共查询到20条相似文献，搜索用时 281 毫秒
1.
《蚕业科学》2017,(4)
进行有性生殖的开花植物在形成染色体减半的生殖细胞过程中发生的减数分裂,与花粉的育性有很大关系。多倍体桑树具有生长旺盛、叶片肥大、叶质优良和抗逆性较强等特点,但是花粉的育性较低。从细胞学水平观察同源四倍体桑品种陕桑402-1花粉母细胞(PMCs)减数分裂以及小孢子的形成过程,分析多倍体桑树花粉育性降低的原因。观察发现PMCs减数分裂过程与花蕾大小有一定的相关性,当花蕾直径在0.71~1.54 mm之间时,PMCs处于减数分裂时期。在减数分裂过程中观察到了多价体、落后染色体和分裂不同步等异常情况:处于中期Ⅰ的染色体构型以二价体和四价体为主;四分体时期则出现了二分体、三分体、含微核的异常四分体以及多分体现象。观察小孢子发育分为4个时期,包括四分体时期、单核期、单核靠边期、双核期。初步推测陕桑402-1的PMCs在减数分裂过程出现上述异常情况,是导致其花粉育性降低的细胞学因素。 相似文献
2.
6种根茎型禾草PMC减数分裂及花粉形态的研究 总被引：1，自引：0，他引：1
对3种赖草属植物和3种偃麦草属植物花粉母细胞的减数分裂过程中花粉粒形态、饱满度和生活力进行了观察与比较研究,结果表明赖草、大赖草、中间偃麦草、巴顿硬叶偃麦草、茹莎娜硬叶偃麦草的PMC减数分裂过程中存在分裂期不同步现象;巴顿硬叶偃麦草和茹莎娜硬叶偃麦草在后期Ⅰ同源染色体分离时产生染色体桥的异常现象,巴顿硬叶偃麦草在中期Ⅰ出现染色体落后现象;PMC减数分裂的胞质分裂方式为连续型;赖草属中,大赖草的3-细胞花粉百分率高于2-细胞花粉;偃麦草属中,巴顿硬叶偃麦草的3-细胞花粉百分率高于2-细胞花粉,而中间偃麦草的3-细胞花粉百分率低于2-细胞花粉,其花粉生活力高于其它种. 相似文献
3.
老芒麦细胞遗传学特性分析 总被引：1，自引：0，他引：1
通过对老芒麦（Elymus sibiricicus）根尖细胞和花粉母细胞分裂过程中的染色体形态和行为特征的观察分析,结果表明：老芒麦染色体数目为2n=28,核型公式：2n=4x=28=16m＋10sm＋2M,属1A核型,染色体组型属对称型。通过对花粉母细胞减数分裂的几个典型过程中染色体行为的观察显示,终变期同源染色体配对率高,后期Ⅰ、后期Ⅱ染色体同步均衡分离,产生的配子具有恒定数目染色体。几种不同方法测定其花粉生活力表明老芒麦花粉育性较高。 相似文献
4.
对3种赖草属植物和3种偃麦草属植物花粉母细胞的减数分裂过程中花粉粒形态、饱满度和生活力进行了观察与比较研究，结果表明：赖草、大赖草、中间偃麦草、巴顿硬叶偃麦草、茹莎娜硬叶偃麦草的PMC减数分裂过程中存在分裂期不同步现象；巴顿硬叶偃麦草和茹莎娜硬叶偃麦草在后期Ⅰ同源染色体分离时产生染色体桥的异常现象，巴顿硬叶偃麦草在中期Ⅰ出现染色体落后现象；PMC减数分裂的胞质分裂方式为连续型；赖草属中，大赖草的3－细胞花偻百分率高于2－细胞花粉；偃麦草属中，巴顿硬叶偃麦草的3－细胞花粉百分离高于2－细胞花粉，而中间偃麦草的3－细胞花偻百分率低于2－细胞花粉，其花偻生活力高于其它种。 相似文献
5.
6.
二倍体和四倍体多花黑麦草×苇状羊茅杂种 F_1 花粉母细胞减数分裂染色体具有较高的配对水平,单价体少,二价体多。存在低频率的三价体、四价体和较低频率的五价体,表明多花黑麦草和苇状羊茅染色体之间存在同源或部分同源和异源苏会配对,F_1 正常花粉频率平均为0～18.2%,不同杂交组合甚至同一组合不同植株均有很大的差异。F_1 的回交结实率很低,平均为0.05粒种子/小穗,且易与多花黑麦草回交。杂种后代自交结实率与其亲本一样均很低。开放授粉结实率则随着世代的增加显著提高,F_1 代平均仪为0.4%,至第五代高达65.5%。杂种后代越夏性以 F_1为最强,平均达79.9%,介于双亲之间或与苇状羊茅相近,随着世代的增加越夏性则逐渐丧失。推测越夏性丧失与杂种后代群体过早或过多地丢失苇状羊茅染色体,减少了优良基因重组的机会有关。育性正常、越夏性较强的黑麦草型第四代选系“891”的获得,表明把苇状羊茅的越夏性部分地转移到多花黑麦草中是可行的。 相似文献
7.
3.染色体数的异常染色体数的异常,大致分为异数性、异倍性以及由两类以上染色体数细胞构成个体的镶嵌式型。前者由精子和卵子形成减数分裂时和受精后体细胞分裂时染色体不分离引起。而染色体的异倍性,是受精时产生多精核受精和多卵核受精,以及受精后卵分裂时仅仅发生染色体的复制、而不伴随细胞分裂 相似文献
8.
9.
本文用植物染色体制片新方法一去壁低渗法对四川省的50多个野生桑树品种进行了染色体倍数性的鉴定。在其中发现了七个六倍体。它们分别是平4号、平5号、平6号、平7号、平8号、糯岩桑、剑14号。其余40多个品种为二倍体。在发现的六倍体桑中,有5个原产于四川省平武县,一个于其相邻的剑阁县,另一个原产叫南的会东县。并从细胞遗传学的角度探讨了三倍体和六倍体桑的形成机制。均为在成熟分裂时的退行现象(regresion)所致。即在成熟分裂的某时期,遭遇寒流,则分裂中止进行。第一分裂中期如果出现退行现象,则省略后期直接进入中间期,因此形成的巨大核为复旧核(resti tution hucreus),这就形成了不还原染色体数的配子,而且多能生殖,此配子和正常的几配子受精即成为3倍体。3倍体桑树在减数分裂时,如因寒流的影响,也极易形成3n的配子,3n配子互相受精,即成为六倍体。在四川发现大量的六倍体,这时桑树的遗传学研究和多倍体育种都具有重要的意义。通过六倍体和二倍体交杂,得到4倍体,可以应用于生产。 相似文献
10.
11.
Growth rate and physiology of steers grazing tall fescue inoculated with novel endophytes 总被引：2，自引：0，他引：2
Nihsen ME Piper EL West CP Crawford RJ Denard TM Johnson ZB Roberts CA Spiers DA Rosenkrans CF 《Journal of animal science》2004,82(3):878-883
Cattle grazing tall fescue (Festuca arundinacea Schreb.) often develop fescue toxicosis. This condition is thought to be caused by ergot alkaloids produced by the endophyte Neotyphodium coenophialum. Endophytes from wild tall fescue plants, which do not produce ergot alkaloids, were transferred into the endophyte-free tall fescue germplasm, HiMag. The novel associations also lacked the ability to produce ergot alkaloids. Our objective was to determine whether cattle grazing these novel endophyte associations showed signs of fescue toxicosis. At the Fayetteville, Arkansas location, tester steers (n = 72) were assigned to one of four pasture treatments: endophyte-free HiMag tall fescue (HiMag-); 'Kentucky-31' tall fescue infected with its native, toxic endophyte (KY+); and two novel endophyte-infected tall fescue associations, HiMag4 and HiMag9. At the Mount Vernon, Missouri location, steers (n = 54) were used to test three of the four cultivars (HiMag9 was not tested). Ergot alkaloid concentrations in the forage of HiMag4 and HiMag9 were low or undetectable. Respiration rate, rectal temperature, ADG, and hair scores were measured during the grazing period. Blood was collected via jugular venipuncture and used for prolactin, aspartate aminotransferase, alkaline phosphatase (ALP), lactate dehydrogenase (LDH), cholesterol, triglyceride, and creatinine analysis. Weight gains by steers grazing HiMag4 and HiMag9 did not differ from those of steers grazing HiMag-, but were greater than gains (P < 0.05) by steers on the KY+ treatment. Steers grazing KY+ had higher (P < 0.05) respiration rates, rectal temperatures, and hair scores than did steers grazing novel endophyte and HiMag- pastures. Prolactin, ALP, cholesterol, LDH, and triglycerides all were suppressed (P < 0.05) in steers grazing KY+ compared with steers grazing novel endophyte and HiMag- pastures. Steers grazing the novel endophyte tall fescues did not suffer from the decreased weight gains and toxicities associated with fescue toxicosis, resulting in enhanced animal production. 相似文献
12.
Johnson JM Aiken GE Phillips TD Barrett M Klotz JL Schrick FN 《Journal of animal science》2012,90(7):2402-2409
A 2-yr grazing experiment was conducted with crossbred steers (8 to 10 mo and with initial BW of 304 kg ± 34 kg in 2008 and 277 kg ± 24 in 2009) to evaluate animal performance and pasture responses of a late maturing tall fescue [Lolium arundinaceum (Schreb.) Darbysh; KYFA9301] population infected with the AR584 novel, non-toxic endophyte (Neotyphodium coenophialum; NE9301) as compared with Kentucky 31 fescue infected with the common toxic endophyte strain (KY31), 'Jesup' MaxQ fescue infected with the AR542 endophyte (MaxQ), and endophyte-free KYFA9301 (EF9301). Treatments were assigned for seeding in 1.0-ha pastures in a randomized complete block design with 3 replications. Pastures were grazed from 6 May to 23 July in 2008 (76 d) and 2 April to 25 June in 2009 (84 d). Each pasture was grazed with 4 tester steers and put-and-take steers were used to maintain forage mass at 2,500 ± 250 kg DM/ha. Shrunk BW was taken at initiation and termination of grazing each year. Rectal and skin temperatures were recorded, and jugular blood was collected each year at approximately d 28, 56, and study completion. Forage samples were collected at 2-wk intervals for analyzing CP, IVDMD, ADF, and NDF. Responses were analyzed with mixed models, and preplanned orthogonal contrasts were used to compare KY31 with non-toxic fescues, EF9301 vs. novel endophyte fescues, and NE9301 vs. MaxQ. All steer responses were similar (P > 0.10) among the non-toxic fescues. Average daily gains and total BW gain/ha for the 3 non-toxic fescues were greater (P < 0.001) than for KY31. Rectal/skin temperatures for the 3 non-toxic fescues were less (P < 0.001) and serum prolactin concentrations were greater (P < 0.01) than for KY-31. Pasture carrying capacity was greater (P = 0.003) for KY31 than the 3 non-toxic fescues and was greater for EF9301 (P = 0.017) than the 2 novel endophyte fescues. However, stocking rates (kg BW/ha) at the initial and midpoint days of grazing were similar (P > 0.40) among endophyte-fescue combinations, but by the end of the grazing season, stocking rate was greater (P < 0.001) for KY31 than for the non-toxic fescues and was greater (P = 0.053) for NE9301 than for MaxQ. Results indicated that NE9301 is as effective as EF9301 and MaxQ in improving BW gain and alleviating fescue toxicosis and that NE9301 can provide greater carrying capacities than MaxQ in late June and July. 相似文献
13.
二倍体和四倍体野生鸭茅遗传特性比较研究 总被引：11，自引：2，他引：9
采用细胞遗传学，生化遗传学的方法，对我国亚热带地区几个二倍体和四倍体野生鸭茅的核型，花粉母细胞减数分裂染色体配对行为，不同生育期的酯酶和过氧化物酶同功酶进行比较研究。结果表明，供试野生二倍体鸭茅之间，各四倍体之间的同源性较高，遗传差异较小；二倍体与四倍体之间，在核型，花粉数量，种，子千粒重，酯酶和过氧化物酶等方面都有很大差异；二倍体和四倍体野生鸭茅的花粉母细胞减数分裂虽然正常，但花粉育性和结实率不 相似文献
14.
Beck PA Gunter SA Lusby KS West CP Watkins KB Hubbell DS 《Journal of animal science》2008,86(8):2043-2055
Increased costs of annual establishment of small grain pasture associated with fuel, machinery, and labor are eroding the profitability of stocker cattle enterprises. Interest has therefore increased in development of cool-season perennial grasses that are persistent and high quality. This study occurred on 24 ha (divided into thirty 0.81-ha paddocks) located at the University of Arkansas Division of Agriculture Livestock and Forestry Branch Station, near Batesville. Two tall fescue (Festuca arundinacea Schreb.) cultivars infected with novel endophytes (NE), Jesup infected with AR542 endophyte (Jesup AR542), and HiMag infected with Number 11 endophyte (HM11) were established in September 2002. Jesup AR542 and HM11 were compared with endemic endophyte Kentucky 31 (KY-31) tall fescue; wheat (Triticum aestivum L.) and cereal rye (WR, Secale cereale L.) planted in September 2003, 2004, and 2005; and annual ryegrass [RG, Lolium perenne L. ssp. multiflorum (Lam.) Husnot] planted in September 2004 and 2005. Each year, 3 steers (3.7 steers/ha) were placed on each pasture for fall and winter grazing, and 5 steers (6.2 steers/ha) were placed on each pasture for spring grazing. Animal performance is presented by year in the presence of a year x treatment interaction (P < 0.01). Body weight gain per hectare of steers grazing NE tall fescue was greater (P < 0.01) than those of KY-31 and WR during 2003 to 2004, whereas in 2004 to 2005, BW gain per hectare of steers grazing NE and RG did not differ (P < or = 0.29) and was greater (P < 0.01) than that of WR, which was greater (P < 0.01) than that of KY-31. During 2005 to 2006, BW gain per hectare was greater (P < 0.01) for steers grazing RG than those of NE and WR, which did not differ (P > or = 0.14). Body weight gain per hectare was least (P < 0.01) for steers grazing KY-31. Average net return of NE tall fescue was greater (P < 0.01) than KY-31, but profitability of NE did not consistently differ from cool-season annuals. Across the 3-yr study, NE tall fescue produced net returns per hectare of $219; this level of profitability would require 4 yr for a new planting of NE tall fescue to break even. Novel endophyte tall fescues offer potential benefits related to decreased risk of stand establishment of annual forage crops, longer growing season, and acceptable animal performance. 相似文献
15.
16.
L M Lauriault C T Dougherty N W Bradley P L Cornelius 《Journal of animal science》1990,68(5):1245-1253
Livestock grazing endophyte (Acremonium coenophialum Morgan-Jones and Gams)-infected tall fescue (Festuca arundinacea Schreb.) perform poorly due to tall fescue toxicosis, especially when animals are under heat stress. In order to determine whether thiamin promotes recovery from tall fescue toxicosis, 1 or 0 g of thiamin per day, as mononitrate, was fed orally to adult Angus (Bos taurus) cows (380 +/- 8 kg) grazing either tall fescue pasture with and without endophyte or alfalfa (Medicago sativa L.). A tethered grazing system employing a split-plot design was used to estimate intake and components of ingestive behavior. No significant differences attributable to thiamin supplements were seen in rates of intake and biting, grazing time and intake per bite when cows grazed endophyte-infected tall fescue during the first 4 d of exposure. When cows grazed endophyte-infected (greater than 95%) tall fescue with 2,091 micrograms/g loline alkaloids after 4 d of exposure, the untreated animals ingested herbage dry matter (DM) at 1.19 kg/h, whereas the cows receiving thiamin ate 1.57 kg/h (P less than .05). Cattle achieved these rates of DM intake by forming bites of 1.0 and 1.2 g DM at 24 and 26 bites/min when treated with 0 and 1 g of thiamin per day, respectively. Thiamin supplements had no effect on ingestive behavior of cows grazing endophyte-free tall fescue or alfalfa after exposure to these forages for 4 d. Responses to thiamin generally were greater when cattle grazing endophyte-infected tall fescue were exposed to heat stress. Oral thiamin supplementation may alleviate tall fescue toxicosis of beef cattle during warm weather. 相似文献
17.
对亲本披碱草(Elymus dahuricus)和野大麦(Hordeum brevisubulatum)及其杂种F1和BC1代体细胞染色体数和花粉母细胞(PMC)减数分裂染色体行为进行观察和分析。结果表明:亲本披碱草的染色体数为2n=42,野大麦为2n=28;正、反交杂种F1染色体数均为35;BC1代染色体发生了数目上的差异,变异范围为28~35,并出现很多非整倍性植株;披碱草的PMCMI二价体配对频率很高,野大麦PMCMI出版少量的四价体、三价体和单价体,但以二价体占优势;正反交杂种F1减数分裂不规则,单价体的普遍存在是造成杂交不育的重要原因;BC1代的PMCMI单价体频率较F1代有所下降,二价体频率有所增高,有些株系的环状二价体占绝对优势,这为杂种育性恢复提供了细胞学依据。 相似文献
18.
Parish JA McCann MA Watson RH Hoveland CS Hawkins LL Hill NS Bouton JH 《Journal of animal science》2003,81(5):1316-1322
Nonergot alkaloid-producing endophytes from New Zealand were inserted into tall fescue (Festuca arundinacea) cultivars in an attempt to address the problem of fescue toxicosis in grazing sheep. A 3-yr grazing study was conducted to determine lamb performance and to evaluate toxicosis in lambs grazing nonergot alkaloid-producing endophyte-infected (AR542 or AR502), endophyte-free (E-), or wild-type toxic endophyte-infected (E+) Jesup tall fescue or nonergot alkaloid-producing endophyte-infected (AR542) Georgia-5 tall fescue. Replicated 0.11-ha tall fescue paddocks were established at the central Georgia Branch Station during September 1997 and stocked with lambs from spring 1998 through autumn 2000. Mean ergot alkaloid concentrations were higher (P < 0.01) in E+ forage than in AR542, AR502, and E- tall fescue, and ergot alkaloid concentrations in E- plants and plants infected with AR542 and AR502 were low. Forage availability did not differ (P = 0.92) across treatments during autumn and was higher (P < 0.05) in Georgia-5 AR542 than in Jesup AR502 and E+ pastures. Initial serum prolactin (PRL) concentrations did not differ (P = 0.58) across treatments during autumn, but were higher on Jesup AR542 than E+ during spring. Post-treatment serum PRL concentrations were depressed (P < 0.01) on E+ compared with AR542, AR502, and E- in both spring and autumn. Signs of heat stress were observed in E+ lambs during periods of high ambient temperatures. Mean post-treatment rectal temperature and mean stocking rate exhibited treatment x year interactions (P < 0.05). Lamb ADG was higher (P < 0.05) on AR542, AR502, and E- than on E+ tall fescue. Similarly, gain/hectare was higher (P < 0.015) on AR542, AR502, and E- than on E+. Tall fescue pastures containing AR542 and AR502 endophytes yielded lamb performance that did not differ from that on E- tall fescue and which was superior to performance on E+ tall fescue. Depressed PRL concentrations and elevated rectal temperatures as indicators of toxicosis were evident only in lambs grazing E+ tall fescue, suggesting that nonergot alkaloid-producing endophyte-infected tall fescue is a viable alternative for alleviating tall fescue toxicosis. 相似文献
19.
C T Dougherty L M Lauriault N W Bradley N Gay P L Cornelius 《Journal of animal science》1991,69(3):1008-1018
Livestock grazing endophyte (Acremonium coenophialum)-infected tall fescue (Festuca arundinacea Schreb. cv. Kentucky 31) at high ambient temperatures may suffer from fescue toxicosis. Adult Angus cows (Bos taurus) were fed 0 to 1 kg/d of 70% infected tall fescue seed containing about 4.4 g of loline alkaloids in factorial combination with thiamin at 0 or 1 g/d. Cows assigned to the zero level of tall fescue seed received a supplement of equivalent energy and protein. Ingestive behavior was measured at 1330 to 1430 EDT during two 4-d periods in two consecutive weeks in August on alfalfa (Medicago sativa L.) pastures using a tethered grazing system. Alfalfa intake per measured grazing session of cows given tall fescue seed declined linearly (P less than .01) as air temperatures during grazing increased above 25 degrees C, largely because of shorter grazing meals. Thiamin increased alfalfa intake per measured grazing session by extending grazing time. Alkaloids in ingested endophyte-infected tall fescue induce thiamin deficiencies in cattle that result in symptoms of tall fescue toxicosis. 相似文献
20.
为探索植物对重金属的修复作用以及自身对重金属污染的生理效应,以基质盆栽高羊茅(Festuca arundinacea)幼苗为试验材料,比较分析了不同铅胁迫下,高羊茅的生理生化效应.结果表明:随着胁迫时间的延长,不同铅浓度下的高羊茅叶片中超氧化物歧化酶(SOD)和过氧化物酶(POD)活性整体变化为先升后降,POD变化趋势较为缓慢,表明低浓度或短时间内铅可快速诱导高羊茅保护酶活性.叶绿素总量变化为低浓度(500,1000 mg·L-1)下先增加后下降,高浓度下则为持续下降,表明高羊茅可能通过增加叶绿素来适应低铅胁迫,而高浓度下则失去了这种调节能力.3个铅浓度下的丙二醛(MDA)含量与胁迫时间及胁迫浓度均为正相关,表明随着胁迫浓度和时间的增加,细胞膜脂过氧化作用加强.脯氨酸含量在500,1000 mg·L-1铅浓度下随时间增加为先降后升,1500 mg·L-1浓度下则相反,但均高于对照,表明经铅胁迫后细胞的渗透调节能力增强.3个浓度下的可溶性糖含量变化均随时间表现出降-升-降,最终显著降低,整个变化过程低于对照.因此在铅胁迫过程中,这些生理特性的变化表明在低铅胁迫时高羊茅表现为积极适应和抵抗,而在高铅胁迫下则表现为忍耐和受损. 相似文献