Discovery of 2n gametes in tetraploid oat Avena vaviloviana

Summary Sexual polyploidization via the action of 2n gametes (gametes with the sporophytic chromosome number) has been identified as the most important evolutionary mode of polyploidization among plant genera. This study was conducted to determine whether 2n gametes are present in the tetraploid level of the genus Avena (2n=4×=28) Twenty tetraploid Avena lines, representing four species and one interspecific hybrid, were screened for pollen grain size in order to differentiate between n and 2n pollen. Avena vaviloviana (Malz.) Mordv. line PI 412767 was observed to contain large pollen grains at a 1.0% frequency. Cytogenetic analyses of pollen mother cells of PI 412767 revealed cells with double the normal chromosome number (i.e., 56 chromosomes at metaphase I and anaphase I). The mode of chromosome doubling was found to be failure of cell wall formation during the last mitotic division that preceded meiosis. The resulting binucleate cells underwent normal meiotic divisions and formed pollen grains with 28 chromosomes. Based on the formation and function of 2n gametes, three models involving diploid and tetraploid oat lines are proposed to describe possible evolutionary pathways for hexaploid oats. If stable synthetic hexaploid oat lines could be developed by utilizing 2n gametes from diploid and tetraploid oat species through bilateral sexual polyploidization, the resulting hexaploids could be used in breeding programs for transferring genes from diploids and tetraploids to cultivated hexaploids.     

All hermaphrodite progeny are derived by self-pollinating the sunrise papaya mutant

Self‐pollination of a hermaphroditic cultivar normally gives a ratio of 2 : 1 hermaphrodite to female papayas with genotypes M₂m and mm, respectively. Much effort has been dedicated to marking the sexual types of papaya at the seedling stage to distinguish hermaphroditic from female papayas. A hermaphroditic papaya mutant (SR*) has been obtained, derived from the ‘Sunrise’ papaya cultivar mutant. Self‐pollination of the mutant resulted in all progenies being hermaphroditic. The genotype of the female was lethal, as a result of a lethal gene being linked to the mm female gene complex in this case. However, a 3 : 1 segregation ratio was obtained from the progeny of the hermaphroditic cultivar ‘Thailand’ crossed with SR*, indicating that all genotypes survived. Homozygous genotypes (M₂M₂) would be lethal according to Storey's model. Randomly selected F1 plants of the ‘Thailand’ SR* combination were self‐pollinated to obtain an F₂ generation. The F₂ segregation ratio suggested that the SR* mutant had a different form of the M₂ allele, now designated as M_@, which allowed the dominant M_@M₂ to survive in cross combinations. Genetic study has proved that SR* has the M_@ml genotype, a new mutant. It is capable of producing all hermaphroditic papaya progenies.     

30%己乙水剂对玉米根系生理活性的调控效应

以玉米品种农大3138为材料，在大田和PVC管栽条件下研究了应用植物生长调节剂30%己乙水剂对玉米根系生理活性的影响，结果表明，玉米6叶期用400 mg/L 30%己乙水剂叶面喷施处理，可增加根系干重，显著提高第8层根（气生根）量，提高拔节期和籽粒形成期1～4层根、6～7层根的活力；提高拔节期和籽粒形成期1～4层根中蔗糖转化酶活性。15N示踪试验结果表明，30%己乙水剂处理提高了玉米灌浆期氮的累积，增加了向果穗和根系的分配，提高了根系伤流量和根系中氨基酸含量。30%己乙水剂处理后，玉米根系中生长素、细胞分裂素、赤霉素、脱落酸等激素含量的变化同根系生理活性变化相应，特别是通过根系伤流液向地上部输送细胞分裂素的能力增强，可能是整株生长发育改善的重要原因。30%己乙水剂施用提高玉米产量11.7%。     

Intraspecific somatic and sexual hybridisation between dihaploid lines of Solanum tuberosum L.: evaluation of morphological traits and resistance to late blight Phytophthora infestans (Mont.) de Bary in the foliage

Intraspecific tetraploid somatic and sexual hybrid plants have been resynthesised following protoplast fusion and by sexual crosses between two dihaploid potato (Solanum tuberosum) lines each possessing complementary agronomic traits. The dihaploid PDH 40 possesses good tuber shape and yield but has foliage susceptibility to late blight (Phytophthora infestans). On the other hand, the dihaploid PDH 727 possesses resistance to blight in the foliage but has a low yield of small and irregular shaped tubers. Since it was only possible to use a partial selection strategy based on culture media to facilitate recovery of somatic hybrid plants-further morphological and esterase isozyme based characterisations were performed to identify somatic hybrid plants from amongst the non-hybrid plant material. When the blight resistance of both the intraspecific somatic and sexual hybrid plants was assessed there was no significant difference in the mean resistance value and it was intermediate between those of their parents. However, the range of resistance was much wider among the sexual hybrids than among the plants derived from somatic fusion. An assessment of tuber yield between tetraploid sexual and somatic hybrids showed no significant difference and it was higher than that of either parent value. The implication of these results in the context of potato genetics and breeding is discussed.     

Clinical features and their course of pituitary carcinoma with distant metastasis in a dog

An 11-year-old male toy poodle with neurological symptoms was diagnosed with a macroscopic pituitary tumor, which produced adrenocorticotropic hormone. Radiation therapy with a linear accelerator was performed for the pituitary tumor, and resulted in good local tumor control. However, serum endogenous adrenocorticotropic hormone concentrations were uncontrollable even after the tumor disappeared. Abdominal computed tomography revealed splenic masses, and splenectomy was performed. Histopathological examination of the surgical specimen showed tumor cells with eosinophilic and finely granular cytoplasm suggestive of endocrine origin. Since these cells were positive for adrenocorticotropic hormone, the case was diagnosed as a pituitary carcinoma with distant metastasis. Necropsy revealed multiple metastases to the abdominal organs. This is the first case report describing canine pituitary carcinoma with distant metastasis.     

不同密度甘肃马先蒿寄生和内生真菌互作对紫花针茅内源激素及生物碱含量的影响

根寄生植物是禾草生长过程中的一种生物逆境,禾草内生真菌能增强其对生物或非生物逆境的耐受能力;然而,有关禾草内生真菌对不同密度根寄生逆境下禾草生长、内源激素水平和生物碱含量变化的研究鲜有报道。基于此,通过开展温室盆栽试验,以建立根寄生关系的带菌(E+)和未带菌(E-)紫花针茅及根寄生植物-甘肃马先蒿为研究对象,比较E+和E-紫花针茅在不同甘肃马先蒿寄生强度下生长、内源激素和生物碱含量变化。结果表明,与未寄生紫花针茅相比,随着甘肃马先蒿密度增加,紫花针茅生物量降低80%,株高、分蘖数和根长均降低25%,吲哚乙酸、脱落酸含量分别增加43%和51%,细胞分裂素含量降低50%。内生真菌侵染显著提高紫花针茅生长特性,增加内源激素和生物碱含量;带菌紫花针茅在根寄生逆境下生物碱含量持续增加,同时甘肃马先蒿利用根部木质部通道可获取寄主内生真菌合成的生物碱。由此可见,内生真菌通过调控紫花针茅体内有关生长和逆境预警相关内源激素水平及改变生物碱含量的方式增强紫花针茅对甘肃马先蒿根寄生逆境的耐受能力,为利用禾草内生真菌共生体修复甘肃马先蒿型退化草地提供新视角。     

GA3和6-BA对高加索三叶草根蘖芽生长及内源激素含量的影响

为了研究植物生长调节剂赤霉素(GA₃)和6-苄氨基腺嘌呤(6-BA)对高加索三叶草根蘖芽生长发育及内源激素含量的影响,在不同浓度的GA₃(0对照、300、600、900 和1200 mg·L^-1)和6-BA(0对照、25、50、100和200 mg·L^-1),对其根蘖芽生长后的植株高度、叶片数、叶绿素含量和内源激素含量(地上部分和地下部分)进行测定与分析。结果表明:与对照相比,所有GA₃处理均显著增加了株高(P<0.05)。尤其在600 mg·L^-1 GA₃处理下,平均株高为21.33 cm(高于对照处理4.12倍)。GA₃还促进了叶绿素a的合成,最显著效果是在600 mg·L^-1 GA₃处理下,叶绿素a的浓度为0.92 mg·g^-1(高于对照76.92%) (P<0.05)。GA₃对叶绿素b含量无显著影响(P>0.05)。在6-BA所有处理浓度下,株高约为对照处理2.6倍,并且对于叶片数,6-BA处理比GA₃处理更敏感,在200 mg·L^-1时最多,高于对照2.99倍。 6-BA显著促进了叶绿素a和b的积累(P<0.05)。内源激素含量在整个处理浓度下均显示出对外源激素应用的剂量反应。对于地上植物部分,600 mg·L^-1的外源GA₃引起内源玉米素(ZT),GA₃和生长素(IAA)分别增加约23.84%,55.71%和137.99%,而脱落酸(ABA)减少约44.09%。与对照相比,外源200 mg·L^-1 6-BA使内源ZT,GA₃和IAA含量分别提高了约293.23%,49.71%和49.84%,而ABA降低了约52.48%。对于地下植物部分,内源激素变化与地上部分植物的响应大致相似,明显不同在于外源同样浓度GA₃(600 mg·L^-1)和6-BA(200 mg·L^-1)处理引起的ABA降低要少(分别为15.15%和28.26%)。总之,600 mg·L^-1 GA₃和200 mg·L^-1 6-BA是促高加索生长发育的最佳浓度。     

饲粮添加甜菜碱对巴马香猪繁殖性能、初乳成分及血浆代谢物和繁殖激素含量的影响

本试验旨在研究饲粮添加甜菜碱对巴马香猪繁殖性能、初乳成分及血浆代谢物和繁殖激素含量的影响。选取3~7胎次巴马香猪40头,随机分为2组,每组20头,单栏饲养。对照组饲喂基础饲粮,试验组在基础饲粮中添加3.5 kg/t甜菜碱盐酸盐。试验期为母猪配种后第3天至分娩后第21天。结果表明:与对照组相比,饲粮添加甜菜碱显著降低仔猪死亡率(P<0.05),增加断奶仔猪数(P=0.087);饲粮添加甜菜碱显著增加初乳中乳蛋白和尿素氮含量(P<0.05);饲粮添加甜菜碱显著降低妊娠第75天血浆总蛋白(TP)含量(P<0.05),显著降低妊娠第105天血浆TP含量和谷草转氨酶(AST)活性(P<0.05),显著增加妊娠第75天血浆碱性磷酸酶(ALP)活性以及产后第7天血浆AST和ALP活性(P<0.05),且妊娠第105天血浆ALP活性呈增加趋势(P=0.073);饲粮添加甜菜碱显著降低妊娠第45天血浆催乳素(PRL)、孕酮(PROG)、促卵泡素(FSH)和雌二醇(E2)含量以及妊娠第75天血浆PRL和PROG含量(P<0.05),且妊娠第75天血浆E2含量(P=0.061)和妊娠第105天血浆FSH含量(P=0.062)呈下降趋势。综上所述,饲粮添加甜菜碱可改善初乳成分和血浆代谢物含量,降低血浆繁殖激素含量,进而增加断奶仔猪数。     

非洲菊离体快速繁殖技术

以非洲菊品种107-2幼嫩花蕾为外植体进行离体快速繁殖技术研究。结果表明:外殖体诱导愈伤组织并分化不定芽的适宜培养基为1/2 MS 10.00 mg·L-1 BA 0.50 mg·L-1 IAA,培养10 d以后,愈伤组织诱导率达100%,培养60 d以后,芽的分化率达93.5%;芽增殖的适宜培养基为MS 0.2 mg·L-1 BA 5.0 mg·L-1 KT 0.3 mg·L-1 IAA,培养30 d以后,芽的增值系数为2.5,苗体生长健壮、翠绿,小苗高度可达2.3 cm;壮苗生根的适宜培养基为1/2 MS 0.15 mg·L-1IAA,培养22 d以后,生根率可达95%,每株苗平均根数为3.6条,平均根长为1.2 cm,小苗植株翠绿挺拔,根系粗壮,移栽后都能成活。