Weed diversity of the family Poaceae in Bangladesh Agricultural University campus and their ethnobotanical uses

A taxonomic study on the weeds of the family Poaceae growing throughout the Bangladesh Agricultural University campus was carried out to determine species diversity of grasses in the campus. A total of 81 species under 46 genera and 2 subfamilies of the family Poaceae were collected and identified; their uses in various ailments were also recorded. Out of the three subfamilies, no weed from the subfamily Bambusoideae was found. Among the genera, Digitaria, Eragrostis, Brachiaria, Panicum, Echinochloa and Sporobolus were most dominant in context to number of species with a total of 29 species. While 28 genera were represented by single species each in BAU campus; of these 15 genera were in Bangladesh as well. Some of them are major and obnoxious weeds in different crop fields including staples rice and wheat. The flowering period will be helpful for the management of respective weed population. Many of these weed species have high economical, ethnomedicinal and other uses. The phenological study of these weed taxa will be helpful in managing weeds of the family Poaceae of this campus as well as the whole country without affecting the agro-ecosystem by keeping the weed population below a threshold level.


Introduction
The family Poaceae (conserved name Gramineae), universally known as grass family, is the fifth largest plant family, following the Asteraceae, Orchidaceae, Fabaceae and Rubiaceae.It is the second most diverse family among monocotyledons (Bouchenak-khelladi et al., 2010), with 780 genera and around 12,000 species of cosmopolitan distribution (Christenhusz and Byng, 2016).They are most plentiful in tropical and northtemperate semi-arid regions with seasonal rainfall.In Bangladesh, the family is represented by 3 subfamilies viz.Bambusoideae, Panicoideae and Pooideae, with 113 genera and 285 species (Ahmed et al., 2008).All staple food and cereals like rice, wheat, corn, etc. is from this family.These grasses provide a vegetative cover, feed/fodder for animals, controls nutrient cycling, adds organic matter, acts as a soil binder, serves as an important source of genetic materials for crop improvement and used in the beautification of the landscapes.On the other hand, about 25% weeds of the world are monocotyledonous (Bryson and Carter, 2008); and grasses are one of the most troublesome and difficult group to control (Lym and Travnicek, 2015) because of their highly adaptive mechanisms and allelopathic properties (Noor et al., 2012).They sometimes act as an alternative host of different diseases and pests in the absence of main crops.The outbreak of diseases occurs again when the relevant agricultural crops are cultivated in the field.Thereby, the cost of production is increased and the quality of the products is reduced.Bangladesh Agricultural University (BAU) is the largest university in Bangladesh and it covers about 486 hectares of land.It is situated in the Mymensingh division under the Old Brahmaputra Floodplain, Agroecological zone 9, of Bangladesh (UNDP, 1988).Three major topographic types like plain area, slightly undulated area and basin-shaped low lying area are present in the BAU campus which facilitates a wide range of habitats such as wetlands, marshy lands, open fields, bare lands, etc. (Sarwar and Prodhan, 2011;Jannat-E-Tajkia et al., 2018).The soil category of the region varies from clay, clay loam to sandy loam (UNDP, 1988).The mean annual rainfall is 244.15 mm and the temperature varies from 11.9º to 32.5º C. The weather of this campus is not characterized by large extremes of heat, cold and rainfall.The winter period (November-December) is cool and almost rainless; whereas the summer season (June-October) is hot and humid, and during summer 90% or more of the whole rain occurs.This diverse climatic condition provides a suitable condition for the growth of grasses in the BAU campus.
In Bangladesh, the detailed taxonomic studies of weeds have been neglected by both the practising plant taxonomists and/or the agricultural scientists.Despite

ARTICLE INFO
the plenty of grasses in BAU campus, no momentous taxonomic study on grasses of this region has been made in the current years but only weeds of different specific crops were studied (Shabi et al., 2018).Some studies were carried out on the occurrences of sedges in the BAU campus (Sarwar and Prodhan, 2011;Jannat-E-Tajkia et al., 2018), but the species diversity of grasses in the campus was not conducted.Therefore, the current survey aimed at making an intensive taxonomic study of the weeds of Poaceae family in the BAU campus including their habitat, flowering period, ethnobotanical uses and economic importance; which may be useful for the green management practices and for getting higher economic benefits.

Materials and Methods
A rigorous field survey was carried out of the weeds of Poaceae family grown in BAU campus during 2015 to 2016.During the survey, fresh flowering samples were collected through the year round by frequent field visits (once a week).Other related information e.g., habitat, location, date, flowering time, crop/plant association, etc. were recorded during the field collection and by searching from published literature and online resources.Fresh samples were dried well for making voucher specimens.The collected fresh or dried specimens were identified by matching with herbarium specimens or published literature or consulting with experienced taxonomist at the Bangladesh National Herbarium, Dhaka.All the specimens are preserved in Prof. Dr. Arshad Ali Herbarium at the Botanical Garden, Department of Crop Botany, Bangladesh Agricultural University.The information related to use were collected from the published literature (Ahmed et al., 2008;Sarwar and Prodhan, 2011).

Results and Discussion
A sum of 81 grass weed species under 46 genera and 2 sub-families of the family Poaceae were found in BAU campus (Table 1).The subfamily Panicoideae was represented by 31 genera and the subfamily Pooideae by 15 genera.Though crops from the subfamily Bambusoideae were present in the campus, weeds from this group were not found (Fig. 1) due to the limited selection of crops for the cultivation.Among the 46 genera, the most dominant 6 genera were Digitaria with 9 species, followed by Brachiaria (5), Panicum (3), and Echinochloa (3) which are from the subfamily Panicoideae and Eragrostis (6) and Sporobolus (3) are from the subfamily Pooideae.Moreover, these six genera together account for 29 species (35.8%) out of 81 weed species of this family in the BAU campus (Table 1).Again 28 genera were represented by single species each in BAU campus; of which 15 genera are represented by single species in Bangladesh as well.They are Axonopus, Dimera, Erianthus, Heteropogon, Ichnanthus, Imperata, Ottochloa, Pseudechinolaena, Urochloa, Zoysia, Aeluropus, Dactyloctenium, Elytrophorus, Hygroryza and Leersia (Ahmed et al., 2008; Table 1).The first nine of them were from Panicoideae and the rest were from the subfamily Pooideae.
The findings of this study revealed that some of these weeds are very common and major weeds in the rice, wheat, jute and other crop fields (Table 1; Bor, 1960;Gilliland, 1971).The most important grass weeds of Poaceae family in terms of their adverse effect on agriculture include Cynodon dactylon, Echinochloa crus-galli, E. colona, Eleusine indica, Imperata cylindrica, ranking 2 nd , 3 rd , 4 th , 5 th , and 7 th among the world's worst weeds, respectively (Holm et al., 1977;USDA, 2012).Some of them are very common weeds in garden crops like Digitaria sanguinalis, Pennisetum glaucum, etc.All of them are present in BAU campus (Table 1).
The ethnomedicinal and other uses of weeds from Poaceae family are much diversified (Table 1; Fig. 2) and also recorded in different ethnobotanical references (Uddin, 2006;Ahmed et. al., 2008).Some of them are very palatable fodder for cows, buffaloes, elephants, etc.Many of them are good soil binder and used as raw materials for paper industry, to decorate and soil binder for lawn and turf (Table 1).They have also a great medicinal use.Some of them are tonic for bone fracture, rat bite, bellyache after child birth, internal hemorrhage, convulsion, constipation, cardiac and liver diseases, etc. (Table 1; Fig. 3).
The proper management activities for weedy grasses are diverse.Cultural methods such as roguing, hoeing, tillage, different mulches or cover crop, draft ploughing, etc. are still used in the world to manage weeds including grasses and sedges (Shear, 1985).But, a cultural method of control such as mowing alone will not successfully manage certain perennial grass weeds rather it can prevent seed production if mowing intervals are shorter than the time necessary to set fertile spikelets (Shear, 1985).Therefore, it is necessary to know flowering periods to control the grass weeds.The phenologies were recorded here could be used to control them and these showed a wide variation (Table 1).Therefore, the grass weed populations can be managed below the critical level if proper steps can be taken before flowering.Therefore, the judicious and improved cropping pattern should be developed for additional high economic return from grass weeds of the family Poaceae without hampering our agro-ecosystem and crop yield as well.Fodder (Gilliland, 1971) 2 Acroceras zizanioides (Kunth) Dandy − Oat grass June-October Roadside, in or around watermarshy land, shady area etc.
Crab grass, Goose grass, Crowfoot grass June-August Dry and wetlands, lawns, vegetable gardens, roadsides, wastelands and lowlands Weed, Fodder with cyanogenetic effect but used at young (Bor, 1960) Poaceae grasses in BAU and their uses Fodder (Bor, 1960) Oplismenus compositus (L.) P.Beauv Bashawa, Gohur Bamboo leaf grass August-September Undergrowth in tree plants and other shady places
The flowering period of these weeds will be helpful for the management of weed population.A good number of these weeds have various economic, ethnomedicinal and other uses.Many of them are good fodder, soil binder, used as lawn and turf grass and have high medicinal value.The knowledge generated from the present research would be helpful for the management practices of grass weeds as well as for getting high economic benefits from beneficial species.

Fig. 1 .
Fig. 1.Subfamilial distribution of genera of the family Poaceae from the BAU campus