Low Genetic Diversity Suggests a Single Introduction and Recent Spread of Tomato chlorosis virus in Brazil

By comparing the partial nucleotide sequences of the heat shock protein HSP70 homologue gene, we assessed the genetic diversity of Brazilian tomato isolates of Tomato chlorosis virus (ToCV), as well as their relationship with other ToCV isolates found worldwide. The Brazilian ToCV isolates shared 99.9–100% nucleotide identity, which indicates low genetic diversity. Brazilian ToCV isolates showed a closer evolutionary relationship to those from Mediterranean countries. Based on these results, the origin of Brazilian ToCV isolates and the possible number of introductions of the virus into Brazil are discussed.     

Some Aspects of the Enzyme Activities Involved in Coenzyme A Biosynthesis in Various Microorganisms

The distribution of the enzyme activities relating to CoA biosynthesis from pantothenic acid in various microorganisms and the effect of CoA on these activities are described.

High activities of partial reactions involved in CoA biosynthesis were surveyed in various type culture strains involving bacteria, actinomycetes, lactic acid bacteria, molds, and yeasts. Generally, higher activities were found in bacteria. CoA inhibited the phosphorylation of pantothenic acid, and resulted in a decrease of CoA production in all the CoA producing strains, while only a little inhibition by CoA was observed in the other reactions, and CoA production from pantothenic acid 4′-phosphate by Brevibacterium ammoniagenes IFO 12071 was not repressed even in the presence of 4mm of CoA. Extracellular excretion of the enzymes of CoA biosynthesis was observed when cells were in contact with sodium lauryl sulfate. Degrading activity against CoA and that against AMP were relatively lower in CoA producing strains when compared with those in other strains. It was confirmed that Brown’s route of CoA biosynthesis operates in Brevibacterium ammoniagenes IFO 12071.     

氮素和刈割对桂牧1号杂交象草光合作用、产量和品质的影响

采用L16(45)正交试验设计,研究了喀斯特地区桂牧1号杂交象草光合生理特性、产量和品质对不同施氮水平、刈割次数、刈割强度的响应。结果表明,施用氮肥显著增加了桂牧1号杂交象草的叶绿素a、b和叶绿素总含量、净光合速率、产量及营养成分含量,肥效最佳水平是1000kg·hm-2·a-1。刈割次数显著影响桂牧1号杂交象草的净光合速率、叶绿素含量和牧草营养成分含量,刈割过2～3次,桂牧1号光合作用能力显著提高,而每年刈割3～4次,牧草的营养品质最优。刈割强度对粗蛋白含量影响显著,对其他营养成分含量和产量均无显著影响,以5或20cm刈割强度为最优。综合各指标结果,提出了喀斯特地区栽培桂牧1号杂交象草获得高产优质的最优方案,即施氮1000kg·hm-2·a-1,刈割牧草3次,刈割强度为5或20cm。     

桂北丰水梨园土壤养分与叶片营养的相关性分析

选取桂北地区有生理异常现象发生的丰水梨园,以成年结果树为研究对象,通过检测年生长周期内梨树叶片矿质营养元素、土壤养分的含量,分析不同时期梨树叶片营养元素和土壤养分含量及其动态变化规律,探讨年生长季内叶片营养与土壤养分之间的相关关系。结果表明:(1)在生长季节内,丰水梨叶片中N、P、K含量丰富;营养元素含量随时间的变化幅度均为P最大,N、K较小,但均未达到显著水平(P>0.05)。(2)梨园土壤中有机质、水解性N含量丰富,有效P、速效K含量普遍偏高;年生长周期内土壤速效N、P、K含量随时间的推移变化较大,均达显著水平(P<0.05),而有机质含量则相对稳定。(3)梨树叶片N含量与土壤有机质、水解性N、有效P、速效K含量呈显著正相关关系(P<0.05);叶片P和K含量与土壤水解性N含量分别呈显著负相关和正相关关系(P<0.05),而与土壤有机质、有效P、速效K相关关系不明显。     

超早熟栽培草莓花芽分化进程的扫描电镜观察

于2011年7月23日至8月24日,对草莓品种‘红颜’进行低温(夜温为17～20℃变温)、短日照(黑暗时间为16 h)处理,从处理之始到花序现蕾,约每3～5 d取样1次,实体解剖镜下解离草莓顶芽,材料均用FAA固定,临界点干燥,扫描电镜观察,以确定保护地栽培草莓的花芽开始分化始期,为生产中草莓尽早适期定植提供依据.根据扫描观察的微形态特征,将草莓花芽分化的全过程分为花芽未分化期、花芽分化始期、生殖顶端膨大期、花序分化期、顶花花萼与花瓣形成期、雄蕊形成期和雌蕊形成期共7个时期.花芽未分化期,顶芽一直处于营养生长阶段;花芽分化始期,草莓顶芽逐步由尖锐、狭窄的营养顶端向平坦、宽大的生殖顶端发育;生殖顶端膨大期,生殖顶端隆起而膨大;花序分化期,顶花序逐步分化出顶花原基和侧花原基;顶花花萼、花瓣形成期,花萼(包括副萼)、花瓣原基相继分化完成;雄蕊形成期,两轮雄蕊原基相继分化形成;雌蕊形成期,大量雌蕊原基逐步隆起,心皮原基逐步卷合、完成花芽分化.研究认为,草莓的定植期以生殖顶端充分膨大期为宜,即低温短日照处理15～20 d后即可定植大田.     

Response of the physiological parameters of mango fruit (transpiration,water relations and antioxidant system) to its light and temperature environment

Depending on the position of the fruit in the tree, mango fruit may be exposed to high temperature and intense light conditions that may lead to metabolic and physiological disorders and affect yield and quality. The present study aimed to determine how mango fruit adapted its functioning in terms of fruit water relations, epicarp characteristics and the antioxidant defence system in peel, to environmental conditions. The effect of contrasted temperature and light conditions was evaluated under natural solar radiation and temperature by comparing well-exposed and shaded fruit at three stages of fruit development. The sun-exposed and shaded peels of the two sides of the well-exposed fruit were also compared.     

Occurrence and molecular detection of bipartite begomovirus on tomato in Southern India

Abstract

Begomoviruses are major constraint in tomato production across the world. In India, tomato production is affected by both monopartite and bipartite begomoviruses. Monopartite were reported to infect tomato crop across India. However, bipartite were reported to infect tomato in Nothern India. In the current study, seventy begomovirus symptomatic tomato samples were collected from southernstates of India and analysed using PCR-based specific primer. The analysis revealed that 45 of them were monopartite, 23 of them were bipartite and 8 bipartite also showed the presence of betasatellite. This is the first report of bipartite begomovirus infecting tomato in Southern India.     

Target leaf spot of tomato incited by Corynespora cassiicola,an emerging disease in tomato production under Gangetic alluvial region of West Bengal,India

Abstract

Tomato (Lycopersicon esculentum Mill.) is a cosmopolitan vegetable and widely cultivated in almost all the countries of the world including India. Irreversible investment – production ratio for tomato cultivation in recent Indian agricultural systems arise the question, is there any biotic backlogs responsible for such a production loss. Our present investigation is based on this fact. Target leaf spot disease of tomato is caused by Corynespora cassiicola, a serious and emerging disease in India. Prolonged real time surveillance of this disease on tomato from 2010–11 to 2016–17, reflects some remarkable features of pathogenic progress in Gangetic alluvial region of West Bengal. This pathogen is the natural barrier for tomato production with a disease severity ranged between 35% and 58% which ultimately causes tremendous loss of tomato foliage and fruits. C. cassiicola was identified on the basis of morpho-cultural (ITCC Accession No. 7542) and molecular characterization (Genbank Accession No. KJ767193). Homology searching of internal transcribed spacer region of CcHaTom isolate was highly matched with Genbank Accession No. KP666184 (Cynodondactylon/India), AB873045 (Vitex negundo/India) and JN541214 (Malvaviscus concinnus/USA) with 95% similarity. Phylogenetic analysis established that KJ767193 and C. cassiicola retrieved sequences were conspecific from a common ancestral origin, which supports its neighbourhood with this fungal pathogen. Optimum temperature between 24 and 25?°C, coupled with 80–85% relative humidity triggered the disease progress. From the emerging scenario, C. cassiicola infecting tomato is the real threat for indigenous cultivars.     

Analysis of the chromosomal distribution of transposon-carrying T-DNAs in tomato using the inverse polymerase chain reaction

We are developing a system for isolating tomato genes by transposon mutagenesis. In maize and tobacco, the transposon Activator (Ac) transposes preferentially to genetically linked sites. To identify transposons linked to various target genes, we have determined the RFLP map locations of Ac- and Dissociation (Ds)-carrying T-DNAs in a number of transformants. T-DNA flanking sequences were isolated using the inverse polymerase chain reaction (IPCR) and located on the RFLP map of tomato. The authenticity of IPCR reaction products was tested by several criteria including nested primer amplification, DNA sequence analysis and PCR amplification of the corresponding insertion target sequences. We report the RFLP map locations of 37 transposon-carrying T-DNAs. We also report the map locations of nine transposed Ds elements. T-DNAs were identified on all chromosomes except chromosome 6. Our data revealed no apparent chromosomal preference for T-DNA integration events. Lines carrying transposons at known map locations have been established which should prove a useful resource for isolating tomato genes by transposon mutagenesis.     

Transition from absolute to quantitative short-day control in Nicotiana tabacum cv. Maryland Mammoth

The response in vitro of thin cell layers, excised from different stem regions of Nicotiana tabacum cv. Maryland Mammoth plants at various developmental stages, was studied under different photoperiodic treatments. The aim was to determine at which stage of plant development, and in which region of the stem, the absolute short-day requirement, indispensable for the induction of the flowering process in this genotype, becomes quantitative and whether it remains short-day. The explants were cultured on a medium suitable for flower neoformation, and were exposed for 30 days to the following treatments: continuous darkness, 8 h light/16 h dark per day, 16 h light/8 h dark per day, and continuous light. The first flowers on explants were observed from plants that were still in the vegetative state, but whose apex showed an accelerated production of axillary vegetative buds, as observed histologically. These explants were excised from the first 10 internodes below the first node with a leaf ≥ 5 cm in length (apical site), and produced flowers only under short-day treatment. When the apical dome initiated the organization of the terminal flower, the apical site explants developed flowers under both short-day and long-day treatments. At the same stage, explants from the 15th to the 20th internode below the first leaf ≥ 5 cm in length also formed flowers, but only under short-day. When the plant showed a complete inflorescence, flowers were also present on explants from the most basal stem internodes and from the inflorescence branches. At this stage, flower neoformation occurred under all treatments; however, under short-day the number of explants showing flowers not associated with vegetative buds on the same sample greatly exceeded that observed under other treatments, as did the mean number of flowers per explant (except the basal regions). In conclusion, in the post-inductive phases of the flowering process, the photoperiodic requirement of this genotype is always short-day. The superficial tissues of the stem require either absolute or quantitative short-day treatment, depending on their position on the stem and the stage of evolution of the flowering process in the terminal apex.