中间偃麦草和长穗偃麦草解剖结构的扫描电镜观察

运用扫描电镜观察了中间偃麦草Elytrigia intermedia和长穗偃麦草E. elongata的根、茎、叶以及根茎的形态解剖结构,结果显示：2种植物的根形态均由表皮、皮层和中柱组成,表皮着生大量根毛,内皮层细胞壁5面加厚,在横切面上呈马蹄形;茎与根茎的维管束分内外两圈分布,中央有髓腔;叶片形态由表皮、叶肉和叶脉3部分构成,表皮细胞包括长细胞、附属物、气孔器细胞和泡状细胞。中间偃麦草和长穗偃麦草的叶片表皮微形态上存在显著差异,其中长穗偃麦草叶脉上分布3～4列乳突,而中间偃麦草叶脉上则分布3～4列刺毛,另外在根皮层细胞中发现了发达的类似通气组织的结构,产生原因亟待进一步研究。     

21份偃麦草属牧草苗期耐盐性评价

对21份国外引进的野生偃麦草属种质材料在不同梯度NaCl胁迫下,通过存活率、株高、根茎比、生长胁迫指数和叶片伤害率的测定,利用主成分分析法和隶属函数法,综合评价其耐盐性.结果表明:随着盐浓度增大,偃麦草属材料除伤害率外,其它指标与对照相比均有所下降.根据综合评价值可知,其耐盐性由强到弱为ZXY03P-388,ZXY03P-349,ZXY03P-433,ZXY04P-210,ZXY04P-257,ZXY04P-77,ZXY03P-463,ZXY03P-480,ZXY04P-25,ZXY03P-368,ZXY03P-491,ZXY04P-176,ZXY04P-29,ZXY04P-490,ZXY04P-6,ZXY03P-444,ZXY04P-103,ZXY03P-318,ZXY03P-271,ZXY03P-289,ZXY04P-157.     

偃麦草属5种植物种子发育过程中生理生化的研究

对偃麦草属5种植物种子发育特性研究表明,其种子在成熟过程中水分含量呈下降的趋势,达50%含水量后下降非常迅速;干物质重量随种子的成熟逐渐增加,进入生理成熟期趋于稳定;偃麦草属植物种子成熟后含水量、干鲜重和千粒重存在种间显著差异,其中长根茎的巴顿硬叶偃麦草种子含水量、干鲜重和千粒重最低,种子较小。发芽实验结果表明,偃麦草属5种植物种子发育存在明显种间差异,种子发芽率与根茎的发育程度呈负相关,根茎越长,其休眠程度越严重。采用电导率值能够较好地反映种子间活力差异。偃麦草属植物种子发育过程中种子活力逐渐提高,直至种子进入生理成熟期（水分含量40%～50%）达到最高。     

Under‐sown cover crops and post‐harvest mowing as measures to control Elymus repens

Two potential control methods for Elymus repens, which do not disturb the soil, are post‐harvest mowing and competition from under‐sown cover crops. Our aim was to quantify the effect of cover crop competition and mowing on E. repens and to evaluate the potential for combining the two methods. We present a two‐factorial split‐plot experiment conducted at three locations in Sweden, in two experimental rounds conducted in 2011–2012 and 2012–2013. A spring cereal crop was under‐sown with perennial ryegrass, red clover or a mixture of the two (subplots). Under‐sown crops were either not mowed, or mowed once or twice post‐harvest (main plots). This was followed by ploughing and a new spring cereal crop the next year. Mowing twice reduced autumn shoot biomass by up to 66% for E. repens and 50% for cover crops compared with the control, twice as much as mowing once. Pure ryegrass and mixture treatments reduced E. repens shoot biomass by up to 40% compared with the control. Mowing twice reduced rhizome biomass in the subsequent year by 35% compared with the control, while the pure red clover treatment increased it by 20–30%. Mowing twice and treatments including red clover resulted in higher subsequent grain yields. We concluded that repeated mowing has the potential to control E. repens, but a low‐yielding cover crop has insufficient effect on rhizome biomass. Clover–grass mixtures are of interest as cover crops, because they have the potential to increase subsequent crop yield and even at low levels they reduce E. repens above‐ground autumn growth.     

中间偃麦草和长穗偃麦草染色体核型分析

选用从国外引进的中间偃麦草(Elytrigia intermedia)和长穗偃麦草(E.elongata)种子为材料,采用根尖压片法进行细胞染色体核型分析。结果表明,中间偃麦草染色体数目为2n=6x=42,染色体相对长度组成为：10L+10M2+12M1+10S,核型公式为：K(2n)=6x=42=34m+8sm,属于“2B”类型。长穗偃麦草染色体数目为2n=10x=70,染色体相对长度组成为:10L+22M2+30M1+8S,核型公式为：K(2n)=10x=70=38m+22sm+8st+2t,属于“2B”类型。本研究结果可以为中间偃麦草和长穗偃麦草的细胞学特性和遗传机制的研究提供理论依据。     

偃麦草盐胁迫下转录组分析

为探究偃麦草（Elytrigia repens）耐盐分子机制,本试验以耐盐差异显著的E36与E42为试验材料,对180 mmol·L^-1 NaCl处理0 d和3 d的叶片进行转录组测序。结果显示：转录组测序共获得80 735个Unigene,在NR数据库中共有10个同源性较高的物种;将差异表达基因进行KEGG功能注释,其中E42盐处理3 d和0 d对比产生的差异表达基因在植物病原体相互作用、淀粉和蔗糖代谢、苯丙烷类生物合成等方面有显著富集,E36盐处理3 d和0 d对比产生的差异表达基因在核糖体代谢、亚油酸代谢、碳代谢中具有显著富集;对E42盐处理0 d与3 d Unigenes进行对比,获得159个与耐盐相关差异表达基因,同样E36在盐处理下,获得61个与耐盐相关基因;对比代谢通路发现,E36和E42在光反应-捕光蛋白途径有明显差异;经qRT-PCR验证差异表达基因结果与转录组数据一致。偃麦草耐盐及敏盐种质在盐胁迫下光合调控、脯氨酸及过氧化物代谢在转录表达上均呈现显著差异。     

Concurrent avian malaria and avipox virus infection in translocated South Island saddlebacks (Philesturnus carunculatus carunculatus)

Abstract

CASE HISTORY: Outbreaks of mortality in South Island saddlebacks (Philesturnus carunculatus carunculatus) that had been translocated to two offshore islands in the Marlborough Sounds of New Zealand were investigated during the summer of 2002 and 2007. Both outbreaks were associated with a severe decrease in numbers of saddlebacks of up to 60% of approximately 200 birds.

CLINICAL AND PATHOLOGICAL FINDINGS: Many of the surviving birds were in poor condition, and had skin lesions on the legs and head. Necropsy showed pale liver and lungs, and a swollen spleen. Histopathology revealed schizonts resembling Plasmodium spp. within the cytoplasm of many hepatocytes and splenic histiocytes. The skin lesions consisted of epithelial proliferations containing numerous Bollinger bodies typical of avipox virus (APV) infection. Two different APV were isolated, using PCR, from two different birds exhibiting skin lesions. Each isolate had 100% sequence homology with APV members from either Clade A or Clade B. In addition, PCR analysis revealed that the Plasmodium elongatum present in infected birdsbelonged to a strain that was endemic in the population of North Island saddlebacks (Philesturnus carunculatus rufusater).

DIAGNOSIS: Concurrent infections with Plasmodium spp. haemoparasites and APV were identified as the likely cause of death in the birds examined.

CONCLUSIONS AND CLINICAL RELEVANCE: Although the Plasmodium spp. identified is thought to be endemic to saddlebacks in New Zealand, the affected birds were likely to be immunocompromised by concurrent APV infection or through lack of genetic diversity. Both the introduced mosquito Culex quinquefasicatus and the native mosquito Culex pervigilans are likely vectors for both these diseases, and the provision of water supplies less favourable to mosquito-breeding is recommended.     

Evidence for common genetic mechanisms controlling the tolerance of sudden salt stress in the tribe Triticeae

Previous studies in several Triticeae species have suggested that salt tolerance is a polygenic trait, but that genes on some chromosomes confer better tolerance to salt stress than others. This suggests an intriguing possibility that there may be a similar basis for salt tolerance in the species of the tribe Triticeae. In this study, chromosomal control of the tolerance to sudden salt stress, measured as the mean rate of leaf elongation in solution cultures with a single increment of 200 mM NaCl, was investigated in the genomes of cultivated barley (Hordeum vulgare L.), rye (Secale cereale L.), and Dasypyrum villosum (L.) Can-dargy by using disomic addition lines of individual pairs of chromosomes or chromosome arms of each of the three species in the ‘Chinese Spring’ wheat genetic background. It was observed that the chromosomes of homoeologous groups 3, 4, and 5 in barley, 5 and 7 in rye, and 4 and 6 in D. villosum carry loci with significant positive effects on salt tolerance. Increased doses of chromosomes of group 2, however, reduce or do not increase the tolerance to salt stress. These results are in agreement with a previous study of the tolerance of this salt stress regime in wheat and wheatgrass Lophopyrum elongatum. A ranking analysis of the chromosomal effects within each genome of the five Triticeae species investigated in this and previous studies revealed that the chromosomes of homoeologous groups 3 and 5 consistently confer large positive effects on the tolerance of sudden salt stress, while the chromosomes of homoeologous group 2 in increased dose have no or negative effects on the tolerance. This strongly suggests that species of the tribe Triticeae share some common genetic mechanisms of tolerance of sudden salt stress. The findings in this study give credence to the proposal that wild relatives can be exploited in the development of wheat cultivars with greater tolerance to salt stress.     

Genetic variation within eight populations of perennial forage grasses

Information on both mean performance and genetic variation is important in determining the value of germplasm for breeding via recurrent selection. The objectives of this experiment were to evaluate different methods of controlling spatial variation for forage yield, and to estimate genetic variances and heritability in eight perennial forage grass populations. Polycross families of two populations of smooth bromegrass (Bromus inermis Leyss.), two populations of hybrid wheatgrass (Elytrigia×muctonata (Opiz ex. Bercht.) Prokud.), and four populations of orchardgrass (Dactylis glomerata L.) were field tested for 2 years. Spatial variation was present in all three progeny tests, but was well accounted for by either the incomplete block design or a nearest neighbour analysis (NNA) of yield potentials. Low rank correlations between adjusted family means for the incomplete block design vs. the NNA created the unanswered question of which would provide a more appropriate estimate of family mean performance. Genetic variation was detected in six out of eight populations for forage yield, four out of six populations for ground cover, all four orchardgrass populations for maturity and one of four orchardgrass populations for leafspot reaction (caused by Drechslera spp.). Excessive year-family interactions prevented detection of genetic variation for leafspot reaction in the other populations. Heritability estimates ranged from 0.30 to 0.42 for forage yield. In all three species, there was a trend toward a negative relationship between population mean and genetic variance, suggesting that less elite populations may need to contribute other traits to be useful in the short term.     

Characterization of high-molecular-weight glutenin subunit genes from Elytrigia elongata

Three high‐molecular‐weight glutenin subunit (HMW‐GS) genes from Elytrigia elongata (Host) Nevski were characterized by determining the coding sequences of two x‐type subunit genes Ee2.1 and Ee1.9, and one y‐type subunit gene Ee1.8 with 2082, 1938 and 1788 bp, respectively. The numbers of amino acids in the central repeat domains of Ee2.1, Ee1.9 and Ee1.8 were considerably fewer than the other known HMW‐GSs with substitutions, insertions and/or deletions involving a single or more amino acid residues. Moreover, an extra cysteine (Cys) was found in the repeated domain of x‐type subunit Ee2.1. The difference in the number and position of Cys residues might be associated with the good dough quality. The extra Cys in the good‐quality subunit Dx5 was at the beginning of the repetitive domain, while the extra Cys in Ee2.1 was at the central repetitive domain. Evolutionary relationships between the HMW‐GSs from E. elongata and the known HMW‐GSs were estimated. It transpired that Ee1.9, Ee2.1 and Bx7 were clustered into one subgroup with high bootstrap values, while Ee1.8 was closely related to Ay.