female flowers (r = -0.543**) and number of male flowers (r = -0.457**). The chemical
composition and nutritional profile differed significantly (p<0.05) among the genotypes in
the proximate, mineral, phytochemical and the anti-nutrient analyses. The results revealed
that Pumpkin fruits are very rich in crude protein, minerals (calcium, phosphorus, sodium
and iron), phytonutrients (lycopene, ascorbic acid and β-carotene) and crude fibre but low in
crude fat, phytate, tannin and moisture content. The result of the cytological work
established a diploid chromosome number of 2n=40 for Cucurbita species at the metaphase
stage.
TABLE OF CONTENTS
Title page …………………………………………………………………………………………………………………. i
Certification ……………………………………………………………………………………………………………. ii
Dedication ……………………………………………………………………………………………………………… iii
Acknowledgement ………………………………………………………………………………………………….. iv
Co-Authored Articles From This Work ……………………………………………………………………… vi
Table of contents …………………………………………………………………………………………………….vii
List of Tables ………………………………………………………………………………………………………. viii
List of Figures ……………………………………………………………………………………………………….. ix
List of Plates ……………………………………………………………………………………………………………. x
Abstract ………………………………………………………………………………………………………………… xi
Introduction ……………………………………………………………………………………………………………. 1
Literature Review ……………………………………………………………………………………………………. 4
Materials and Methods …………………………………………………………………………………………… 13
Results …………………………………………………………………………………………………………………. 21
Discussion ……………………………………………………………………………………………………………. 58
Conclusion ……………………………………………………………………………………………………………. 68
References ……………………………………………………………………………………………………………. 69
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CHAPTER ONE
INTRODUCTION
Cucurbita belongs to the family, cucurbitaceae which consist of about 118 genera and 825
species (Jeffrey, 1990). The member are warm season annuals, thriving in hot and humid
weather (Omafra, 2000) and have spreading growth pattern with tendrils at the leaf axils.
They are important fruit vegetables that are widely grown in the tropics. Leaves are borne
singly and may be simple or lobed. Pumpkin is relatively deep rooted and can tolerate dry
condition fairly well. However, extended dry period will result in poor fruit set or poor fruit
development and size (Omafra, 2000). It can also tolerate wet condition fairly well but it can
induce or increase foliar diseases and fruit rots. The flowers vary considerably in colour and
shape and are pollinated by various wild bees (Hurd et al., 1988). The pumpkin flowers are
borne on the axils of the leaves, the males on long peduncles and the females on short
peduncles. The female flower contains an inferior ovary (Pumpkin, 2007). Cucurbita is
considered as one of the most morphologically variable genera in the entire plant kingdom
(Robinson et al., 1976). Nee (1990) reported that Cucurbita is one of the first plants to be
domesticated and that the species are collectively referred to as pumpkin.
Pumpkin is a very important traditional food crop and a great deal of genetic variability has
been reported (Montes-Hernandez and Equiarte, 2002). Lust (1983) and Chopra et al. (1986)
reported that pumpkin has high nutritional value. Virtually all parts of the plant can be used
for food. Hedrick (1972) stated that pumpkin fruit is a high valued edible fruit; and the fruits
can be consumed mature and immature, (Whitaker and Bohn, 1950 and Merrick, 1995). It is
consumed either by boiling (leaves and fruits) or by roasting or baking (seeds) (Facciola,
1990). Pumpkin is rich in nutrient, the seeds can be dried and ground into powder and used
with cereals in making bread and cakes while, the seeds are diuretic, tonic and vermifuge.
(Chopra et al., 1986). Pumpkin leaves, fruits, flowers and seeds are all protective and healthgiving
food. They are rich in vitamin A. and in dietary fiber.
The sub-saharan Africa is not implicated as a centre of origin for Cucurbits. Therefore, the
available cultivars are reported to have been introduced by transoceanic traders (Whitaker,
1949). Extensive research works have been carried out on this crop by great researchers in
America and Europe. Carlos (1998) reported that cultivated Cucurbits have many things in
common; they are extremely diverse in fruit characters. Some are large fruited, others are
small fruited, and every gradation between these extremes does exist.
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The principal justification for plant collection is to obtain natural variability that can be
useful in producing germplasm pools for crop improvement. The Cucurbits have diverged
from the original descendants of their common progenitor (Benneth, 1970). The Shannon-
Weiner Diversity Index is one of the most widely used species diversity indices for
examining overall community characteristics. It was derived from a function, used in the
field of information and has been adapted by ecologists to describe the average degree of
uncertainty of predicting the species of an individual picked at random from the community.
The uncertainty of occurrence increases both as the number of species increases and as the
individuals are distributed more and more evenly among, the species already present.
Kempon and Wedderburn (1978) suggest that this Shannon’s index rely heavily on the
abundance of the most common species which may fluctuate widely on year to year basis,
and suggests the use of a third diversity index.
The different descriptions of the Cucurbits by different authors have given the classification
of the Cucurbita species a controversial status. Many European authors have identified three
primary groups namely; Cucurbita pepo group, which includes, C pepo, C moschata, C
maxima and C argyrosperma species. The Cucurbita veruscosa group comprises all the
warty varieties of Cucurbits and C. melo group is the scalloped squash (Paris et al., 2002).
Linnaeus listed four species of Cucurbita, all of which were classified as C. pepo species by
Duchesue (1968). This is because they were related and cross compatible. Duchesue (1968)
isolated two distinct species namely; C. maxima named after the large fruit size and C.
moschata for the musky flavour. Duchesue classified C. pepo as C. poplymorpha in
recognition of its extreme variability within the species (Paris, 2001). The CWF (2007)
shared the views of the European authors on the description of the warty varieties but
classified them as C. veruscosa. Earlier work (Decker, 1988) suggested that there was a
relationship between C. pepo and C. texana and that many edible forms are included in the
C. pepo complex. Crossibility studies reported by Margaret (2007) revealed that crosses
between species are hard to make and their progenies are highly sterile, thus crosses by
natural introgression are very unlikely.
Cucurbita (pumpkin) is one of the under utilised crops and its existence is presently being
threatened due to neglect. In Africa, pumpkin is viewed as a traditional food crop and, thus
has not benefited from the same level of research efforts dedicated to other crops. Limited
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information is available on the identification and classification, the nutritional value and
chromosome number and descriptions of the Nigerian Cucurbita species. Considering the
extreme divergence of the Nigerian genotypes, this present study was initiated with the
following objectives:
i) To characterize some Nigeria Cucurbita genotypes with respect to their
morphology and nutrient composition.
ii) To determine the chromosomal architecture of Cucurbita species.
iii) To provide a clue as to the relationship that exists among the various Cucurbita
forms.
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