Assessment of the response of carrot somaclones to Pythium violae, causal agent of cavity spot

Cavity spot is a major disease of carrots, causing cavities on the surface of the root. Available commercial varieties show a range of susceptibility but no significant resistance. Seed progeny from 46 tissue culture-derived carrot ( Daucus carota ) somaclones were screened for viability, then 19 selected somaclone families were sown under glasshouse conditions, along with commercial cultivars (Bertan, Nandor, Bolero and Vita Longa) as controls. Mature roots were exposed to Pythium violae in a cavity spot bioassay to determine their response as measured by disease incidence and severity. Some somaclones formed fewer lesions than the least susceptible control cultivar, Vita Longa. Seven somaclonal families that showed a range of susceptibility were sown under field conditions and the assessment was repeated. Although there was little relationship between glasshouse and field-trial results, under field conditions one of the somaclones had a mean incidence of disease, as estimated by transformed data, of 1·9 compared with 37·9 for the most susceptible somaclone and 3·5 for Bolero, the most resistant commercial cultivar. The results indicated that significant genetic variation in susceptibility to cavity spot disease was present in the somaclones.     

Effect of Drechslera (Helminthosporium) sacchari Toxin upon the Permeability of Sugarcane Leaf and Callus Tissues

Sugarcane leaves and calli from highly susceptible and resistant varieties to eyespot disease were used to evaluate the Drechslera sacchari toxin effect at different concentrations and incubation times by measuring electrolyte leakage. This expression of disease resistance was observed not only in the leaf but also in the callus. Furthermore, the growth of resistant calli MS medium supplemented with DS toxin, was higher when compared to the susceptible ones. The possibility of obtaining resistant somaclones is confirmed.     

EFFICIENT CALLUS INDUCTION AND PLANT REGENERATION FROM IMMATURE EMBRYO CULTURE OF TRITICUM AESTIVUM L. - THINOPYRUM INTERMEDIUM ALLEN DISOMIC ADDITION LINES

An efficient plant regeneration system was developed from the immature embryos of Triticum aestivum L. Thinopyrum intermedium alien disomic addition lines, which resistant to powdery mildew. The protocol was based on a series of experiments involving the callus induction and differentiation. The experiment studied the effects ofmature embryos. We found that the embryembryo size on callus induction and differentiation of the immature embryos. We found that the embryo size is critical for the establishment of embryogenic callus. Immature embryos (0.8 ~ 1.5 ram) showed high ability to produce embryogenie callus capable of regenerating green plants. The medium Murashige and Skoog‘ s (MS) added with 2mg/L 2, 4-diehlo-rophenoxyacetic acid (2, 4-D) gave the best embryogenic callus induction, maintenance and regeneration. The embryogenic callus maintained high regeneration during six subcultures in the callus induction medium. Suitable time ofpartialdesiccation could effectively improve the regeneration capacity of the callus cultured for 3-4 month. Bud green spot and root green spot were observed during the differentiation of callus and the difference between them was described. Regenerated shoots were rooted on half-strength MS medium containing 0.2 mg/L Naphthalene acetic acid (NAA). Plants were successfully transferred to soil and grew well. This efficient plant regeneration system provides a foundation for the study of somaclonal variation of Triticum aestivum L.- Thinopyrum intermedium alien disomic addition lines.     

High frequency regeneration and heritable somaclonal variation in Brassica juncea

Summary Multiple shoot formation in cotyledonary callus of Indian mustard (Brassica juncea cv. Prakash) was induced on modified MS media supplemented with high cytokinin (kinetin or zeatin) and low IAA concentrations. Complete plants were obtained on prolonged incubation of shoots on the same medium. 6-Benzyladenine alone or in combination with IAA or NAA did not support plantlet regeneration. A total of 71 plants were transferred to greenhouse. The seed, however, could be collected from 37 plants only. The seed was sown in the field to evaluate the material for somaclonal variation in R₁ generation. Data were recorded for yield, plant height, number of primary branches, siliqua number, 1,000 seed weight and oil content. Somaclonal lines showed tremendous amount of variation for all the characters studied. A number of plants in this generation showed significantly higher yield and/or other improved agriculturally important characteristics as compared to the control. A line with dwarf plant type was also identified. A number of plants were selected from this generation and carried forward to R₂ generation. Most of these lines bred true in R₂ generation. The material seems to be very promising for future breeding programmes.     

Colchine-induced aneuploids from cell culture of sugarcane

Summary Sugarcane (Saccharum spp.) clones are amenable to gross chromosome manipulation due to their high polyploid nature (2n=100–120). This study was conducted to analyze the effects on plant morphology of altering chomosome number via callus culture. Callus cultures from clone H69-9092 were established, and plants were regenerated following colchicine treatment of cultured cells. Cytological analysis showed that variant somaclones were aneuploids with a wide range in chromosome numbers (2n=66–196). Some 22 visually distinct somaclones were planted in 1.35 m² plots with five replications to compare morphological and quality characteristics with H69-9092 at 8 months of growth. Extreme morphological variation was observed between somaclones, but coefficients of variation for quality factors-fibers %, refractometer solids %, pol %, and juice purity-and stomatal length were smaller than those for morphological traits associated with stalk volume and leaf area. Significant negative correlations were found between chromosome number and most morphological traits, e.g., stalk length (r=-0.58), number (r=-0.69), diameter (r=-0.54) and volume (r=-0.65); internode length (r=-0.57); and leaf area (r=-0.48). A positive correlation was found between chromosome number and stomatal length (r=-0.66). No significant correlations were found between chromosome number and quality factors. Aneuploids with higher than parental chromosome number had reduced growth. However, depression in growth was generally not observed in somaclones lower in chromosome number than the parent.Published with the approval of the Director as Paper No. 598 in the Journal Series of the Experiment Station, Hawaiian Sugar Planters' Association.     

Somaclonal variation as a source of resistance to eyespot disease of sugarcane

After 10 years of evaluation in different locations with high levels of incidence of disease, a group of sugarcane somaclones derived from callus tissues was selected for eyespot resistance. Resistance evaluations of four somaclones were performed under field and laboratory conditions. The results confirmed the superiority of two somaclones, one resistant and one tolerant to eyespot disease. Restriction analysis of mitochondrial DN A revealed that the two somaclones had a different DNA organization which distinguished them both from each other and from the donor plant; the restriction profile was similar however to that of the resistant control done. Restriction patterns of a third somaclone, also resistant, were similar to those of the donor plant. Differences among the somaclones were also evident when using a maize ribosomal DNA probe.     

甘蔗组培亚无性系性状研究

通过愈伤组织获得6个不同基因型品种的亚无性系,并对其性状进行研究。结果表明,甘蔗组培亚无性系存在不同程度的变异。一般第一代表现为分蘖和茎数增加,茎径变小,糖锤度降低;第二代性状差异有所缩小。部分品种的亚无性系第一代出现许多变异类型。第二代表现较为复杂,有的变异可重演,有的则消失。过氧化物酶和脂酶同功酶的测定结果也显示出亚无性系与供体间的差异,表明某些性状的变异是遗传变异。     

普通小麦与偃麦草属间杂种体细胞无性系的建立

本试验以小麦与堰麦草属间杂种的幼嫩叶片、茎节、叶鞘和幼穗为外植体进行了离体培养。结果表明，不同基因型和不同外植体之间的愈伤组织诱导率及分化率都存在明显差异，愈伤组织的诱导率及分化率均以幼穗外植体为最高，余者较低。最终，建立了各种供试基因型的体细胞无性系。