不同氮素形态配比对菜用甘薯产量和品质的影响

菜用甘薯存在产量低、品质差以及在种植过程中由于不合理施肥造成生态环境恶化等问题,因此,针对以上问题开展本研究。氮肥作为农业肥料投入的主要部分,是影响菜用甘薯产量和品质的重要因素,通过设置不同氮素形态配比处理,根据菜用甘薯茎尖产量和品质相关指标的变化,揭示菜用甘薯产量和品质对氮素形态配比的响应机制,为提升菜用甘薯产量和品质的同时减轻因不合理施肥造成环境污染提供理论依据。本研究为大田试验,供试品种为生产上主栽的2个菜用甘薯品种‘福薯18’（F18）和‘鄂薯10号’（E10）,采用两因素裂区试验设计,设5个氮素形态配比处理为：（1）NH₄⁺-N∶NO₃^--N∶CONH₂-N =1∶1∶1 (N₁);（2）NH₄⁺-N∶NO₃^--N∶CONH₂-N = 1∶0∶2 (N₂);（3）NH₄⁺-N∶NO₃^--N∶CONH₂-N = 2∶0∶1 (N₃);（4）NH₄⁺-N∶NO₃^--N∶CONH₂-N = 1∶2∶0 (N₄);（5）NH₄⁺-N∶NO₃^--N∶CONH₂-N = 2∶1∶0 (N₅)。研究结果表明,N₄和N₅处理均可显著提高菜用甘薯的茎尖产量、总酚含量、总黄酮含量、可溶性糖含量、苯丙氨酸解氨酶(PAL)酶活性和IbPAL基因表达量;同一时期不同处理间差异显著,随着生育期的不断推进,各项指标的变化呈先升后降的趋势,其中以N₄处理效果更为显著,除可溶性糖含量在N₃处理下最低外,其他各项指标均在N₂处理下最低,由相关性分析证实,总酚、总黄酮和可溶性含量及PAL酶活性与IbPAL基因表达量呈显著正相关,而可溶性糖含量与基因表达量呈负相关,表明可溶性糖含量的变化与IbPAL基因表达无相关性;由氮素形态配比处理可知,相对于N₂和N₃处理,N₄和N₅处理为植株提供了更多的NO₃^--N,由此推断NO₃^--N在菜用甘薯生长发育过程中起到更为重要的促进作用,而CONH₂-N在本研究中对甘薯产量和品质的促进作用并不突出。而N₄处理即NH₄⁺-N∶NO₃^--N∶CONH₂-N = 1∶2∶0的配肥方案是促进菜用甘薯产量和品质提升的最佳配施组合。本研究结果可为合理配肥以获得理想的作物产量和品质提供理论依据,为在其他作物上开展相关研究提供参考。     

水培蔬菜净化凡纳滨对虾养殖塘水质效果研究

采用3种浮植方式水培水蕹菜、羽衣甘蓝、生菜,进行蔬菜种类、浮植方式筛选,并以最佳品种与浮植方式浮植规模化养虾塘,进行水生菜生长状况与净化虾塘水质效果试验.结果表明,水蕹菜为生长良好、可有效净化养虾水质的蔬菜品种,以绳结式浮植方式培植水蕹菜可获得最佳的生长效果;据此将水蕹菜以绳结式浮植于规模化养虾塘.对虾生态养殖试验探讨了水蕹菜对虾塘水质的净化效果及对虾生长状况的影响,结果表明,种植水蕹菜虾塘和对照塘中对虾输出的TN、TP分别为36.21％、21.01％和32.03％、17.98％.种植塘收获水蕹菜重量为初始种植重量的32.5倍,具有一定经济价值,特别是能有效去除塘水中TN、TP,去除率分别为5.86％和3.73％.试验期间,种植塘的TAN、TN、TP、PO43--p及CODMn含量均低于对照塘.种植塘对虾终末体长、体重、饵料系数均优于对照塘,对虾产量(4768.75±111.69 kg/hm2)也高于对照塘(4 120.46±90.00 kg/hm2).这种生态养殖模式不仅可有效净化水质,减少养殖废水对环境的污染,还能提高对虾养殖的经济效益.     

甘薯茎线虫诱导抑制差减杂交cDNA文库的构建及表达序列标签分析

以甘薯(Ipomoea batatas(L.)Lam.)抗茎线虫病品种鲁薯3号为材料,利用抑制差减杂交(suppression subtractive hybridization,SSH)技术,构建了甘薯茎线虫诱导的甘薯块根cDNA文库.从中筛选出1379个阳性克隆进行测序,用CAP3软件聚类拼接,得到185个unique EST.Blast2Go比对ESTs,并进行GO功能分类,结果发现151条非重复序列与已知基因同源性很高,占全部非重复序列的81.6%.已知功能的EST涉及植物的能量代谢、信号转导、抗病防卫、蛋白质合成等多方面.通过对已知功能的基因进行分析,推测促分裂原活化蛋白激酶、丝氨酸/苏氨酸蛋白激酶、过氧化氢酶、几丁质酶、葡聚糖酶等可能参与甘薯接种茎线虫后相关的抗性反应.实时荧光定量PCR分析结果表明,与抗茎线虫病相关的4个基因在甘薯接种线虫后不同时间点具有不同的表达模式.     

低温胁迫对甘薯S-腺苷甲硫氨酸合成酶mRNA表达水平的影响（英文）

[Objective] The mRNA expression level changes of S-adenosylmethionine synthetase(SAMS)under low temperature stress was studied.[Method]Total RNA were extracted from leaves,stem and earthnut of sweet potato 0,12,24,48 and 72 h after low temperature treatement.mRNA expression level was analyzed by reverse expression and Real-time PCR technique.[Result]The expression quality of the gene extracted from leaves,stem and earthnut increased and the expression quality reached the peak point 24,72 and 72 h after low temperature treatment respectively.The expression change of earthnut was the biggest.[Conclusion]Low temperature was good for increasing mRNA expression of relevart genes.     

Adaptation and stability analysis of sweet potato varieties for low-input systems in Uganda

Sixteen sweet potato varieties were evaluated for fresh storage root yield in 20 trials during 2000–2001 for three seasons in four locations in Uganda. Of the 16 varieties, 11 were developed by farmers and five by a central breeding programme. The behaviour of the varieties was quantified in terms of wide adaptation (genotypic mean across trials), specific adaptation (genotypic predictions for specific locations) and stability (Shukla stability variance). With respect to all three aspects of yield behaviour, farmer varieties performed on average better than the official varieties. The results illustrate the potential that farmer varieties can have in the improvement of sweet potato in Uganda and other regions where high diversity of sweet potato landraces exists.     

Inheritance and stability of the virus-resistant gene in the progeny of transgenic sweet potato

Viral diseases of sweet potato are very prevalent and often seriously damaging to the plants. In particular, the severe strain of the sweet potato feathery mottle virus (SPFMV‐S) causes ‘obizyo‐sohi’ disease in Japan. In order to confer viral resistance against SPFMV using current biotechnology, a transgenic sweet potato has been produced, introducing hygromycin‐resistant (hpt) and SPFMV‐S coat protein (CP) genes, which have shown a significant resistance to SPFMV‐S. In the breeding programme, it is important to confirm that the viral resistance conferred in T₀ plants can be inherited by their progeny. In the present study, progeny were obtained from crosses between the transgenic T₀ and a non‐transgenic variety of sweet potato. The results showed that the CP gene was inherited by the next generation and that the stability of viral resistance was also confirmed. Thus, this production system for the virus‐resistant transgenic sweet potato is useful in practical breeding.     

Plant regeneration in sweet potato (Ipomoea batatas L., Convolvulaceae)

The application of new techniques for improvement of sweet potato crops, particularly including the exploitation of somaclonal variation, gene transfer by genetic transformation and somatic hybridization, requires the control of plant regeneration from tissue cultures. Shoots can easily be regenerated from explants of stems, petioles, leaves and roots, while callus cultures do not produce any shoots. The potential of somatic embryogenesis and plant regeneration via embryogenesis was evaluated for 10 cultivars of sweet potato. Protocols for plant regeneration from cultured protoplasts have also been developed. Since mesophyll was resistant to enzyme digestion, fragments of stems and petioles, callus and cell suspensions were used as source of protoplasts of sweet potato. Series of transfers of protoplast-derived calluses, particularly those which had been obtained from in vitro plants, to media containing a high level of zeatin resulted in successful formation of shoots in only two sweet potato cultivars. In addition, the embryogenic potential was irreversibly lost through protoplast culture, since protoplasts isolated from embryogenic cell suspensions developed into non-embryogenic callus. Consequently, an alternative protocol is being successfully developed to improve plant regeneration from cultured protoplasts of sweet potato, involving first root formation from which shoots can then be regenerated. Preliminary evaluation in field conditions in Gabon revealed that plants regenerated from cultured protoplasts exhibited a great genetic variability in their growth and tuber formation in particular. This revised version was published online in July 2006 with corrections to the Cover Date.     

Interspecific hybrids from cross incompatible relatives of sweetpotato

Summary Hybrids were obtained from Ipomoea interspecific crosses through ovule culture. The hybridity of the progeny obtained from I. triloba × IitI. trifida and (I. triloba × I. lacunosa) × I. batatas (4x) crosses was established by comparisons of floral morphology and analyses of peroxidase and esterase isozymes. The hybrids displayed the inflorescence type and sepal shape and texture of their male parents, while corolla size and anther and nectary color tended to be intermediate to their parents. The isozyme banding patterns of the hybrids contained bands present in the patterns of each of their parents. Pollen grain viability, measured by aceto-carmine stainability, was 44.1%, 92.3% and 82.4%, respectively, for the I. triloba × I. trifida hybrid and the (I. triloba × I. lacunosa) × I. batatas (4x) hybrids, H₁ and H₂. A controlled pollination study revealed that the I. triloba × I. trifida, and the (I. triloba × I. lacunosa) × I. batatas (4x) hybrids, H₁ and H₂ were partially self fertile with 6%, 70% and 13%, respectively, of the pollinated flowers producing viable seed. Success in backcrossing and sib-mating varied with the cross combination.     

Variance component estimations and allocation of resources for breeding sweetpotato under East African conditions

In Africa, average sweetpotato storage root yields are low and breeding is considered to be an important factor in increasing production. The objectives of this study were to obtain variance component estimations for sweetpotato in this region of the world and then use these to determine the efficiency of variety trials and breeding systems. From an incomplete series of variety trials in Kenya and Uganda (comprising 15 genotypes, three locations, two crop durations and three seasons) variance components were estimated ‐ using the REML method ‐ for the following traits: storage root yield, biomass production, harvest index, storage root dry matter and the Elston index which was used to aggregate all four traits. The storage root yield of clones across all 12 environments ranged from 15.2 to 33.0 t/ha. The variance components were significant for all traits, except the genotype by season interactions for storage root dry matter. The efficiency of selection systems was determined for total test capacities of 450 and 900 plots and using not more than five locations. Two‐stage selection was 17‐81% more efficient than one‐stage selection after two seasons of testing. Two‐stage selection was optimized under the restriction of using at least two locations at step 1. Trials with two locations and one replication at step 1 and five locations and two replications at step 2 were appropriate both for selecting for storage root yield and for simultaneously selecting for storage root yield, biomass production, harvest index and storage root dry matter content by using the Elston index. There are indications that such an allocation of resources for breeding sweetpotato is also appropriate for other regions in Sub‐Saharan Africa.     

Progress in improving aluminium tolerance in the perennial grass,phalaris

Aluminium (Al) tolerance of 11 cultivars, breeding populations and accessions of the perennial grass, phalaris (Phalaris aquatica L.), was investigated in low ionic strength nutrient solutions. The populations were chosen to determine whether a program to improve the tolerance of phalaris to acid soils had resulted in improved Al tolerance. Populations derived by backcrossing genes from a more Al-tolerant species, P. arundinacea L. (AT populations), were significantly more Al tolerant than populations based on pure P. aquatica. Smaller levels of improvement in Al tolerance had also been achieved within P. aquatica through a combination of selection in Al solutions and at acid soil field sites. The response of roots and shoots to Al stress was similar. Some differences in ranking were obtained depending on whether Al tolerance was defined by actual growth in Al solution or growth relative to the zero Al treatment. Performance in nutrient solution containing Al was highly correlated with second year yield and persistence at a field site with acid soil high in Al to depth. Actual root dry weight in nutrient solution containing Al gave a slightly higher correlation with the field data than root weight relative to the zero control. A tendency for root dry weight to segregate in the presence of Al was observed in some P. aquatica populations but not in the AT populations. It was concluded that a significant improvement in the Al tolerance of phalaris has been achieved through a program to introgress genes from P. arundinacea into P. aquatica.