Mistletoe presence on five tree species of Samaru area , Nigeria

The infestation of trees by mistletoe within Samaru is very high and alarming and there is little or no records on the type of mistletoe species found parasitic on tree species within this area. In order to document and know the species richness of mistletoe within this region, the study was aimed at determining the different species of mistletoe parasitic on Albizzia lebbeck, Citrus grandis, Khaya senegalensis, Terminalia mantaly and Terminalia catappa within Samaru, Nigeria. The study site was divided into four sampling areas based on the presence of the studied species, and the infection of the trees by mistletoes. In each of the sampling areas, the leaves of mistletoes found parasitic on each of these tree species were collected. The study indicated that from all the sampling areas, A. lebbeck was infected by six different species of mistletoe: Tapinanthus dodoneifolius, Tapinanthus globiferus, Globimetula braunii, Globimetula oreophila, Englerina lecardii and Tapinanthus belvisii; C. grandis, T. catappa and T. mantaly each had four different species found parasitic on them, and K. senegalensis had three different mistletoes species parasitic on it. A. lebbeck had the highest number of different mistletoe species found parasitic on it while K. senegalensis had the lowest. G. braunii and T. globiferus were the most common mistletoe species found parasitic on all the targeted host trees while T. dodoneifolius was found parasitic only on A. lebbeck and T. catappa and E. lecardii was found parasitic only on A. lebbeck and C. grandis respectively in the study area. In conclusion, among the studied tree species, A. lebbeck was the most vulnerable to mistletoe attack in the study area and G. braunii and T. globiferus were less host specific.

Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License families: Misodendronaceae, Eremolepidaceae, Santalaceae, Viscaceae and Loranthaceae (Der and Nickrent, 2008, Malecot and Nickrent, 2008, Vidal-Russell and Nickrent, 2008).The largest family of this mistletoe is Loranthaceae which has 75 genera and over 900 species (Judd et al., 2002).Among them, six major genera are found in Nigeria, namely: Tapinanthus, Agelanthus, Loranthus, Globimetula, Phragmanthera and Englerina.Tapinanthus is far more widespread in the Nigeria savanna (Johri and Bhatnagar, 1972;Omolaja and Gamaye, 1998).Mistletoe, in Yoruba speaking area in Nigeria, it is called 'afomo', in Igbo 'apari' while in Hausa it is called 'kauci' and 'children's matches' in Eastern Cameroon presumably due to the match-like shape of the flower (Oluwole et al., 2013).
All mistletoes are hemi-parasites, bearing evergreen leaves that photosynthesize but depend on their host mainly for water and mineral nutrients (Milius, 2000).These mistletoes grow on a wide range of host trees, and it may reduce their growth and eventually they can kill the trees with heavy infestation.
Seeds of most mistletoe are spread by birds that eat the fruits (Cowles, 1964) or by the wind.The mistletoe seed germinates on the branch of a host tree or shrub and in its early stages of development it is independent of its host.Later it forms a haustorium that penetrates the host tissue and takes water and nutrients from the host plant (Milius, 2000).
Many of these parasitic plants (mistletoes) can simultaneously parasitize many host species.Since different host species may supply a parasite with different resources, a mixture of host species may be superior to a single host alone.Boussium et al. (2004) reported that mistletoe (T.globiferus) parasitized 126 species, and believed that it is less specific compared to other mistletoe species.Despite the large host range of the majority of parasitic plants, many also show high levels of host preference.In mistletoe plants, host choice can be considerably influenced with relatively abundant hosts (Norton and Carpenter, 1998;Norton and De Lange, 1999), host characteristics such as branch size, age and height and the duration of association between the host and the parasite (Didier et al., 2009).
It has been observed that in Samaru, the infestation of trees by mistletoe is very high and generates great concern in the local people as these mistletoes result in the reduction of vegetation and fruit production of trees in the region.Also, there is little or no records on the type of mistletoe species found parasitic on tree species within this area.As such, in order to document the number of mistletoe species and record the rate of infestation of trees in this region, this study is aimed at determining the presence of different mistletoe species on some selected trees with medicinal importance within Samaru (Zaria, Nigeria).

Collection of mistletoes
In each of the sampling areas, three separate plants of each of A. lebbeck, C. grandis, K. senegalensis, T. mantaly and T. catappa were randomly chosen based on the heavy infestation of their branches with different species of mistletoe and fresh leaves of the mistletoes found parasitic on it were collected.The samples were taken to the herbarium unit of the Department of Biological Sciences, Ahmadu Bello University (Zaria) for further identification.

Counting of host plants
Each of the sampling areas was according to its size divided into clusters.Sampling areas A, BZ, DAC and ABU main campus were divided into 34, 27, 20 and 40 clusters respectively and each cluster was 200 m in size.And the number of A. lebbeck, C. grandis, K. senegalensis, T. mantaly and T. catappa within each of the clusters was noted, taking note of those infected and uninfected by mistletoes.

Infestation of trees by mistletoe
The results revealed that, all the selected tree species were infected in virtually all the sampling areas and there was significant relationship between the infected and uninfected tree species in all areas except T. catappa which had insignificant relationship between its infected and uninfected trees in all the sampling areas at P<0.05 (Table 1). A. lebbeck in sampling area A was the highest in number of trees compared to other areas.However, the A. lebbeck in area BZ had the highest percent (77.27%) of infection whereas the ones in ABU main campus had the least (45.80%) (Table 1).
K. senegalensis and C. grandis in area A, were the highest in number of trees, however, it had the least percent (29.48 and 56.41% respectively) of infection by mistletoes while those in sampling area BZ had the highest percent (57.71 and 80.00% respectively) compared to those in other areas (Table 1).ABU main campus had the highest number of T. mantaly as well as the percentage of those infected by mistletoes (61.33%) whereas in area BZ none of the T. mantaly there was infected (Table 1).
Also, ABU main campus had the highest number of T. catappa, however, area A had the least percent (25.00%) of those infected by mistletoes whereas those in area BZ had the highest percent (66.67%) of infection (Table 1).All the tree species except T. catappa, had significant relationship between the infected and uninfected in each of the sampling areas (Table 1).

Level of infestation of tree species by mistletoe
In comparison of each tree species from all sampling areas, A. lebbeck had the highest level of infestation by mistletoes (58.26%) than other tree species.However, the level of the infestation was significantly similar to those of other tree species (Table 1).

Species of mistletoe identified on the targeted host trees in area A
On A. lebbeck, four different species of mistletoe were identified, include: G. oreophila, G. braunii, T. globiferus and T. dodoneifolius.And on T. catappa were found two species of mistletoe: T. dodoneifolius and G. braunii.However, on C. grandis, K. senegalensis and T. mantaly was only found one species of mistletoe in each tree species (G.braunii, T. globiferus and G. oreophila, respectively).

Species of mistletoe identified on the targeted host trees in area BZ
In area BZ (Figure 1), two species of mistletoe were identified on A. lebbeck, known as T. belvisii and T. dodoneifolius, and on C. grandis and K. senegalensis, only G. oreophila was identified, where on T. catappa, only G. braunii was identified.T. mantaly was part of the targeted host tree before which was not found in the area (Table 2).

Mistletoe species identified on the targeted host trees in DAC
From the sampling area DAC (Figure 1), three species of mistletoe identified on A. lebbeck were E. lecardii, T. dodoneifolius and G. oreophila.However, C. grandis and T. mantaly had two species of mistletoe each (T.globiferus, E. lecardii, T. belvisii and T. globiferus, respectively).T. catappa and K. senegalensis had one species of mistletoe each, which was identified as: T. belvisii and G. oreophila, respectively (Table 2).

Mistletoe species identified on the targeted host trees in ABU main campus
In the sampling area ABU (Figure 1), three species of mistletoe (G.oreophila, T. dodoneifolius and T. belvisii) were found parasitic on A. lebbeck.On T. catappa and K. senegalensis, two species of mistletoe were found on each tree species (T.globiferus, G. braunii and G. braunii and T. globiferus respectively).Citrus grandis which was one of the targeted host tree was not found in the area (Table 2).
The summary of the observasions from all the sampling sites showed that, G. braunii and T. globiferus were the most common mistletoe species found parasitic on all the targeted host Norton and Carpenter (1998) who reported that the relatively abundance of citruses and guava in the study area influenced the host choice of mistletoe.Overton (1994) also similarly reported that the characteristics such as branch size, age, and height of a host plant can have a strong effect on mistletoe attachment resulting in size related mistletoe infection patterns.It was also observed that, out of the several species of mistletoe obtained from these five different host trees, T. globiferus and G. braunii were the most common and found parasitic on all the five host trees.This could be due to their seeds being very sticky in nature than other mistletoe seeds, thus enhances their distribution by birds and other animals (Del Rio et al., 1996;Aukema, 2004).It can also be as a result of their being less host specific compared to the other mistletoe species (Boussim et al., 2004).

Conclusions
These findings revealed that mistletoes could parasitize a variety of tree species with few of them having special preference to certain type of host plants.Factors like abundance of host plant and vulnerability (host characteristics) of the host plant could influence the parasitization of plant by mistletoe.Among the five studied tree species, A. lebbeck was the most parasitized and vulnerable to mistletoe attack in Samaru and G. braunii and T. globiferus were the most common species of mistletoe on the five host tree species.Therefore, percentage rate of infestation of A. lebbeck in the study area demands the attention of authority in that region for quick measures so as to curtail the infestation, thus, preventing it from being endangered or threatened to extinction.Further studies on mistletoe species richness and the rate of infestation of other tree species within Samaru should be encouraged so as to know the presence of other species of mistletoe not identified in this study and the tree species that could be endangered or threatened by mistletoes.
Ahmadu Bello University, Zaria for helping in identifying the plant samples.

Figure 1 .
Figure 1.Map of Samaru with the location of sampling areas.

Table 1 .
Selected host tree species in each of the sampling areas indicating number of those infected and those uninfected by mistletoes.