Nodal Cuttings Research Articles

English

The effect of exogenous phytohormones and sucrose on micropropagation and microtuberization from nodal cuttings of Manihot esculenta was studied. Direct and indirect organogeneses were established from these explants. When nodal cuttings were cultured in the presence of 0.01 to 0.1 mg.L-1 of BAP or NAA there was induction of the budding of axillary buds, with the highest percentages of nodal cuttings with axillaries buds budded of 98 and 73% with 0.07 mg.L-1 BAP and 0.05 mg.L-1 NAA, respectively. When sub cultured in the presence of 0.05 to 0.1 mg.L-1 NAA, the nodal cuttings with axillaries buds budded produced yellowish and friable callus with the highest percentage of callogenesis of 59.8% with 0.08 mg.L-1 NAA. The highest fresh weight of callus of 1334.7 mg was obtained with 0.07 mg.L-1 of NAA. When sub cultured in the presence of 0.05 to 0.1 mg.L-1 BAP, the nodal cuttings and callus induced shoots with the highest percentages of 72.3% and 92.3% for nodal cutting and callus respectively with 0.08 mg.L-1. Also, the highest numbers of shoots per nodal cutting 17.9 and per callus 28.1 were obtained with 0.08 mg.L-1. Multiple shoots, when isolated from nodal cuttings or callus and sub cultured in the presence of different ratio of BAP/NAA, differentiated into plantlets. With 0.07/0.05 mg.L-1 and 0.08/0.05 mg l-1 ratio, all shoots (100%) gave rise to plantlets with the highest growth parameters (14.8 ± 3.1 to 15.3 ± 1.7 cm of high, 12.3 to 12.7 leaves and 7.8 to 8.3 roots). These plantlets were used to induce microtubers on the basal medium supplemented with 0.1 to 0.6 mg.L-1 of NAA or Kin or NAA/Kin ratio and 10 to 60 g.L-1 sucrose. The ratio NAA/Kin of 0.4/0.4 mg.L-1 combined with 20 to 30 g.L-1 sucrose was more effective on the microtuberization than NAA and Kin used separately. In fact, it gave rise to 57.8 to 61.3% of plantlets which produce microtubers with the highest number of microtuber per plantlet (4 to 5), the highest diameter (130.4 to 131.8 mm) and the highest fresh weight of microtubers (403.3 to 408.1 mg). When the plantlets were acclimatized in different substrates, 100 % survived in the mixture red soil/black soil at equal volume (V/V) These results of this work show that BAP, NAA, and Kin used separately or in ratio can be used for organogenesis and micropropagation in Manihot esculenta var TMS 96/0023 in vitro.   Key word: NAA, Kin, BAP, sucrose, organogenesis, microtuberization, cassava.

Transcriptome analysis of indole-3-butyric acid-induced adventitious root formation in nodal cuttings of Camellia sinensis (L.).

Tea (Camellia sinensis L.) is a popular world beverage, and propagation of tea plants chiefly depends on the formation of adventitious roots in cuttings. To better understand potential mechanisms involved in adventitious root formation, we performed transcriptome analysis of single nodal cuttings of C. sinensis treated with or without indole-3-butyric acid (IBA) using the Illumina sequencing method. Totally 42.5 million RNA-Seq reads were obtained and these were assembled into 59,931 unigenes, with an average length of 732 bp and an N50 of 1292 bp. In addition, 1091 differentially expressed unigenes were identified in the tea cuttings treated with IBA compared to controls, including 656 up- and 435 down-regulated genes. Further real time RT-PCR analysis confirmed RNA-Seq data. Functional annotation analysis showed that many genes were involved in plant hormone signal transduction, secondary metabolism, cell wall organization and glutathione metabolism, indicating potential contributions to adventitious rooting. Our study presents a global view of transcriptome profiles of tea cuttings in response to IBA treatment and provides new insights into the fundamental mechanisms associated with auxin-induced adventitious rooting. Our data will be a valuable resource for genomic research about adventitious root formation in tea cuttings, which can be used to improve rooting for difficult-to-root varieties.

A node-capacitated Okamura–Seymour theorem

The classical Okamura-Seymour theorem states that for an edge-capacitated, multi-commodity flow instance in which all terminals lie on a single face of a planar graph, there exists a feasible concurrent flow if and only if the cut conditions are satisfied. Simple examples show that a similar theorem is impossible in the node-capacitated setting. Nevertheless, we prove that an approximate flow/cut theorem does hold: For some universal c > 0, if the node cut conditions are satisfied, then one can simultaneously route a c-fraction of all the demands. This answers an open question of Chekuri and Kawarabayashi. More generally, we show that this holds in the setting of multi-commodity polymatroid networks introduced by Chekuri, et. al. Our approach employs a new type of random metric embedding in order to round the convex programs corresponding to these more general flow problems.

<b>Dormancy of 'Imperial Gala' apple and 'Hosui' pear tree buds in a region of low chill occurrence

The objective of this work was to evaluate the dormancy dynamic of Imperial Gala apple tree buds and Hosui pear tree buds in a region of low chill occurrence. Experiments were conducted between April and August in 2007 and 2008. Branches were collected every two weeks from an orchard at Porto Amazonas (Parana State, Brazil). On the last sampling day, an additional set of branches was collected and refrigerated between 4°C and 7°C for 1,440 hours. Dormancy was evaluated using a biological test of single node cuttings isolated in growth chambers (GC) at 25°C with 16 hours of light exposure. The number of chill hours (CH) and chill units (CU) for the region were recorded. The two species were evaluated in separate experiments. We used 11 completely randomized treatments with four replicas for each species. The peak of endodormancy for the Imperial Gala apple tree buds occurred in early June 2007 and from middle June to early July in 2008. The endodormancy of the Hosui pear tree buds oscillated between April and August in 2007 and peaked between June and early July in 2008.

Métodos biológicos para avaliar a brotação de gemas em macieira para modelagem da dormência

A biological method was developed to evaluate the dormancy state of apple buds under controlled conditions. Cuttings (20-25 cm long) of ‘Castel Gala’ and ‘Royal Gala’ were sampled during the winter period, evaluating different cold and heat regimes to induce budbreak. Contrasts were tested in plant material processing (single node x intact cuttings), cold storage method to break dormancy in incubator chambers (planted in pots with floral foam x wrapped in plastic film, vertically or horizontally) and budbreak method in plant growth chambers (base immersed in water x planted in floral foam). Intact cuttings stored vertically in the cold represented better the natural interactions between buds than single node cuttings. Budbreak of lateral buds was strongly influenced by apical dominance. Wrapping cuttings in plastic film optimized internal space usage in the incubators and the number of evaluated buds, compared to planting cuttings in pots. During the warm period in the growth chambers, intact cuttings on floral foam resulted in better bud preservation and survival throughout the evaluation period, compared to cuttings with bases immersed in water. The most suitable conditions to evaluate dormancy evolution in apple buds used plastic-wrapped intact cuttings stored vertically during the cold period, with budbreak evaluation in the warm period after planting the cuttings in floral foam. Standardization of methodology helps to obtain better results in the development of physiological models of dormancy.

Evaluation of aeroponics for clonal propagation of Caralluma edulis, Leptadenia reticulata and Tylophora indica - three threatened medicinal Asclepiads.

The present study explores the potential of aeroponic system for clonal propagation of Caralluma edulis (Paimpa) a rare, threatened and endemic edible species, Leptadenia reticulata (Jeewanti), a threatened liana used as promoter of health and Tylophora indica (Burm.f.) Merill, a valuable medicinal climber. Experiments were conducted to asses the effect of exogenous auxin (naphthalene acetic acid, indole-3-butyric acid, indole-3-acetic acid) and auxin concentrations (0.0, 0.5, 1, 2, 3, 4 or 5gl(-1)) on various root morphological traits of cuttings in the aeroponic chamber. Amongst all the auxins tested, significant effects on the length, number and percentage of rooting was observed in IBA treated nodal cuttings. Cent per cent of the stem cuttings of C. edulis rooted if pre-treated with 2.0 gl(-1) of IBA for 5min while 97.7% of the stem cuttings of L. reticulata and 93.33% of stem cuttings of Tylophora indica rooted with pre-treatment of 3.0 gl(-1) of IBA for 5min. Presence of at least two leaves on the nodal cuttings of L. reticulata and T. indica was found to be a prerequisite for root induction. In all the species, the number of adventitious roots per cutting and the percentage of cuttings rooted aeroponically were significantly higher than the soil grown stem cuttings. Shoot growth measured in terms of shoot length was significantly higher in cuttings rooted aeroponically as compared to the cuttings rooted under soil conditions. All the plants sprouted and rooted aeroponically survived on transfer to soil. This is the first report of clonal propagation in an aeroponic system for these plants. This study suggests aeroponics as an economic method for rapid root induction and clonal propagation of these three endangered and medicinally important plants which require focused efforts on conservation and sustainable utilization.

English

Potato seeds degenerate over time due to systemic diseases (viruses and bacteria wilt), whose detections are mostly evident during later stages of epidemiology. Potato varieties released by Institute of Agricultural Research for Development (IRAD) Bambui recorded a drop in yields of approximately 50% within 20 years indicating that the varieties had started degenerating and thus required cleaning. A study was conducted in 2012 and 2013 at IRAD Bambui (Cameroon) to evaluate the rate of shooting in four improved IRAD potato varieties: Cipira, Tubira, Mafo and Bambui wonder. Liquid and solid media stocks prepared according to the International Potato Center (CIP)’s protocol were used. A randomized complete block design with four replications was used. Number of shot out nodes and average shoot length were collected after 28 days. The average number of shot out nodes in liquid and solid media in all the varieties ranged from 87.5 to 100, with the solid medium yielding better results, 97.5 to 100% in all the potato varieties as compared to liquid medium, 8.75 to 97.5%. The average shoots length in the liquid and solid media ranged from 4.95 to 10.56 cm. The analysis of variance revealed that there were significant differences at p = 0.05 between potato varieties studied. The liquid medium showed better results (8.49 to 10.5 cm) in all the varieties compared to the solid medium (4.59 to 6.08 cm) but the plantlets suffered from vitrification and asphyxiation forming callus. From the results obtained, the following conclusions may be drawn: shoot proliferation of potato tissues are reduced in stationary liquid medium as a result of vitrification and asphyxiation; potato nodal cuttings have faster growth in liquid medium than in solid medium. It is therefore recommended that solid medium should be used over stationary liquid medium in potato micropropagation because the loss of plant tissues in the liquid medium as a result of vitrification and asphyxiation can be very high.   Key words: Potato, media, growth, shoots, Cameroon.

Flower yield and quality of two rose cultivars grown in phenolic foam LC slab and phenolic foam RC slab in comparison to perlite and rockwool slab

Two standard cut rose (Rosa hybrida) ‘Rock Fire’ and ‘Feel Lip’ were propagated by single nodal cuttings. Each cutting with a five-leaflet leaf was stuck in a rockwool cube (Delta, 5 cm × 5 cm × 5 cm, Grodan Co., Ltd., Denmark) on May 16, 2011. After 32 days, rooted uniform saplings were transplanted onto the four different growing media, perlite (Pergreen, No. 1, G-Biotech Co., Ltd., Korea), rockwool slab (Delta, 100 cm × 20 cm × 7.5 cm, Grodan Co. Ltd., Denmark), phenolic foam LC slab (100 cm × 20 cm × 7.5 cm, Smithers Oasis Co., Ltd., Korea), or phenolic foam RC slab (100 cm × 20 cm × 7.5 cm, Smithers Oasis Co., Ltd., Korea), laid out in a completely randomized design on a bench in a commercial grower’s plastic house. The nutrient solution was supplied uniformly through a drip irrigation system. The irrigation frequency was dependent on amount of solar radiation. Yield and quality of harvested flower stems were measured for five successive harvests during a period of 11 months. Growth parameters measured were stem length, stem diameter, number of five-leaflet leaves per stem, stem fresh weight, number of harvested cut flowers per ten plants by grade, total yield, and tissue contents of inorganic elements. Measured growth parameters, such as stem length, number and quality of harvested stems, and contents of inorganic elements, were similar in all the tested growing media, except perlite in which these values were the lowest. The results obtained suggests that the widely used rockwool slab can be replaced with the new phenolic medium such as phenolic foam LC slab for commercial scale hydroponic productions of cut roses.

The Influence of Biochar on Growth of Lettuce and Potato

Pot experiments were conducted in a glasshouse to determine the growth pattern of lettuce, true potato seedlings (TPS) and single node cuttings of TPS in response to biochar. The treatments were arranged in a randomized complete block design with 5 treatments (0, 10, 30, 50 and 100 t ha−1) of biochar from greenwaste with 5 replications in lettuce, 10 in TPS and 5 in single node cuttings of TPS. The observations recorded on growth parameters showed that biochar had significant effect on growth of lettuce but no consistent effect on growth of TPS and single node cuttings. Among the biochar rates, 30 t ha−1 had the greatest influence on overall growth of lettuce. The pH and electrical conductivity increased as the biochar rates increased in all experiments. These results provide an avenue for soil management system by using biochar as an amendment in horticultural crops. However, their verification in the field is important for specific recommendations.

On the connectivity preserving minimum cut problem

In this paper, we study a generalization of the classical minimum cut problem, called Connectivity Preserving Minimum Cut (CPMC) problem, which seeks a minimum cut to separate a pair (or pairs) of source and destination nodes and meanwhile ensure the connectivity between the source and its partner node(s). For this problem, we consider two variants, connectivity preserving minimum node cut (CPMNC) and connectivity preserving minimum edge cut (CPMEC). For CPMNC, we show that it cannot be approximated within αlogn for some constant α unless P=NP, and cannot be approximated within any poly(logn) unless NP has quasi-polynomial time algorithms. The hardness results hold even for graphs with unit weight and bipartite graphs. For CPMEC, we show that it is in P for planar graphs.

Investigation of Nutritional Composition and Vegetative Propagation of Two Leafy Vegetables

There is little known of the nutritional content of underutilized leafy vegetables and the efficacy of vegetative propagation of these plants. The nutrient content of Solanecio biafrae (Oliv. & Hiern) C. Jeffrey and Clerodendrum volubile P. Beauv. was measured, and the efficacy for mass vegetative propagation was determined. Protein, fat, ash, crude fiber, and carbohydrate contents of S. biafrae were either the same as or lower than previously reported. Protein, fat, ash, and crude fiber of C. volubile were lower than previously reported. The requirement for vitamin C can be met by consuming 400 g of S. biafrae or 200 g of C. volubile per day. The K and Ca contents in S. biafrae were lower and higher, respectively, than previously reported, and other elements, including Fe, were lower than previously reported. Elemental composition of C. volubile was either the same as, lower, or higher than previously reported. Tip and softwood cuttings of C. volubile were best for vegetative propagation and S. biafrae can be propagated vegetatively using two to three nodal cuttings. Both vegetables can be used for in vitro regeneration.

Towards the propagation of a critically endangered tree species Anisoptera scaphula

Anisoptera scaphula (Roxb.) Kurz, the tallest tree species in Bangladesh, is critically endangered worldwide due to its poor natural regeneration. This study describes the appropriate regeneration technique for A. scaphula through seed germination and clonal propagation by stem cutting. The fastest and highest germination percentage (65) was observed in dewinged seeds sown inverted orientation with half buried position (T10) followed by dewinged seeds (62.5%) sown horizontally in full buried (T7) and delayed germination with lowest percentage (15) was in control (T0). Optimum initial growth was also shown when seedlings were developed from the seeds under T7. Both winged and dewinged seeds sown vertically in full buried or half buried position produced curved seedlings. However, dewinged seeds sown in horizontal or inverted (winged side down) position produced otherwise i.e., straight seedlings. The highest rooting percentages (63%) and maximum number of root (4.8) per cutting were obtained when one node cuttings treated with 0.8% IBA solution followed by 0.4% IBA in turn affecting for better survival and growth of rooted cuttings in the nursery conditions.

Micropropagation of Stevia Plant from Nodal Segments

The experiment was conducted to develop and establish a reproducible protocol for plantlet regeneration in Stevia. Nodal cutting explants were cultured in Murashige and Skoog (MS) medium supplemented with different concentrations and combinations of ?-Napthaleneacetic acid (NAA) and 6-Benzylamino purine (BAP). The combination of NAA at 1.0 mgl-1 and BAP at 1.0 mgl-1 resulted in the highest percentage (100%) of callus initiation. The maximum shoot regeneration and development of shoot was observed at the same combination. The developed shoots from nodal cuttings, upon transfer to the MS medium containing indole butyric acid (IBA) at 0.1mgl-1 resulted in best rooting within 8 days.DOI: http://dx.doi.org/10.3329/pa.v19i2.16914 Progress. Agric. 19(2): 21 - 26, 2008

Recursive algorithm for k-cycle preclusion problem in k-ary n-cubes

In order to measure the fault tolerance ability of the parallel computers which take the k-ary n-cube as underlying topology, by constructing the minimum node set whose removal will lead to every k-ary 1-cube in the k-ary n-cube faulty, a recursive algorithm for finding the k-ary 1-cube subnet preclusion node cut of the k-ary n-cube was proposed. It is proved that at least kn- 1nodes need to be damaged if a rival wants to destroy all k-ary 1-cubes in the k-ary n-cube. The result indicates that there are still undamaged k-ary 1-cubes in the parallel computers which take the k-ary n-cube as underlying topology if the number of the faulty nodes does not exceed kn- 1- 1.

Improving micropropagation of Dioscorea cayenensis–Dioscorea rotundata complex by the use of nodal cuttings and microtubers

Yams (Dioscorea spp.) are tuber crops used as staple food in Africa because of their nutritional value. In contrast to the inefficiency of traditional method of planting, micropropagation by nodal cuttings allows to increase the multiplication and the rapid production of pathogen-free plant material. In this work, micropropagation of yam from both nodal cuttings and microtubers was first tested and compared. It appears that microtubers rapidly develop shoots, more rapidly than nodal cuttings. Respectively 16 and 28 weeks are needed to obtain 10 cm high shoots. In a second time, the two techniques of multiplication were used in parallel to improve the multiplication rate. So, one nodal cutting after 28 weeks of culture can be subcultured as nodal cuttings (for 28 other weeks) and as microtuber parts (for 16 weeks). At the end of each subculture of nodes or microtubers, nodal cuttings and microtubers were cut and subcultured. This technique allowed obtaining more rapidly a lot of microtubers. The use of nodal cuttings allowed obtaining about 3×104 cuttings in two years. The additional use of the formed microtubers and the division of the microtubers at the subculture in three parts increased this multiplication rate by 15. The importance of this work was to consider microtubers not only as final planting product, but also to include them in the in vitro multiplication protocol to drastically increase the production of cuttings and finally of microtubers.

In vitro multiplication of Wthnia somnifera auxiliary buds for mass propagation

Wthnia somnifera of family Solanaceae commonly known as Amukkara or Ashwaganda is animportant medicinal perennial herb with long tapering roots. The roots arc widely used in ayurvedicmedicine and prescribed for hiccup, female disorders, cough and rheumatism. Wild and cultivatedforms are available and cultivated plants differ in morphological and therapeutical action from wildones. The annual requirement 01'42347 kg is imported from India spending Rs. 2, 840,449 (lUCN ,20(5). Development ofa method for in vitro mass production of this valuable species would substantiallyreduce the import cost and generate employment opportunities. This study was conducted to developan ill vitro protocol for mass production of W somniferaIn vitro grown seedlings ofW. somniferaweie used to excise single nodal cuttings and cultured onMS (Murashige & Skoog, 1962) medium. The effect ofNAA (0, 0.1,0.2 mg/I) in combination withBAP (0.5., 1.0, 1.5 mg/l) on shoot proliferation was tested in solid and liquid MS media containing twolevels of sucrose (3% and 4%). Proliferation (number of plant lets produced) was observed at weeklyintervals.Highest shoot proliferation rate (I: 20) was observed in solid MS medium containing 3% sucrose and1.5mg/1 BAP after two months. In solid MS medium with 4% sucrose and 1.0 rng/l BAP 1: 10 shootprol iferation rate was observed after two months. During the same time period I: IS shoot prol iferationrate was observed in solid MS medium with 3% sucrose, 0.5 mg/l BAP and 0.2 mg/l NAA, where I:12 proliferation rate was observed when BAP concentration increased up to 1.0 mg/l. Solid MS mediaboth with 3% and 4% sucrose levels and 0.5 mg/l BAP showed some proliferated shoots while othersolid cultures were not proliferated. However cultures containing NAA in addition to BAP enhancerooting of proliferated shoots before transferring the separated shoots to rooting media. The explantsin liquid MS medium with 4% sucrose and 1.0 mg/I BAP, proliferation initiated in one week andgavc 1:40 shoot multiplication rate after two months. Rest of the liquid cultures with different BAPand NAA combinations were not proliferated within the same time duration.Finally it can be concluded that highest shoot proliferation of W sonmifera through single nodalcuttings can be obtained on liquid MS medium with 4% sucrose and 1.0 mg/l BAP.

STUDIES ON THE VEGETATIVE PROPAGATION OF Gymnema sy/vestry (MASBEDDA)

Gymnema is a woody, extensively branched perennial vine well known as a medicinal plant withanti-diabetic properties. The extract of leaves contains gymnemic acid and a mixture oftriterpene-glycosides known as gymnemosides, which were found effective in reducing bloodsugar by acting indirectly through the stimulation of insulin secretion ofthe pancreas. Further, itwas found that, it reduces the serum cholesterol levels, stimulate circulatory system and alsoused in treating snakebites. Thus, Gymnema has a ready demand in local and foreign market ofherbal products, causing over exploitation of natural habitats, at the face of the lack of systemiccultivation. In this background, the current study was carried out to develop a cost effectiveprotocol for the rapid multiplication of Gymnema.It was a challenging task to find out sufficient amount of planting material, since Gymnema is avery rare species of plant. After an extensive survey, few authentic mother vines were identifiedfrom two locations in Matara district and one location in Monaragala district. The l't and theimmediate phase of propagation studies were conducted on vegetative propagation, since thecollection of seeds was extremely difficult. Three types of stem cuttings (2-3 nodal cuttings withleaves) i.e.; softwood (green, terminal portions), semi-hardwood (middle portion) and hardwood(basal portion) were used with hormone treatments and different potting mixtures. Applicationof Secto (NAA 0.3% + Thiram 0.2% in WP form) resulted 80% success in root formationfollowed by 50% success with the application of Clonex (3-IBA, 3mg/L in paste form)compared to 10% success observed in the control.It could be clearly observed from the results that, Gymnema can be vegetatively propagated bythe use of stem cuttings of specially the semi-hardwood type. Auxin based commercial rootinducing hormone mixtures can be effectively utilized to improve the success of root formationin Gymnema. A potting medium with desirable properties i.e. high moisture holding capacitywhile maintaining good aeration can further enhance the success of vegetative propagation.Thus, it can be concluded from the results that, the mass propagation of Gymnema can beachieved within a reasonably short period of time (less than one year) by using the techniquedeveloped.

ROSE DEVELOPMENT UNDER BLUE LIGHT ENVIRONMENT: BEHAVIOUR OF THREE CULTIVARS OF ROSE BUSHES

Ornamental plant shape is one of the main criteria of plant sale value. Under horticultural practices, plant shape is classically modulated through the use of growth regulators that enhance plant capacity. Increasing concern about environmental preservation encourages for the search of new environmental-friendly practices. Light is known to be the environmental factor that most affects plant architecture and thus plant shape. Using specific light quality rather than chemicals could not only contribute to preserve the environment, but also cause new aesthetical effects on plant shape. With this objective, we studied the impact of blue light on three rose cultivars, Rosa hybrida 'Radrazz', Rosa hybrida 'Meiratcan' and Rosa chinensis 'Old Blush'. Plants were grown from single node cuttings under white (Mastec 36 Watt; white/33 cool neons), or blue light (Philips TL-D 36, Watt/18, blue neons) at an equal photosynthetic efficiency (110 mu mol.m(-2).s(-1)) until the end of flowering of second order axes. Surprisingly, plants grown under blue light had normal vegetative and floral developments: for the cultivars 'Radrazz' and 'Old Blush', morphological and architectural characteristics as length and diameter of first and second order axes, number and localisation of second order axes, number and length of metamers, were similar between the two light treatments. However, for Rosa hybrida 'Meiratcan', both organogenesis and growth were slightly affected by blue light with a decrease of metamer number, axis length and axis diameter for the order 1 axes and a decrease of the number of order 2 axes. These results thus reveal the strong adaptive properties of rose plants to their light environment, but the effects of blue light are cultivar dependent. As far as horticultural practices are concerned, testing the effect of blue light on a cultivar is necessary before deciding if blue light is an efficient treatment to modulate or change rose plant shape.

Rapid assessment of resistance of tissue-cultured water yam (Dioscorea alata) and white guinea yam (Dioscorea rotundata) to anthracnose (Colletotrichum gloeosporioides Penz.)

Yam anthracnose is caused by the pathogen Colletotrichum gloeosporioides Penz. and has been identified as the most important biotic constraint to yam production worldwide. Rapid assessment of the disease is vital to its effective diagnosis and management. In this study, tissue-cultured yam plantlets of five lines of Dioscorea alata and nine of D. rotundata were rapidly assessed for their reactions to two isolates of yam anthracnose. The plantlets, obtained from meristem of the nodal cuttings, were grown for 8 weeks on Murashige and Skoog (MS) basal medium, acclimatised for 3 weeks, hardened for an additional 3 weeks, arranged in screen house in completely randomised design and sprayed with spore inocula prepared from 7 day-old culture of the two strains of Colletotrichum gloeosporioidies Penz. The relative resistance of the different Dioscorea spp. was evaluated using three disease indices – severity at seventh day after inoculation, SD7; area under disease progress curve, AUDPC; and disease severity rate, Rd. A modified rank-sum classification method put TDa 1425 and TDr 2040, with rank sum of 2.0 each, as resistant. TDr 2121, TDr 2287 and TDr 2048 were susceptible with rank sum of 27.50, 25.50 and 24.50, respectively. Dioscorea alata TDa 1425 and Dioscorea rotundata TDr 2040 were recommended in areas endemic with yam anthracnose, and also as parent lines while breeding for resistance to anthracnose.

Micropropagation of Bauhinia variegata L. from Tissue Culture

Bauhinia variegate L. is a multipurpose tree and its micropropagation holds great promise in agroforestry. The sterilized seeds were first inoculated on Murashige and Skoog (MS) medium. Nodal cuttings from these seedlings grown in vitro were used as explants for micropropagation. Nodal cutting inoculated on the medium with various concentrations of BAP (benzyl-aminopurine) and NAA (£- naphthalene acetic acid) and separately generated varied results. Best propagation was recorded on MS medium supplemented with 1.0 ?M BAP with 0.05 ?M NAA. Propagated plants were successfully acclimatized and rooted in pots (6 cm diameter) containing soil and sand in1:1 ratio and then finally transferred to the field. All the data generated were analysed statistically using SPSS statistical package. Nepal Journal of Science and Technology Vol. 13, No. 1 (2012) 39-41 DOI: http://dx.doi.org/10.3126/njst.v13i1.7397