Effects of soil temperature and moisture on stem canker (Rhizoctonia solani) disease of potatoes

Summary Potato seed pieces bearing one sprout were inoculated with cultures ofRhizoctonia solani, planted in pots of compost at 45, 60, 75 or 90% water holding capacity (whc) and incubated at 5, 10 or 15 °C. Shoots emerged after 2–3 wk at 15°C, 3–4 wk at 10 °C and after 9–11 wk at 5 °C and stem canker recorded after emergence, was severe at 10 and 15 °C but slight at 5 °C. Soil moisture had less effect on emergence but stem canker was more severe in dry (45 % whc) than moist soils (75 and 90 % whc). The relationship between time of shoot emergence and stem canker severity is discussed.     

Effect of leaves on microtubers produced from potato single-node cuttingsIn Vitro

Microtubers are used to propagate, to store, and to transport potato clones. Culturing single-node explants from potato plantletsin vitro without subtending leaves was reported to result in plantlets with lower vigor and a higher coefficient of variation. The effect on microtuber productionin vitro of leaf area and the presence or absence of leaves on potato single-node cuttings was investigated as an extension of the above study. Stock plantlets of potato cvs Atlantic, Kennebec, Russet Burbank, and Shepody were cultured under a 16-h photoperiod. Single-node cuttings were excised and grown in a high-sucrose tuberization medium in darkness. Leaf area did not affect the frequency, size, or weight of microtubers of cvs Katahdin and Russet Burbank. The absence of leaves reduced microtuber diameter for Russet Burbank; whereas Atlantic, Kennebec, and Shepody were unaffected. Mean fresh weight of microtubers was reduced when leaves were removed for all cvs except Atlantic. No effect of the removal of the leaf was observed for mean dry weights of microtubers from all cvs, although microtubers from single-node cuttings without leaves accumulated significantly more percent dry matter than those with leaves. Rapid multiplication facilities may therefore wish to consider conserving resources such as media, vessels, and growth room space by culturing explants without leaves for the production of microtubers.     

Reduction in vigour of leafless potato cuttings in vitro

Summary Removing the leaves from single node potato cuttings in vitro allows propagules to be placed in culture vessels at increased densities with the intent of saving resources and space. Under light intensities of 22 watts^m−2, the removal of the subtending leaf resulted in fewer nodes, shorter plantlets, smaller leaf area, and lower fresh and dry weights of 4-week-old plantlets of cvs Atlantic, Kennebec, Russet Burbank and Shepody. Fewer nodes and reduced plantlet height may result in inefficient multiplication protocols because fewer propagules are available and shorter internodes make dissection more difficult. The coefficient of variation for the various growth parameters was greater when propagules lacked leaves, indicating that the variability of the plant material for propagation was increased. A reduction of vigour and growth was still evident when plantlets of cv. Shepody were grown for 6–8 weeks.     

A quantitative method for the determination of cyclopropenoid fatty acids in cottonseed, cottonseed meal, and cottonseed oil (Gossypium hirsutum) by high-performance liquid chromatography

Cyclopropenoid fatty acids (CPFAs), found in cottonseed, have been shown to have detrimental health effects to susceptible livestock. Previous quantitative analytical methods for the determination of CPFAs expressed these acids in terms of their relative abundance with respect to other fatty acids in the oil, necessitating the concurrent analysis of other fatty acids. The proposed analytical method describes the quantitation of three relevant CPFAs for cotton (malvalic acid, sterculic acid, and dihydrosterculic acid) in cottonseed in micrograms per gram fresh weight of sample. The method involves extraction of the oil, saponification, and derivatization of the free fatty acids with 2-bromoacetophenone to give the phenacyl esters. These esters are then separated by dual-column reverse-phase high-performance liquid chromatography and quantitated via external standards. This is the first method to include external calibration standards for CPFAs and, as such, is capable of direct quantification with no further data conversion required. CPFA data generated from the analysis of cottonseed, cottonseed meal, and cottonseed oil produced in the United States in 2002 are presented.     

Effect of Partial Waxy Wheat on Processing and Quality of Wheat Flour Tortillas

The processing and quality of wheat flour tortillas prepared with partial waxy and normal flour were evaluated. Control procedures and formula were utilized with water absorption varied to obtain machineable doughs. Amylose content was lower in most partial waxy compared with normal wheats. The type of wheat starch did not affect most dough properties or tortilla diameter. Tortilla height and opacity were adversely affected by the decreased amount of amylose in partial waxy wheats. Sufficient leavening reactions occurred early in baking (after 10 sec) to yield an opaque disk, but some baked tortillas lost opacity and become partially transparent after baking. Starch gelatinizes, disperses, and retrogrades concurrently with the leavening reaction during the short (<30 sec) baking time. Amylose functionality during baking and cooling appears to be involved in the retention of air bubbles in tortillas.     

Comparative Effects of 1BL/1RS Translocation in Relation to Protein Composition and Milling and Baking Quality of Soft Red Winter Wheat

Forty grain samples, derived from six soft red winter wheat lines with 1BL/1RS and four genotypes without the translocation, grown in four diverse environments, were used to assess test weight, flour yield, protein content of grain and flour, rheological properties, and end-use characteristics in cakes and cookies. Wheat lines with 1BL/1RS had similar or higher mean test weights than lines without the translocation. Mean flour yields were similar for the two groups. Test weight was not predictive of flour yield. Mean values for grain moisture, grain protein, and rheological properties, as measured by farinograph for mixing time stability and mixing tolerance index, were similar for wheat lines with and without 1BL/1RS. In several cases, flour from lines with 1BL/1RS produced dough with greater mixing tolerance and cakes with higher volume and softer texture than did check lines without the translocation. However, the translocation in these soft red winter wheat lines resulted in higher farinograph water absorption by the flour and decreased cookie spread. The results of this study were novel in that end-use, specifically baking quality of soft wheat lines with 1BL/1RS, varied dramatically depending on whether cookies or cakes were evaluated. Therefore, use of single-product baking tests may lead to false conclusions regarding end-use quality of 1BL/1RS soft wheat. Direct comparison between a pair of sister lines with and without 1BL/1RS indicated that the translocation had adverse effects on quality as exemplified by lower flour yield, greater farinograph water absorption, and reduced cookie diameter. However, the 1BL/1RS line had greater mixing tolerance and similar cake volume and texture scores in comparison to its sister line. In summary, 1BL/1RS lines were identified in which quality characteristics exceeded those of control cultivars and commercial flours. Genetic background and environmental factors probably affected milling and baking quality to a greater extent than the translocation. Many of the negative quality attributes previously associated with 1BL/1RS are probably due to genetic background effects and, therefore, could be greatly diminished with improvement of the genetic background in which the translocation resides.