This review considers the development of herbicide-resistant weed biotypes in Australia. Biotypes of the important annual weed species, capeweed, wall barley, and hare barley are resistant to the bipyridylium herbicides paraquat and diquat. These resistant biotypes developed on a small number of alfalfa fields that have a long history of paraquat and diquat use within a distinct geographical area in central western Victoria. The resistant biotypes are controlled by alternative herbicides and pose little practical concern. Some populations of wild oat are resistant to the methyl ester of diclofop. Of greatest concern is the development of cross resistance in biotypes of rigid ryegrass to aryloxyphenoxypropionate, cyclohexanedione, sulfonylurea, and dinitroaniline herbicides. The cross-resistant rigid ryegrass infests crops and pastures at widely divergent locales throughout the cropping zones of southern Australia. The options for control of cross-resistant rigid ryegrass by herbicides are limited. A biotype of rigid ryegrass on railway tracks treated for 10 yr with amitrole plus atrazine has resistance to amitrole and atrazine and other triazine, triazinone, and phenylurea herbicides. Management tactics for cross resistance are discussed.

Three triazine-resistant biotypes of grass weeds, hood canarygrass (Phalaris paradoxa L. # PHAPA), ryegrass (Lolium rigidum Gaud.), and slender foxtail (Alopecurus myosuroides Huds. # ALOMY) were collected along roadsides on the coastal plain of Israel that had been treated repeatedly with s-triazine herbicides. Resistant biotypes (R) survived up to 4 kg ai/ha of atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] applied pre-and postemergence, while susceptible (S) biotypes were killed by 0.25 kg/ha. R and S biotypes were equally sensitive to diuron [N′-(3,4-dichlorophenyl)-N,N-dimethylurea]. Electron transport in chloroplasts isolated from R biotypes was not affected by atrazine, whereas in S biotypes electron transport was inhibited 50% by 0.4 to 1.0 μM atrazine. Chloroplasts from both biotypes were equally sensitive to diuron. These data indicate that the R biotypes have a plastidic mode of resistance to atrazine. In addition, seedlings of R biotypes exhibited resistance to triazinone herbicides. The R biotype of hood canarygrass was more tolerant to postemergence application of diclofop {(±)-2-[4-(2,4-dichlorophenoxy)phenoxy] propanoic acid}.

Sucrose[ratio ]sucrose fructosyltransferase (SST) activity was partially purified from whole shoots of Lolium rigidum by a combination of affinity chromatography, gel filtration and anion-exchange chromatography. The SST activity co-eluted with some fructan[ratio ]fructan fructosyltransferase (FFT) and invertase activities and consequently the partially purified preparation was termed the fructosyltransferase (FT) preparation.

The SST-like activity in the FT preparation was purified 214-fold and had an apparent molecular mass of 84000. The FT preparation contained several peptides with an apparent pI of 4·6–4·7. When assayed with sucrose concentrations up to 600 mM, the FT preparation synthesized 1-kestose at all concentrations, and synthesized 6-kestose at concentrations of 150 mM and greater. The Km of 1-kestose production was 0·2 M. When the FT preparation was assayed at a concentration of activity approximately half that measured in fresh tissue with 100 mM sucrose, 1-kestose, or 6G-kestose as substrates, fructans of degree of polymerization (DP) [les ]5 were synthesized.

A partially purified FFT activity, free of SST and invertase activities, which synthesized β-2,1-glycosidic linked oligofructans of DP [les ]6, was combined in vitro with the FT preparation (FFT-FT preparation) to give a ratio of SST[ratio ]FFT activities similar to that measured in crude enzyme extracts from L. rigidum. The FFT-FT preparation synthesized oligofructans when assayed with 100 mM concentrations of sucrose, 1-kestose or 6G-kestose, but was not able to synthesize fructans of DP [ges ]6 even after extended assays of up to 10 h. The FFT-FT preparation was also assayed with 100 mM sucrose with small amounts of concentrated sucrose added periodically during the assay to maintain the substrate concentration. In this assay, the FFT-FT preparation synthesized fructans up to an apparent DP of 17 or greater. The fructans of DP [ges ]6 synthesized in the assay appeared to form two molecular series containing both β-2,1- and β-2,6-glycosidic linked fructosyl residues with terminal or internal glucosyl residues. The apparent rate of SST activity in the assay of the FFT-FT preparation was greater than that measured in a similar assay of the FT preparation alone which did not result in fructans with DP [ges ]6. It was concluded that the FFT-FT preparation, when assayed with a continual supply of sucrose, contained a factor which promoted synthesis of fructans of DP [ges ]6 and synthesis of β-2,6-glycosidic linkages between fructosyl residues.

Fructan: fructan fructosyltransferase (FFT) activity was purified about 300-fold from leaves of Lolium rigidum Gaudin by a combination of affinity chromatography, gel filtration, anion exchange and isoelectric focusing. The FFT activity was free of sucrose: sucrose fructosyltransferase and invertase activities. It had an apparent pI of 4·7 as determined by isoelectric focusing, and a molecular mass of about 50000 (gel filtration). The FFT activity utilized the trisaccharides 1-kestose and 6G-kestose as sole substrates, but was not able to use 6-kestose as sole substrate. The FFT activity was not saturated when assayed at concentrations of 1-kestose, 6G-kestose or (1,1)-kestotetraose of up to 400 mM. The rate of reaction of the FFT activity was most rapid when assayed with 1-kestose and was less rapid when assayed with 6G-kestose, (1,1)-kestotetraose or (1,1,1)-kestopentaose. The FFT activity when assayed at a relatively high concentration of enzyme activity (approximately equivalent to about half the activity in crude extracts per gram fresh mass) did not synthesize fructan of degree of polymerization > 6, even during extended assays of up to 10 h. When assayed with a combination of 1-kestose and uniformly labelled [14C]sucrose as substrates, the major reaction was the transfer of a fructosyl residue from 1-kestose to sucrose resulting in the re-synthesis of 1-kestose. Tetrasaccharide and 6G-kestose were also synthesized. When assayed with 6G-kestose and [14C]sucrose as substrates, the major reaction of the FFT activity was the synthesis of tetrasaccharide. However, some synthesis of 1-kestose and re-synthesis of 6G-kestose also occurred. When 6G-kestose was the sole substrate for the FFT activity, synthesis of tetrasaccharide was 2·7 to 3·4-fold slower than when 1-kestose was used as the sole substrate. Owing to differences in the fructan [ratio ] sucrose fructosyltransferase activity of the FFT with each of the trisaccharides, net synthesis of tetrasaccharide by the FFT was altered significantly in the presence of sucrose. The magnitude of this effect depended on the concentration of the trisaccharides. In the presence of sucrose, 6G-kestose could be a substrate of equivalent importance to 1-kestose for synthesis of tetrasaccharide.

The products formed by a fructan [ratio ] fructan fructosyltransferase (FFT) activity purified from Lolium rigidum Gaudin were identified after gas chromatography-mass spectrometry of partially methylated alditol acetates, electrospray ionization-mass spectrometry and reversed-phase high-performance liquid chromatography. The FFT activity synthesized oligofructans up to degree of polymerization (DP) 6, but did not synthesize fructans of DP > 6 even when assayed with (1,1,1)-kestopentaose for up to 10 h. The FFT activity when assayed with 1-kestose or 6G-kestose synthesized fructan with fructosyl residues almost exclusively linked by β-2,1-glycosidic linkages. When assayed with 1-kestose, the FFT activity synthesized tetrasaccharides and pentasaccharides with an internal glucosyl residue. The predominant tetrasaccharide was (1&6G)-kestotetraose and the predominant pentasaccharide was (1&6G,1)-kestopentaose. By comparison, tetrasaccharides and pentasaccharides extracted from L. rigidum also contained predominantly β-2,1-glycosidic linked fructans with an internal glucosyl residue. The only exception was that one of the pentasaccharides contained β-2,1- and β-2,6-glycosidic linked fructosyl residues. This pentasaccharide was not synthesized by the FFT activity. The role of this FFT activity in formation of oligofructans in L. rigidum is discussed.