A morphometric study of the restinga ecotype of Anacardium occidentale (Anacardiaceae): wild coastal cashew populations from Piauí, Northeast Brazil

Abstract

The infraspecific taxonomy of wild Anacardium occidentale is little studied. We investigated whether wild populations on coastal dunes in Piauí, Brazil differed from non‐wild populations. Ten populations were sampled and twenty one morphological variables were measured. Variation within and between populations was investigated with univariate and multivariate statistics. Dune populations were mostly more similar to one another than to domesticated ones. There was significant correlation between inter‐population geographical distance and morphological dissimilarity. Classification methods showed 96.4% successful assignment to the dune category and 86% to 100% to dune populations individually, but dune and non‐dune populations overlap morphologically. Dune populations had shorter, broader leaves, shorter drupes and fewer secondary veins. Non‐dune coastal populations showed strongest similarity to dune populations. Populations distant from the coast were most divergent. The population from the cerrado region was most distinct, with thicker leaf blades and narrower petioles. The dune populations are recognised as the “restinga ecotype” of A. occidentale. Correlation of dissimilarity and distance may result from gene flow and/or non‐inherited environmental effects. Ecology and nomenclature (including the vernacular “cajuí”) of the restinga ecotype are reviewed. Further comparison of restinga populations is needed along the Brazilian coastline and with natural cerrado populations.

Physicochemical characterization of ‘Cerrado’ cashew (Anacardium othonianum Rizzini) fruits and pseudofruits

“…Initially, A. othonianum was treated as a synonym for the commercial cashew, A. occidentale 8 . Studies targeting the diversity of natural field populations like agronomic and plant breeding studies, such as Gomes et al 9 and Andrade et al, 10 have nevertheless recognized A. othonianum as a distinct species, essentially a wild Cerrado form. In general, the wild fruits of Anacardium ssp.…”

Genetic diversity in wild populations of the restinga ecotype of the cashew (Anacardium occidentale) in coastal Piauí, Brazil

“…These germplasm collections have been the basis of many studies that aimed to compare the genetic diversity of cashew accessions from different regions. Some used morphological markers (see references in Andrade et al 2019;Bionoset 2019), but genotyping with molecular markers such as isozymes, RAPDs, ISSRs, AFLP, microsatellites and ITS sequence data is now more usual, sometimes in combination with morphological descriptors; these studies have been carried out predominantly on material from India (e.g. Dhanaraj et al 2002;Rout et al 2002;Samal et al 2002;Archak et al 2003a, b;Samal et al 2003;Desai 2008;Archak et al 2009;Thimmappaiah et al 2009;Dashmohapatra et al 2014;Sethi 2015;Jena et al 2016), Brazil (e.g.…”

“…Studies have shown that in Asia and Africa cashews have a relatively narrow genetic base (Aliyu 2012;Archak et al 2009) and diversity within the natural South American range of the species would be expected to be greatest. However, the genetic and phenotypic variability of natural populations in Brazil remains poorly known as there are few such studies (Andrade et al 2019). Biosystematic investigations of A. occidentale have been hampered by difficulties in determining its species limits and the status of populations as natural, naturalised or domesticated (Johnson 1972(Johnson , 1973Mitchell and Mori 1987).…”

“…Biosystematic investigations of A. occidentale have been hampered by difficulties in determining its species limits and the status of populations as natural, naturalised or domesticated (Johnson 1972(Johnson , 1973Mitchell and Mori 1987). As regards the former, various publications have reported on plants determined as A. microcarpum Ducke or A. othonianum Rizzini (see Andrade et al 2019 for further details), which taxonomists consider conspecific with A. occidentale (Mitchell and Mori 1987;Luz et al 2019). In regard to infraspecific taxonomy, Mitchell and Mori (1987) discussed the long history of human use of A. occidentale and its transport around the globe and put forward an informal classification of this species consisting of two natural forms centred in Brazil, a cerrado ecotype occurring in the interior and a restinga ecotype along the coast, both known locally as "cajuí".…”

“…In regard to infraspecific taxonomy, Mitchell and Mori (1987) discussed the long history of human use of A. occidentale and its transport around the globe and put forward an informal classification of this species consisting of two natural forms centred in Brazil, a cerrado ecotype occurring in the interior and a restinga ecotype along the coast, both known locally as "cajuí". The coastal populations can be regarded as wild wherever they are a component of natural restinga vegetation on sandy substrates (Araujo et al 2019), including stabilised dune fields (Johnson 1972(Johnson , 1973Lima 1986;Mitchell and Mori 1987;Barros 1991;Freitas and Paxton 1998;Rufino et al 2007;Andrade et al 2019).…”