The place of cucumber (Cucumis sativus L.) in Africa was considered insignificant for years due to its previously assumed limited uses. However, it has now gained recognition as one of the important market vegetables in the tropics because of the continued awareness of the numerous health benefits attached to its consumption. This has progressively affected its cultivation and thereby, increased outbreak of diseases and insect pests of the crop. High incidence of insect and disease infestations occur in Cucumis sativus L. due to extreme temperatures, heavy rainfall and high humid condition resulting there from, causing huge losses through reduction in yield, lowered quality of harvested produce and increased cost of production. More than 30 pests and diseases are known to contribute to the losses recorded on the crop in Africa, some of which will be discussed in this chapter.

Ocimum species have a combination of reproductive system which varies with the locality and cultivar. We have studied here the reproductive mechanisms of five variants of three Ocimum species in Nigeria, namely: Ocimum canum Sims., O. basilicum L., and O. americanum L. Flowers from each variant were subjected to open and bagged pollination treatments of hand self-pollination, spontaneous self-pollination and emasculation. All open treatments of the five Ocimum variants produced more fruit and seed than the corresponding bagged treatments. The two O. canum variants and O. basilicum ‘b1’ produced high fruit and seed set in the open and bagged treatments of spontaneous self-pollination. Ocimum basilicum ‘b2’ and O. americanum produced higher fruit and seed set in the self-pollination open treatment but significantly lower fruit and seed set in the bagged treatment. Fewer fruit and seeds were produced in the emasculated open treatments but none in the emasculated bagged treatments of the five Ocimum variants. The floral foragers comprising of bees, wasps and butterflies visited the Ocimum species to collect pollen or nectar in the open treatments. The two O. canum variants and O. basilicum ‘b1’ variant reproduced mainly through autogamy but O. basilicum ‘b2’ and O. americanum showed mixed reproduction of autogamy and outcrosssing. Insect visitation to the flowers enhanced pollination resulting in higher fruit and seed set in all the Ocimum species studied.

The genus Ocimum maintains rich diversity of species through natural and artificial outcrossing. Africa is named as one of the epicentres of plant diversity including numerous Ocimum species. Cytological evidence has attributed such diversity to extensive genome augmentation through selection, speciation, polyploidy and hybridization. This study identified polyploidy as the major natural phenomenon that drives successful hybridization programs or otherwise, within and among four Ocimum species studied and showed rate of gene exchange among the concerned species. All Ocimum species and variants used were grown for two generations before hybridization experiments were carried out. Interspecific and intraspecific reciprocal crossing was done. The crossed flowers were monitored for flower abortion and fruit formation. The resulting progenies from successful crosses were raised along with their parents and evaluated for all identifiable agronomic character differences and similarities. All viable seeds resulted from crosses involving at least one polyploid parent (tetraploids O. basilicum, O. canum and O. americanum). The intra- and interspecific hybridization programs recorded success within O. basilicum and between O. basilicum and tetraploid O. canum. Hybridization within O. canum was difficult due to differences in ploidy levels of O. canum parents used. Hybrid progenies obtained within O. basilicum parents (b1 and b2) and between b2 and tetraploid O. canum possessed morphological characters related to b2 parent while offspring from crosses between b1 and c1 combined characters from both parents. Pollen fertility in both O. basilicum and O. canum parents and their reciprocal crosses was more than 50 percent. O. basilicum displayed higher gene exchange capacity than other species. O. kilimandscharicum and O. americanum parents exhibited allopatric behaviour and low crossability with other seemingly sympatric species used in the study. Genome imbalance and incompatibility were associated with some of the possible causes of sterility.

Senna Mill. is a complex plant group known to have underlying biological ambiguity, due to the high similarity that exists among its morphological attributes consequently making identification of closely related species very difficult. Considering the medicinal and nutritional values of some members of this genus, it is therefore important to employ a reliable and robust technique to delimit the members of this plant group. The present study employed morphological characters, chromosome counts and matK and rbcL primer markers to delimit and elucidate the phylogenetic relationship that exists among the seven Senna species from Ile-Ife, Nigeria. The cluster analysis of the studied morphological traits grouped S. podocarpa, S. alata and S. siamea on one hand. At the same time, the result showed that S. occidentalis, S. hirsuta, S. obstusifolia and S. sophera were closely related on the other hand. A chromosome count of x=18 was recorded in S. podocarpa and S. obstusifolia, x=20 in S. occidentalis x=22 in S. alata and S. hirsuta, and x=24 in S. siamea and S. sophera. There was a 100% yield in PCR amplification of the Senna species studied. The DNA sequences ranged from 546 to 843 base pairs and the phylogenetic tree revealed that S. podocarpa was genetically distant from the other species. Moreover, the phylogenetic tree resolution showed similarities among the Senna species studied, the Nigerian Senna and other Senna species referenced sequences obtained from NCBI. Despite similarities among these seven Senna species, they could be distinguished by the morphological attributes employed for their characterization. There is an addition of x=10 to the already known basic chromosome numbers in Senna. The chromosome numbers were greatly varied from previous counts and therefore have limitations as taxonomic tools.

Multiple sequence analysis is one of the most widely used model in estimating similarity among genotypes. In a bid to access useful information for the utilization of bush mango genetic resources, nucleotide sequences of eight bush mango (Irvingia gabonensis) cultivars were sourced for and retrieved form NCBI data base, and evaluated for diversity and similarity using computational biology approach. The highest alignment score (26.18), depicting the highest similarity, was between two pairs of sequence combinations; BM07:BM58 and BM12:BM69 respectively, while the least score (19.43) was between BM01: BM13. The phylogenetic tree broadly divided the cultivars into four distinct groups; BM07, BM58 (cluster one), BM01 (cluster 2), BM15, BM13 and BM35 (cluster 3), and BM12, BM69 (cluster 4), while the sequences obtained from the analysis revealed only few fully conserved regions, with the single nucleotides A, and T, which were consistent throughout the evolution. Results obtained from this study indicate that the bush mango cultivars are divergent and can be useful genetic resources for bush mango improvement through breeding.