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WILD COMMON BEAN IN THE CENTRAL VALLEY OF COSTA RICA: ECOLOGICAL DISTRIBUTION AND MOLECULAR CHARACTERIZATION1

WILD COMMON BEAN IN THE CENTRAL VALLEY OF COSTA RICA: ECOLOGICAL DISTRIBUTION AND MOLECULAR CHARACTERIZATION1
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   Agronomía Mesoamericana Universidad de Costa Rica pccmcz@cariari.ucr.ac.cr  ISSN (Versión impresa): 1021-7444COSTA RICA   2004 Rosa Inés González Torres / Rodolfo Araya Villalobos / Eliana Gaitán Solís / Daniel G. Debouck WILD COMMON BEAN IN THE CENTRAL VALLEY OF COSTA RICA: ECOLOGICAL DISTRIBUTION AND MOLECULAR CHARACTERIZATION Agronomía Mesoamericana, año/vol. 15, número 002 Universidad de Costa Rica Alajuela, Costa Rica pp. 145-153  INTRODUCTION Wild relatives of crops have long been known assources of disease resistance, adaptation to stresses andnovel variability. In the case of common bean Phaseolusvulgaris L., there are published reports about theirinterest for bruchid resistance (Cardona et al. 1990),photosynthetic efficiency (Lynch et al. 1992) andtolerance to salinity (Bayuelo-Jiménez et al. 2002), andsome progress has been reported in including these traitsinto elite cultivars (Singh 2001). While the evaluation of wild bean resources surely deserves further attention(Singh 1999), the identification of additionalpopulations in the wild is a prerequisite for any futureprogress, as their extinction means loss of anyenhancement possibility (Freytag & Debouck 2002).On the other hand, the increased acreage plantedwith transgenical crops in tropical and subtropicalcountries (James 2003) invites to document carefullythe distribution of genetically compatible wild speciesas a basic preliminary step for their safe introductionand management (Rissler & Mellon 1996). Commonbean is a current target of genetic transformation, anddifficulties in achieving effective transformation mightbe overcome soon (Svetleva et al. 2003). Gene flow hasbeen shown to occur in common bean landraces andwild sympatric and conspecific forms in Colombia,Peru, and Mexico (Beebe et al. 1997b; Papa & Gepts2003, respectively). There are some preliminary reportsabout the presence of gene flow in Costa Rica (Araya et al. 2001; González-Torres et al. 2003). AGRONOMÍAMESOAMERICANA15(2):145-153. 2004 WILD COMMON BEAN IN THE CENTRALVALLEYOFCOSTARICA: ECOLOGICALDISTRIBUTION AND MOLECULARCHARACTERIZATION 1 RESUMEN Frijol silvestre en el Valle Central de Costa Rica:distribución ecológica y caracterización molecular. Estetrabajo presenta una actualización sobre la distribución de lasformas silvestres de fríjol común en Costa Rica, su ecología ysu caracterización molecular. Ala fecha 22 poblaciones fueronencontradas en cuatro cuencas alrededor del Valle Central, ge-neralmente en vegetaciones ruderales (frecuentemente bordesde cafetales), con estatuto de conservación variable (desdeprotegido a amenazado). Su caracterización molecular indicasu pertenencia al acervo genético mesoamericano. Varios mar-cadores indican una variabilidad aumentada en las formas sil-vestres y permiten inferir la presencia de un fenómeno de flu- jo genético e introgresión desde materiales cultivados. Palabras claves: Phaseolus vulgaris , genética depoblaciones, biología de la conservación, América Central,flujo de genes. 1 Recibido para publicación el 16 de junio del 2004. 2 CIATGenetic Resources Unit. 3 Estación Experimental FBM, Universidad de Costa Rica. Correo electrónico: avillalo@cariari.ucr.ac.cr 4 CIATBiotechnology Unit ABSTRACT Wild common bean in the Central Valley of CostaRica: ecological distribution and molecularcharacterization. This work offers an update on thedistribution of wild common bean in Costa Rica, its ecologyand molecular characterization. To date 22 populations havebeen discovered in four watersheds around the Central Valley,usually in man-made habitats (often sides of coffeeplantations), under varying conservation status (from protectedto threatened). Molecular characterization indicates that thewild common bean belong to the Mesoamerican gene pool.Different markers indicate an increased genetic diversity insome wild populations, and allow to hypothesize the presenceof gene flow and introgression from cultivated materials. Key words: Phaseolus vulgaris , population genetics,conservation biology, Central America, gene flow.  Rosa Inés González Torres 2 , Rodolfo Araya Villalobos 3 , Eliana Gaitán Solís 4 , Daniel G. Debouck  2  GONZÁLEZ et al .: W ILDCOMMONBEANIN C OSTA R ICA Knowledge about the distribution of wild commonbean in native habitats of tropical and subtropicalAmerica has progressed substantially (Gepts &Debouck 1991, Toro Ch. et al. 1990), since the earlyrecords for Argentina (Burkart 1941) and Guatemala(McBryde 1947). Records for Central America outsideMexico are relatively few (Freytag & Debouck 2002).Wild P. vulgaris has been reported from Honduras(Beebe et al. 1997a), El Salvador (Toro Ch. et al. 1990), and Nicaragua (Delgado Salinas 2001). Itspresence in Panama is doubtful: Brücher (1988) hasclaimed it “in the Chiriquí mountains”, but no recordsare available (Freytag & Debouck 2002; Lackey &D’Arcy 1980).In Costa Rica, the presence of wild common beanwent long unnoticed: it was not reported in the ‘Flora of Costa Rica’(Standley 1937), nor in the ‘Costa RicanNatural History’(Boucher 1983). Brücher (1988)claimed to have found it in the “departamento of SantaCruz”, but there is no department under that name inCosta Rica. The first record for this country seems to beby Debouck et al. (1989), from the province of SanJosé. These early findings were confirmed by morerecords from other provinces (Araya et al. 2001). Thegermplasm accessions resulting from these germplasmexplorations have been characterized later on (Tohme et al. 1996, Toro Ch. et al. 1990), and were shown to beclose to Guatemalan accessions in the so-calledMesoamerican genepool (Gepts et al. 2000). TheircpDNAhaplotype ‘H’seems however unique, althoughbelonging to a lineage widely distributed in CentralAmerica and Colombia and rooted in the Pacific range(Chacón 2001).The objective of this note is to provide an updateabout the distribution of wild common bean in CostaRica, its ecology and conservation status, andcharacterization through molecular markers. MATERIALS & METHODS For the disclosure of wild populations, we applieda technique of ecogeographic surveying describedelsewhere (Debouck 1988), taking into account theresults of previous works (Debouck et al. 1989; ArayaVillalobos et al. 2001). For the molecularcharacterization, we used seeds and seedlings of 443individuals coming from six populations collected in1987, 1998 and 2003: Chagüite (102), Zarcero (48),Aserrí (84), Tarbaca (18), Jérico (64), and Quircot(119). Seed storage protein phaseolin and two enzymes(diaphorase and peroxydase) were analyzed followingthe protocol by Lareo et al. (1993) and Ramírez et al. (1987), respectively. The interpretation of thediaphorase pattern was done along Sprecher (1988),while we followed the procedure by Koenig & Gepts(1989) for peroxydase. Nine loci of microsatelliteswere studied along the protocol by Gaitán-Solis et al. (2002). Polymorphism of non-coding regions of chloroplast (cp) DNAwas studied along a procedure of RFLPs-PCR developed by Chacón (2001). RESULTS Distribution, ecology and current conservationstatus To date twenty-two populations of wild commonbean are known for Costa Rica, and distributed in fourwatersheds in the central part of that country (Table 1;Figure 1): Virilla, Candelaria, Pirrís and Reventazón.For our purpose, we found useful to split the Candelariaand Pirrís watersheds, while both contribute to theParrita watershed (Gómez Pignataro 1986). Tenpopulations have been found in the Central Valley orwatershed of Río Virilla (ending into Río Grande deTárcoles): seven on the southern slope (#2097 Tarbaca,2111 Aserrí, 3136 San Miguel Desamparados, 3137Bebedero, 3140 Parque Iztarú, 3143 Hda. Tres Ríos,and 3178 Guatuso), and three on the northern slope(#3106 Chagüite, 3132 Zarcero, and 3133 SabanaRedonda). Ten populations have been found in theupper valley of Río Grande de Candelaria: six on thenorthern slope (# 3131 Jérico, 3134 Tranquerillas, 3135Chirogres, 3147 El Tigre, 3148 Manzano, and 3190Vuelta de Jorco), and four on the southern slope (#3184 Río Tarrazú, 3186 Bajo Los Angeles, and 3188and 3189 in the surroundings of San Andrés).The mountainous range that separates these twowatersheds – Cerros de Cedral o de Escazú – has thusthe largest number of populations: thirteen (7+6). Onepopulation has been found in the upper valley of RíoReventazón (# 3126 Quircot), which is the only one sofar on the Atlantic slope of the continental divide (Fig.1). One population has been found in the upper valleyof Río Pirrís (# 3168 Copey), the southernmostpopulation to the southeast of the country. Our attemptsto find wild common bean in other parts of Costa Rica,namely the upper Río Savegre, Río División and RíoChirripó Pacífico have failed so far. There might still beone population in the watershed of Río Pirrís (the slopenorth of San Marcos de Tarrazú, but heavily cleared forcoffee plantations), and one on the slope of FilaBustamante. All vegetation types where it thrives, once 146AGRONOMÍAMESOAMERICANA15(2):145-153. 2004  reported on maps of life zones (Bolaños M. and WatsonC. 1993, Gómez Pignataro 1986, Herrera and GómezPignataro 1993, Tosi 1969), have been visited.Wild common bean is usually found in subhumidmontane forests (bmh-P, bh-MB and bmh-MB: ArayaVillalobos et al. 2001) at intermediate altitudes (Table1), now largely cleared for coffee plantations andreplaced by urban areas. These are seasonal forests witha marked dry season (Matamoros 1996). In this habitat,the end of the rainy season coincides with the floweringperiod, and mists are not frequent; bean plants thusescape pressures from diseases such as anthracnose androot rots, as well as drought stresses, and seed dispersalwill occur during the dry season (3-4 months; lateDecember to April) (Araya Villalobos et al. 2001).Germination of wild bean will occur from Julyonwards, with flowering in September. Carpenter bees,bumble bees and honey bees have been seen as activein the pollination at Quircot, Jérico, and SabanaRedonda, as indicated by the field notes.While certain wild bean populations seem stable(e.g. Aserrí, Bebedero, San Miguel), others areendangered. There are important variations indemography of wild bean populations (as observed for# 2097, 3148), likely due to important climaticvariations (rainfall) from one year to another, so acritical assessment of the conservation status is noteasy. The site of Zarcero has been converted into aquarry, and the population # 3132 seems gone.Urbanization with the conversion of srcinal land intohousing compounds is a threat to population # 3178 in2003-2006. In Quircot the use of atrazin in maize hasvirtually eliminated the wild bean # 3126 from certainplots. In Chirogres and Copey, weeding has seriouslyreduced the wild bean to just a very few plants. Coffeeplantations and use of herbicides therein haveeliminated the population # 3131. Paradoxally, theincluding of a population (# 3140) into a protected area,viz. Parque Iztarú, may not guarantee high numbers of plants, as the closing of the forest canopy restricts lightand increases disease pressures. GONZÁLEZ et al .: W ILDCOMMONBEANIN C OSTA R ICA 147AGRONOMÍAMESOAMERICANA15(2):145-153. 2004 Table 1 – List of populations of wild common bean found, sites, watershed, coordinates and year. Costa Rica. Collector’s Province, district, closestsiteWatershedLongitudeLatitudeAltitude YearNumber(masl)found 1. 2097San José, TarbacaVirilla sur84°07’W9°49’N 1750 19872. 2111San José, AserríVirilla sur84°07’W9°52’N 156019873. 3106Alajuela, Carrizal, ChagüiteVirilla norte84°10’W10°06’N 1510 19984. 3126Cartago, San Nicolás, QuircotReventazón83°56’W9°54’N 1540 19985. 3131San José, Desamparados, JericóCandelaria n84°03 W9°49 N 1540 19986. 3132 Alajuela, Alfaro Ruiz, ZarceroVirilla norte84°23’W10°10’N 161020027. 3133 Alajuela, Poas, Sabana RedondaVirilla norte84°14’W10°07’N 1380 20028. 3134 San José, Aserrí, TranquerillasCandelaria n84°07’W9°48’N 1500 20029. 3135 San José, Aserrí, ChirogresCandelaria n84°06’W9°48’N 1480 200210. 3136 San José, Desamparados, San MiguelVirilla sur84°04’W9°5 l’N 1370 200211. 3137 San José, Escazú, BebederoVirilla sur84°10’W9°54’N 1600 200212. 3140 Cartago, La Unión, Pque IztarúVirilla sur83°58’W9°54’N 1750 200213. 3143 Cartago, La Unión, Hda Tres RíosVirilla sur83°59’W9°54’N 1500 200214. 3147 San José, Aserrí, El TigreCandelaria n84°06’W9°49’N 1450 200315. 3148 San José, Desamparados, ManzanoCandelaria n84°05’W9°49’N 1370 200316. 3168San José, Sta. María de Dota, CopeyPirrís83°57’W9°39’N1600200317. 3178San José, Desamparados, GuatusoVirilla sur84°02’W9°51’N1380 200318. 3184San José, San Pablo, Río TarrazúCandelaria s 84°01’W9°44’N1450 200319. 3186San José, San Gabriel, Bajo Los AngelesCandelaria s84°05’W9°44’N1200200420. 3188San José, San Gabriel, Sn Andrés León Cor.Candelaria s84°05’W9°43’N1250200421. 3189San José, San Gabriel, Sn Andrés León Cor.Candelaria s84°05’W9°43’N1300200422. 3190San José, San Gabriel, Vuelta de JorcoCandelaria n84°08’W9°43’N14802004  GONZÁLEZ et al .: W ILDCOMMONBEANIN C OSTA R ICA Molecularcharacterization Dominant phaseolin types for the six populationswere ‘Simple-4’(83.4 %) and ‘S’(10.43 %) (Table 2).‘M1’was observed in the populations of Aserrí andTarbaca, while ‘S’phaseolin was noted in thepopulations of Jérico and Quircot.In the six populations analyzed for diaphorase, theDia 100 pattern was found in 94% of the cases, while theDia 95 pattern was found in 14 individuals of Chagüite,Jérico and Quircot. For peroxydase (PRX) individualsdisplayed mainly the Prx 100 allele; however 35individuals out of 197 showed the Prx 98 allele in thepopulations of Quircot, Zarcero, Jérico and Chagüite(one case). 148AGRONOMÍAMESOAMERICANA15(2):145-153. 2004 Figure 1. Distribution of wild common bean in the Central Valley of Costa Rica (base map: IGN-DGAC, 1991). Solid square: Reventazón, one population; solid heart: Pirrís, onepopulation; closed circles: Virilla north, 3 populations; solid triangles: Virilla south, 7populations; crosses: Candelaria north, 6 populations; and closed stars: Candelaria south,4 populations. Dotted line represents the continental divide, while the other lines limitthe different watersheds (see text).
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