Genetic relationships in Saccharum complex germplasm collections based on morphological and molecular markers

and is a cross-pollinator, so information about the genetic relationship between the accessions in germplasm collections is very important for selecting the prospective parent in crossbreeding. This research aims to determine the phylogenetic relationship of 24 Saccharum complex accessions and to verify the grouping of accessions using 37 morphological and three microsatellite molecular markers. Interpretation of morphological and molecular data was obtained from the analysis using the NTYSYpc-2.02i program. The results show that within the 24 accessions analyzed using morphological markers, some accessions did not cluster as the classification at the conservation time. This difference is due to the morphological markers, descriptions of characters that do not appear are considered as the same variables though in different morphological characters, so this increases the value of genetic similarity among accessions analyzed. In contrast, the grouping of molecular markers shows that each accession was grouped according to the classification at the conservation time. These accessions had a low genetic similarity of 0.20 with a broad genetic distance of 0.80. This broad genetic distance indicates that the twenty-four accessions have a distant genetic relationship with one another, so that the genetic diversity of these accessions is relatively high. The high genetic diversity in germplasm collections improves its potential as a crossing parent to obtain a high heterosis effect.

Characterization and gas exchange in accessions of Saccharum complex under salinity in the Sub-middle São Francisco, Brazil

ABSTRACT Salinity is one of the factors that most limit agricultural yield in the Brazilian semi-arid region. In this context, the present study aimed to evaluate the leaf gas exchange and biometric characteristics of accessions of the Saccharum complex subjected to salt stress. The experiment was carried out in a greenhouse, installed at Embrapa Semiárido, in Petrolina, PE, Brazil. The experimental design was in randomized blocks, with the treatments represented by 19 accessions belonging to different genera/species, being 10 accessions of Saccharum officinarum (BGCN 6, BGCN 91, BGCN 104, BGCN 127, BCGN 90, BGCN 101, BGCN 102, BGCN 118, BGCN 125 and BGCN 122), two accessions of Saccharum spp. (BGCN 87 and BGCN 89), one accession of Saccharum hybridum (BGCN 88), one accession of Saccharum robustum (BGCN 94), four accessions of Erianthus arundinaceus (BGCN 117, BGCN 119, BGCN 120 and BGCN 123) and one accession of Miscanthus spp., with three repetitions. Biometric characteristics, chlorophyll index and leaf gas exchange of the accessions were evaluated when they were subjected to irrigation with salinized water (6.0 dS m-1). E. arundinaceus accessions (BGCN 120 and BGCN 123) showed the highest photosynthetic rate, transpiration rate, plant height and leaf length, indicating greater adaptability to salt stress and could be promising in breeding programs.

A new combination in the genus Tripidium (Poaceae: Andropogoneae)

The genus Tripidium Scholz in Valdés & Scholz (2006: 664) (Poaceae: Andropogoneae) currently includes six species, distributed in Asia, southern Europe, and northern Africa, with the greatest diversity in India (Welker et al. 2019). The species of Tripidium have traditionally been treated as part of the “Saccharum complex”, formed by sugarcane [S. officinarum Linnaeus (1753a: 54)] and relatives, being included either in the genus Saccharum Linnaeus (1753a: 54) (e.g., Clayton & Renvoize 1986, Shouliang & Phillips 2006) or in Erianthus Michaux (1803: 54) (e.g., Mukherjee 1958, Besse et al. 1997). However, recent nuclear and plastome phylogenies (Welker et al. 2015, 2019, Lloyd Evans et al. 2019, Welker et al. in press) have unequivocally demonstrated that Tripidium belongs to a different lineage from sugarcane and relatives and thus should be accepted as a genus distinct from Saccharum or Erianthus. According to the plastome phylogeny of Welker et al. (in press), Tripidium is sister to the newly circumscribed subtribe Rottboelliinae, which comprises the genera Rottboellia Naezén (1779: 23) s.str. and Coix Linnaeus (1753b: 972).

On the Validity of the Saccharum Complex and the Saccharinae Subtribe: A Re-assesment

The ‘Saccharum Complex’ represents an hypothetical collective of species that were supposedly responsible, through interbreeding, for the origins of sugarcane. Though recent phylogenetic studies have cast doubt on the veracity of this hypothesis, it has cast a long shadow over the taxonomics of the Andropogoneae and the Saccharinae subtribe. Though evidence suggests that Saccharum s.s. is comprised of only three true species, according to Kew’s GrassBase there are as many as 34 species in Saccharum s.l. Our recent work has shown that many of these species are millions of years divergent from Saccharum. As the Saccharum complex represents the species that sugarcane breeders attempt to introgress into sugarcane, and as the Saccharinae, in its current form, covers almst 12 million years of Andropogoneae evolution an update on the extents of the Taxonomic and customary groupings is much needed. Based on the latest sequence based phylogenies and the inclusion of traditional taxonomics we develop an integrated view of the Saccharinae + Saccharum complex species in the context of the major groupings within the Andropogoneae. We use this phylogeny to re-circumscribe the limits of both the Saccharinae subtribe and the Saccharum complex group of interbreeding species.

The endemic ‘sugar canes’ of Madagascar (Poaceae, Saccharinae: Lasiorhachis) are close relatives of sorghum

Crop wild relatives are important but often poorly known. This is the case for subtribe Saccharinae (Poaceae: Andropogoneae), which includes sugarcane (Saccharum) and sorghum (Sorghum). We present a phylogenetic and taxonomic account of the Malagasy endemic genus Lasiorhachis, previously included in Saccharum. New plastome and nuclear sequences were assembled from genome skimming data. Phylogenetic analyses of whole plastomes place Lasiorhachis as sister to Sorghum and only distantly related to the interbreeding Saccharum complex. This is also supported by analyses of nuclear ITS and partial assemblies for eight low-copy regions. Some nuclear regions suggest that Lasiorhachis is closer to Sorghum section Sorghum than other Sorghum spp. sometimes segregated as Vacoparis. We present a full taxonomic treatment of Lasiorhachis with an identification key, synonymy, typification, descriptions, drawings and a distribution map of the three species, all endemic to the central highlands of Madagascar. Lasiorhachis species occupy contrasting ecological niches and at least one of them, L. viguieri, has significance for ecosystem function. As crop wild relatives of sorghum, Lasiorhachis species should be included in germplasm collections.