番茄心室形成的遗传规律初探

应用番茄多心室自交系和少心室自交系进行正交、反交及F1代自交和回交,对双亲及获得的正反交F1、F2及回交各世代植株的心室数进行遗传分析。结果表明:少心室为不完全显性,回交效应显著,正反交差异不显著,呈现核遗传,细胞质作用不显著。番茄心室数符合加性-显性模型,以加性效应为主,属不完全显性;控制心室数的最少主基因对数是1对,还受到其他微效基因的控制。番茄心室数广义遗传力为69.44%,狭义遗传力为52.98%。     

番茄的耐盐性与耐盐转基因番茄

由于土壤盐渍化的日益加剧导致作物大量减产,通过基因工程的方法将耐盐基因转入作物,培育耐盐作物新品种是开发利用盐碱地的一种经济、有效的手段.番茄是一种栽培广泛,具有重要经济价值的蔬菜,又是基因工程的模式生物之一,开展番茄耐盐性研究具有重要意义.分析了番茄的耐盐性和转耐盐基因番茄的研究现状.     

beta-Galactosidases in Ripening Tomatoes

Tomatoes (Lycopersicon esculentum L.) contained a high level of β-galactosidase activity which was due to three forms of the enzyme. During tomato ripening, the sum of their activities remained relatively constant, but the levels of the individual forms of β-galactosidase changed markedly. The three enzymes were separated by a combination of chromatography of DEAE-Sephadex A-50 and Sephadex G-100. During ripening of tomatoes, β-galactosidases I and III levels decreased but the β-galactosidase II level increased more than 3-fold. The three enzymes were optimally active near pH 4, and all were inhibited by galactose and galactonolactone. However, the enzymes differed in molecular weight, K_m value with p-nitrophenyl-β-galactoside, and stability with respect to pH and temperature. β-Galactosidase II was the only enzyme capable of hydrolyzing a polysaccharide that was isolated from tomatoes and that consisted primarily of β-1, 4-linked galactose. The ability of β-galactosidase II to degrade the galactan and the increase in its activity during tomato ripening suggest a possible role for this enzyme in tomato softening.     

Phytochrome-mediated Carotenoids Biosynthesis in Ripening Tomatoes

Red light induced and far red light inhibited carotenoid biosynthesis in ripening tomatoes (Lycopersicon esculentum Mill.) when compared to controls kept in the dark. Red illumination following far red illumination reversed the inhibitory action of far red light on carotenoid biosynthesis, suggesting a phytochrome-mediated process. Quantitation of individual carotenoids favored the hypothesis of two separate carotenoid biosynthetic pathways in tomatoes.     

Translocation of Photosynthate in Curly Top Virus-infected Tomatoes

Photosynthate translocation in single leaflets of healthy and curly top virus-infected tomatoes was investigated using ¹⁴C as a marker. The amount of radioactivity found in plant parts not exposed to ¹⁴CO₂ was substantially lower in diseased than in healthy plants. The time lag for the appearance of ¹⁴C in the petiole was considerably longer in the infected plants than in the healthy. The kinetics of disappearance of ¹⁴C from the lamina during the 24-hour period following labeling showed a strong retention of recent assimilates within the diseased leaf, not accompanied by increased immobilization into insoluble forms. Sucrose was the predominant compound participating in photosynthate transport in both healthy and diseased leaves. The amount of ¹⁴CO₂ fixed was approximately 40% lower in curly top virus-infected leaves than in healthy leaves.     

Geminiviruses Associated with Diseased Tomatoes in Cuba

Tomato plants displaying symptoms of yellowing and leaf curling were analysed for the presence of geminiviruses. Two distinct geminiviruses were present in the plants studied. One had a genome size and coat protein gene sequence similar to the Israeli strain of tomato yellow leaf curl virus (TYLCV), while the other had a smaller genome size than TYLCV that could not be amplified using primers specific for Israeli TYLCV. The presence of the Israeli strain of TYLCV has been reported in other Caribbean islands, but not in Southern Florida (USA) which is close to those islands where TYLCV has been detected. This suggests that the introduction of the Israeli strain of TYLCV to the Caribbean area may have occurred within recent times.     

Analysis of Some Pesticide Residues in Tomatoes in Ghana

Pesticide residues, both natural and synthetic, can be found in most of the things we eat, for example, fruits, vegetables, bread, meat, poultry, fish, and the processed foods made from them. Some of this pesticide contamination is legal, but does this mean it is safe? Much of it is illegal, with residues found in excess of regulatory safe levels. Identifying and determining the level of trace contaminants in our food and environment is critical in protecting and improving human health and the environment. This study evaluates the residue levels of select pesticides used on tomato crops in Ghana that are likely to have accumulated in the tomatoes during application. The results obtained confirm that pesticide residues were indeed present in the tomatoes and further analysis quantified the amount present. Analysis of some organochlorine and organophosphorus residue levels in the fruits indicated that chlorpyrifos, which is an active ingredient of pesticides registered in Ghana under the trade name dursban 4E or terminus 480 EC for use on vegetables, has the greatest residue level of 10.76 mg/kg. The lowest residue level observed was that of pirimiphos-methyl with 0.03 mg/kg. Human health risk assessment was performed on the results obtained from the analysis using Human Health Evaluation computerized software-RISC 4.02. The risk assessment showed cancer risk for adults and children due to the presence of endosulfan and chlopyrifos. Endosulfan is not registered in Ghana as a pesticide for use on vegetables, therefore the detection of endosulfan in several samples indicates misuse of agrochemicals among Ghanaian farmers.     

Oat Phytochrome Is Biologically Active in Transgenic Tomatoes

To determine the functional homology between phytochromes from evolutionarily divergent species, we used the cauliflower mosaic virus 35S promoter to express a monocot (oat) phytochrome cDNA in a dicot plant (tomato). Immunoblot analysis shows that more than 50% of the transgenic tomato plants synthesize the full-length oat phytochrome polypeptide. Moreover, leaves of light-grown transgenic plants contain appreciably less oat phytochrome than leaves from dark-adapted plants, and etiolated R1 transgenic seedlings have higher levels of spectrally active phytochrome than wild-type tomato seedlings in direct proportion to the level of immunochemically detectable oat polypeptide present. These data suggest that the heterologous oat polypeptide carries a functional chromophore, allowing reversible photoconversion between the two forms of the molecule, and that the far-red absorbing form (Pfr) is recognized and selectively degraded by the Pfr-specific degradative machinery in the dicot cell. The overexpression of oat phytochrome has pleiotropic, phenotypic consequences at all major phases of the life cycle. Adult transgenic tomato plants expressing high levels of the oat protein tend to be dwarfed, with dark green foliage and fruits. R1 transgenic seedlings have short hypocotyls with elevated anthocyanin contents. We conclude that a monocot phytochrome can be synthesized and correctly processed to a biologically active form in a dicot cell, and that the transduction pathway components that interact with the photoreceptor are evolutionarily conserved.     

Proline Accumulation in Leaves of NaCl-sensitive and NaCl-tolerant Tomatoes

Proline (Pro) accumulation in leaf discs of the NaCl-treated salt sensitive Lycopersicon esculentum was higher than in the salt tolerant L. pennellii. The magnitude of Pro accumulation differed when leaf discs of both species were floated in the light or under darkness, and in various incubation media: buffer solutions (pH from 3.9 to 7.8), abscisic acid, isobutyric acid, NH4Cl, malate, citrate, and mixtures of NaCl and KCl, NaCl and CaCl2, and NaCl and mannitol. Under darkness, Pro accumulation in L. esculentum was not regulated by salts. Conversely, the light-independent NaCl-induced Pro accumulation observed in L. pennellii became light-dependent when CaCl2 was added. The different expression patterns of Pro accumulation reinforce the proposal of two Pro metabolic pathways in the domestic and the wild tomatoes.