Intriguing taxonomic case of Pratylenchus vandenbergae : recognition as a separate species and its significant impact on various crops

Abstract

The genus Pratylenchus encompasses a diverse group of nematodes with significant implications in Agriculture. Only 24 Pratylenchus spp. have been reported in Africa to date. However, cryptic biodiversity within the genus Pratylenchus exists, suggesting actual diversity of Pratylenchus nematodes maybe underestimated. Undescribed and cryptic species could complicate nematode management strategies, quarantine, biodiversity conservation and food security efforts. Because Pratylenchus spp. vary in pathogenicity and reproduction, accurate characterization is essential in agriculture and could have implications on crop production. Fig. 4 BOF Fig 3 Bayesian inference phylogenetic relationships within the genus Pratylenchus of Clade VI (Subbotin et al., 2008; Troccoli et al., 2016) generated from the A) 18S rDNA and D2-D3 of 28S rDNA and B) ITS rDNA gene sequences. New sequences of Pratylenchus vandenbergae stat. nov. are indicated in bold. A Phylogenetic analysis A B Fig. 3 Table 1. Comparison of Pratylenchus vandenbergae stat. nov. with morphologically similar species Morphological comparisons In conclusion, pathogenicity studies, host susceptibility and life cycle studies show that Pratylenchus vandenbergae stat. nov. is an important agricultural pest with a wide distribution and this study provides a comprehensive understanding of its interactions with various hosts. This underscores the need for improved surveillance and management strategies of this nematode to curb further spread. Morphological analysis Fig. 1 Pratylenchus vandenbergae stat. nov. lindrawings. (a, b) Female anterior region, (c) en face view, (d) entire body of female, (e–g) variation in lateral lines (e, juvenile mid-body; f, g vulva region), (h–k) variation in tail shape. Fig.2 Light and scanning electron microscopy (SEM) photographs of Pratylenchus vandenbergae stat. nov. (a–d) Female anterior and pharyngeal regions, (e–g) SEM images of female head region, (h) female reproductive system, (i) entire female and juvenile body, (j) lateral field in female mid-body, (k) vulva region, (l, m) SEM images of female vulva region, (n–r) variation in tail shape and tail tip of female, (s–u) SEM images of female tail. Pratylenchus vandenbergae stat. nov., previously misidentified as P. bolivianus due to sequence similarities despite molecular and morphological differences Pathogenicity and Lifecycle Table 3. Reproductive potential and susceptibility index of various crops to Pratylenchus vandenbergae stat. nov. Fig. 6 Pratylenchus vandenbergae stat. nov. exihibits a life cycle of similar length to Pratylenchus penetrans in carrot discs, but demonstrates considerably greater reproduction Fig. 5 Acid fuchsin-staining revealed the presence of Pratylenchus vandenbergae stat. nov. within the roots of OKHALE-1 and KNE1034 finger millet genotypes Fig. 4. Pratylenchus vandenbergae stat. nov considerably reduced shoot and root weight in OKHALE-1 but not KNE1034 Pratylenchus populations were isolated from finger millet in Kenya and from maize, potato, tomato and soybean from South Africa. Based on light microscopy and sequences of D2-D3 of 28S rDNA and internal transcribed spacer (ITS) of rDNA, these populations were found to be conspecific and molecularly identical to P. teres teres, and to P. teres vandenbergae based on sequences of D2-D3 of 28S rDNA and the heat shock protein Hsp90. However, due to discernible morphological differences compared to the original description of P. teres and their distinct geographical distribution, Pratylenchus vandenbergae stat. nov. is recognized as a separate species.