Two new annual weeds in Morocco: Amaranthus palmeri and Chenopodium ficifolium subsp. ficifolium ( Amaranthaceae )

Tanji, A.: Two new annual weeds in Morocco: Amaranthus palmeri and Chenopodium ficifoli-um subsp . ficifolium ( Amaranthaceae ). — Fl. Medit. 33: 91-99. 2023. — ISSN: 1120-4052 printed, 2240-4538 online. During recent field surveys with special emphasis on the weeds occurring in Moroccan farm-lands and gardens, two new weed species were discovered for the first time in the country. Amaranthus palmeri plants have been collected in October 2020 along streets in Rabat and in a corn field in Tit Mellil (East of Casablanca), it is to be considered naturalized in Morocco. Chenopodium ficifolium subsp. ficifolium plants have been observed in a public garden in February 2022 in Berrechid, it is to be considered casual alien in Morocco. These reports indicate that Morocco needs more thorough botanical explorations especially in urban areas and agroecosystems. Both species enrich the Amaranthaceae of the country, but could be a threat to biodiversity, sustainable agriculture, food security, and human livelihoods.


Introduction
In Morocco, there are nearly 200 introduced weed taxa, involuntarily brought by humans or by other means such as rivers, winds, birds, etc… (Fennane & al. 2023).Exotic plants coming into areas outside their natural range threaten biodiversity and pose a huge global threat to sustainable agriculture, food security, and human livelihoods (see e. g.Lambdon & al. 2008; Early & al. 2016; Gervilla & al. 2019; Arianoutsou & al. 2021).Furthermore, their spread and impact is growing due to climate change, globalisation, trade, and tourism.

Distribution and ecology in Morocco
Several plants of A. palmeri have been found on October 2, 2020, in Rabat and in an irrigated corn (Zea mays L.) field near Tit Mellil, East of Casablanca (33° 30′ 36′′ N, 7°9 23′ 41′′ W, 180 m altitude) (Fig. 1).They were at the flowering and fruiting stages, and stems were 2 to 3 m tall and drew my attention.They were growing in an area where daily temperatures in summer usually exceed 30 C, nightly temperatures are around 20 C, and the photoperiod is 14 hours.Palmer amaranth is therefore considered, under local climatic conditions, a summer annual weed naturalized in Morocco.

Description
Several references provided detailed descriptions of Palmer amaranth plants (Ward & al. 2013; Roberts & Florentine 2022, etc.).The plant is dioecious, erect, up to 3 m tall, with a deep taproot system.Stems are reddish-green, highly branched.Leaves are alternate, obovate (1.5-7 × 1-3 cm), with entire margins, glabrous, petioled, some with a whitish Vshaped central spot.The synflorescence is structured as erect linear spikes (up to 60 cm) along with several small clusters of flowers (2 to 4 mm).Bracts of pistillate flowers are 4-6 mm, longer than tepals.Bracts of staminate flowers are 4 mm long, equaling or longer than outer tepals.Tepals of pistillate flowers are 1.7-3.8mm, acuminate, mucronulate.Tepals of staminate flowers are unequal, 2-4 mm, apex acute.Inner tepals have prominent midribs excurrent as rigid spines.Utricles are tan to brown, obovoid to subglobose, 1.5-2 mm, shorter than tepals.Fruits are obovoid, small (about 1.5 mm diameter), with thin walls and containing a single small (about 1 mm diameter) dark-red to brown seed.

Chorology
Native to the North American Southwest (from southern California to Texas) and northern Mexico, alien, often invasive in North America as well as in South America and other continents (see e.

Notes
Amaranthus palmeri is an herb with C4 photosynthetic pathway which translates into a very fast-growing, competitive weed that can grow 0.18-0.21cm per growing degree day (Horak & Loughin 2000).Palmer amaranth interference reduced dry edible bean yield by 77% at a weed density of 2 plants m -1 row compared to the weed-free control (Miranda & al. 2021).Each plant is able to produce 200,000 to 600,000 seeds when growing without plant competition (Keeley & al. 1987).It is among the most troublesome and economically important weed species as a result of its high genetic diversity, a deep root system, rapid growth rate, high fecundity, high competitiveness, high water use efficiency, tolerance to high temperatures and drought, and ability to develop herbicide resistance (Ward & al. 2013; Leon & Van Der Laat 2021; Roberts & Florentine 2021; Milani & al. 2021).Menges (1987Menges ( & 1988) ) reported inhibition of crop growth resulting from Palmer amaranth's allelopathic properties.Considering the potential economic impact of this species, the EPPO Panel on Invasive Alien Plants suggested its addition to the EPPO Alert List (EPPO 2023).Palmer amaranth possesses toxic properties including high concentrations of nitrates and oxalates that are harmful to livestock (Yu & al. 2021).

Distribution and ecology in Morocco
In Morocco, two plants of Chenopodium ficifolium subsp.ficifolium were found for the first time on February 12, 2022, in a public garden in Berrechid, 20 km South of Casablanca (33° 15′ 33′′ N, 7° 34′ 53′′ W, 220 m altitude) (Fig. 2).Both plants were at the vegetative stage.They were removed, planted in a pot, and kept outdoors at home until maturity.In February, daily temperatures are usually 20 to 25 C, nighlty temperatures are 10 to 15 C, and the photoperiod is 12 hours.Figleaved goosefoot is therefore considered a fall/winter annual plant (Fig. 2).It is a new weed, and is to be considered as a casual alien.
Various compounds were isolated from Chenopodium ficifolium plants (Gohar & al. 2002).Furthermore, Le Dang & al. (2010) found that extracts of C. ficifolium have insecticidal properties for controlling Aphis gossypii infesting cucumber plants.Subedi & al. (2021) reported that C. ficifolium is a potential diploid model system for the genetic study of quinoa.
Two subspecies are usually recognized within Chenopodium ficifolium: subsp.ficifolium and subsp.blomianum (Clemants & Mosyakin 2003).These subspecies are distinguished mainly by their pericarp, seed testa sculpture, and leaf shape (Mosyakin 2016).The subsp.blomianum occurs in southern and southeastern Asia as well as in the USA, and differs from C. ficifolium subsp.ficifolium in having leaves with spreading basal lobes almost perpendicular to the central lobe and seeds with shallow elongate depressions (Mosyakin 2016).Clemants & Mosyakin (2003) reported that in Europe C. ficifolium occasionally hybridizes with other species, including C. album.

Conclusion
Two new aliens belonging to Amaranthaceae s. lat.have been discovered for the first time in Morocco in human-made habitat (urban areas and agroecosystems).They were probably introduced into the country by tourists, imported animals, crop seed, vehicles, or machinery.These newly introduced weed species indicate that the country needs more thorough botanical explorations.They inevitably enrich the Flora of Morocco, but pose a huge global threat to biodiversity, sustainable agriculture, food security, and human livelihoods.In fact, Amaranthus palmeri and Chenopodium ficifolium subsp.ficifolium have the capacity to become invasive weeds in agricultural systems, cities, and uncropped areas.

Fig. 1 .Fig. 2 .
Fig. 1.Amaranthus palmeri: a) distribution in the map of Morocco; b) details of the inflorescence; c) stem; d) leaves; e) habit.Photos by the author.