The use of asulam to control Bromus sterilis in ryegrass crops grown for seed

Asulam applied in April 1981 and 1982 gave good control of established plants of Bromus sterilis growing in Italian and perennial ryegrass crops grown for seed. Doses of 1–3 kg a.i./ha reduced numbers of weed inflorescences by 65–90%. The results also showed that there was no effect on crop heading and further suggested that seed yield had not been reduced. Two pot experiments also indicated the efficacy of asulam at 0·5-2 kg a.i./ha applied pre-emergence and further study of such treatment in the autumn during the establishment of a ryegrass seed crop is warranted.     

The effect of glyphosate on the viability of seed potato tubers

Summary Glyphosate applied to a growing crop of potatoes adversely affected the growth of the harvested tubers in the following season. Some effects were produced at 0.018 kg/ha^*, equivalent to ca 1 % of a commercial application rate. Symptoms were more severe at higher rates.     

The response of a perennial ryegrass (Lolium perenne L.) seed crop to nitrogen fertilizer application in the absence of moisture stress

Responses of perennial ryegrass (Lolium perenne L.) to nitrogen (N) fertilizer application rates and timings vary widely, because water is often limiting. Yield response to N fertilizer application during autumn, late‐winter and spring, and the associated efficiency of use of these inputs, was assessed under conditions of non‐limiting soil moisture during two, one‐year lysimeter studies in Canterbury, New Zealand. There were significant (P < 0·05) increases in seed and herbage yields with increasing N fertilizer application. Seed yields differed with year; greatest yields were 300 g m^?2 in 1996 and 450 g m^?2 in 1997. Seed head numbers (r²=0·77), seeds head^?1 (r²=0·92) and herbage yield (r²=0·92) were the major determinants of seed yield in both years. Irrigation required to maintain the soil between 70% and 90% of field capacity was directly related (r²=0·94 and 0·99 in 1996 and 1997 respectively) to increases in herbage yield. Seed yield, seed quality (thousand seed weight and percentage of seed > 1·85 mg), efficiency of water use, efficiency of N fertilizer use and apparent N fertilizer recovery were greatest when N fertilizer was applied at a rate of 50 kg N ha^?1, 50 or 100 kg N ha^?1 and 150 kg N ha^?1 in autumn, late‐winter and spring respectively; further increases in spring N fertilizer stimulated vegetative growth, but not seed yield. As a management strategy, applying N fertilizer to match the N requirements of the crop during the reproductive stage of growth will result in high yields of high quality seed while minimizing environmental impact.     

Precipitation during anthesis reduces seed set in perennial ryegrass

In perennial ryegrass seed production, the establishment of seed yield potential occurs until the point of anthesis. However, utilizing potential seed yield is predominately focused on processes after anthesis, namely seed set (%) and seed filling. In practice, seed yield is the product of the number of harvested seeds remaining after cleaning and average seed weight. For this study, the anthesis patterns and seed set were recorded in a diploid variety grown in seed production fields in three different Danish regions with contrasting weather conditions and investigated in 2013 and 2014. Increases in the total precipitation during anthesis reduced the anthesis synchrony and the seed set, which ranged from 50% to 66%. Under semi‐controlled environmental conditions in which the influence of precipitation was excluded, the seed set was found to be influenced by the floret position in the spikelet and ranged from 73% in the florets in basal positions to 25% in the distal florets. It is suggested that a lower number of florets per spikelet will reduce the anthesis period. These results may provide insights for breeding programmes focused on increasing seed yield.     

Genome-wide markers for seed yield and disease resistance in perennial ryegrass

The market success of perennial ryegrass(Lolium perenne L.) cultivars depends on sufficient seed production, as they are propagated by seed. However, breeding for high quality forage production reduces seed yield, and breaking the negative correlation would help to overcome the problem. The foliar disease crown rust is another factor affecting reproductive capacity and thereby seed yield. We evaluated seed yield-related traits and resistance to crown rust in a collection of commercial cultivars and ecotypes of perennial ryegrass and identified genome-wide markers associated with the traits. The study revealed high variation between the ecotype and cultivar groups as well as between years. A genome-wide association study identified 17 DNA single-nucleotide polymorphisms(SNPs) of which eight were associated with crown rust and nine with flag-leaf length. The SNP markers were located within or near predicted genes functioning in defense against pathogens. The identified genes are strong candidates for a further in-depth functional study to continue unravel determination of leaf architecture and crown rust resistance in perennial ryegrass.     

Water use and water-use efficiency of perennial ryegrass swards as affected by the height and frequency of cutting and seed rate

The effects of cutting height (20 and 44 mm), frequency (once every 2 weeks April-September inclusive and twice a year) and seed rate (250 and 20 kg ha^-1) on the water use and herbage yield of perennial ryegrass swards, for 3 years after sowing, were compared.
Frequent cutting and a low cutting height reduced water use in the first year only. In later years infrequent cutting led to higher yields and higher water-use efficiencies, but did not affect total water use or the shape of the soil water profile. Seed rate influenced sward composition and the pattern of water use, but not total water use. The swards from the low seed rate had a lower stubble biomass and tiller density, and extracted relatively more water at depths of 75 and 85 cm and less at depths of 15 and 35 cm, than the swards derived from the high seed rate.
The ratio of actual: potential evapotranspiration was reduced as the soil water deficit increased and was lowest in the summer after a dry spring. Cutting height and frequency during summer were shown not to be effective methods of either conserving water or manipulating the effective rooting depth of an established sward.     

Carry-over effects of sprouting and haulm destruction in the potato seed crop

Summary Seed of differing maturity dates of cv.Arran Pilot andMajestic were produced by planting sprouted and unsprouted mother tubers and by either destroying the foliage 2–3 weeks before senescence or allowing natural maturity to take place. Seed from crops of earlier natural maturity sprouted earlier and inArran Pilot grew faster if sprouting was encouraged soon after harvest. Other small differences in sprout growth were recorded, but none of the treatments applied to the first generation crop affected the time of emergence, stem number, growth of foliage or tubers in the second generation crop.

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Zusammenfassung An der Edinburgh School of Agriculture Farms wurden zwei Versuche w?hrend je zwei Jahren (1963–65 und 1964–66) durchgeführt, um die Einflüsse des Vorkeimens und der Krautvernichtung bei der 1. Generation Pflanzgut (Mutterknollen) auf das Keimwachstum, Pflanzenwachstum und den Ertrag im Nachbau (2. Pflanzgutgeneration) zu untersuchen. Beide Versuche umfassten die SortenArran Pilot undMajestic. Einzelheiten der Verfahren sind in Tabelle 1 angegeben. Durch das Vorkeimen des für die Pflanzguterzeugung benützten Saatgutes (1. Pflanzgutgeneration) wurde das Reifedatum im Vergleich zu dem nicht vorgekeimten Saatgut beiArran Pilot um 5–16 Tage, beiMajestic um 10–20 Tage vorverlegt (Abschnitt Material und Methoden). In Versuch II (Abbrennen des Krautes 2–3 Wochen vor der natürlichen Reife) wies das geerntete Pflanzgut beider Sorten einen um 2–3% niedrigeren Trockensubstanzgehalt auf als bei natürlicher Reife (Tabelle 3). Pflanzgut, erzeugt von vorgekeimten (N¹, Nc¹ und M¹) Mutterknollen (sog. 1. Pflanzgutgeneration) zeigte in Versuch I, nicht aber in Versuch II, ein früheres Auskeimen (Tabelle 4) als Pflanzgut von nicht vorgekeimten (O¹) Mutterknollen. Die Einflüsse der Vorkeim-Behandlungen auf die Keimzahl, Keiml?nge und die Entwicklung waren unterschiedlich, aber in Versuch II bildeten Saatknollen vonArran Pilot der früh vorgekeimten (N¹) Mutterknollen l?ngere Keime als jene von sp?t vorgekeimten (M¹) oder nicht vorgekeimten (O¹) Best?nden (Tabelle 5). Saatgut von abgebrannten Best?nden (B.D.) vonArran Pilot, nicht jedoch vonMajestic, brachte kürzere Keime als Saatgut von natürlich ausgereiften Best?nden (MAT). Es zeigte sich kein Einfluss irgendeiner bei den Mutterknollen angewendeten Vorkeim- oder Krautvernichtungsbehandlungen auf die Anzahl der Stengel (Tabelle 7), das Pflanzenwachstum oder auf die Ertr?ge (Tabelle 8) des Nachbaues (2. Pflanzgutgeneration). Es kann daraus geschlossen werden, dass in Nordwest-Europa die Unterschiede in den Reifezeiten, die durch das Vorkeimen der Mutterknollen oder durch das frühe Abbrennen des Krautes hervorgerufen werden, ohne bedeutenden Einfluss auf die Leistungen des erzeugten Nachbaues bei der Pflanz- oder Speisekartoffelerzeugung bleiben.

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Résumé Deux expériences, s'étendant chacune sur deux années (1963–65 et 1964–66) et portant chacune sur les variétésArran Pilot etMajestic, ont été réalisées à la ferme de l'Ecole d'Agriculture d'Edimbourg pour déterminer les effets de la prégermination et de la destruction du feuillage effectuées sur une première génération d'une culture de plants, sur le développement des germes, le développement de la culture et la production de la seconde génération. On trouvera les traitements détaillés dans le tableau 1. La prégermination de la première génération avance la date de maturité, de 5–16 jours chezArran Pilot et de 10–20 jours chezMajestic, par rapport aux plants non germés (Matérials et méthodes). Dans l'expérience II, la destruction complète du feuillage 2–3 semaines avant la maturité naturelle diminue la teneur en matière sèche des plants de 2–3% par rapport à la maturité naturelle, et cela chez les deux variétés (tableau 3). Dans l'expérience I mais non dans l'expérience II, les plants issus de la récolte d'une première génération prégermée (N, Nc¹ et M¹) germent plus t?t (tableau 4) que les plants récoltés non prégermés (O¹). Les effets des traitements de prégermination sur le nombre, la longueur des germes et sur le développement sont variables mais dans l'expérience II les plants d'Arran Pilot issus de la première génération germée précocement (N¹) produisent des germes plus longs que ceux issus de cultures germées tardivement (M¹) ou non prégermées (O¹) (tableau 5). ChezArran Pilot mais non chezMajestic, les plants issus de cultures défanées (B.D.) donnent des germes plus courts que les plants provenant de cultures qui ont pu atteindre leur maturité naturelle (MAT). Il n'appara?t aucun effet, ni de la prégermination, ni de la destruction du feuillage appliqué à la première génération de production de plants, sur le nombre de tiges (tableau 7), le développement de la culture ou la production (tableau 8) en seconde génération. Il est conclu que, dans le Nord-Ouest de l'Europe, la variation des dates de maturité causée par la prégermination du plant-mère ou la destruction prématurée des fanes n'a guère d'influence sur les productions de plants ou de pommes de terre de consommation dans la génération suivante.

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Edinburgh School of Agriculture Miscellaneous Publication No. 501.     

Effect of seed crop management on the potential seed yield of contrasting white clover varieties.

Three contrasting white clover varieties, Olwen (large-leaved), Menna (medium-leaved) and S184 (small-leaved) were sown with and without a grass companion in 30 cm drills. Two grazing and one mechanical spring defoliation managements were imposed. Counts of the total number of inflorescences and of the percentage in various ripeness categories were made throughout the period of seed crop development to determine the pattern of inflorescence development and optimum harvest date. Inflorescence numbers were greatest in cv. S184 and least in cv. Olwen and, in general, varieties produced both more inflorescences and a greater proportion of ripe inflorescences when grown under spring defoliation managements similar to those for which they were bred. Thus, cv. Olwen produced more ripe inflorescences, and a lower proportion of brown inflorescences (semi-ripe), after mechanical defoliation while cv. Menna produced more ripe inflorescences following mechanical defoliation and rotational grazing. However, cv. S184 produced more ripe inflorescences under both grazing managements than under mechanical defoliation. Optimum harvest date was not affected by management or variety, total inflorescence number and maximum ripe inflorescences having reached a peak on 11 September. However, varieties differed in the proportion of ripe and brown (semi-ripe) inflorescences on this date, with cv. Menna and cv. S184 containing a significantly higher proportion of brown inflorescences than cv. Olwen, The implications of these differences in inflorescence development, the proportions of inflorescences in the various ripeness categories and their contribution to seed yield are discussed in relation to the management of white clover seed crops and harvesting method under UK climatic conditions.     

Effect of seed crop management on potential seed yield of contrasting white clover varieties

An experiment is described in which the effects of different spring managements on the potential seed yield and seed yield components of three white clover cultivars of contrasting leaf types were assessed. Cv. S184, the small-leaved variety, produced more but smaller inflorescences than CVS Olwen, a large-leaved variety, or Menna, a medium-leaved variety. However, cv. Olwen, produced inflorescences with more florets, seeds per inflorescence and a higher seed yield per ten inflorescences than the other cultivars. Both potential seed yield and the individual yield components were influenced by management. Cv. Olwen produced more inflorescences and a higher potential seed yield under a cutting system than under grazing systems, which reduced the number and size of the inflorescences. Cvs S184 and Menna were less influenced by management system and performed similarly under cutting and grazing. The highly significant relationship between the number of ripe inflorescences and potential seed yield showed clearly that high seed yields are only achieved if the crop is harvested when the number of ripe inflorescences is at a maximum. The relatively short duration of the period of maximum ripe inflorescences emphasized the importance of determining the correct harvesting date, although weather conditions also play an important part in deciding when to harvest. Florets per inflorescence, seed set and 1000 seed weight remained relatively constant over the harvest period, and were not influenced by harvest date. The results are discussed in relation to the management of white clover seed crops and the importance of climatic conditions during seed production.     

The combined use of fertilizer nitrogen and white clover on grazed ryegrass swards

A 1-year grazing experiment with dairy cows is described in which the milk yield and herbage intake from a sward of S23 perennial ryegrass alone receiving fertilizer N at an annual rate of 360 kg ha⁻¹ were compared with those from a ryegrass-white clover var. Blanca sward given a total N application of 180 kg ha⁻¹. Both treatments gave virtually the same total milk yield of about 12500 kg ha⁻¹ over a 20-week grazing season.     

Herbicides and seed production by two perennial ryegrass cultivars grown in weed-free conditions

The effects of five herbicides on seed yield and viability of perennial ryegrass cv. S24 were tested at two sites. Benzoylprop-ethyl, chlorfenpropmethyl, difenzoquat, ethofumesate and flam-prop-isopropyl were safe to use at doses recommended for use in other crops. When applied at three times the recommended dose, only difenzoquat reduced the yield and germination of seed and benzoylprop-ethyl reduced seed germination. The recommended doses of difenzoquat and ethofumesate were safe when applied on cv. Barlenna at different growth stages. Difenzoquat reduced seed yield only after three times the recommended dose was applied to tillered plants. Ethofumesate, even at three times the recommended dose, did not affect seed yield but plant numbers were reduced by early treatment. The results suggest that the herbicides tested may be safe to use in perennial ryegrass seed crops at the recommended doses but more work is needed on the safety of difenzoquat in relation to crop growth stage.     

A comparison of seed harvesting methods for perennial ryegrass treated with the growth retardant paclobutrazol

Methods of harvesting seed of perennial ryegrass cv. S24 treated with the growth retardant paclobutrazol applied at spikelet initiation at a rate of 2.0 kg active ingredient ha⁻¹ were examined in 1982. The greatest seed yield (2202 kg ha⁻¹) was obtained from swathing the crop at 35% seed moisture content and combining 2 days later, but this was not significantly different from that obtained from swathing at 48% seed moisture content or double direct combining at 35% seed moisture content. Seed yields from a single direct combining at either 35% or 25% seed moisture content were significantly lower than those of other treatments.     

Relationships and influence of yield components on spaced-plant and sward seed yield in perennial ryegrass

Adequate seed production is essential for cultivar success in perennial ryegrass turf and forage industries, but improvement is limited by the complexity of yield components and low-rank correlations between selection and production environments. This study examined seed yield components among 20 perennial ryegrass entries in both spaced plantings (selection environment) and swards (production environment) at two locations in Minnesota. Competitive (23 plants/m²) and non-competitive (3 plants/m²) spaced-plant nurseries were tested. Competitive spaced-plant total yield was highly correlated with sward yield (r_s = 0.64 and 0.66, p < 0.01) at both locations, whereas the non-competitive environment showed no correlation. Structural equation modelling (SEM) was used to explore the indirect and direct relationship of fall vegetative growth, winterkill, and yield components on total seed yield in all environments. Fertile tiller number (spikes plant⁻¹/m⁻²) exhibited both strong direct and indirect influence on total seed yield in all environments. However, the importance of fertile tiller number in the SEM was reduced with increased plant competition. The SEM showed that both weight per spike and seed yield per spike influenced total yield in spaced plants; however, neither consistently predicted total sward yield. The ratio of these two traits (g seed spike⁻¹/g spike⁻¹) gave an index of fertility that was easy to measure and had a superior correlation with sward yield at two locations (r_s = 0.81 and 0.54, p < 0.05) when spaced plants were under competition. Results suggest that increasing competition in spaced plantings and selecting for spike fertility may more accurately identify superior plant material compared to lower competition environments.     

The effect of green crop lifting on the contamination of seed potato tubers by pathogenicErwinia spp.

Summary In the Netherlands seed potato crops are harvested when still green, the haulm being destroyed before harvest. We compared the effect on the contamination of seed potatoes byErwinia carotovora subsp.atroseptica (Eca) andE. chrysanthemi (Ech) of the common method of haulm destruction by flailing and chemically destroying remaining stems, with the recently developed green crop lifting method. After chenical haulm destruction the levels of contamination with both Eca and Ech surviving cold storage were found not to differ significantly from those after green crop lifting. Losses due to watery wound rot (Pythium ultimum) were considerable in the warm and humid conditions during 1991, especially after green crop lifting.     

The incidence of vims-like symptoms and ryegrass mosaic virus in perennial ryegrass pastures in the West of Scotland

In 1972 and 1973 fields of perennial ryegrass in the West of Scotland were surveyed for ryegrass mosaic virus (RMV). Visual determinations of foliar symptoms were made in the field and leaf samples were collected for diagnosis of the virus by electron microscopy and by sap transmission to S22 Italian ryegrass. In 1972, ninety-eight fields were surveyed and virus-like symptoms were observed in 59%, but tests showed that only 21% were infected with RMV. In the more extensive 1973 survey, 201 fields selected on a stratified random basis were examined and whilst 45% had virus-like symptoms only 5% proved to be infected with RMV. Symptoms were most readily seen in fields which had a high percentage of long, lush perennial ryegrass. Analysis of data collected in 1973 on management practices did not reveal any obvious association between the incidence of virus-like symptoms and the cutting and grazing regimes, the grazing animal used or the level of nitrogen applied.     

甘蔗育种、引种新理念的探讨

在科技生产力和甘蔗糖业大发展时期，对甘蔗育种目标、引种方向、良种理念已作了新探讨；在育种、引种方向上提出了“高、大、硬、强、脱”新的理念。     

Effect of tillage systems and herbicide treatments on weed abundance and diversity in a glyphosate resistant crop rotation

The effect of exclusive application of glyphosate and glyphosate in combination with residual herbicides on weed species density and composition in summer crops was studied over 2 years. Field experiments consisted of three rotations including soybean and maize glyphosate-resistant cultivars in two tillage systems. Regardless of the tillage system, both glyphosate application alone and in combination with residual herbicides had a pronounced impact on the reduction in density and richness of summer herbaceous annual weeds, but the effect was greater with glyphosate in combination with residual herbicides.