Control biológico de la marchitez del chile (Capsicum annuum L) causada por Phytophthora capsici mediante cepas nativas de Trichoderma spp de suelos productores

Abstract

La principal enfermedad que ataca al cultivo de chile Capsicum annuum L. es la marchitez, causada por Phytophthora capsici L., a la cual se tribuyen pérdidas hasta de 100%. En Tetela de Ocampo se ha presentado de forma recurrente y para su control se ha optado por el uso de fungicidas, lo que conlleva a una menor rentabilidad y a estimular la resistencia del patógeno. Una alternativa para su control es la búsqueda de antagonistas nativos con alta capacidad de biocontrol. Trichoderma spp. ha sido el más utilizado con este fin; sin embargo un factor que puede limitar su capacidad contra el patógeno es la posible dificultad de establecerse en suelos diferentes en donde fue aislado. Con el objetivo de evaluar la efectividad de cepas nativas de Trichoderma spp. asociadas a la rizósfera del cultivo de chile y de suelos no cultivados; se evaluaron nueve cepas de dichos antagonistas contra de tres cepas P. capsici (nativas). En condiciones in vitro se evaluó la tasa de desarrollo (TD), esporulación, tipo de antagonismo y porcentaje de inhibición de Trichoderma spp. En vivero se evaluó el peso seco de raíz y parte aérea (PsR y PsA) y las unidades formadoras de colonias (UFC) del sustrato a través del tiempo. En invernadero se determinó la severidad, el área bajo la curva del progreso de la severidad (ABPS), N° de plantas muertas, PsR, PsA, UFC y área foliar. La mayor TD y esporulación se detectó en S3A3 y S3A4. Se detectó homogeneidad (in vitro) de todos los antagonistas en el control de P. capsici. En vivero, el mayor peso seco fue obtenido con S3A3, aunque el mayor número de UFC se observó con T4(3), T-5(2) y TP1S1. Cuando se inoculó P. capsici en invernadero, S3A3 y TP1S1 presentaron menor ABPS y por ende menor mortalidad y mayor área foliar. S3A3 promovió mayor peso seco, aunque el mayor número de UFC en suelo se obtuvo con T-5(2), T4(3) y TP1S1. Las cepas nativas S3A3 y TP1S1 promovieron mayor crecimiento y tienen mayor potencial de controlar la marchitez en suelos y plantas de chile de Tetela de Ocampo. _______________ BIOLOGICAL CONTROL WILT OF CHILE (Capsicum annuum) CAUSED BY Phytophthora capsici BY STRAINS NATIVE OF Trichoderma spp. SOIL PRODUCERS. ABSTRACT: The main disease affecting pepper crops Capsicum annuum L. is caused by Phytophthora capsici L., to which losses can be as high as 100%. In Tetela de Ocampo it has appeared recurrently and growers have chosen the use of fungicides for disease control. This option has turned the crop less profitable and may induce pathogen resistance. An alternative for disease control is the use of native antagonists with high biocontrol capacity. Trichoderma spp. has been the most widely used organism for this purpose; however, a factor that may limit its ability against the pathogen is the difficulty settling in soils different to where it was isolated. In order to evaluate the effectiveness of native strains of Trichoderma spp. against P. capsici, strains associated to the rhizosphere of peper crops and non-native strains were evaluated (nine strains of Trichoderma spp. and three P. capsici). Under in vitro conditions the rate of development (TD), sporulation, type of antagonism and percent of inhibition of Trichoderma spp were assessed. In nursery, the dry weight of roots and aerial parts (PSR and PsA) and colony forming units (CFU) in substrate over time was evaluated. The area under the disease progress curve, number of dead plants, PSR, PsA, UFC and leaf area was determined in soil grown plants. Best TD and sporulation was detected in S3A3 and S3A4; however all antagonists behave similarly on P. capsici. In the nursery, the largest dry weight was obtained with S3A3, S3A4 and A2S2P3, although the greatest UFC was observed with T4 (3), T-5 (2) and TP1S1. In the greenhouse the S3A3 and TP1S1 native strains had lower ABPS and thus lower mortality and greater leaf area. S3A3 promoted greater dry weight, although the largest number of CFU in soil was obtained with T-5 (2), T4 (3) and TP1S1. Native strains TP1S1 and S3A3 promoted greater growth and have greater potential for wilt control in soils from Tetela de Ocampo than the rest of strains.