Parasitism by an ichneumonid wasp, Bathyplectes sp., on the clover leaf weevil, Hypera punctata, was investigated for over 10 years in the field of the white clover in Tsukuba, Ibaraki Prefecture. ...The rate of parasitism fluctuated annually, and sometimes reached more than 30%. High rate of parasitism was observed in third and fourth instar larvae of H. punctata; the maximum rate was 42.6%. The trend of annual fluctuation on parasitism since 1996 was similar at two experimental sites, although the maximum rate of parasitism was different between the two experimental sites. This suggests that such an annual trend of parasitism could be commonly observed through the relatively wide area around the study site.
The predominant root-knot nematode in New Zealand pastures is Meloidogyne trifoliophila, and a recurrent selection program in Trifolium repens has developed resistance to this species. No data are ...available, however, on the mechanisms of resistance in T. repens or resistant genotypes of T. semipilosum. The development of M. trifoliophila in roots of T. repens and T. semipilosum was examined weekly after a 2-day inoculation with eggs. More second-stage juveniles (J2) were found in two resistant genotypes of T. repens than in two susceptible ones 1 week after inoculation. J2 did not develop further in resistant genotypes, but in susceptible plants development proceeded to the adult stage, visible at 4 weeks after inoculation. The mode of action of resistance to M. trifoliophila in T. repens and in T. semipilosum was compared after a 24-hour inoculation with J2. Numbers of J2 per root tip ranged from 0 to 12 with a median of one for each species. At 24 hours after inoculation (HAI), similar numbers of J2 were seen in the cortex oriented toward the root tip in both resistant and susceptible genotypes of both plant species. At 48 HAI, accumulations of J2 were seen in the meristem in both resistant and susceptible genotypes of both plant species. At 72 HAI, differences in nematode responses were evident between resistant and susceptible genotypes of both plant species; in susceptible roots, J2 heads were embedded in the developing stele. At this time, a browning reaction in resistant genotypes of both plant species indicated a hypersensitive response, and differences in the reaction were recorded between T. repens and T. semipilosum. More study is needed to determine whether the resistance reaction in T. semipilosum is suitable for introgression or insertion into T. repens.
Wide variation in results exists in the literature on the effectiveness of composts to sustain the phosphorus (P) nutrition of crops. The aim of this work was to assess the importance of some soil ...and composts properties on the utilization of compost-P by white clover (Trifolium repens L.). This study was carried out with samples collected from four composts made from solid kitchen and garden wastes, and with two soil samples taken from the A horizon of a P-rich sandy acidic Dystrochrept and of a P-limited clayey calcareous Eutrochrept. Changes in the amount of inorganic P (Pi) isotopically exchangeable within 1 min (E1min) were measured during 32 weeks in incubated soil-composts or soil-KH2PO4mixtures where P sources had been added at the rate of 50 mg P kg−1 soil. Uptake of compost-P or KH2PO4-P by white clover was measured on the same amended soils during 16 weeks. In both soils, the application of composts resulted after 32 weeks of incubation in E1min values ranging between those observed in the control without P and those observed in the KH2PO4treatment, i.e., in values ranging between 4.2 and 5.9 mg P kg−1 in the sandy acidic soil and between from 1.6 to 4.3 mg P kg−1 in the clayey calcareous soil. The total coefficient of utilization of compost-P (CU-P) by white clover reached values in both soils for the four composts ranging between 6.5% and 11.6% of the added P while in the presence of KH2PO4 the CU-P reached values ranging between 14.5% in the clayey calcareous soil and 18.5% in the sandy acidic soil. Results obtained in the sandy acidic soil suggest, that white clover initially used a fraction of the rapidly exchangeable compost P, while at a latter stage plant roots enhanced the mineralisation of compost organic P and took up a fraction of the mineralized P. These relations were not observed in the clayey calcareous soil probably because of its high sorbing capacity for P. In the sandy acidic soil, composts application increased the uptake of soil P by the plant from 31.4 mg P kg−1 soil in the control without P to values ranging between 37.9 to 42.7 mg P kg−1 soil in the presence of composts. This indirect effect was related to a general improvement of plant growth conditions in this soil induced by compost addition (from 9.9 g DM kg−1 soil in the control without P to values ranging between 14.0 to 16.1 g DM kg−1 soil in the presence of composts) and/or to the release of Al- or Fe bound soil P to the solution due to soil pH increase following compost application. Finally the total coefficient of utilization of P (CU-P) derived from KH2PO4 and composts was related to the total amount of N exported by white clover in the P-limited clayey calcareous soil but not in the P-rich sandy acidic soil. This suggests that in a soil where N2 biological fixation is limited by low P availability, the CU-P of a compost by white clover is not only related to the forms of P present in the compost but also to its effect on N nutrition. However, it is not clear whether this improved N nutrition was due to compost mineralisation, or to an indirect compost effect on the N2 biological fixation.
Reduction of stocking rates and fertilizer inputs are recommended for maintaining or enhancing biodiversity of semi-natural habitats. White clover population could be affected by changes in ...grasslandproduction intensity. The aim of the present study was to investigate the white clover response on N application and stocking density. Three-year experiment was carried out on semi-natural grassland that was rotationally grazed with sheep. Three levels of N fertilizer were applied: 35, 100 and 150 kg N ha-1 (N35, N100 and N150, respectively) and two levels of stocking density were managed: 68 and 119 animal units ha-1 (ZP68 and ZP119, respectively) to investigate their effect on white clover dry matter (DM) yield, white clover content, frequency and regenerative ability. White clover DM yield and its content in the sward was not affected by the stocking density. The white clover content decreased during the experiment. The effect of N application on regenerative ability parameters was not constant and depends on the part of the vegetation season. These results indicate that the white clover is an unstable floristic component in the type of grassland investigated under applied management practice. However, reduction in N inputs is necessary to improve performance and the regenerative ability of the white clover.
In the present study, we have cloned and characterised three full-length and two partial cysteine protease-encoding genes from a white clover (
Trifolium repens) genomic library. The five genes could ...be assigned to three groups based on their nucleotide and deduced amino acid sequences and they belong to the C1 family of cysteine proteases. Semi-quantitative RT-PCR analysis revealed that the three groups of genes were expressed in nodules but not in root, leaves, petioles and internodes. Transcription of two of the gene groups was initiated in the nodules 24 days after inoculation while the third group initiated transcription at a slightly later stage. In situ hybridisation analysis assigned the transcriptional activity to the senescing zone of the nodules. Comparative semi-quantitative RT-PCR analyses of two
T. repens genotypes revealed no differences with respect to timing, specificity and quantity of gene transcription between the two genotypes. Southern blot analysis suggested the presence of two to three loci for each of the three groups with some degree of polymorphism between the two genotypes. The identified
T. repens cysteine protease genes showed high homology to cysteine proteases from
Astragalus sinicus,
Alnus glutinosa and
Medicago truncatula. These cysteine proteases all show enhanced/specific expression in the senescing zone of nodules.
Isozymes were used to study the putative ancestors of white clover ( Trifolium repens L.). Ten enzymes were examined, and 18 loci were resolved via starch-gel electrophoresis for accessions ...representing T. repens, Trifolium isthmocarpum, Trifolium nigrescens, Trifolium occidentale and Trifolium uniflorum, in addition to two more distantly related species, Trifolium alpinum and Trifolium purseglovei. Nei's genetic identities indicate that T. uniflorum and T. nigrescens are the closest relatives of T. repens. The isozyme data thus support a hypothesis that the two genomes of the tetraploid T. repens could have been derived from hybridization between T. nigrescens and T. uniflorum. This conclusion is further supported by shared alleles between T. repens, T. nigrescens and T. uniflorum. However, the origin of T. repens is somewhat obscured by the presence of shared alleles between T. repens and both T. occidentale and T. isthmocarpum, suggesting that introgression of genes from the latter two species into T. repens may also have taken place. High values of genetic identity are shared between T. occidentale with T. nigrescens and T. uniflorum, also indicative of introgression. Alternatively the presence of shared alleles among the five species may reflect their recent common ancestry.
Three change-over design experiments investigated the origin of hydrogen sulphide in the rumen head-space gas of dairy cows, comparing the effects of single iso-S additions of methionine, cysteine ...and sodium sulphate, as well as the effects of single meals of fresh ryegrass or white clover. The concentration of hydrogen sulphide in rumen gas declined close to zero within 4 h after withdrawal of the previous feed. Sulphur sources were then given to cows and concentrations of hydrogen sulphide recorded in rumen head-space gas at 30-min intervals. Cysteine addition (8 g) led to a rapid (within 30 min) and a large (490 and 957 p.p.m. respectively in two experiments) increase in hydrogen sulphide concentration. Concentrations were significantly less following methionine addition. Increasing levels of cysteine addition led to significant increases in hydrogen sulphide concentrations (P < 0.001 for the linear effect), although peak hydrogen sulphide was delayed and concentrations remained higher for longer with the highest (12 g) addition of cysteine (P < 0.01 for the 'cysteine level' x 'time' interaction). The increase in concentration of hydrogen sulphide from sodium sulphate was smaller (230 p.p.m.) and slower (2 h) than for cysteine. Despite the much higher intake of cystine for white clover in comparison with perennial ryegrass (P < 0.001), there was almost no increase in hydrogen sulphide concentration in rumen head-space gas from cows fed white clover. It seems likely that this is associated with the use of sulphur to produce thiocyanate to detoxify the hydrogen cyanide from cyanogenic white clover.
Results are presented from the UN/ECE ICP Vegetation (International Cooperative Programme on effects of air pollution on natural vegetation and crops) experiments in which ozone(O(3))-resistant ...(NC-R) and -sensitive (NC-S) clones of white clover (Trifolium repens cv. Regal) were exposed to ambient O(3) episodes at 14 sites in eight European countries in 1996, 1997 and 1998. The plants were grown according to a standard protocol, and the forage was harvested every 28 days for 4-5 months per year by excision 7 cm above the soil surface. Biomass ratio (NC-S/NC-R) was related to the climatic and pollutant conditions at each site using multiple linear regression (MLR) and artificial neural networks (ANNs). Twenty-one input parameters e.g. AOT40, 7-h mean O(3) concentration, daylight vapour pressure deficit (VPD), daily maximum temperature were considered individually and in combination with the aim of developing a model with high r(2) and simple structure that could be used to predict biomass change in white clover. MLR models were generally more complex, and performed less well for unseen data than non-linear ANN models. The ANN model with the best performance had five inputs with an r(2) value of 0.84 for the training data, and 0.71 for previously unseen data. Two inputs to the model described the O(3) conditions (AOT40 and 24-h mean for O(3)), two described temperature (daylight mean and 24-h mean temperature), and the fifth input appeared to be differentiating between semi-urban and rural sites (NO concentration at 17:00). Neither VPD nor harvest interval was an important component of the model. The model predicted that a 5% reduction in biomass ratio was associated with AOT40s in the range 0.9-1.7 ppm x h (microl l(-1) h) accumulated over 28 days, with plants being most sensitive in conditions of low NO(x), medium-range temperature, and high 24-h mean O(3) concentration.
Este trabalho foi desenvolvido com o objetivo de analisar aspectos fenológicos e produtivos de leguminosas nativas (Adesmia latifolia, A. tristis) e exóticas (Lotus corniculatus, L. uliginosus, ...Trifolium repens), em função do estádio fenológico no primeiro corte: vegetativo (CEV) e florescimento (CEF). As plantas foram estabelecidas em monocultura, no campo, e avaliadas entre maio/2000 e setembro/2001, em Passo Fundo, Rio Grande do Sul. Após o primeiro corte, as plantas foram desfolhadas em intervalos de 45 dias. Foram realizadas nove desfolhações no manejo CEV e sete no CEF. O estádio fenológico no primeiro corte influenciou a produção de massa seca (MS) de T. repens (CEV= 9.000 kg/ha de MS, CEF = 7.000 kg/ha de MS) e A. tristis (CEV = 4.000 kg/ha de MS, CEF = 8.000 kg/ha de MS). O L. corniculatus produziu cerca de 15.000 kg/ha de MS e A. latifolia, de 2.000 a 3.000 kg/ha de MS, independentemente do manejo. O L. uliginosus não floresceu, produzindo 7.000 kg/ha de MS no manejo CEV. As espécies nativas mostraram baixa persistência, com morte de plantas (A. tristis) e estolões (A. latifolia) no final da estação de crescimento. A maior produção de T. repens foi na primavera e a das espécies de Lotus, no verão.This work had the objective to evaluate phenological and productive aspects of native (Adesmia latifolia, A. tristis) and exotics legumes (Lotus corniculatus, L. uliginosus, Trifolium repens) as for the phenological stage on first-cutting: vegetative (CEV) and flowering (CEF). The plants were established as monoculture in the field and evaluated between May/2000 and September/2001, in Passo Fundo, Rio Grande do Sul. After the first cutting the plants were defoliated in 45 days intervals. There were nine cuttings in CEV-management and seven in the CEF-management. The phenological stage on first-cutting modified significantly (P<0,05) the dry matter (DM) production of T. repens (CEV = 9.000 kg/ha of DM, CEF = 7.000 kg/ha of DM) and A. tristis (CEV = 4.000 kg/ha of DM, CEF = 8.000 kg/ha of DM). L. corniculatus produced about 15.000 kg/ha of DM and A. latifolia, 2.000 to 3.000 kg/ha of DM, regardless the management. L. uliginosus did not flowered, producing 7.000 kg/ha of DM in the CEV-management. The native legumes showed poor persistence with death of the plants (A. tristis) and stolons (A. latifolia) at the end of the growing season. The highest production of the T. repens was in the spring and for the Lotus species, in the summer.
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