Evaluation of seed production potential in white clover (Trifolium repens L. varietal improvement programmes

The components of actual and potential seed yield were examined in field experiments on a wide range of varieties of white clover (Trifolium repens L.). The factors affecting seed yield under conditions typical of management regimes used in the production of commercial seed crops were assessed in two experiments. In the first, carried out on spaced plants, considerable diferences are shown between six varieties across the range of leaf sizes in the distribution and profuseness of inflorescence production through the flowering season. In the second, carried out in plots, typical on-farm criteria were used to choose a single harvest date. Significant variation was found between varieties, including representatives of different leaf size categories, for seed yield components that include number of inflorescences m^?2, number of florets per inflorescence and harvestable seed weight. Large-leaved varieties tended to produce more seeds per floret and higher seed weights per inflorescence, whereas small-leaved varieties gave the highest number of inflorescences ^?2. However, the small-leaved variety AderDale, selected for strong peduncles, was exceptional, giving high values for all seed yield components. The impact of weather conditions on many seed yield components (e.g. total number of inflorescences) was demonstrated by the differences between the 2 years of the experiment. However, other characterstics, e.g. number of florets per inflorescence and number of seeds per floret, did not vary between years. Deviations from potential seed yield were assessed fromthe perspective of commerical seed production. The implications of these results for the production of white clover varieties with increased seed yields under UK conditions are discussed.     

Persistence of Ladino white clover ecotypes and its relationship with other agronomic traits

Sixteen landraces and twelve natural populations of Ladino white clover, and six large-leaved control varieties, were assessed in Lodi (southern Lombardy, Italy) under a mowing regime for persistence, defined as ratio between clover dry matter (DM) yield over the last two years and clover DM yield over the five-year crop cycle. Clover content in the sward was on average 35·2% in the fourth year and only 5·5% in the fifth year. Natural populations showed greater persistence and larger variation for this feature than landraces. Six natural populations were more persistent and higher yielding in the long-term than the Italian variety Espanso and one of these populations performed better than the best of the control varieties, namely Lune de Mai and Olwen, at P < 005. Persistence of the ecotypes was positively associated with stolon density and DM yield assessed in the third year, and to intemode length, whilst it was inversely related to seed yield and its components, especially the production of seed heads, so that hardly any ecotype could combine good persistence with high seed yield. This study discusses the potential use of these genetic resources in white clover breeding and suggests stolon density as a low-cost, approximate indicator of long-term yield.     

Establishment and production of common sainfoin (Onobrychis viciifolia Scop.) in the UK. 2. Effects of direct sowing and undersowing in spring barley on sainfoin and sainfoin-grass mixtures

The dry matter (DM) yield and herbage quality of swards of sainfoin ( Onobrychis viciifolia ), meadow fescue ( Festuca pratensis ,) and tetraploid perennial ryegrass ( Lolium perenne ) grown in monocultures and in four sainfoin:grass mixtures (0·33 sainfoin:0·66 meadow fescue, 0·66 sainfoin:0·33 meadow fescue, 0·33 sainfoin:0·66 perennial ryegrass and 0·66 sainfoin:0·33 perennial ryegrass), established by direct sowing or undersowing in spring barley, were investigated over 3 years in a field experiment in the UK. Direct sowing produced a mean yield across all species and mixtures of 1·8 t DM ha⁻¹ in the establishment year, whereas undersowing produced no measurable yield except for that of the spring barley. Undersowing reduced the yields of sainfoin and sainfoin-grass mixtures in the first full-harvest year but not in the second. The annual yield of a monoculture of sainfoin was 7·53 t DM ha⁻¹ and that of sainfoin-grass mixtures was 8·33 t DM ha⁻¹ averaged over 3 years. Both sainfoin and the sainfoin-grass mixtures had higher annual DM yields than the grass monocultures. The mixture of 0·66 sainfoin:0·33 meadow fescue gave the highest mean annual yield (9·07 t DM ha⁻¹) over the 3 years. There was a higher proportion of sainfoin maintained in mixtures with perennial ryegrass than with meadow fescue. The proportion of sainfoin in sainfoin–meadow fescue mixtures declined from 0·62 in the first year to 0·32 in the third year, whereas the proportion in sainfoin–perennial ryegrass increased from 0·48 in the first year to 0·67 in the second year and remained stable in the third year.     

Seed production in white clover (Trifolium repens L.). II. Effect of autumn defoliation on potential seed yield and seed yield components

A field experiment was conducted to assess the effect of autumn defoliation treatments on inflorescence production, potential seed yield and yield components of white clover cv Makibashiro. Between 10 July and 10 October 1992, white clover swards were subjected to one of three treatments: monthly cutting to 3–4 cm (4DEF), cutting to 3–4 cm on 10 August and 10 October (2DEF), and no cutting (control). The total numbers of inflorescences and the proportion of inflorescences in different development categories were counted throughout the period of seed crop development to determine the pattern of inflorescence development and optimum harvest date. There were consistent significant differences in inflorescence density between treatments. Plots which received the 2DEF treatment produced significantly more inflorescences than did the no-defoliation (control) and 4DEF-treatment plots. In this particular year the optimum harvest date (date at which the proportion of ripe inflorescences and potential seed yield was highest) was 26 July, approximately 30 d after peak flowering. Defoliation treatments had no effect on optimum harvest date. However, treatments differed in potential seed yield and ripe inflorescences on this date. The 2DEF treatment gave the highest potential seed yield because there were significantly more ripe inflorescences than either the contol or 4DEF plots. Control plots produced inflorescences with more florets than the other two defoliation treatments, but the differences were not always significant. Seed number per pod was higher in inflorescences obtained from previously defoliated plots than from control plots. The 1000-seed weight was significantly lower in inflorescences developed in 4DEF plots than those developed in 2DEF and control plots. The results are discussed in relation to the management of white clover seed crops and the importance of canopy structure and light intensity for seed production.     

Variation in inflorescence characters and inflorescence development in ecotypes and cultivars of Lolium perenne L.

A sufficient database of seed yield components is the prerequisite to predict which component contributes most to the seed yield complex and to dissect the biology of the complex quantitative trait seed yield. Phenotypic variation of eleven vegetative and reproductive traits was characterized for 2481 individuals from fifty Lolium perenne L. (perennial ryegrass) ecotypes and cultivars. Considerable levels of among‐ and within‐population variation were found across several inflorescence characters. Principal component and canonical variate analysis separated ecotypes from cultivars, and cultivars generally had later dates of ear emergence, better spring and summer growth, longer rachis length and more spikelets per spike than ecotypes. Strong positive relationships were seen between inflorescence characters using both correlation and regression analyses. The strong relationship between rachis length and other inflorescence characters suggested that rachis length could be used as a performance predictor for several other characters of the spike. This phenotypic study has helped to determine basic patterns of morphological diversity and correlations between characters. It is discussed in which way further developmental genetic studies can be directed.     

Alfalfa (Medicago sativa L.) seed yield and quality under different forage management systems and irrigation treatments in a Mediterranean environment

Alfalfa (Medicago sativa L.) is widely grown as a forage crop due to its good quality characteristics and high adaptability. However, seed yield is generally considered to be of secondary importance and is characterized by fluctuating yields with often poor seed quality. A field experiment using five alfalfa cultivars (Equipe, Iside, Lodi, Robot, Romagnola) was carried out in 1995, 1996 and 1997 at Foggia (southern Italy) to evaluate the effects of four defoliation practices (H1: crop mown during early plant growth; H2: plant desiccation by chemical agent at the end of February; H3: crop mown at early flowering; H4: never cut) and two irrigation treatments (I: irrigation applied from April to beginning of seed filling; NI: non-irrigated control) on seed yield, seed yield components and seed quality (as determined by seed germination with and without accelerated ageing (AA)). The relationships between yield components (stems per m², pods per stem, seeds per pod, 1000-seed weight) were determined by path-coefficient analysis. Irrigation significantly increased seed yield; on average doubling the control yield over the three seasons. However, the potential seed yield (calculated from seed yield components) was, on average, five times the actual seed yield. The two mowing treatments produced consistently higher seed yields than either desiccated or untreated swards. Cultivar differences were evident for seed yield, with Equipe having the highest value (40% higher than the mean of the other cultivars). Irrigation improved the yield primarily because it led on average a greater than four fold increase in the density of stems (the most influential yield component). By contrast, seeds per pod and 1000-seed weight increased in the absence of irrigation. Defoliation treatments had little effect on stems per m², seeds per pod and seed weight, whereas pods per stem were reduced by desiccation. Path analyses calculated across irrigation treatments and years revealed that stems per m² had the largest positive direct effect on alfalfa seed yield under each harvest management (path-coefficient values ≥0.89), and its indirect effects on seed yield via other traits were negligible. Seed quality, as measured by germination percentage both before and after AA, remained relatively consistent across both defoliation and irrigation treatments and cultivars, but was anomalously low in the 1997 irrigated crops. Overall, the highest seed yields were obtained under irrigated conditions when crops were mown during early growth or at early flowering. The potential seed yield of alfalfa varieties is sufficient to guarantee a profitable seed harvest. However, the harvest efficiency of the combine-harvester was low (20% of the potential seed yield); thus, more appropriate harvest techniques should be used.     

Grain yield and yield components as affected by forage removal in winter and spring triticale

Two field experiments were carried out under irrigation and high fertility in northeastern Spain during 1992 and 1993. Ten triticale genotypes, five of spring growth habit and five winter types, were tested for their suitability for both forage and grain. Forage removal reduced grain yield per plant by about 17%, but did not have any significant effect on plant density, ear density or tiller number per plant. Tiller mortality was greater in winter types (65%) than in spring triticales (25%), but was not affected by cutting. Decreases in grain yield following cutting could be attributed to reductions in the number of grains per spike and kernel weight. Cutting decreased the number of grains per spike by about 9% by reducing the two components, spikelets per head and grains per spikelet. The average spike length was 10·6 cm in the uncut treatment and 10·1 cm in the dual-purpose plots. Cutting reduced thousand kernel weight by about 7% in winter triticales, and around 10% in spring types, both in main spike and in first tiller. The effect of a forage harvest on yield components was in general similar for both types of triticale. Cutting when jointing commenced induced changes in the relative importance of yield components influencing future grain yield. The yield components reduced by cutting were the most important contributors to grain yield after forage removal.     

Feasibility of Improving Unmanned Aerial Vehicle-Based Seeding Efficiency by Using Rice Varieties with Low Seed Weight

Unmanned aerial vehicle (UAV) has offered a promising platform for rice direct seeding that can substantially reduce labor input in the crop establishment process. However, the insufficient payload capacity of UAV-based seeders is currently limiting its intensive and large-scale use for rice direct seeding. This study indicated a large variation in seed weight across varieties, ranging from 15.0 to 36.5 mg and 14.0 to 31.3 mg for inbred and hybrid varieties, respectively, with average seed weights of 25.3 mg for inbred and 24.7 mg for hybrid varieties. Seed weights of 160 out of 4 106 inbred varieties and 17 out of 311 hybrid varieties ranged from 15.0 to 20.0 mg. Reducing seed weight from 25.0 to 15.0 mg increased the seeding area per UAV flight by 67% regardless of inbred and hybrid varieties, although the absolute increase in seeding area for hybrid variety was greater than that for inbred variety because of the difference in seeding rate. The grain yield of inbred varieties was reduced when the seed weight was less than 24 mg. Moreover, 87% of inbred varieties with a seed weight ≤ 20 mg were distributed in South China where rice consumers prefer small rice grains. Therefore, the use of low-seed-weight inbred varieties for improving UAV seeding efficiency might be considered in South China. Unlike inbred rice, 64% of hybrid varieties had higher grain weights compared with their seed weights, and reducing seed weights did not necessarily cause yield loss. Therefore, the small-seed-and-large-grain strategy in hybrid rice could be used for improving UAV seeding efficiency without yield loss. This strategy can be considered for improving UAV seeding efficiency in rice production regions other than South China.     

Effect of plant density on stolon growth and development of contrasting white clover (Trifolium repens) varieties and its influence on the components of seed yield

Plants of two contrasting white clover varieties (cv. Aberystwyth S184 and Olwen) were planted in the field in spring in each of 2 years at four densities (9, 25, 49 and 100 plants m⁻²) in 1-m² plots. The effect of plant density on stolon growth and development and the components of seed yield was subsequently measured.
Stolon growth and development was influenced by plant density, variety and year. At low plant densities both white clover varieties produced longer primary stolons than at higher densities. Plant density, however, had no significant effect on the number of inflorescences at harvest. At the high stolon densities there were significantly fewer reproductive nodes per primary stolon than at the lower plant densities. Plant density did not significantly affect any other seed yield components, but the number of inflorescences at harvest, florets per inflorescence, seed set per floret and 1000-seed weight were all significantly influenced by both variety and year.
The relationship between the vegetative and reproductive growth of white clover is discussed in relation to plant density, variety and climate and the possible role of defoliation managements on inflorescence development.     

Sward maintenance of Lolium multiflorum by slurry seeding

A field investigation into the effect of slurry seeding on the dry-matter yield and persistence of an Italian ryegrass sward was assessed over a 3-year period (1984–86) under a regime of three cuts per season combined with sheep grazing in early spring and late autumn. Results showed that slurry plus seed treatments produced up to 30% more herbage dry matter and a significantly higher tiller density than where no slurry or seed were used. Slurry application with and without seed also reduced the proportion of weed grasses ( mainly Poa spp.) in the sward. It is concluded that slurry seeding is a useful technique for extending the productive life of an Italian ryegrass sward.     

晚播晚栽机插水稻群体生长特征及其调控策略

目的 探究水稻机械化移栽应用中长期存在的晚播晚栽机插稻的特殊应用价值,方法 在苏南设置大田试验,分析了晚播晚栽机插水稻的产量表现及其群体生产特征,并设置密度和穗肥施用处理,解析栽培措施对晚播晚栽机插水稻群体发育和产量形成的影响。结果 机插水稻晚播晚栽产量出现一定程度的下降,主要原因是单位面积穗数和每穗粒数降低。晚播晚栽机插稻群体高峰苗出现时间相对前移,茎蘖成穗率则明显下降。同化物质积累和运转均受到一定影响,抽穗期茎鞘中非结构性碳水化合物积累下降,茎鞘物质输出率和转换率也呈下降趋势。可见,晚播晚栽机插水稻存在物质生产和产量形成的必然劣势。增加栽植密度,单位面积穗数显著增加,干物质积累量上升,产量明显提高。在同一密度条件下,随着穗肥施氮量水平的提高,产量表现为先上升后下降的趋势,过多穗肥施用不利于晚播晚栽机插稻结实期的物质积累。较高密度配合适宜水平的穗肥施用,可提     

Flowering and true seed production in potato (Solanum tuberosum L.). 2. Effects of stem density and pruning of lateral stems

Summary Field experiments were carried out to evaluate the effect of stem density and pruning of lateral stems on flowering and true seed production in potato (Solanum tuberosum L.). Increasing stem density reduced flowering, berry and seed production from every inflorescence in all cultivars. Increasing density increased the proportion of primary flowers in the total number of flowers per plant and reduced the proportion of flowers on lateral stems, but its effect on the quality of the seed production was small. Differences in total seed production were principally determined by differences in flowering. There was an interaction between stem density and cultivars for the number of flowers produced and on the yield of true seed per m². Pruning lateral stems enhanced flowering of the main stem and decreased the total number of flowers per plant, but it did not affect berry and seed production from main-stem inflorescences.     

Potential seed yield of white clover varieties

Fifteen varieties of white clover were sown in order to assess the seed yielding ability of new and potential varieties and to examine those plant factors which affect seed yield. Counts were made on number of inflorescences m^-2, proportion of ripe inflorescences and other inflorescence and seed characters. The data were used to compute potential seed yields.
Average potential seed yields were 276 and 76 kg ha^-1 in the first and second year, respectively. The decrease in the second year seed yields underlines the overriding effect of adverse weather conditions during the critical June to August period. The major effect was a reduction in the number of inflorescences produced, the number of florets per inflorescence and seeds per floret.
Some of the new listed varieties have a significantly higher seed potential than SI00, e.g. Menna (+ 38%) and Olwen (+28%), and this should facilitate the production of adequate seed supplies of British bred varieties.     

Seed yielding ability of landraces of lucerne in Italy

Seed yield is of crucial importance for the marketing of lucerne varieties. Statistical records for farmers’ production of certified seed suggested a slightly higher seed‐yielding ability of Italian landraces over improved varieties (proportionately 0·052). The aims were to: (i) assess the variation among landraces, and compare the germplasm of landrace and improved varieties, for seed‐yielding ability; and (ii) investigate the relationships between seed yield, environment of origin and forage yield of the landraces. Thirteen farm landraces belonging to the seven commercial ecotypes of northern Italy and four improved varieties were evaluated for seed yield in the third cropping year and for herbage yield over twelve harvests. Landraces differed in seed yield and herbage yield (P < 0·05). Landrace material, compared with variety germplasm, showed a non‐significant trend towards higher seed yield (proportionately 0·047) and had similar herbage yield and plant density at the onset of the third cropping year. Seed yield of landraces was unrelated to forage yield and was associated with frequent mowing and earlier year of seed production on its farm of origin.     

Nitrogen utilization efficiency of safflower hybrids and open-pollinated varieties under Mediterranean conditions

The identification of the factors determining nutrient utilization of safflower (Carthamus tinctorius L.) is useful for the successful introduction of the crop to the cropping system of a region. A field study was conducted to compare and analyze the relative importance of the various component traits causing variation in nitrogen utilization efficiency (NUE) of safflower under Mediterranean conditions. Ten genotypes, four hybrids and six open-pollinated varieties, were grown for two growing seasons without irrigation, on a silty clay (Typic Xerorthent) soil. Seed yield varied greatly among genotypes and ranged from 923 to 3391 kg ha⁻¹. Hybrids showed a mean seed yield superiority of 12.5% against varieties. Seed yield was the most important component of seed N yield and its contribution to the total variation in seed N yield among genotypes was at least 53%. NUE for biomass production during the seed-filling period was lower compared to that during the vegetative period. Genotypes differed in NUE for seed production (NUE_s) and the differences followed those of nitrogen harvest index (NHI). The contribution of NHI to the total variation in NUE_s among genotypes was much greater compared to that of yield per unit seed nitrogen and accounted for more than 79%. NUE_s is positively correlated with seed yield, suggesting that high yield was probably associated with more efficient exploitation of nitrogen. NUE_s is negatively correlated with (leaf + stem) N concentration at maturity, meaning that low straw N concentration may be indication of higher NUE_s. Results indicated that selection for NUE in safflower should be based on multiple criteria rather than just one criterion and also should be accompanied by evaluation for seed yield to ensure an improvement in both traits.     

Survival of plants of common sainfoin (Onobrychis viciifolia Scop.) in competition with two companion grass species

A 2-year experiment on competition between sainfoin ( Onobrychis viciifolia Scop.), meadow fescue ( Festuca pratensis ) and tetraploid perennial ryegrass ( Lolium perenne ) was conducted using plants grown in plastic containers outdoors. Root and shoot systems of sainfoin and the grasses were separated in order to investigate full and no competition of root and shoots, at two planting ratios (0·33 grass:0·66 sainfoin and 0·66 grass:0·33 sainfoin). Survival of sainfoin plants was lower at the higher grass:sainfoin ratio. More sainfoin plants died in the winter than during the growing season. Root competition had no effect on survival of sainfoin plants, but shoot competition reduced survival of sainfoin plants during one growing season. Companion grass species had no effect on survival of sainfoin plants, except in the first winter, when fewer sainfoin plants survived when grown with meadow fescue than perennial ryegrass.     

THE EFFECT OF CUTTING COCKSFOOT (DACTYLIS GLOMERATA L.) GROWN FOR PRODUCTION OF SEED

An experiment is described in which cocksfoot, grown for production of seed, was cut annually for 3 years in either autumn, winter or spring. No significant increases in yield of seed/ac were obtained from any treatment compared with an uncut control, and a cut in late April in one year seriously reduced the yield of seed. Additional N applied after a defoliation in October did not increase the yield of seed compared with that from plots which were cut at the same time but not fertilized. The production of tillers was not affected by cutting on any date. The percentage fertility of tillers was increased by cutting in the first year, when the number of tillers was smallest; the fertility was less consistently affected in the second year, and was generally unaffected in the third year. The weight of seed produced per ear was usually reduced by the cutting treatments. In the third year of the experiment it was shown that the penetration of light to the base of the shoots was increased substantially by defoliation, but it is deduced that maximum interception of light by the whole plant is more important for the production of seed than increasing by cutting that proportion which penetrates to the base of the plant.     

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.     

White clover seed production from mixed swards: effect of sheep grazing on stolon density and on seed yield components of two contrasting white clover varieties

A trial was carried out over two harvest years to assess the effect of sheep grazing and closing date on stolon density and seed yield components of two contrasting white clover varieties and to determine the potential for producing clover seed from mixed swards in an integrated livestock/seed production system.
Overall, the small-leaved cv. S184 had a higher stolon density at closing and harvest than the large-leaved cv. Olwen, but only significantly so in 1987. Stolon density at closing was generally increased by delaying closing. Varieties also differed in their response to closing date. Stolon density of cv. S184 in both harvest years, generally increased with later closing whilst cv. Olwen was less influenced by closing date and at all dates in 1987, and all but one date in 1986 was not significantly different from the ungrazed treatment.
Delay of closing significantly increased stolon density at harvest on all closing dates in 1987 but had no effect in 1986. Varieties responded similarly to a delay in closing but the magnitude of increase of cv. Olwen was less than that of cv. S184.
The seed yield components of both cv. S184 and cv. Olwen were influenced by closing date, but the effect differed between years. Although there was some initial increase in inflorescence production, delaying closing after inflorescence buds appeared on the stolon reduced inflorescence number of cv. Olwen in both years but reduced inflorescence number in cv. S184 in 1986 only. However, inflorescence size, seed yield per inflorescence and the proportion of ripe inflorescences at harvest was reduced in both years. Cultivar S184 produced more inflorescences than cv. Olwen in both years and in both years tolerated later closing than cv. Olwen.
The effect of sheep grazing and closing date is discussed in relation to stolon removal and the suitability of particular leaf types for this system of seed production.     

Establishment and production of common sainfoin (Onobrychis viciifolia Scop.) in the UK. 1. Effects of sowing date and autumn management on establishment and yield

The effects of sowing date and autumn management of sainfoin ( Onobrychis viciifolia Scop.) were investigated over 3 years in the UK. Replicated plots were sown between April and September in 2003 and 2004. Autumn management treatments were early and late cutting carried out in the establishment year and in subsequent years. Dry matter (DM) yields were measured over 3 years. One harvest was taken from April to July sowings in the establishment year and three harvests in each of the following years. DM yields from sowings in April and May were 2·8 and 3·3 t DM ha⁻¹, respectively, in the establishment year, which were higher ( P  <   0·001) than from sowings in June and July. Sowings from April to July yielded 10·9–12·5 t DM ha⁻¹ in the first full-harvest year, and 9·5–11·5 t DM ha⁻¹ in the following year. Sowings in August and September only gave 5 t DM ha⁻¹ year⁻¹. Early-autumn cutting of an established sward reduced yields of sainfoin at the second harvest in the first and second full-harvest years. Sowing in May had the lowest proportion of weed species (0·06) in the establishment year, and sowing in July had the highest (0·53). Crude protein concentration increased as the seasons progressed from 149·8 to 230·1 g kg⁻¹ DM.