Critical photoperiods for tuberization: A screening technique with potato cuttings

Seedling populations segregating for the critical photoperiod that controls tuberization may be screened by a cutting technique. Plants are grown under daily photoperiods which are at first long (e.g., 20 hours) and which are shortened at two-week intervals. Apical cuttings and single-node, sub-apical cuttings are taken at the end of each two-week period. The cuttings are maintained in a mist chamber under a 20-hour photoperiod for 10–14 days. The photoperiod that first promotes tuberization on cuttings may be considered as the critical photoperiod.     

A field screening technique for drought tolerance studies in potatoes

Summary A major objective of plant breeding programmes in semi-arid conditions is the selection of more drought-tolerant plant material. An irrigation system has been developed to assist in water use and drought tolerance screening studies of potato genotypes in the confined space of a rain shelter. The line-source principle was used as a departure point for the design of an irrigation boom, attached to the roof structure of a rain shelter. Five water regimes were achieved by using nozzles that differed in discharge rate and three genotypes per rain shelter were evaluated simultaneously. Crop production functions could be established for the different genotypes. The system shares some disadvantages of the typical line-source, such as the simultaneous irrigation of all plots and water treatments are not randomised. The main advantage above traditional plot systems, which would use drip or micro irrigation under rain shelters, is the ease of management.     

Internodal elongation: A potential screening technique for heat tolerance in potato

Summary In pot culture experiments over 2 consecutive years, 20 potato genotypes of varying heat tolerance were grown under long day conditions and heat stressed by being exposed to high (38 °C/21 °C mean day/night) temperature. The percent increase in mean internode length of heat stressed plants over those grown at normal temperatue (25°C/16°C day/night) was correlated with the percent tuber dry matter yield of the heat stressed plants (r=0.618, P=0.01). In the same 20 genotypes, grown under short day conditions at normal temperature, the fraction of leaf bud cuttings exposed to high night temperature (23°C) that produced tuber initials correlated with the percentage increase in internode elongation in stem cuttings exposed to 25°C compared with those exposed to 15°C (r=0.680. P=0.01). Thus the relative changes in internode elongation are related to thermal tolerance, and it is suggested that this can be used as a selection criterion for heat tolerance.     

A rapid screening technique for drought resistance in potato (Solanum tuberosum L.)

Summary The reduction in growth in the dark of leaf dises floated over polyethylene glycol 6000 solution of water potential −0.4 MPa, relative to the growth of similar leaf dises floated over water for the same period, varied in the range 10–87% in 28 genotypes. The growth reductions in the genotypes tested were in general agreement with what is known about their drought resistance. Publication No. 906, Central Potato Research Institute, Simla.     

In vitro bioassays for salinity tolerance screening of potato

Summary Three in vitro bioassays (single-node cutting, root tip segment and microtuberization) gave similar results in ranking the salinity (NaCl) tolerance of several potato genotypes (Solanum spp.) and were verified by tuber yield criteria in a field lysimeter trial with salinized irrigation water. Salinity stress consistently depressed growth in the single-node cutting and root tip segment bioassays, reduced microtuber yield in the microtuberization bioassay and decreased tuber yield in field lysimeters. The single-node cutting bioassay was simpler to perform than the root tip segment and microtuberization bioassays and did not exclude certain genotypes as did the microtuberization bioassay. The single-node cutting bioassay can be recommended as a substitute for more labour-intensive and costly field assessments of salinity effects of yield.     

A field screening technique for evaluating rice germplasm for drought tolerance during the vegetative stage

A rapid method of testing direct-seeded rainfed rices (Oryza sativa L.) for drought reaction, concurrently with, but separately from, evaluation for agronomic traits and reaction to various stresses, is needed for early identification of desirable genotypes. Thus, a technique which quantifies soil moisture stress for screening thousands of cultivars and breeding lines for drought tolerance during the vegetative stage was developed. Seeds were drilled on dry granular clay soil (Andaqueptic Haplaquoll) in the field, then sprinkler-irrigated every 4 days for 37 days. As the soil dried, each entry was visually scored for drought reaction at 0.1–0.2, 0.4–0.5 and 0.8–1.0 MPa soil moisture tension (smt) at 20-cm soil depth. Entries were visually scored for drought recovery 10 days after the field was reirrigated. A total of 38 691 rices was tested in the dry seasons from 1978 to 1985. The 8-year screening test showed reproducibility of results in the field as indicated by the consistent scores of drought-tolerant and susceptible control cultivars within and across years. Ten germplasm accessions repeatedly performed similar to, or better than, the drought-tolerant control. There were ten outstanding drought-tolerant breeding lines, six of which were progenies of moderately tolerant Nam Sagui 19 from Thailand. The 20 outstanding selections likewise had consistent drought-tolerant scores across years, irrespective of duration of stress, which ranged from 31 to 54 days.     

Relative salinity tolerance of potato cultivars assessed byin vitro screening

One hundred and thirty European and North American potato cultivars were assayedin vitro for salinity (NaCl) tolerance. A modified single-node cutting bioassay was used in which cultivars were exposed to a range of NaCl levels (0, 40, 80, and 120 mM), in a Murashige and Skoog-based medium, for 1 month. Evaluations were performed twice for each cultivar at each salt level, using five single-node cuttings. Six vegetative growth parameters (shoot and root lengths, fresh and dry weights) were measured at the time of harvest and corrected for differences in cultivar vigor. These relative values were subjected to multivariate cluster analysis. The sum of the relative rankings at 40, 80, and 120 mM NaCl partitioned the cultivars into 8 units. The cultivars Amisk, BelRus, Bintje, Onaway, Sierra, and Tobique were in the most salinity tolerant unit and in the top cluster group for vigor with the exception of Tobique. These cultivars can be recommended for further study.     

Soil-based screening for iron toxicity tolerance in rice using pots

The objective of this study was to assess the reliability of pot-based screening method for iron (Fe) toxicity tolerance in rice using soils from hot spots. Five lowland rice varieties with known reaction to Fe toxicity were grown in pots in a screen house for three seasons. Fe-toxic soils from two hot spot fields – Edozighi, Nigeria and Niaouli, Benin were used and soil from Africa Rice Center (AfricaRice) experimental farm, Cotonou, Benin was included as control. Leaf bronzing score (LBS) was determined at different stages, and grain yield was determined at maturity. Heritability was estimated using data across the three seasons. High heritability was recorded for LBS and grain yield. Grain yield reduction in stress treatment relative to control varied from 15 to 56% depending on the variety and soil. Bao Thai, Suakoko 8, and WITA 4 had better performance under Fe toxicity in terms of LBS, yield and relative yield reduction, whereas Bouake 189 and IR64 had poorer performance. Grain yield and LBS were significantly correlated but negatively at 60 days after sowing (DAS). Overall, the results found in this experiment were consistent with previous field studies. Therefore, pot screening using soils from hot spots can be used by rice breeding programs to reliably assess Fe toxicity tolerance ex situ.     

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.     

Use of single-leaf cuttings of potato for efficient mass propagation

Summary Potato stock plants of five commercially propagated varieties, which derived from tissue culture, were grown at a low light irradiance in non-aseptic conditions. The plants produced tiny-leaved etiolated stems, which were a good source of cuttings for further propagation. The method was tested by growing micropropagated and cutting propagated plants as three lines of stock plants, based on different clonal generations, and which were repeatedly harvested for cuttings. There was wide variation in the multiplication capacity among the varieties used. The most productive variety produced more cloned potato plants than when micropropagated in vitro. Stock plants derived from single-leaf cuttings produced more new cuttings than when derived from tissue culture. The growing facilities used were simple and inexpensive and could be set up anywhere. The method is economically competitive due to the need of only very simple and inexpensive growing rooms, and would be worth using particularly in developing countries and also in advanced potato production. All the cuttings of different harvests rooted well and the last propagated cuttings of the lines were still free of prevalent viruses although using simple growing facilities.     

Tubers from leaf-bud cuttings: A tool for potato seed certification and breeding programs

The use of leaf-bud cuttings as a tool for rapid clonal increase was studied in 6 cultivars. Small tubers were obtained directly from leaf-bud cuttings maintained for 7 weeks in sand-filled pots or benches. The tubers ranged in size up to 1 1/4 inches (3cm) in diameter. The number of leaf-bud cuttings ranged from 37 to 288, depending on size of mother plant. They averaged 114 cuttings. Almost all of the leaf-bud cuttings produced tubers. The procedure is fast, simple, and provides for rapid increase of selected stocks.     

Potato (Solanum spp.) production using apical cuttings and tuberlets under three contrasting environments of Vietnam

Potato production from rooted apical cuttings or from small tubers (l–20g) produced in high density beds has great potential in Asia. This is particularly important in non-traditional warmer environments. This research was conducted to assess the feasibility of producing many small tubers in high density beds. A second objective compared tubers from beds with transplanted rooted cuttings and traditional seed tubers for growth and yield in the field. Tuberlet production in beds exceeded 2000/m² with a density of 1000 plants/m² under optimal growing conditions while under high temperatures only about 1.25 tuberlets/plant were produced. In field experiments, transplanted cuttings yielded 20 t/ha in the mid and high elevation areas, only slightly less than tuberlets of 5–10g while at the hot site, yields were generally only 8 to 10 t/ha for both materials. Larger healthy seed tubers produced significantly higher yields at the low and high elevation sites. Tuberlets of 1–5g were also able to give yields of 20 t/ha in the mid-elevation site. These results indicate that cuttings and small tuberlets are two ways of growing potatoes which need to be further evaluated for socioeconomic assessment by farmers.     

A systematic identification of cold tolerance genes in peanut using yeast functional screening system

Peanut(Arachis hypogaea L.) is a thermophilic crop, and low temperature leads to a significant reduction in annual yields. Despite a few cold tolerant germplasms or cultivars have been discovered and developed, molecular mechanisms governing peanut cold tolerance is poorly understood. Identification of keys genes involved in cold tolerance is the first step to address the underlying mechanism. In this study, we isolated and characterized 157genes with potentials to confer cold tolerance in peanu...     

A promising approach for bio-finishing of cotton using immobilized acid-cellulase

In this research, cellulases were immobilized on Eudragit S-100 to minimize the tensile strength loss of cotton fabric caused by the enzymatic hydrolysis. About 76 % of the enzyme activity and 81 % of the amount of protein were recovered after the immobilization process, and the immobilized cellulase exhibited good reuse ability. The immobilized cellulase had the better adsorptive performance on cotton than the free cellulase. In addition, the results revealed that the catalytic efficiency of the immobilized cellulase on cotton was degradation, perhaps because the diffusion of the enlarged cellulase molecules is significantly inhibited in the interior of the cotton fiber. Moreover, the cotton fabric treated with the immobilized cellulase showed less weight and strength losses. SEM pictures further indicated that the cotton fabric treated with the immobilized cellulase suffered less damage.     

Field screening for resistance to potato smut in Peru

Field trials carried out between 1982 and 1984 to evaluate potato clones and cultivars for their resistance to potato smut indicated that from a total of 179 accessions tested seven were resistant during the three-year tests. Five accessions were resistant during two consecutive trials but then there were not enough tubers available for a retest for the third time. Accessions that were resistant during the three consecutive field trials included Peruvian cultivars Cuzco, Mariva, Mi Peru, Participación and Revolución, and CIP’s clones 376181.5 and 6956.52.     

A rapid micro-starch quantitation method for potato callus and its application with potato tubers

The procedure described was developed as a micro-starch method for potato callus tissue (0.1-0.2% starch on a fresh weight basis) and then evaluated with macro-starch samples of potato tubers harvested during three physiological stages of development. This method consisted of the following steps: (a) a mild alkaline-sonic extraction of starch from lyophilized 80% aqueous ethanol-washed samples, (b) starch hydrolysis of the neutralized, filtered extracts by 1 N HC1, and (c) the determination of liberated glucose by the specific glucose oxidase system. Results with this procedure were as sensitive and accurate (SD ± 0.86%) as with other starch-specific methods with more extensive starch isolation and purification steps.