Glyphosate-resistant rigid ryegrass has been identified in California, but research has yet to elucidate the resistance mechanism. The objectives of this study were to examine the differences between sensitive and resistant rigid ryegrass in absorption and distribution of glyphosate, in vivo and in vitro absorption by chloroplasts, and shikimic acid accumulation after glyphosate treatment. Foliar absorption and distribution of 14C-glyphosate did not differ 1 to 3 d after treatment (DAT) between the susceptible (S) and resistant (R) biotypes. Absorption of 14C-glyphosate by isolated chloroplasts also did not differ between the S and R biotypes. After foliar application of 14C-glyphosate, chloroplasts were isolated from treated leaves from both biotypes. Accumulation of 14C-glyphosate in the chloroplasts did not differ between the two biotypes. Shikimic acid level increased significantly in the S biotype after treatment with glyphosate at 2.24 kg ai ha−1 to levels 10-fold greater than in the R biotype 11 DAT. Shikimic acid in the germination media at 2 to 5 mM did not affect seed germination of S and R biotypes but drastically decreased the length of coleoptiles of both at 5 DAT. Thus, biotype differences in sensitivity or metabolism of shikimic acid do not explain differences in sensitivity to glyphosate.

The occurrence of glyphosate-resistant weeds has been reported after more than 20 yr of extensive use. Rigid ryegrass that evolved resistance to glyphosate was found in Australia and in California. Glyphosate-resistant rigid ryegrass plants were collected from northern California and selected through generations 8 and 5 to segregate the most resistant (R) and sensitive (S) biotypes. The eighth generation of R and the fifth generation of S biotypes survived 6.72 and died from 0.11 kg ae ha−1 glyphosate, respectively. The objectives of this study were to evaluate the role of metabolism in the observed resistance, to study the effect of glyphosate on the activity of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS; EC 2.5.1.19), and to characterize the EPSPS gene in R and S rigid ryegrass. Neither quantitative nor qualitative difference was observed in the metabolism of 14C-glyphosate between the biotypes. Activity of constitutive EPSPS decreased more significantly in the S than R biotype in the presence of 5, 50, 500, and 5,000 µM glyphosate. Inhibition of 50% (I50) of the EPSPS activity by glyphosate was more than 90-fold in S compared to R biotype. Decreased EPSPS sensitivity in the R biotype appeared to be a major contributor to glyphosate resistance in rigid ryegrass from California. Fragments of the EPSPS gene containing 1,320 nucleotides were isolated from mRNA of S and R biotypes. A single nucleotide mutation from cytosine (C) to thymine (T) was identified at nucleotide 301 of the truncated EPSPS gene of the R biotype. This mutation changed the amino acid code from proline (Pro) to serine (Ser), which was similar to that reported for the glyphosate-resistant goosegrass from Malaysia and correlated with glyphosate insensitivity of EPSPS.

Glyphosate resistance was found in a rigid ryegrass population in northern California. A sample of the resistant plants were collected and grown under greenhouse conditions. The objective of this study was to evaluate glyphosate resistance in the progeny of the collected plants by recurrent selection, obtain the homozygous resistant and sensitive lines to establish dose-response curves, and to determine the inheritance of glyphosate resistance in rigid ryegrass. Diverse levels of resistance were observed in the first generation with survival of 89, 59, 45, and 9% from glyphosate at 1x, 2x, 4x, and 8x respectively, where x = 1.12 kg ha−1isopropylamine salt of glyphosate. Clones of plants that died from 1x were allowed to produce seed and were further subjected to recurrent selection to generate the most sensitive plants (S lines), which died from 0.125x glyphosate. The most resistant plants (R lines) were generated from the survivors receiving 8x glyphosate. The ratio between I50rates for the glyphosate resistant and the glyphosate sensitive plants was > 100-fold. The R and S lines were crossed reciprocally and F1progeny of both (R × S) and (S × R) showed intermediate resistance. These survived up to 2x glyphosate. The F2progeny were generated by intercrossing of F1plants. The ratio of sensitive, intermediate, and resistant plants in the F2population before the treatment of glyphosate at 0.125x followed by 8x was 1 : 16, 14 : 16, and 1 : 16 respectively, which corresponded to the Mendelian segregation ratio of two genes. The results indicated that the inheritance of glyphosate resistance in rigid ryegrass from California appeared to be nuclear, incompletely dominant, multigenic, and pollen-transmitted with no indication of maternal inheritance.

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M. Simarmata, L. Susanti and N. Setyowati (2016). Utilization of manure and green organic composts as alternative fertilizers for cauliflower production. Journal of Agricultural Technology 12(2):311-319.Cauliflower (Brassica oleraceavar. botrytis) is a vegetablecrop which isgrown over the world. Cultural practices of vegetables production are always dealing with fertilization technologies either using mineral fertilizers, organic fertilizers, or a combination of mineral and organic fertilizers. This study was aimed to determine the effect of reduced the dose of mineral fertilizers and substituted by organic fertilizers from compost ofcow manure and compost of trailing-daisy weeds (Wedelia trilobata).A single factorevaluated was arranged in a completely randomized design (CRD) as follows: treatment of a mineral fertilizer with nitrogen, phosphate, and potassium applied at10, 20 and 30 days after planting at arecommended dose (T 1 ), compost of trailing-daisy weedsat 20 ton ha -1 (T 2 ), compost of cow manure at 20 ton ha -1 (T 3 ), 50% of T 1 + compost of trailing-daisy weedsat 20 ton ha -1 (T 4 ), 50% of T 1 + compost of trailing-daisy weedsat 10 ton ha -1 (T 5 ), 50% of T 1 + compost of cow manure at20 ton ha -1 (T 6 ), 50% of T 1 + compost of cow manure of 10 ton ha -1 (T 7 ), and without fertilizer as a control (T 0 ). Each treatment was repeated five times so that overall there were 40 plantsin40 polybags. The results showed that thefertilizer combinationswere significantly affectedplant height, shoot fresh weight, dry weight of total plant biomass,and curd yield of cauliflower. The highest plant height and shoot fresh weight were observed in the treatment of 50% of mineral fertilizers combined with compost of trailing-daisy weeds at 10 ton ha -1 (T 5 ), the highest of total dry weight of plants were observed in the treatment of cow manure compost (T 3 ), and the highest curd yield of cauliflowerswas observed inthe treatment of 50% of mineral fertilizers combined with cow manure compostat 20 ton ha -1 (T 6 ). In conclusion, organic fertilizers from compost of trailing-daisy weeds (Wedelia trilobata) and from cowmanure can be used as an alternative fertilizer to substitutemineral fertilizers on the cauliflower production.