Search

The flat mite Dolichotetranychus australianus (Womersley, 1943) – a significant pest of Cynodon turfgrasses in Australia and Africa – is redescribed on the basis of new Australian material collected from C. dactylon (bermudagrass, green couchgrass) and its hybrid C. dactylon × transvaalensis. All active life stages are described, leg chaetotaxy is provided, anomalous features are noted and the specimens compared with type material. The species is widespread in Queensland and is probably present anywhere that C. dactylon is grown in Australia, as indicated from its presence in other states. Photographs of its colonies and damage to turfgrass are presented, and damage symptoms are compared with similar damage caused by Aceria cynodoniensis (Trombidiformes: Eriophyidae). Dolichotetranychus summers Pritchard and Baker, 1952 known from C. dactylon in California, is redescribed from type material and confirmed as a species distinct from D. australianus, with both sexes of D. summersi lacking genital set...

Identification of the five noxious weedy Sporobolus species from non-weedy and native species in Australia is extremely difficult. Furthermore, seeds of these species, which are found in commercial seed lots, are morphologically indistinguishable. The lack of a reliable identification protocol is contributing to the rapid spread of these noxious weedy species within Australia. A polymerase chain reaction-restriction fragment length polymorphism approach carried out on nuclear ribosomal DNA (rDNA) internal transcribed spacer (ITS) sequences was used to create a molecular diagnostic tool. To develop this tool, 40 ITS sequences generated from 14 Sporobolus species were used. A restriction enzyme (MvnI) was identified which could cut the ITS sequences from the noxious weedy species into two approximately equal fragments, while not cutting those from all other species. When tested on 23 randomly selected seed samples, identification was accomplished with 100% accuracy, suggesting a possible application in seed certification programmes. © 2010 The Authors. Weed Research

Available evidence suggests that there are at least two locations for dormancy mechanisms in primary dormant seeds: mechanisms based within the embryo covering structures, and mechanisms based within the embryo. Mechanisms within the covering structures may involve mechanical, permeability and chemical barriers to germination. Mechanisms within the embryo may involve the expression of certain genes, levels of certain plant growth regulators, the activity of important respiratory pathways or the mobilisation and utilisation of food reserves. In addition, some embryos may be too immature to germinate immediately and must undergo a further growth phase before germination is possible. An individual species could have one or several of these various dormancy mechanisms and these mechanisms need to be understood when selecting treatments to overcome dormancy. The way in which certain dormancy breaking agents are thought to work is discussed and practical applications of such agents in field situations are explained.

A new species of tarsonemid mite, Steneotarsonemus hippodromus sp. nov., is described from kikuyu grass Pennisetum clandestinum (Poaceae). The new species is the fifth species of the subgenus Steneotarsonemoides. Keys to the subgenera of Steneotarsonemus and species of Steneotarsonemoides are provided, as is a list of species in each subgenus of Steneotarsonemus.

Based on morphological features alone, there is considerable difficulty in identifying the 5 most economically damaging weed species of Sporobolus [viz. S. pyramidalis P. Beauv., S. natalensis (Steud.) Dur and Schinz, S. fertilis (Steud.) Clayton, S. africanus (Poir.) Robyns and Tourney, and S. jacquemontii Kunth.] found in Australia. A polymerase chain reaction (PCR)-based random amplified of polymorphic DNA (RAPD) technique was used to create a series of genetic markers that could positively identify the 5 major weeds from the other less damaging weedy and native Sporobolus species. In the initial RAPD profiling experiment, using arbitrarily selected primers and involving 12 species of Sporobolus, 12 genetic markers were found that, when used in combination, could consistently identify the 5 weedy species from all others. Of these 12 markers, the most diagnostic were UBC51490 for S. pyramidalis and S. natalensis; UBC43310, 2000, 2100 for S. fertilis and S. africanus; and OPA20850 and UBC43470 for S. jacquemontii. Species-specific markers could be found only for S. jacquemontii. In an effort to understand why there was difficulty in obtaining species-specific markers for some of the weedy species, a RAPD data matrix was created using 40 RAPD products. These 40 products amplified by 6 random primers from 45 individuals belonging to 12 species, were then subjected to numerical taxonomy and multivariate system (NTSYS pc version 1.70) analysis. The RAPD similarity matrix generated from the analysis indicated that S. pyramidalis was genetically more similar to S. natalensis than to other species of the ‘S. indicus complex’. Similarly, S. jacquemontii was more similar to S. pyramidalis, and S. fertilis was more similar to S. africanus than to other species of the complex. Sporobolus pyramidalis, S. jacquemontii, S. africanus, and S. creber exhibited a low within-species genetic diversity, whereas high genetic diversity was observed within S. natalensis, S. fertilis, S. sessilis, S. elongates, and S. laxus. Cluster analysis placed all of the introduced species (major and minor weedy species) into one major cluster, with S. pyramidalis and S. natalensis in one distinct subcluster and S. fertilis and S. africanus in another. The native species formed separate clusters in the phenograms. The close genetic similarity of S. pyramidalis to S. natalensis, and S. fertilis to S. africanus may explain the difficulty in obtaining RAPD species-specific markers. The importance of these results will be within the Australian dairy and beef industries and will aid in the development of integrated management strategy for these weeds.

The entire internal transcribed spacer (ITS) region, including the 5.8S subunit of the nuclear ribosomal DNA (rDNA), was sequenced by direct double-stranded sequencing of polymerase chain reaction (PCR) amplified fragments. The study included 40 Sporobolus (Family Poaceae, subfamily Chloridoideae) seed collections from 14 putative species (all 11 species from the S. indicus complex and three Australian native species). These sequences, along with those from two out-group species [Pennisetum alopecuroides (L.) Spreng. and Heteropogon contortus (L.) P. Beauv. ex Roemer & Schultes, Poaceae, subfamily Panicoideae], were analysed by the parsimony method (PAUP; version 4.0b4a) to infer phylogenetic relationships among these species. The length of the ITS1, 5.8S subunit and ITS2 region were 222, 164 and 218 base pairs (bp), respectively, in all species of the S. indicus complex, except for the ITS2 region of S. diandrus P.Beauv. individuals, which was 217 bp long. Of the 624 characters included in the analysis, 245 (39.3%) of the 330 variable sites contained potential phylogenetic information. Differences in sequences among the members of the S. pyramidalis P.Beauv., S. natalensis (Steud.) Dur & Schinz and S. jacquemontii Kunth. collections were 0%, while differences ranged from 0 to 2% between these and other species of the complex. Similarly, differences in sequences among collections of S. laxus B.K.Simon, S. sessilis B.K.Simon, S. elongatus R.Br. and S. creber De Nardi were 0%, compared with differences of 1–2% between these four species and the rest of the complex. When comparing S. fertilis (Steud.) Clayton and S. africanus (Poir.) Robyns & Tourney, differences between collections ranged from 0 to 1%. Parsimony analysis grouped all 11 species of the S.�indicus complex together, indicating a monophyletic origin. For the entire data set, pair-wise distances among members of the S. indicus complex varied from 0.00 to 1.58%, compared with a range of 20.08–21.44% among species in the complex and the Australian native species studied. A strict consensus phylogenetic tree separated 11 species of the S. indicus complex into five major clades. The phylogeny, based on ITS sequences, was found to be congruent with an earlier study on the taxonomic relationship of the weedy Sporobolus grasses revealed from random amplified polymorphic DNA (RAPD). However, this cladistic analysis of the complex was not in agreement with that created on past morphological analyses and therefore gives a new insight into the phylogeny of the S.�indicus complex.