Mechanisms of resistance to groundnut rosette

Rosette (caused by rosette assistor virus, groundnut rosette virus and satellite RNA) resistance in 3 groundnut genotypes (ICGV-SM 90704, ICG 12991 and JL 24) was evaluated, using a vector or mechanical transmission of the virus complex. Branches from rosette-infected plants (groundnut cv. Malimba) were grafted onto 23-day-old healthy stocks of the 3 genotypes, grown in pots in a greenhouse. Eighteen days after grafting, all the new shoots of ICG 12991 and JL 24 stocks showed severe rosette symptoms. The differences in rosette incidence recorded from the graft transmission and field observations may involve resistance to Aphis craccivora. Thus, an experiment was carried out to assess the vector performance on the 3 genotypes. Thirty days after sowing the 3 genotypes in pots in a greenhouse, young leaves were exposed to 5 viruliferous A. craccivora alatae (winged). Aphids were counted 10 days after infestation (DAI) on each plant. Exposed plants were left in a greenhouse up to 60 days after infestation to record rosette symptoms. Results indicated highly significant differences in aphid population counts between the 3 genotypes. At 10 DAI, increased numbers of aphids (alatae plus nymphs) were observed on ICGV-SM 90704 and JL 24, with an average of 93 and 96 aphids per plant, respectively. In contrast, aphid number on ICG 12991 fell from 5 to 3 per plant. There were also significant differences in disease expression at 60 DAI, since JL 24 showed 100% disease incidence, while no symptoms were noted on ICG 12991. Only mild symptoms were observed on ICGV-SM 90704

Spatiotemporal Separation of Groundnut Rosette Disease Agents

Analysis by triple-antibody sandwich enzyme-linked immunosorbent assay of groundnut samples from fields in two seasons from different regions of Malawi showed the absence of groundnut rosette assistor virus (GRAV) from some plants showing groundnut rosette disease symptoms and the presence of GRAV in some symptomless plants. Viruliferous Aphis craccivora collected from fields transmitted either GRAV alone, groundnut rosette virus (GRV) with its satellite RNA (sat RNA), or all three agents together, in different proportions. More plants became infected with all three agents when increasing numbers of potentially viruliferous aphids were used per plant, suggesting a dosage response. Electrical penetration graph studies of aphid stylet activities indicated successful transmission of GRV and its sat RNA during both the "stylet pathway phase" and salivation into sieve elements, whereas GRAV was transmitted only during the latter phase. Aphids transmitted all three agents together only during the salivation phase. Reverse-transcriptase polymerase chain reaction testing of viruliferous aphids and of inoculated plants revealed no correlation between the presence of all three agents in prospective aphid vectors and their simultaneous transmission to groundnut plants. These results show that separation of the groundnut rosette disease agents occurs over time and space

Screening Groundnut Breeding Lines for Resistance to Aphids, Aphis craccivora Koch

Some 37 F6 breeding populations were compared with 4 control varieties in a screenhouse study to combine rosette virus [groundnut rosette umbravirus] resistance with resistance to the vector Aphis craccivora. Following artificial infestation, mean aphid populations were recorded 10 and 15 days after infestation. The genotype ICG 12991 had the lowest rate of nymph development, low fecundity and smaller aphids compared with the controls

Technological options that respond to demands and market opportunities with focus on crops and livestock

Technology development is a core area of agricultural research, and the increasing global focus on client-demand and market oppourtunities is intended to increase its releance and effectiveness. This theme focuses on the achievements of and lessons learnt from technological optipns developed for crop and livestock systems including breeding, management practices and processing and appropriate technolgies, knowledge, information and methods that enhance productivity, value addition and the competitiveness of the products in both national and international markets. A number of research providers as well as public sector bodies such as national agricultural systems and universities, non-governmental organisations which have links to broad farmer networks have become increasingly involved in research activities. Consequently, agricultural researchers have and are continually developing a broad range of technological options to secure the production of safe food and non food cash crops and to achieve the most efficient and ecologically sound use of natural resources; soil, water and energy. It is however apparent that farmers prefer packages of information not just pest management strategies alone but a total package including other aspects such as soil and weed management options

Condensed tannin levels and resistance of groundnuts (Arachis hypogaea) against Aphis craccivora

A strong negative relationship was found between the concentrations of procyanidin, a condensed tannin, in the leaf bud petioles of seven genotypes of groundnut (Arachis hypogaea) and fecundity of the aphid Aphis craccivora on the same genotypes. Genotype EC 36892 contained the highest amount of procyanidin per weight of fresh petiole (ca 0.7%) and aphids feeding on this genotype produced significantly fewer offspring than aphids reared on genotypes with low procyanidin levels. It is proposed that testing for high procyanidin concentrations may provide plant breeders with a quick and relatively simple method to screen new groundnut genotypes for resistance against Aphis craccivor

Groundnut rossette: A virus disease affecting groundnut production in Sub-Saharan Africa

Groundnut (peanut, Arachis hypogaea L.) is cultivated in the semiarid tropical and subtropical regions of nearly 100 countries on six continents between 40°N and 40°S (Fig. 1). For people in many developing countries, groundnuts are the principal source of digestible protein (25 to 34%), cooking oil (44 to 56%), and vitamins like thiamine, riboflavin, and niacin (65)..

Identification and mapping of AFLP markers linked to peanut (Arachis hypogaea L.) resistance to the aphid vector of groundnut rosette disease

Groundnut rosette disease is the most destructive viral disease of peanut in Africa and can cause serious yield losses under favourable conditions. The development of disease-resistant cultivars is the most effective control strategy. Resistance to the aphid vector, Aphis craccivora, was identified in the breeding line ICG 12991 and is controlled by a single recessive gene. Bulked segregant analysis (BSA) and amplified fragment length polymorphism (AFLP) analysis were employed to identify DNA markers linked to aphid resistance and for the development of a partial genetic linkage map. A F2:3 population was developed from a cross using the aphid-resistant parent ICG 12991. Genotyping was carried out in the F2 generation and phenotyping in the F3 generation. Results were used to assign individual F2 lines as homozygous-resistant, homozygous-susceptible or segregating. A total of 308 AFLP (20 EcoRI+3/MseI+3, 144 MluI+3/MseI+3 and 144 PstI+3/MseI+3) primer combinations were used to identify markers associated with aphid resistance in the F2:3 population. Twenty putative markers were identified, of which 12 mapped to five linkage groups covering a map distance of 139.4 cM. A single recessive gene was mapped on linkage group 1, 3.9 cM from a marker originating from the susceptible parent, that explained 76.1% of the phenotypic variation for aphid resistance. This study represents the first report on the identification of molecular markers closely linked to aphid resistance to groundnut rosette disease and the construction of the first partial genetic linkage map for cultivated peanu

Litterfall, litter decomposition and associated nutrient fluxes in Pinus halepensis: influence of tree removal intensity in a Mediterranean forest

The online version of this article (doi:10.1007/s10342-015-0893-z) contains supplementary material, which is available to authorized users[EN] Our knowledge about the influence of silvicultural treatments on nutrient cycling processes in Mediterranean forests is still limited. Four levels of tree removal were compared in an Aleppo pine forest in eastern Spain to determine the effects on litterfall, litter decomposition and the associated nutrient fluxes after 12 years. Removal treatments included clearfelling, two shelterwood intensities (60 and 75 % of basal area removed) and untreated controls. Twelve years later, the basal area removed still explained 60 % of litterfall mass variance and 60 % of C, 52 % of N, 45 % of P, 17 % of K, 47 % of Ca and 60 % of Mg return variances. Litter decomposed somewhat more slowly in clearfellings compared to controls (p = 0.049), accumulated more Ca and released less K compared to the other three treatments. This was explained by contamination with mineral particles due to the poorly developed O horizon in clearfellings. We conclude that the management practices reduced the nutrient return via litterfall, but the nutrient release through decomposition seems poorly sensitive to canopy disturbance. In order to accurately quantify the harvesting impacts on nutrient cycling in this Mediterranean forest system, it is necessary to measure the litterfall of the understory layer.This work has been supported by a fellowship from the Generalitat Valenciana, Conselleria de Educacion, Formacion y Empleo awarded to L. Lado-Monserrat (BFPI/2008/041). Silvicultural treatments were carried out by the Mediterranean Centre for Environmental Studies (CEAM) through programme "I + D en relacion con la restauracion de la cubierta vegetal y otros aspectos de investigacion forestal". Dataloggers and probes were provided by the Generalitat Valenciana through Project "Efecto de diferentes sistemas de aclareo de masa forestal sobre la disponibilidad de agua, nutrientes y la regeneracion de la masa arborea y arbustiva en parcelas de pinar" (GV06/126). We acknowledge Joana Oliver, Ruth M. Tavera and Daniel Fortanet for their help in the laboratory and in the field. The authors wish to thank Francisco Galiana for his assistance, including help in fieldwork and providing information about the experimental design of the silvicultural treatments. Thanks also go to Rafael Herrera from the Centro de Ecologia, Instituto Venezolano de Investigaciones Cientificas, Caracas, Venezuela and two anonymous reviewers for critically reviewing the manuscript.Lado Monserrat, L.; Lidón, A.; Bautista, I. (2015). Litterfall, litter decomposition and associated nutrient fluxes in Pinus halepensis: influence of tree removal intensity in a Mediterranean forest. European Journal of Forest Research. 134(5):833-844. https://doi.org/10.1007/s10342-015-0893-zS8338441345Almagro M, Martínez-Mena M (2012) Exploring short-term leaf-litter decomposition dynamics in a Mediterranean ecosystem: dependence on litter type and site conditions. Plant Soil 358:323–335Alvarez A, Gracia M, Vayreda J, Retana J (2012) Patterns of fuel types and crown fire potential in Pinus halepensis forests in the Western Mediterranean Basin. For Ecol Manage 270:282–290Austin AT, Vivanco L (2006) Plant litter decomposition in a semi-arid ecosystem controlled by photodegradation. Nature 442:555–558Bates JD, Svejcar TS, Miller RF (2007) Litter decomposition in cut and uncut western juniper woodlands. J Arid Environ 70:222–236Binkley D (2008) Three key points in the design of forest experiments. For Ecol Manage 255:2022–2023Blair JM, Crossley DA Jr (1988) Litter decomposition, nitrogen dynamics and litter microarthropods in a southern Appalachian hardwood forest 8 years following clearcutting. J Appl Ecol 25:683–698Blanco JA, Zavala MA, Imbert JB, Castillo FJ (2005) Sustainability of forest management practices: evaluation through a simulation model of nutrient cycling. For Ecol Manage 213:209–228Blanco JA, Imbert JB, Castillo FJ (2006) Influence of site characteristics and thinning intensity on litterfall production in two Pinus sylvestris L. forests in the western Pyrenees. For Ecol Manage 237:342–352Blanco JA, Imbert JB, Castillo FJ (2008) Nutrient return via litterfall in two contrasting Pinus sylvestris forests in the Pyrenees under different thinning intensities. For Ecol Manage 256:1840–1852Blanco JA, Imbert JB, Castillo FJ (2011) Thinning affects Pinus sylvestris needle decomposition rates and chemistry differently depending on site conditions. Biogeochemistry 106:397–414Caldentey J, Ibarra M, Hernández J (2001) Litter fluxes and decomposition in Nothofagus pumilio stands in the region of Magallanes, Chile. For Ecol Manage 148:145–157Christensen JH, Krishna Kumar K, et al. (2013) Climate phenomena and their relevance for future regional climate change. In: Stocker TF, Qin D, Plattner G-K et al (Eds.) Climate change 2013: the physical science basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USACortina J, Vallejo VR (1994) Effects of clearfelling on forest floor accumulation and litter decomposition in a radiata pine plantation. For Ecol Manage 70:299–310Entry JA, Rose CL, Cromack K Jr (1991) Litter decomposition and nutrient release in ectomycorrhizal mat soils of a Douglas fir ecosystem. Soil Biol Biochem 23:285–290Fabbio G, Merlo M, Tosi V (2003) Silvicultural management in maintaining biodiversity and resistance of forests in Europe—the Mediterranean region. J Environ Manage 67:67–76Galiana F, Pérez-Badía R, Camarero E, Estruch V, Currás R (2001) Estimación de la Radiación solar incidente en pinares de Pinus halepensis sometidos a tratamientos selvícolas de cortas finales. In: Junta de Andalucía. Consejería de Medio Ambiente (Ed.) Actas del III Congreso Forestal Español. Junta de Andalucía. Granada (Original in Spanish)García-Plé C, Vanrell P, Morey M (1995) Litter fall and decomposition in a Pinus halepensis forest on Mallorca. J Veg Sci 6:17–22González Utrillas N, González Pérez E, Galiana F (2005) Variación del crecimiento diametral de la masa de pinar de carrasco en cortas finales experimentales, en los montes de Tuejar y Chelva (Valencia). IV Congreso Forestal Español. Zaragoza. Soc. Esp. Cien. For. (Original in Spanish)Guo LB, Sims REH (1999) Litter decomposition and nutrient release via litter decomposition in New Zealand eucalypt short rotation forests. Agric Ecosyst Environ 75:133–140GVA (1995) Mapa de Suelos de la Comunidad Valenciana. Chelva (666). Proyecto LUCDEME (Icona), Centro de Investigaciones sobre Desertificación y Conselleria d’Agricultura i Mig Ambient. Generalitat Valenciana. Valencia, Spain. (Original in Spanish)Hennessey TC, Dougherty PM, Cregg BM, Wittwer RF (1992) Annual variation in needle fall of a loblolly pine stand in relation to climate and stand density. For Ecol Manage 51:329–338Inagaki Y, Kuramoto S, Torii A, Shinomiya Y, Fukata H (2008) Effects of thinning on leaf-fall and leaf-litter nitrogen concentration in hinoki cypress (Chamaecyparis obtusa Endlicher) plantation stands in Japan. For Ecol Manage 255:1859–1867Jonard M, Misson L, Ponette Q (2006) Long-term thinning effects on the forest floor and the foliar nutrient status of Norway spruce stands in the Belgian Ardennes. Can J For Res 36:2684–2695Kim C, Sharik TL, Jurgensen MF (1996a) Canopy cover effects on mass loss, and nitrogen and phosphorus dynamics from decomposing litter in oak and pine stands in northern Lower Michigan. For Ecol Manage 80:13–20Kim C, Sharik TL, Jurgensen MF (1996b) Litterfall, nitrogen and phosphorus inputs at various levels of canopy removal in oak and pine stands in northern lower Michigan. Am Midl Nat 135:195–204Kim C, Son Y, Lee WK, Jeong J, Noh NJ, Kim SR, Yang AR, Ju NG (2012) Influence of forest tending (Soopkakkugi) works on litterfall and nutrient inputs in a Pinus densiflora stand. For Sci Technol 8:83–88Kimmins JP (2004) Forest ecology, a foundation for sustainable management and environmental ethics in forestry. Prentice-Hall, New JerseyKimmins JP, Mailly D, Seely B (1999) Modelling forest ecosystem net primary production: the hybrid simulation approach used in FORECAST. Ecol Modell 122:195–224Klemmedson JO, Meier CE, Campbell RE (1990) Litter fall transfers of dry matter and nutrients in ponderosa pine stands. Can J For Res 20:1105–1115Kunhamu TK, Kumar BM, Viswanath S (2009) Does thinning affect litterfall, litter decomposition, and associated nutrient release in Acacia mangium stands of Kerala in peninsular India? Can J For Res 39:792–801Lytle DE, Cronan CS (1998) Comparative soil CO2 evolution, litter decay, and root dynamics in clearcut and uncut spruce–fir forest. For Ecol Manage 103:121–128Molina AJ, Del Campo AD (2012) The effects of experimental thinning on throughfall and stemflow: a contribution towards hydrology-oriented silviculture in Aleppo pine plantations. For Ecol Manage 269:206–213Navarro FB, Romero-Freire A, Del Castillo T, Foronda A, Jiménez MN, Ripoll MA, Sánchez-Miranda A, Hutsinger L, Fernández-Ondoño E (2013) Effects of thinning on litterfall were found after years in a Pinus halepensis afforestation area at tree and stand levels. For Ecol Manage 289:354–362Olson JS (1963) Energy storage and the balance of producers and decomposers in ecological systems. Ecology 44:322–331Pérez Cueva AJ (1994) Atlas Climático de la Comunidad Valenciana. Colección Territori nº 4. Generalitat Valenciana. Conselleria d’Obres Publiques, Urbanisme i Transport, ValenciaPetritsch R, Hasenauer H, Pietsch SA (2007) Incorporating forest growth response to thinning within biome-BGC. For Ecol Manage 242:324–336Prescott CE (1997) Effects of clearcutting and alternative silvicultural systems on rates of decomposition and nitrogen mineralization in a coastal montane coniferous forest. For Ecol Manage 95:253–260Prescott CE (2002) The influence of the forest canopy on nutrient cycling. Tree Physiol 22:1193–1200Prescott CE, Blevins LL, Staley CL (2000) Effects of clear-cutting on decomposition rates of litter and forest floor in forests of British Columbia. Can J For Res 30:1751–1757Roig S, Del Río M, Cañellas I, Montero G (2005) Litter fall in Mediterranean Pinus pinaster Ait. stands under different thinning regimes. For Ecol Manage 206:179–190Sardans J, Peñuelas J, Rodà F (2005) Changes in nutrient use efficiency, status and retranslocation in young post-fire regeneration Pinus halepensis in response to sudden N and P input, irrigation and removal of competing vegetation. Trees 19:233–250Scarascia-Mugnozza G, Oswald H, Piussi P, Radoglou K (2000) Forests of the Mediterranean region: gaps in knowledge and research needs. For Ecol Manage 132:97–109Slovik S (1997) Tree physiology. In: Hüttl RF, Schaaf W (eds) Magnesium deficiency in forest ecosystems. Kluwer Academic Publishers, London, pp 101–214Taylor BR, Parkinson D (1988) Does repeated freezing and thawing accelerate decay of leaf litter? Soil Biol Biochem 20:657–665Torras O, Saura S (2008) Effects of silvicultural treatments on forest biodiversity indicators in the Mediterranean. For Ecol Manage 255:3322–3330Trofymow JA, Barclay HJ, McCullough KM (1991) Annual rates and elemental concentrations of litter fall in thinned and fertilized Douglas-fir. Can J For Res 21:1601–1615Wallace ES, Freedman B (1986) Forest floor dynamics in a chronosequence of hardwood stands in central Nova Scotia. Can J For Res 16:293–302Whitford WG, Meentemeyer V, Seastedt TR, Cromack Jr K, Crossley Jr DA, Santos P, Todd RL, Waide JB (1981) Exceptions to the AET model: deserts and clear-cut forest. Ecology 62:275–277Yin X, Perry JA, Dixon RK (1989) Influence of canopy removal on oak forest floor decomposition. Can J For Res 19:204–21