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1.
Perennial ryegrass (Lolium perenne) plant breeding has delivered several high performing and broadly adapted cultivar-endophyte (Epichloë) combinations for the New Zealand pasture-based livestock industries. However, the trends in key traits and the potential economic value being added to farm systems have not previously been addressed systematically. Rates of gain in yield, nutritive value, phenological and morphological traits, and the economic value of those traits, were estimated among and within ryegrass functional groups (heading date, ploidy) traded commercially between 1973 and 2012. Whole pasture dry matter yield improvements of c. 80 and 60 kg DM/ha per year were identified in in late-season heading diploids and tetraploids respectively. Trends in metabolisable energy were negative within functional groups, but positive when all cultivar-endophyte combinations were included in the analysis due to the addition of tetraploids and late-season heading diploids from the mid-1990s. The estimated trend in overall economic value (all cultivar-endophyte combinations included) was $7/ha per year based on DM yield only, about half the rate of gain previously estimated using small-plot merit testing data. The trend increased to $15/ha per year when ME was included due to the emergence of commercial tetraploids from the early 2000s onwards. Estimated economic gains were high within late-season heading diploids and tetraploids but not mid-season diploids. These trends suggest that, if high performing cultivar-endophyte combinations had been adopted in New Zealand dairy systems, then pasture utilization should have increased by ~1 t DM/ha above the current industry average. Reasons for this apparent discrepancy are discussed.  相似文献   

2.
A comparative study of grazing behaviour, herbage intake and milk production of three strains of Holstein‐Friesian dairy cow was conducted using three grass‐based feeding systems over two years. The three strains of Holstein‐Friesian cows were: high production North American (HP), high durability North American (HD) and New Zealand (NZ). The three grass‐based feeding systems were: high grass allowance (MP), high concentrate (HC) and high stocking rate (HS). In each year seventy‐two pluriparous cows, divided equally between strains of Holstein‐Friesian and feeding systems were used. Strain of Holstein‐Friesian cow and feeding system had significant effects on grazing behaviour, dry matter (DM) intake and milk production. The NZ strain had the longest grazing time while the HD strain had the shortest. The grazing time of cows in the HC system was shorter than those in both the HS and MP systems. There was a significant strain of Holstein‐Friesian cow by feeding system interaction for DM intake of grass herbage and milk production. The NZ strain had the highest substitution rate with the HP strain having the lowest. Hence, response in milk production to concentrate was much greater with the HP than the NZ strain. Reduction in milk yield as a consequence of a higher stocking rate (MP vs. HS system) was, however, greater for the HP and HD strains compared with the NZ strain. The results suggest that differences in grazing behaviour are important in influencing DM intake and milk production.  相似文献   

3.
In North Vietnam, during winter, shortage of herbage constrains the profitability of dairy farming. The first objective of this study was to evaluate the potential of alternative temperate (C3) forage species, namely common oat ( Avena sativa L.), lop-sided oat ( Avena strigosa Schreb.), Italian ryegrass ( Lolium multiflorum L.) and a commercial forage mixture (Avex), to address the shortage of herbage during winter in the mountain regions of North Vietnam. The second objective was to measure the effects of cultural practices (sowing rate, harvest interval and irrigation level) on yield of dry matter (DM), chemical composition, digestibility of DM and metabolizable energy (ME) concentration of herbage from the best adapted C3 species previously tested (lop-sided oat). Four experiments were conducted. Oat species proved to be the best adapted species and produced the highest annual yield of herbage (7600 kg DM ha−1) with a high nutritive value. Yields of DM of lop-sided oat were not affected by sowing rate of seed but increased as the length of harvest intervals increased from 30 to 45 and 60 d ( P  <   0·001). Crude protein concentration, digestibility of DM and ME concentration decreased as the harvest interval increased ( P  <   0·01). Irrigation increased the yields of DM of lop-sided oats by 1·3 ( P  <   0·05) but had no effect on the nutritive value of herbage. It is concluded that both common oat and lop-sided oat are suitable species to provide herbage in the winter for the mountain regions of North Vietnam.  相似文献   

4.
The energy value and chemical composition of 70 herbages harvested over two years as either spring primary growths of increasing maturity (n= 32), summer regrowths (n= 14) or autumn regrowths of increasing maturity (n= 24) are reported. The herbages, which were dominated by perennial ryegrass, were harvested from commercial grassland on four sites in England in1986 (year 1) and 1987 (year 2). Digestibility and energy values were determined in vivo using wether sheep. In year 1, autumn regrowths had significantly (P < 0·05) lower neutral detergent fibre concentrationsthan summer regrowths, and lignin was lower (P < 0·05) in spring than in summer herbages. In year 2, autumn herbages had significantly(P < 0·05) higher concentrations of crude protein and hemicellulose than summer and autumn herbages. Spring herbages had higher concentrations of water-soluble carbohydrates than summer (P 0·01) and autumn (P < 0·001) herbages. A higher (P < 0·05) metabolizable energy (ME) concentration was observed in spring compared with summer herbages in year 2 and in general there was considerably more variability in the values for the spring growths, ME content fell with increasing maturity in spring growths(0·046 and 0·035 MJ kg-1 DM per day; years 1and 2 respectively) and this decline was 3–4 times faster than for autumn-harvested material (0·012 and 0·017 MJ kg-1 DM per day; years 1 and 2 respectively). In both years only immature spring herbages consistently produced ME contents in excess of 11·9 MJ kg-1 DM. For 15 of the herbages the proportion of gross energy intake (GEI) lost as methane was measured directly using respiration chambers. The mean methane energy loss was 0·07 of GEI (range 0·057–0·082). A commonly used publish equation for predicting methane energy loss was shown not to be appropriate, although no relationships could be established between methane energy loss and either energy digestibility in vivo or chemical composition.  相似文献   

5.
Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs (Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs ($ ha?1 calculated as change in operating profit divided by unit change of the trait) for additional DM produced in different seasons of the year in four regions. The EV of early spring DM was consistently high across all regions, whereas EV for late spring DM was moderate to low. Genotype × environment analysis revealed significant reranking of DM yield among ryegrass cultivars across regions. Hence, separate performance values (PVs) were calculated for two mega‐environments and then combined with the corresponding season and region EV to calculate the overall EV for twenty‐three perennial ryegrass and fifteen short‐term ryegrass cultivars. The difference in operating profit between the highest ranked and lowest ranked perennial ryegrass cultivar ranged from $556 ha?1 to $863 ha?1 year?1 depending on region. For short‐term ryegrasses used for winter feed, the corresponding range was $394 to $478 ha?1 year?1. Using PV for DM yield, it was estimated that plant improvement in perennial ryegrass has added $12–$18 ha?1 year?1 (depending on region) operating profit on dairy farms since the mid‐1960s.  相似文献   

6.
Effects of grass silage feed value on intake, dietary sorting, body condition (BC) and body weight (BW) of pregnant and lactating ewes and on liveweight gain (LWG) of their suckling lambs were evaluated. Twin‐bearing ewes were fed ad libitum grass silage of (i) high feed value (HFV), (ii) medium feed value (MFV) and (iii) low feed value (LFV), plus 0·8 kg concentrate in late pregnancy and lactation. The HFV, MFV and LFV silages contained 11·7, 10·8 and 9·3 MJ metabolizable energy (ME) kg?1 DM respectively. The HFV resulted in 8·2 and 15·2 MJ greater ME intake in pregnancy and 14·7 and 21·0 MJ greater ME intake from silage in lactation than MFV and LFV respectively (P < 0·01). Ewes fed the MFV and LFV silages sorted for more digestible particles during eating (P < 0·10). The HFV gave no loss in BC, whereas ewes fed MFV and LFV lost 0·7 and 0·8 units of BC, respectively, during lactation (P < 0·10). There were similar trends in BW. The nursing HFV lambs had 73 g higher daily LWG than the LFV lambs (P < 0·01). In conclusion, the HFV increased the ME intake of pregnant and lactating ewes, resulting in improved BC and BW of lactating ewes and LWG of suckling lambs compared to MFV and LFV.  相似文献   

7.
Although about 225 000 t dry matter (DM) pea straw is produced annually in the UK, no recent data exist with respect to its nutritive value when offered to ruminants. This study, to examine field pea crop waste (straw) from 12 commercial cultivars of combining peas, was therefore undertaken when material grown as part of a European field pea network trial at Reading in 1998 was made available. The straw was subjected to chemical analysis and examined in vitro using the Reading Pressure Technique to generate gas production profiles and to determine both rate and extent of DM and organic matter degradation. Ash and crude protein (CP) concentrations (69 and 65 g kg–1 DM) were generally lower than published values for legume straws but higher, especially CP, than cereal straws. Neutral‐detergent fibre concentrations were slightly lower, and metabolizable energy (ME) values, derived from degradable organic matter assessed in vitro (iOMD), higher than cereal straws, ranging from 6·0 to 8·1 MJ ME kg–1 DM. Both cumulative gas production and rate of gas release varied significantly between cultivars, as did degradation with 96‐h iOMD values ranging from 468 to 602 g kg–1. By combining these with the quantity of material harvested, ME yields for the different cultivars were found to range from 15 to 27 GJ ME ha–1. Considerable, and general highly significant, variation was found between the cultivars examined, which may be used to rank straws with respect to their nutritive value. The cultivars Baccara and Solara followed by Athos and Vital were readily ranked higher than the other cultivars in terms of in vitro fermentation parameters and ME yields. These data suggest that pea straw, although often incorporated into the soil in post‐harvest operations, shows excellent potential as a ruminant forage feedstuff.  相似文献   

8.
Abstract The dry matter (DM) production of Trifolium repens, T. ambiguum and the backcross 1 (BC1) and backcross 2 (BC2) hybrids with T. repens as the recurrent parent were compared in mixtures with an intermediate heading variety of perennial ryegrass (Lolium perenne L.) under a cutting‐only management over 3 harvest years. Plots of parental legume species and backcross hybrids were established from small plantlets and oversown with the companion grass. In the first harvest year, the DM yield of clover in T. repens plots was greater than that in the BC2 plots and both greater than in the BC1 plots, whilst in the second and third harvest years differences between the DM yield of clover in the T. repens and the BC1 and BC2 hybrid plots were small. Similar results were obtained for the DM yield of total herbage. There were also differences in seasonal growth in the first harvest year, when yield of clover in T. repens plots was greater than in the BC1 and BC2 hybrid plots at early cuts but not at later cuts. Few differences in seasonal growth were observed between parental species and hybrids in subsequent harvest years. Comparison of above‐ and below‐ground biomass showed more DM in roots and rhizome of clover in the backcrosses than in the T. repens plots in the second harvest year but differences were less evident in the third harvest year. The clover in the backcross hybrid plots also had fewer stolon growing points per quadrat than the T. repens plots, but the BC2 had more than the BC1 plots. The exploitation of these hybrids in breeding programmes as a strategy to improve the persistence and drought tolerance of white clover is discussed and implications for forage production considered.  相似文献   

9.
Abstract The response of a long‐term, mixed‐species hayfield in Maine, USA, to commercial fertilizers and liquid dairy manure was evaluated over a 6‐year period, including the effects on yield, nutrient concentration and cycling, forage species composition and soil nutrient levels. Nutrient treatments included an unamended control, N fertilizer, NPK fertilizer and liquid dairy manure (LDM). The application rates of plant‐available N, P, and K were constant across treatments. Application of nutrients in any form increased forage yield, generally by 2–4 t dry matter (DM) ha?1 year?1. Yield from NPK fertilizer was 0·05–0·25 higher than from LDM, due to differences in N availability. Yield responses to P and K were minimal and there appeared to be no difference between P and K in fertilizer and manure. The forage sward became increasingly dominated by grass species as the experiment progressed; application of P and K in fertilizer or LDM allowed Agropyron repens to increase at the expense of Poa pratensis. Forage nutrient removal accounted for all applied N and K, and nearly all applied P, throughout the study period, demonstrating the important role these forages can play in whole‐farm nutrient management.  相似文献   

10.
A series of six trials with eight strains of perennial ryegrass at two levels of manuring has now been completed. Results indicate that a moderate application of artificial manures gives a high degree of control over Gloeotinia temulenta infection. The degree of infection may be influenced by climatic conditions. Each strain has a definite inherent susceptibility or resistance to the disease. The most resistant strains are the commercial strains Irish Commercial and Devon Eaver; S24 is the most susceptible, followed by New Zealand Certified Mother Seed.  相似文献   

11.
Immature wheat grain in New Zealand is attacked sporadically by the native insect (bug),Nysius huttoni.This ‘bug-damaged wheat’ contains a bug salivary proteinase, and bread made from this wheat has a characteristically poor loaf volume and texture. Historical baking data suggest variations in wheat cultivar susceptibility to bug damage. This suggestion was tested in two trials (1992/1993 and 1993/1994) on immature wheat using nine or seven New Zealand cultivars and breeding lines enclosed together in nylon mesh cages with and withoutN. huttoni.Visible damage, bug-proteinase levels, electrophoretic protein patterns, and baking properties of the grain were analysed. Both trials showed that susceptibility to bug damage was significantly different amongst cultivars and breeding lines. The ranking of cultivar susceptibility was the same for the two trials, except for cv. Arawa, which was one of the most susceptible cultivars in the first trial, but one of the least susceptible in the second trial. Cultivars Domino and Oroua consistently showed less susceptibility to bug attack. The breeding line WW378 and the cultivar Otane were the most susceptible to bug attack. The high quality bread wheats (Otane, Oroua, Domino and Batten) were less susceptible to the effects of bug proteinase in baking than the poor baking quality wheats (Karamu, WW378, ASPS9927 and ASPS9928). Batten was significantly less susceptible than any other cultivar in test baking. There was no relationship between bug-damage susceptibility and grain characters such as colour, hardness and texture, or head characters such as shape, awns and waxiness.  相似文献   

12.
A field experiment was undertaken between April 2003 and May 2004 in southern Tasmania, Australia, to quantify and compare changes in the nutritive value of perennial ryegrass (Lolium perenne L.), prairie grass (Bromus willdenowii Kunth.) and cocksfoot (Dactylis glomerata L.) under a defoliation regime based on stage of leaf regrowth. Defoliation interval was based on the time taken for two, three or four leaves per tiller to fully expand. At every defoliation event, samples were collected and analysed for acid‐detergent fibre (ADF), neutral‐detergent fibre (NDF) and total nitrogen (N) concentrations and to estimate metabolizable energy (ME) and digestible dry matter (DDM) concentrations. Amounts of crude protein (CP) and metabolizable energy (MJ) per hectare values were subsequently calculated. There was a significantly lower (P < 0·001) NDF concentration for perennial ryegrass compared with prairie grass and cocksfoot, and a significantly lower (P < 0·001) ADF concentration for cocksfoot compared with prairie grass and perennial ryegrass, regardless of defoliation interval. The CP concentration of cocksfoot was significantly greater (P < 0·001) compared with the CP concentrations of prairie grass and perennial ryegrass. The estimated ME concentrations in cocksfoot were high enough to satisfy the requirements of a lactating dairy cow, with defoliation at or before the four‐leaf stage maintaining ME concentrations between 10·7 and 10·9 MJ kg?1 DM, and minimizing reproductive plant development. The ME concentrations of prairie grass (10·2–10·4 MJ kg?1 DM) were significantly lower (P < 0·001) than for cocksfoot (as above) and perennial ryegrass (11·4–11·6 MJ kg?1 DM) but a higher DM production per hectare resulted in prairie grass providing the greatest amounts of ME ha?1.  相似文献   

13.
Abstract The effects of level of concentrate supplementation on the response of dairy cows to grass silage‐based diets containing a constant proportion of fodder beet were examined. Forty Holstein‐Friesian dairy cows of mixed parity were used in a 2 × 5 factorial design experiment. Two basal diet types [grass silage alone or grass silage mixed with fodder beet in a 70:30 dry matter (DM) ratio] were offered ad libitum, and the effects of five levels of concentrate supplementation (mean = 3·0, 5·3, 7·5, 9·8 and 12·0 kg DM per cow d?1) were examined. Concentrate supplements were offered via an out‐of‐parlour feeding system. These treatments were examined in a three‐period (period length = 4 weeks) partially balanced changeover design experiment. Fodder beet inclusion had no significant effect on the estimated metabolizable energy (ME) concentration of the ration (P > 0·001). Total DM intake, estimated ME intake, milk yield, milk protein content and milk energy output all showed significant linear increases with increasing level of concentrate inclusion (P < 0·001) while, in addition, milk yield and milk energy output exhibited a significant quadratic increase (P < 0·01). The inclusion of fodder beet in the diet reduced silage DM intake (P < 0·01) but resulted in an increase in total DM intake and estimated ME intake (P < 0·001). However, inclusion of fodder beet had no significant effect on milk yield (P > 0·05), while increasing milk protein content and milk energy output (P ≤ 0·05). Milk energy output, as a proportion of estimated ME intake, was significantly (P < 0·001) reduced by fodder beet inclusion (0·44 vs. 0·38). Despite large increases in estimated ME intake with the inclusion of fodder beet at all levels of concentrate supplementation, milk energy output responses were small, resulting in an overall reduction in the efficiency of conversion of ME intake into milk energy output. An increased partitioning of dietary ME intake to tissue gain is suggested as the most likely explanation for the observations made.  相似文献   

14.
Three New Zealand grown tomato (Lycopersicon esculentum L.) cultivars, Aranka, Encore, and Flavourine, were analysed for colour (CIELAB L∗ a∗ b∗ values), ascorbic acid, total phenolics, lycopene, and total antioxidant activity (ABTS assay). Colour analyses of the air-dried tomatoes showed that the colour degradation as measured by the L∗ a∗ b∗ values was minimal, and the colour was not significantly different (p < 0.05) between each of the dried cultivars. In general, there was no significant difference (p < 0.01) between the fresh cultivars in terms of antioxidant components or total antioxidant activity. The average values obtained for antioxidant components in the three fresh cultivars were: ascorbic acid, 276 mg/100 g DM, total phenolics, 613 mg gallic acid equivalents (GAE)/100 g dry matter (DM) and lycopene 38 mg/100 g DM. Total antioxidant activity of the fresh cultivars was 2917 μmole Trolox equivalent antioxidant capacity (TEAC)/100 g DM. Following forced air-drying treatment at 42 ∘C for 48 hr, all cultivars showed significant decreases in ascorbic acid, total phenolics and total antioxidant activity, and increases in extractable lycopene contents. This study was undertaken to identify cultivars that would provide the best colour and nutrient contents after commercial air drying.  相似文献   

15.
A novel hybrid stubble turnip, Appin, bred by the Scottish Plant Breeding Station ( Brassica campestris ssp. rapifera cv. Tigra × B. campestris ssp. nipposinica cv. Mizuna) was compared in small-plot cutting trials with stubble turnip ( B. campestris ssp. rapifera cv. Ponda), forage rape ( B. napus ssp. biennis cv. Canard) and fodder radish ( Raphinus sativus cv. Neris) for 3 years, 1975–77, samples being taken from October to December or January each year to cover the likely period of utilization by grazing lambs. Except for the first year, Appin proved to yield less DM than Ponda, and be inferior in digestibility and metabolizable energy (ME) content, though N contents were on occasion higher. Canard had the highest overall ME content. In dry conditions in autumn 1977, Ponda proved the more reliable crop, suffering less depression in yield than other species. Anti-metabolite contents were determined in freeze-dried samples taken in winter 1976-77 and showed Canard to have the most brassica anaemia factor ( S -methyl cysteine sulphoxide): contents of thiocyanate were generally similar between crops.
As the degree of utilization of such forages when grazed can outweigh differences in recorded above-ground DM yields from cutting trials, it was considered that claims of better root anchorage and hence better utilization for Appin warranted evaluation in a grazing trial.  相似文献   

16.
Poor persistence of perennial ryegrass swards is a common problem; however, there is a lack of long‐term studies to understand the mechanisms associated with poor persistence. This study describes an experiment to test the hypothesis that high ryegrass seeding rates (>18 kg seed per ha) reduce long‐term population persistence because of smaller plant size and poorer survival during the first year after sowing. Four cultivars, representing four functional types of perennial ryegrass, were sown at five seeding rates (equivalent to 6, 12, 18, 24 and 30 kg seed per ha) with white clover in three regions of New Zealand. Swards were monitored for 5 years. No evidence was found to indicate a lack of persistence of ryegrass‐based swards sown at higher seeding rates. During the first year, swards sown at higher seeding rates had greater herbage accumulation (except at the Waikato site), greater ryegrass tiller density and greater ryegrass content. This initial impact of high seeding rates had largely dissipated by the fourth year, resulting in swards with similar annual herbage accumulation, tiller density and botanical composition. Similarly, there were relatively few differences among cultivars for these variables. Although high seeding rates did not negatively impact sward persistence, geographical location did, with strong evidence of ryegrass population decline at the Waikato site for all treatment combinations, some decline in Northland, and stable populations in Canterbury. It is possible that productive perennial ryegrass pastures can only be sustained for 4–5 years in some situations, even when the best ryegrass technology and management practices are used.  相似文献   

17.
Dorycnium hirsutum and D. rectum are perennial legumes which may have potential for use as pastures for the control of groundwater recharge in southern Australia. Little is known about the quality of the forage of Dorycnium species for grazing livestock or how these species respond to cutting. The effect of cutting height on plant survival, production of dry matter (DM), the proportion of leaf, edible stem (approximately <5 mm diameter) and woody stem in the DM and the nutritive value of the edible components was investigated. Biomass above five cutting‐height treatments (uncut, ground level, 5–8 cm, 10–15 cm and 15–30 cm above ground level) was removed at 8‐week intervals from plots of D. hirsutum and D. rectum from September 2002 to July 2003. In both species, plants subjected to lower cutting height treatments produced less DM above the height of the cut than those cut at higher heights. DM production declined over time in all treatments. Plants cut to ground level failed to regrow after the second harvest in D. hirsutum and the fourth harvest in D. rectum. Thus, these Dorycnium species were susceptible to high severity defoliations at 8‐week intervals. Negligible inedible woody stem was present in regrowth of both species after 8 weeks but D. hirsutum regrowth had a higher proportion of leaf (0·72) than D. rectum (0·56). Plants left uncut accumulated a large proportion of inedible woody stem in the DM (0·69 in both species) by July 2003, particularly at the base of the plant. Edible DM from regrowth of D. hirsutum and D. rectum had crude protein (CP) concentrations of 120 and 150 g kg?1 DM; dry matter digestibility (DMD) values of 0·45 and 0·58; organic matter digestibility (OMD) values of 0·50 and 0·64; neutral‐detergent fibre (NDF) concentrations of 370 and 290 g kg?1 DM; and acid‐detergent fibre (ADF) concentrations of 260 and 210 g kg?1 DM, respectively. Medicago sativa, grown under similar conditions, had higher digestibility values (0·63 DMD and 0·66 OMD) and similar CP concentrations to D. rectum (140 g kg?1 DM), but higher concentrations of NDF and ADF (410 and 290 g kg?1 DM). Leaf material from both Dorycnium species had a higher nutritive value than edible stems, with DMD and OMD values of leaf of D. rectum being 0·68 and 0·74 respectively. Uncut plants had a much lower nutritive value of edible DM than the regrowth from cut treatments; older material was also of a lower nutritive value. The relatively low nutritive value of even the young regrowth of Dorycnium species suggests that forage quality is a major limitation to its use. Forage of Dorycnium species could be used during periods when other sources of forage are in short supply but infrequent grazing it is likely to produce forage of a low nutritive value.  相似文献   

18.
Ryegrass (Lolium perenne L.) is a putative turf and forage plant characterized as mainly outcrossing in which the extent of self‐fertilization and its consequences has not been investigated. In this study, selfed and half‐sib family seeds were obtained from ten clonally propagated ryegrass plants among which two were endophyte‐free (EF) and eight were endophyte‐infected (EI). Then, 20 seed populations plus two commercial varieties of Speedy and Vigor were sown and evaluated in a biennial experiment for their turf and forage characteristics. Selfing caused significant inbreeding depression for plant fresh and dry weight and leaf length and width in the first year for both EI and EF genotypes. In the second year, only leaf length remained depressed among these characters. Also, for the most growth, turf and reproductive traits, EI populations showed less depression. The presence of endophyte in self‐pollinated populations made an increasing effect for the number of seed per spike and days to heading, although seed weight was reduced. Some of the populations derived from self‐pollination and infected with fungal endophyte including S9 and S10 were even superior to the two commercial varieties in terms of both seed production and turf characteristics. However, for seed‐related characteristics including number of spikes per plant, seed weight and seed yield, EF populations including Speedy and Vigor were more reproductive than EI populations. It is concluded that selfing may increase the discrimination between EI and EF ryegrass plants because endophyte infection may mitigate the negative consequences of inbreeding depression in prone populations.  相似文献   

19.
Host-plant resistance is an effective and economical means of controlling downy mildew (DM) diseases in maize (Zea mays L.). Crosses involving 10 inbred maize lines in all possible combinations (diallel cross) showed that susceptibility to sorghum DM (Peronosclerospora sorghi (Weston and Uppal) C. G. Shaw) is generally inherited as a dominant characteristic. However, progenies of crosses between one of the lines (CM105) resistant to DM, and susceptible lines, showed intermediate levels of resistance, indicating that several genes are involved and that their effects are additive. Progenies of crosses between resistant lines were more resistant than their parents, probably because of interactions between different resistance genes (epistasis). Both additive and non-additive gene action was detected by partitioning gene effects by generation mean in each 16 DM-resistant × DM-susceptible combinations, which indicates that the reactions of maize to DM are governed by several genes (i.e. polygenically) and that the inheritance of resistance is complex. An inbred line from Mexico, Tuxpeno Gpo. 48-Var. 168-1, is a particularly promising general source of resistance to DM.  相似文献   

20.
Kudzu [Pueraria lobata (Willd.) Ohwi.], a vigorous, perennial warm‐season legume, grows widely throughout the south‐eastern United States, predominantly as a volunteer species. It is tolerant of drought and acidic, infertile soils and may have potential as a low‐input forage for livestock. A field experiment was undertaken to determine the effects of cutting date and frequency on yield and nutritive value of kudzu (20‐year‐old stand with no fertilizer or lime inputs) in central Georgia. The cutting treatments included an uncut control, and plots cut once (September), twice (July and September), and three times (June, July, and September) during the 1994 growing season. Dry matter (DM) production and forage quality were determined for total herbage, leaf and stem tissues from quadrat samples taken on all plots in June, July, September, and November (after a killing frost) in 1994, and in June, 1995. Total herbage and leaf DM production was highest for the three‐harvest system and lowest in the no‐cut control plots in 1994, but these results were reversed in the harvest made in 1995. Total herbage production and crude protein concentrations were similar in kudzu cut in the initial summer harvest (either June, July, or September) during the first year. Whole plant and stem in vitro dry matter digestibility (IVDMD) in these samples declined throughout the growing season, while leaf IVDMD was unchanged until the first frost. Kudzu has the potential to be a low‐input forage for livestock, particularly as supplemental drought feed, or as a protein bank for summer or autumn grazing.  相似文献   

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