Addition of Colchicine to Wheat Anther Culture Media to Increase Doubled Haploid Plant Production

Chromosome doubling is critical for obtaining doubled-haploid plants from wheat (Triticum aestivum L.) anther culture. The most common doubling method applies colchicine to the plant. However, colchicine is phytotoxic and can induce a high frequency of plant death. In this experiment, anthers from two wheat genotypes (“Pavon 76” and ‘Centurk’) were placed on nine embryoid initiation media having three sugar sources (maltose, sucrose, and maltose + glucose) with three colchicine concentrations (0.0, 0.1, and 0.2 g · l^-1). Wheat starch was used as a gelling agent. After three days, the anthers were washed and moved to fresh media without colchicine. Increasing the colchicine concentration decreased the number of embryoids produced from 77.4 embryoids/100 anthers to 29.9 embryoids/100 anthers, but did not significantly affect the frequency of plant regeneration (0.49 green plants/embryoid to 0.40 green plants/embryoid), and increased the frequency of doubled-haploid plants (19.0 doubled-haploid plants/100 green plants to 72.3 doubled-haploid plants/100 green plants). Considering the total number of doubled-haploid plants produced, low levels of colchicine added to the initiation media were very effective.     

Effect of Pre- and Post-Kinetin Treatments on Salt Tolerance of Different Potato Cultivars Growing on Saline Soils

Different potato cultivars were subjected to 10 ⁻⁶M kinetin treatment prior to the transplantation in saline soils (pre-kinetin treatment) and to the plants already growing on the saline soils (post-kinetin treatment). The kinetine when applied before the exposure of plants to saline soils showed promotory effects on growth, tuberization and some biochemical parameters of potato at 0.5 % salinity. The degree of inhibition in number of tubers and yield was reduced at 1 % salinity due to pre-kinetin treatment. The level of proline, reducing sugars and sodium was increased in different plant parts to maintain the osmoregulation. However, kinetin did not play any specific role in reducing down the increase in proline content resulted due to salinity. The level of K⁺ was found to be higher at low salinity in all the cultivars of potato. Higher concentrations of proteins and enhanced activity of starch synthetase at low level of salinity suggest the salutary effect of Na⁺ in metabolic functions of plant cells. The nitrate reductase (NR) activity was appeared to be more sensitive than starch synthetase. This could possibly be due to the localization of the enzyme and the cellular concentration of toxic substances increased under stress. Total Glyoalkaloids (TGA) content was reduced at both the salinity levels irrespective of kinetin treatments. On the contrary Na⁺ content was increased in all the treatments of kinetin at both levels of salinity. During this study cvs. Red Lasoda, Patrones and Atom alue approved to be more tolerant as compare to rest of the cultivars tested. This could be a combined effect of genetic setup, amendments in saline soils and pre-kinetin treatments of plants exposed to various regimes of salinity. Furthermore it is argued that salt tolerance limit can be extended upto certain level of salinity by pre-kinetin treatment in potato plants.     

Cytological and Isozyme Evaluation of Tall Fescue × Italian Ryegrass Hybrids

Development of tall fescue (Festuca arundinacea Schreb., 2n = 6x - 42) × Italian rye-grass (Lolium multiflorum Lam., 2n = 2 ×= 14) hybrids would enhance efforts to improve the quality of tall fescue. Two ‘Kentucky 31’ tall fescue בLemtal Italian ryegrass hybrids were obtained via embryo rescue on MS media containing casein hydrolysate, ascorbic acid and sucrose. Chromosome pairing at metaphase I had an average of more than 12 bivalents per cell. Since Festuca-Lolium pairing can account only for seven of the paired chromosomes, intergenomic as well as interspecific chromosome pairing is indicated. There was no cytoplasmic effect on chromosome pairing. To determine if enzymes could be used as genetic markers for distinguishing hybrids from self-contaminants in crosses, zymograms of PGI, 6-PGD, MDH, GOT and ACPH were obtained from parents and hybrids using starch gel etectrophoresis. PGI, 6-PGD and MDH had fewer bands in the diploid ryegrass, as compared with the hexaploid tall fescue and the tetraploid hybrid.     

Quality variations in transgenic rice with a synthetic cry1Ab gene from Bacillus thuringiensis

In order to estimate the potential of transgenic rice, characteristics related to grain quality and starch viscosity were investigated in six japonica lines based on three primary transgenic lines containing a synthetic cry1Ab gene from Bacillus thuringiensis. No significant differences were found between the transgenic lines and the wild type, including negative lines and an untransformed line. All six transgenic lines were comparable in size, milling quality, appearance quality and physicochemical properties to the wild type that were derived from. One exception was that the lines derived from the primary transgenic line TR0‐101 had smaller grains. Crude protein contents were equivalent in all the material tested, but Cry1Ab protein was only detected in grains of transgenic rice and was undetectable in the cooked rice. The viscosity of the starch differed between the transgenic lines, the wild type and other controls, and two transgenic lines had breakdown values (BDV) and setback values (SBV) similar to the wild type. A positional effect of T‐DNA insertion on starch viscosity was found in three primary transgenic lines.     

小麦根部平衡石淀粉含量变化与抗热抗旱性的关系

本文采用定量方法,测定了6个冬小麦品种种苗平衡石淀粉的含量变化,借以评价其抗热-抗旱性。结果指出:陕合6号和旱选10号属于抗热-抗旱性较强的品种,小偃6号、郑引1号和7859-18属于抗热-抗旱性较弱的,而晋农3号居中。进一步表明,种苗平衡石淀粉含量变化的特征与其他抗旱性鉴定方法比较,也可用作鉴定冬小麦抗热-抗旱性的指标。位于植物种苗根冠细胞中的平衡石淀粉,通常在饥饿状况下也不水解。但是,在脱水或过热情况下,则以一定速度水解。抗脱水与耐热性强的作物或品种,水解速度较慢,而抗脱水与耐热性弱的则水解迅速。据此,苏联学者提出并采用以种苗根冠细胞平衡石淀粉的水解速度作为植物抗热-抗旱性指标。具体方法是将种苗主根尖用碘化钾染色,在显微镜下观察,依染色程度用5个等级或占对照的百分数表示。本文以此为基础,采用定量方法测定种苗平衡石淀粉的含量变化,评价6个冬小麦品种的抗热-抗旱性,以期为抗旱育种与农业生产服务。     

Influence of Sucrose and Melibiose on Barley Anther Cultures in Starch Media

Anthers from the barley varieties ‘Arra’, ‘Dissa’ and ‘Ingrid’ were cultured in barley starch gelatinized nutrient media. The importance of osmosis in barley starch medium was studied by using sucrose or an inert carbohydrate, melibiose, as an osmoticum. It was found that in the barley starch medium sucrose was not necessary but energy and carbon could be obtained by tissue enzymatically from the starch. Together with the starch medium melibiose had revolutionary effects OB barley anther cultures. This system not only produced extremely high numbers of embryoids and green plantlets but also drastically reduced the number of albinos.     

A simple and efficient cryopreservation of in vitro-grown shoot tips of `Troyer' citrange [Poncirus trifoliata (L.) Raf. × Citrus sinensis (L.) Osbeck.] by encapsulation-vitrification

Wheat of two strong high-protein and two weak low-protein cultivars from New Zealand and Australia were milled to commercial specifications. All millstreams were tested for α-amylase, β-amylase, falling number, protein, starch, damaged starch, amylose, amylopectin, pentosan and ash. The distribution of β-amylase in millstream flours was more variable among cultivars than α-amylase. Generally, both enzymes had lowest activity in sizing and early reduction flours. α-Amylase was very high in the bran, pollard and germ fractions, in which ash content was very high, whereas β-amylase was low in these fractions. These observations, together with the moderate correlation of α-amylase and poor correlation of β-amylase to ash content, suggest that most α-amylasein flour derives from contamination with bran, pollard and germ, whereas most β-amylase derives from the endosperm. Falling numbers varied between the cultivars, but variation amongst millstreams for each cultivar was low, except for cv. Frame, which had particularly high falling number values (834 and 1197) in second and third break flours. These two flours had some of the highest α-amylase levels and lowest starch levels. However, they also had very high protein content (22 and 26%) and very low starch damage (3.2 and 4.5%), which may contribute to the high falling numbers. When endogenous α-amylase in the flour with the highest falling number was supplemented with high levels of barleyα-amylase, the flour withstood the detrimental effects of α-amylasein baking (sticky crumb, poor crumb texture and loaf volume) better than flours of lower falling number, but did not withstand the effects ofα-amylase on falling number. This revised version was published online in August 2006 with corrections to the Cover Date.     

Isoenzyme Electrophoresis, a Simple Way to Identify 1B/1R Substitutions and Translocations in Wheat

In order to identify 1B/1R translocations and substitutions by simple means in breeding materials, the efficiency of using starch gel electrophoresis of isoenzymes was evaluated. GPI (glucose phosphate isomerase) and MDH (malate dehydrogenase) were tested in 17 lines of wheat which had previously been identified for their 1B/1R status by C-banding. By electrophoresis of these two enzymes the rye substitution of only one wheat chromosome arm could be identified with high accuracy.     

Environmental conditions during root development: Drought constraint on cassava starch quality

Cassava has the reputation of being a drought tolerant crop, however, when deprived of water, plant and root development are affected. This ultimately will translate to an altered starch synthesis expressed by variation of starch quality. The magnitude of which, is influenced by the severity of stress conditions and stage of plant maturity. During early plant development,water stress retards growth, which will only be resumed after the immature plant has received sufficient water. Despite of an increased starch yield, the effect of initial water stress on starch quality is still sustained. In mature plants, starch quality is affected by environmental conditions prior to root harvest, especially the onset of rain after a stress period as indicated by a reduced starch paste. This paper presents the argument for extending the scope of traditional breeding programs beyond selecting for plant growth under drought conditions, to strategies that place greater emphasis on stabilizing starch quality. This revised version was published online in July 2006 with corrections to the Cover Date.     

马铃薯和玉米交联淀粉对馒头抗老化性的研究

采用二次发酵工艺制作馒头,分别添加0.45%、0.55%、0.65%自制的马铃薯和玉米交联淀粉,测定室温下储存0、5、12、24、48、72 h的馒头柔软度,结果表明,两种交联淀粉具有明显的抗老化效果,以0.55%的添加量为宜。