Controlling sprouting in potato tubers using ultraviolet-C irradiance

Legislation limiting the use of chlorpropham (CIPC), the major potato sprout suppressant, has led to a need for new technologies to extend storage life of tubers. Ultra violet C (UV-C) has been used postharvest to reduce disease incidence on many crops, yet its use and efficacy as a sprout suppressant has not been investigated. The aim of this project was to identify the optimum dose and treatment timing of UV-C treatment on potato tubers as an alternative method of sprout suppression to reduce the dependence on chemical sprout suppressants. Up to six potato cultivars over two seasons were treated with varying doses of UV-C ranging from 0 to 30 kJ m⁻² either at harvest or at first indication of dormancy break. The tubers were stored at 9 °C and sprout growth and incidence assessed. Treatment with moderate UV-C doses (5–20 kJ m⁻²) suppressed sprout length and sprout incidence in a range of cultivars. Periderm DNA damage and programmed cell death were not detected in response to any of the UV-C doses. The inactive ABA metabolite, ABA-GE, increased in response to 10 or 20 kJ m⁻² within 72 h of treatment. Multivariate analysis showed a negative relationship between ABA metabolites and sprout growth/incidence during storage. This study found that UV-C reduced sprout growth in potato with no deleterious effects on tuber quality. This suggests potential for further development as an alternative or supplement to conventional sprout suppressant technologies.     

Integration of Lactobacillus plantarum A7 with thyme and cumin essential oils as a potential biocontrol tool for gray mold rot on strawberry fruit

Chemical fungicides have been intensively used in the control of postharvest decay in fruit in postharvest conditions; nevertheless, continuous use of these fungicides has faced two major obstacles: development of pathogen resistance to many key fungicides, and public knowledge on the health and environmental hazards of these compounds. This study evaluated the efficacy of Lactobacillus plantarum A7, thyme (Thymus vulgaris L.) and cumin (Cuminum cyminum L.) essential oils and the combination of these three elements as postharvest biocontrol agents against Botrytis spp. on strawberry fruit. Thyme oil had a remarkable antifungal effect against Botrytis spp. in vitro, whereas an inhibitory effect of cumin oil was achieved in higher concentrations. With thyme oil (2 h after artificial inoculation of the fruit), among three tested concentrations, only the 200 μL/L concentration showed an inhibitory effect on strawberries against Botrytis spp. (91.97%), while higher concentrations of cumin oil were required to prevent decay significantly. Both combinations of L. plantarum+ cumin oil and L. plantarum+ thyme oil completely inhibited the mycelia growth of the pathogens in vitro. Results showed that the combined treatments of strawberry fruit with L. plantarum+ cumin oil (50 μL/L) and L. plantarum+ thyme oil (100 μL/L) resulted in remarkably improved control of Botrytis infections, in comparison to the stand-alone application of L. plantarum A7 or essential oils. Quality (i.e. pH, acidity and ascorbic acid content) and sensory attributes of the strawberry fruit were better in the case of using cumin compared to thyme oil, when a combination of L. plantarum A7 and essential oils was used. This study has demonstrated that the integration of L. plantarum A7 with thyme and cumin essential oils is a potential biocontrol tool as a biofungicide in postharvest stage.     

Effect of postharvest biofumigation on fungal decay,sensory quality,and antioxidant levels of blueberry fruit

Postharvest decay, caused by various fungal pathogens, is an important concern in commercial blueberry production, but current options for managing postharvest diseases are limited for this crop. Four plant essential oils (cinnamon oil, linalool, p-cymene, and peppermint leaf oil) and the plant oil-derived biofungicides Sporan (rosemary and wintergreen oils) and Sporatec (rosemary, clove, and thyme oils) were evaluated as postharvest biofumigants to manage fungal decay under refrigerated holding conditions. Hand-harvested Tifblue rabbiteye blueberry fruit were inoculated at the stem end with conidial suspensions of Alternaria alternata, Botrytis cinerea, Colletotrichum acutatum, or sterile deionized water (check inoculation) and subjected to biofumigation treatments under refrigeration (7 °C) for 1 wk. Sporatec volatiles reduced disease incidence significantly (P < 0.05) in most cases, whereas other treatments had no consistent effect on postharvest decay. Sensory analysis of uninoculated, biofumigated berries was performed utilizing a trained sensory panel, and biofumigation was found to have significant negative impacts on several sensory attributes such as sourness, astringency, juiciness, bitterness, and blueberry-like flavor. Biofumigated fruit were also analyzed for antioxidant capacity and individual anthocyanins, and no consistent effects on these antioxidant-related variables were found in treated berries. Because of limited efficacy in reducing postharvest decay, negative impacts on sensory qualities, and failure to increase antioxidant levels, the potential for postharvest biofumigation of blueberries under refrigerated holding conditions appears limited.     

Insect communities related to wheat and coriander cropping histories and essential oils in the Rolling Pampa, Argentina

Intensive land use in the Rolling Pampa of Argentina have resulted in a mosaic of fields with different cultural histories creating different soil environments, which interact with crops and cropping activities producing a wide range of habitats for insects. Species and functions in canopy structure, food quality and essential oils of the crop–weed associations may vary depending on the field's cropping history and management (i.e. crops, soil degradation, weeding and fertilization). Species composition and functional structure of insect communities may respond to these changes. We studied insect communities in wheat and coriander crops that differed in their canopy structures, essential oil production, and the cropping histories of the fields on which they grew. For this purpose we planted wheat (Triticum aestivum L.), and two coriander (Coriandrum sativum L.) landraces in plots with two levels of weeding and fertilization. The crops were grown in two consecutive years at two locations differing in cropping history and related to this in level of soil degradation. Insects were sampled in all plots at crop full flowering, and were classified and related to agronomic variables and to essential oils using multivariate techniques. Among all the environmental factors tested in this study, year and soil degradation were the main factors explaining insect community structure; and also weed community structure in unweeded plots. The proportion of essential oil components varied with cropping history, suggesting an association among soil properties indicative of soil degradation, plant chemical signals and insect distribution. Although insect community composition varied widely, functional structure was very similar among crop–weed communities. Soil degradation appeared to have affected directly crop–weed communities and insects’ assemblages, since no consistent relationship was found between plant composition and insect community structure. It can be hypothesized that soil degradation might have affected the amount of volatiles produced especially by coriander, generating a “soil degradation scent” that determined the structure in the insect community, and/or the soil itself emitted different signals, in relation to changes in its physical, chemical and biological characteristics.     

Management of potato dry rot

Dry rot is a postharvest fungal disease affecting potato (Solanum tuberosum L.) tubers. The disease, caused by several species of Fusarium such as F. solani var. coeruleum, F. sambucinum, F. oxysporum, F. avenaceum, F. culmorum, results in significant yield losses. Some Fusarium species associated with the disease produce toxins, which are implicated in mycotoxicoses of humans and animals. The pathogens cannot penetrate the tuber through the lenticels or in the absence of wounds and cause infection only if the potato skin is ruptured. The seed tuber is considered as the main source of inoculum although soil infested by Fusarium spp. also constitutes a source of inoculum. Control of the disease, once provided by the fungicide thiabendazole, is now difficult due to the appearance of thiabendazole-resistant strains and the lack of potato cultivars with high levels of resistance to dry rot. An integrated disease management program including detection strategies, appropriate cultural practices and storage conditions (including a wound healing period) along with the use of synthetic chemical fungicides as seed tuber and/or postharvest treatment is recommended to reduce incidence and severity of dry rot. Recent studies also indicate the possibility that generally recognized as safe (GRAS) compounds and microbial antagonists could eventually be integrated into dry rot management strategies.     

Herbicidal Potential and Quantification of Suspected Allelochemicals from Four Grass Crop Extracts

Unknown compounds in crop plants are inhibitory to seed germination and early seedling growth of weed plants. A Petri dish assay showed that barley (Hordeum vulgare L.), oats (Avena sativa L.), rice (Oryza sativa L.) and wheat (Triticum aestivum L.) extracts significantly reduced root growth of alfalfa (Medicago sativa L.), barnyard grass (Echinochloa crus‐galli, Beauv. var. oryzicola Ohwi.) and eclipta (Eclipta prostrata L.). As the concentration of crop extracts increased, root growth of the test plants were significantly reduced. A high‐performance liquid chromatography analysis with nine standard phenolic compounds showed that the concentrations and compositions of allelopathic compounds depend on the extracted plant extracts. Caffeic acid, hydro‐cinnamic acid, ferulic acid, m‐coumaric acid, p‐coumaric acid and coumarin were present in all the crop plant species, and hydro‐cinnamic acid were detected as the highest amount. Coumarin at 10^?3 m significantly inhibited root growth of alfalfa and barnyard grass more than that of eclipta. The research suggests that extracts of barley, oats, rice and wheat have an allelopathic effect on alfalfa, barnyard grass and eclipta and that the findings of bioassay were considerably correlated with the type and amount of causative allelochemicals, indicating that the allelopathic effects on three test plants were ranked in order of wheat (highest), barley, rice and oats (lowest). The results may have value in enabling weed control based on natural plant extracts or crop residues in the fields.     

Reed Canarygrass Forage Yield and Nutrient Uptake on a Year-round Wastewater Application Site

Reed canarygrass (Phalaris arundinacea L.) is often planted at wastewater treatment sites to provide ground cover and remove nutrients. Our overall objective was to determine the forage yield and nutrient uptake under year-round potato wastewater application in northern latitudes. Specifically, we determined the effect of N fertilization rate on forage dry matter yield and N and P uptake by reed canarygrass, and compared the forage yield, persistence and nutrient uptake of reed canarygrass relative to those of orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromis inermis Leyss), timothy (Phleum pratense L.) and quackgrass [Elytrigia repens (L.) Nevski]. With only wastewater application, reed canarygrass had a forage yield of 5.8 Mg ha⁻¹, with N and P uptake of 113 and 30 kg ha⁻¹, respectively. Forage dry matter yield, N uptake and P uptake increased to 14.5 Mg ha⁻¹, 383 kg ha⁻¹ and 64 kg ha⁻¹, respectively, with an N fertilization rate of 224 kg ha⁻¹. Forage yield and N uptake of reed canarygrass, orchardgrass, timothy and smooth bromegrass were similar and exceeded those of quackgrass. Reed canarygrass P uptake exceeded that of the other grasses. Reed canarygrass was less persistent than quackgrass or smooth bromegrass.     

Cover crops and interrow tillage for weed control in short season maize (Zea mays)

Weed competition can cause substantial maize (Zea mays L.) yield reductions. Interseeding maize with cover crops or a combination of interrow cultivation and interseeded cover crops are possible alternative methods of weed control. This study was conducted to examine the potential of interrow cultivation plus cover crops to reduce weed density in maize without reducing the grain yield. Field experiments were conducted in 1993 and 1994 at two sites in Québec to determine the effects of planting 12 cover crops with maize on weed control. Fall rye (Secale cereal L.), hairy vetch (Vicia villosa Roth), a mixture of red clover (Trifolium pratense L.) and ryegrass (Lolium multiflorum Lam), a mixture of white clover (Trifolium repens L.) and ryegrass, subterranean clover (Trifolium subterraneum L.), yellow sweet clover (Meliotus officinalis Lam), black medic (Medicago lupulina L.), Persian clover (Trifolium resupinatum L.), strawberry clover (Trifolium fragiferum L.), crimson clover (Trifolium incarnatum L.), alfalfa (Medicago sativa L.), and berseem clover (Trifolium alexandrinum L.) were seeded at two planting dates, 10 and 20 days after maize emergence. Interrow cultivation was carried out weekly until forage seeding, with a final cultivation being conducted just prior to cover crop seeding. Cover crop planting date did not affect maize yields or the ability of interrow tillage plus cover crops to suppress the development of weed populations. Maize yield was less affected by the interseeded cover crops under conditions of adequate rainfall. Corn planted in fields heavily infested with weeds resulted in substantial yield reductions even when rainfall was adequate. Except for 1993 at l'Assomption interrow tillage plus cover crop treatments had consistently lower weed biomass when compared to the weedy control. Most of the weed control was due to the interrow cultivation performed prior to seeding of the cover crops. The lowest weed density occurred in the herbicide treated plots. The ability of interrow tillage plus cover crops to suppress the development of weeds was affected by the level of weed infestation, the growing conditions and location. The cover crops provide additional weed control but the interrrow tillage or some herbicide application may still be necessary.     

DNA marker-assisted evaluation of potato genotypes for potential resistance to potato cyst nematode pathotypes not yet invading into Japan

One of major objectives of crop breeding is conferring resistance to diseases and pests. However, large-scale phenotypic evaluation for many diseases and pests is difficult because strict controls are required to prevent their spread. Detection of disease resistance genes by using DNA markers may be an alternative approach to select potentially resistant accessions. Potato (Solanum tuberosum L.) breeders in Japan extensively use resistance gene H1, which confers nearly absolute resistance to potato cyst nematode (Globodera rostochiensis) pathotype Ro1, the only pathotype found in Japan. However, considering the possibility of accidental introduction of the other pathotypes, breeding of resistant varieties is an important strategy to prevent infestation by non-invading pathotypes in Japan. In this study, to evaluate the prevalence of resistance genes in Japanese genetic resources, we developed a multiplex PCR method that simultaneously detects 3 resistance genes, H1, Gpa2 and Gro1-4. We revealed that many Japanese varieties possess not only H1 but Gpa2, which are potentially resistant to other pathotypes of potato cyst nematode. On the other hand, no genotype was found to have the Gro1-4, indicating importance of introduction of varieties having Gro1-4. Our results demonstrate the applicability of DNA-marker assisted evaluation of resistant potato genotypes without phenotypic evaluation.     

Evaluation of monocropped and intercropped grain legumes for cover cropping in no-tillage and reduced tillage organic agriculture

Intensive tillage by means of mouldboard ploughing can be highly effective for weed control in organic farming, but it also carries an elevated risk for rapid humus decomposition and soil erosion. To develop organic systems that are less dependent on tillage, a two-year study at Reinhardtsgrimma and Köllitsch, Germany was conducted to determine whether certain legume cover crops could be equally successfully grown in a no-till compared with a reduced tillage system. The summer annual legumes faba bean (Vicia faba L.), normal leafed field pea (Pisum sativum L.), narrow-leafed lupin (Lupinus angustifolius L.), grass pea (Lathyrus sativus L.), and common vetch (Vicia sativa L.) were examined with and without sunflower (Helianthus annuus L.) as a companion crop for biomass and nitrogen accumulation, symbiotic nitrogen fixation (N₂ fixation) and weed suppression. Total cover crop biomass, shoot N accumulation and N₂ fixation differed with year, location, tillage system and species due to variations in weather, inorganic soil N resources and weed competition. Biomass production reached up to 1.65 and 2.19 Mg ha⁻¹ (both intercropped field peas), and N₂ fixation up to 53.7 and 60.5 kg ha⁻¹ (both common vetches) in the no-till and reduced tillage system, respectively. In the no-till system consistently low sunflower performance compared with the legumes prevented significant intercropping effects. Under central European conditions no-till cover cropping appears to be practicable if weed density is low at seeding. The interactions between year, location, tillage system and species demonstrate the difficulties in cover crop species selection for organic conservation tillage systems.     

Potato yield enhancement through intensification of sink and source performances

The combined total annual yield of six major crops (maize, rice, wheat, cassava, soybean, and potato; Solanum tuberosum L.) amounts to 3.1 billion tons. In recent years, staple crops have begun to be used as substitutes for fossil fuel and feedstocks. The diversion of crop products to fuels and industrial feedstocks has become a concern in many countries because of competition for arable lands and increased food prices. These concerns are definitely justified; however, if plant biotechnology succeeds in increasing crop yields to double the current yields, it will be possible to divert the surplus to purposes other than food without detrimental effects. Maize, rice, wheat, and soybean bear their sink organs in the aerial parts of the plant, and potato in the underground parts. Plants with aerial storage organs cannot accumulate products beyond their capacity to support the weight of these organs. In contrast, potato has heavy storage organs that are supported by the soil. In this mini-review, we introduce strategies of intensifying potato productivity and discuss recent advances in this research area.     

Evaluation of Lippia scaberrima essential oil and some pure terpenoid constituents as postharvest mycobiocides for avocado fruit

Mycobiocides are attracting research interest worldwide as possible postharvest pathogen control measures to replace synthetic fungicides. In this study, the application of two essential oils as fungicides was evaluated. Initially, the in vitro antifungal effects of Lippia scaberrima essential oil and three of the major oil components, (d)-limonene, R-(−)-carvone, and 1,8-cineole, as well as that of S-(+)-carvone, were investigated against Colletotrichum gloeosporioides, Lasiodiplodia theobromae, and an Alternaria isolate. The oil and terpenoids caused significant inhibition of the mycelial growth of all the pathogens when applied at a concentration of 2000 μL L⁻¹. The most potent volatile component of L. scaberrima essential oil, able to inhibit all the pathogens tested, proved to be R-(−)-carvone. The efficacy of the essential oil (1000 and 2000 μL L⁻¹) incorporated into the commercial coating was confirmed on fruit inoculated with two of the pathogens. A simulated export trial was done using Lippia essential oil, in addition to Mentha spicata (spearmint) essential oil, as supplements for fruit coatings. Results indicate that essential oils rich in R-(−)-carvone could be valuable alternatives to synthetic fungicides for the postharvest management of avocado fruit. The combination of essential oils with a commercial coating, acceptable to the organic market, offers additional protection to this vulnerable commodity.     

Energy Input and Output Analysis of four Field Crops in California1

Four crops, corn (Zea mays L.), sweet sorghum (Sorghum bicolor L.), fodder beet (Beta vulgaris L.) and sugarbeet (Beta vulgaris L.) were grown in irrigated plots at the experimental farm of the University of California, Davis, in 1980 and 1981. Six fertilizer N levels ranging from 0 to 280 kg ha^?1 were used to estimate the most efficient N input for each of the tested crop in terms of energy input and output analysis. Calculations of cultural energy input costs in relation to potential ethanol yield showed production requirements of: corn 30.9 GJ ha^?1, sweet sorghum 30.4 GJ ha^?1, fodder beet 49.4 GJ ha^?1 and sugarbeet 41.0 GJ ha^?1. Highest average energy inputs were for liquid fuels for operations 35%, irrigation 23% and fertilizer nitrogen 19%. Fodder beet had the highest fermentable carbohydrate yield at 13.05 Mg ha^?1 followed by sugarbeet at 11.5 Mg ha^?1. Sweet sorghum and corn yields were lower at 9.71 and 8.09 Mg ha^?1, respectively. Crop production inputs of energy per liter of potential ethanol were: corn 6.42 MJL^?1 sweet sorghum 5.25 MJL^?1, fodder beet 6.35 MJL^?1 and sugarbeet 5.95 MJL^?1.     

转BADH基因苜蓿T-DNA侧翼序列分析及转化事件特异性分析

为了从分子水平上鉴别不同的转基因株系,以转BADH基因苜蓿的T₀代基因组DNA为模版,采用热不对称交错PCR(TAIL-PCR)方法分离其外源基因插入位点的侧翼序列,获得了B127株系的左翼序列和右翼序列,以及B125、B138、B295和B196株系的左翼序列。侧翼序列特征分析表明,有的T-DNA边界序列被删除,有的边界序列被保留,并填充了一段未知来源的核苷酸序列。根据侧翼序列中插入载体序列和紧邻插入序列的基因组序列特征,分别设计PCR扩增的上、下游引物,并对获得的42个转BADH株系分别进行左、右翼序列的扩增,结果表明,转基因植株B106、B125、B138、B157、B158、B289、B295、B305和B127具有相同的扩增条带,B203、B220、B223和B196具有相同的扩增条带,说明这些株系可能仅来源于2个转化事件。本研究建立的事件特异性检测方法可以准确地将不同的转化株系区别开来。     

Weed Control of Four Higher Plant Species in Paddy Rice Fields in Southeast Asia

Four higher plants, namely glory bowers (Clerodendrum trichotomum L.), jimsonweed (Datura stramonium L.), beggarweed (Desmodium triflorum L.) and Chinaberry (Melia azedarach L.), with the strong allelopathic potential among 19 allelopathic species from Southeast Asia, were tested for their effects on weed emergence in paddy soil and field. In a greenhouse experiment, D. stramonium, D. triflorumand M. azedarach exhibited similar inhibitory magnitude at 1 t ha^?1 achieving more than 90 % weed control. C. trichotomum achieved about 70 % weed reduction at 2 t ha^?1. In paddy fields, D. triflorum was the most promising material for weed control and attained the highest rice yield among treatments, at the concentration of 2 t ha^?1, whereas the inhibition of D. stramonium and M. azedarach was weakened in the greenhouse. No injury of rice plants was observed. These plants might be used as natural herbicides to reduce the dependence on synthetic herbicides.     

Essential oil vapours suppress the development of anthracnose and enhance defence related and antioxidant enzyme activities in avocado fruit

Anthracnose caused by Colletotrichum gloeosporioides is a major postharvest disease in avocados that causes significant losses during transportation and storage. Complete inhibition of the radial mycelia growth of C. gloeosporioides in vitro was observed with citronella or peppermint oils at 8 μL plate⁻¹ and thyme oil at 5 μL plate⁻¹. Thyme oil at 66.7 μL L⁻¹ significantly reduced anthracnose from 100% (untreated control) to 8.3% after 4 days, and to 13.9% after 6 days in artificially wounded and inoculated ‘Fuerte’ and ‘Hass’ fruit with C. gloeosporioides. GC/MS analysis revealed thymol (53.19% RA), menthol (41.62% RA) and citronellal (23.54% RA) as the dominant compounds in thyme, peppermint and citronella oils respectively. The activities of defence enzymes including chitinase, 1, 3-β-glucanase, phenylalanine ammonia-lyase and peroxidase were enhanced by thyme oil (66.7 μL L⁻¹) treatment and the level of total phenolics in thyme oil treated fruit was higher than that in untreated (control) fruit. In addition, the thyme oil (66.7 μL L⁻¹) treatment enhanced the antioxidant enzymes such as superoxide dismutase and catalase. These observations suggest that the effects of thyme oil on anthracnose in the avocado fruit are due to the elicitation of biochemical defence responses in the fruit and inducing the activities of antioxidant enzymes. Thus postharvest thyme oil treatment has positive effects on reducing anthracnose in avocados.     

Antimicrobial and micro Raman spectroscopy of selected Zingiberaceae species from Northeast India

Antimicrobial activity of crude rhizome oils from some important members of Zingiberaceae from Northeast India was carried out in the present study. The plants used were Curcuma amada, C. longa, Zingiber moran, and Z. zerumbet. Rhizomes of the four species were collected and rhizome oil was extracted using six different polar and non-polar solvents. The antimicrobial property of the crude oil was studied against human pathogens using disc-diffusion and viability assay. The rhizome oil of all the 24 extracts exhibited potent antimicrobial activity against all pathogenic bacterial and fungal strains tested. Hydrodistilled fractions of the four species studied showed better effect among all solvents. Water extract of Z. moran was found to be the highest effective antimicrobial agent of all. Antibacterial effect of the water fractions was also characterized against Gram-positive and Gram-negative bacteria using micro Raman spectroscopy. This investigation shows that the essential oils from the wild and domestic species of the family Zingiberaceae from Northeast India are a potential source of bioactive compounds with tremendous medicinal, economic, and therapeutic value. The wild and endemic species Z. moran represents an interesting and promising source of plant-derived antimicrobial agent in the development of new drugs against pathogens.     

Biomass Yield and Essential Oil Yield Variations in Java Citronella (Cymbopogon winterianus Jowitt.), Intercropped with Food Legumes and Vegetables

Java citronella ( Cymbopogon winterianus Jowitt., Family: Poaceae) is a perennial, multiharvest aromatic grass, the shoot biomass of which, on steam distillation, yields an essential oil extensively used in fragrance and flavour industries. It has a long initial lag phase. To utilize the crop resources more efficiently during this lag phase, a field experiment was conducted for two years (1995–97) in semiarid tropical climate to explore the feasibility of intercropping food legumes and vegetables in Java citronella. Among food legumes, greengram ( Vigna radiata (L.) Wilez.), and among vegetables, clusterbean ( Cyamopsis psoraloides D. C., syn. Cyamopsis tetragonoloba (L.) Taub.), tomato ( Lycopersicon esculentum Mill.) and lady's finger ( Abelmoschus esculentus Moench.) as intercrops did not decrease the biomass yield, essential oil yield of Java citronella and produced bonus yields of these crops over and above that of Java citronella. Maximum monetary returns were recorded by Java citronella intercropped with tomato or greengram. Java citronella intercropped with redgram ( Cajanus cajan (L.) Millsp.), horsegram ( Macrotyloma uniflorum (Lam.) Verd. syn. Dolichos biflorus Roxb.) and brinjal ( Solanum melongena L.) suffered significant biomass and essential oil yield reductions. Horsegram proved to be the most competitive intercrop producing least yields and minimum monetary returns.     

Identification of RAPD markers linked to the Ns locus in potato

Using the RAPD method and bulked segregant analysis we identified four RAPD markers linked to a dominant gene Ns, responsible for a hypersensitive reaction of potato (Solanum tuberosum L.) to potato virus S (PVS) infection. The markers OPE15⁵⁵⁰, OPJ13⁵⁰⁰, OPG17⁴⁵⁰ and OPH19⁹⁰⁰ were found to be closely linked to the Ns gene in diploid potato clones. They are situated at 2.6, 3.3, 4.6 and 6.6 cM from Ns, respectively. As a source of the gene, clone G-LKS 678147/60, which is known to carry Ns transferred from S. tuberosum ssp. andigena was used. These RAPD markers were not amplified in resistant tetraploid clones containing Ns derived from the clone MPl65 118/3, also having an andigenum origin. This suggests that there may be two separate loci of Ns in the sources identified, or different alleles with the same specificity at a single locus, or that the genetic background of tetraploids tested results in different RAPD amphlification patterns.