Nueva metodología para la interpretación de la distribución espacial de "Rhizoctonia solani Kühn" en el cultivo de "Vigna unguiculata" L. Walp (fríjol caupí), mediante la aplicación de técnicas geoestadísticas, en la provincia de Holguín, Cuba

Abstract

The experimental research that conform this thesis, has been developed in the productive entities General State Farm “José María Aurecochea” and “Cooperativa de Producción Agropecuaria” (CPA) “Augusto César Sandino”, at the municipality Gibara, Holguin province, in the Provincial Laboratory of Vegetal Health of Holguín, belonging to the Centre of Studies for Arid Agroecosystems of the University of Holguín, Cuba, and in the Soil Science Area of the University of A Corunna, Spain. The aim of this work was to propose a methodology to characterise the structure and the interpretation of the space distribution of Rhizoctonia solani Kühn in the crop of Vigna unguiculata (L.) Walp. (caupí bean) by using geoestatistical techniques, that allow to know with greater objectivity and accuracy the behaviour of the pathogen inside the area evaluated to base the future strategies of handle integrated, facilitate the decision making and an efficiently decrease of the affectations to the crop and to the environment, in the province of Holguín, Cuba. Two different methods of sampling (diagonal sampling and the systematic nonaligned) were used for the evaluation of the pathogen in conditions of field, whereas for the studies in laboratory was applied the Operative Normative Procedures recommended by the Central Laboratory of Vegetal Quarantine of Cuba, and, besides, geostatistical techniques and common statistical analyses of variance, proofs of hypothesis, environmental gradient and concurrence of the species in the environmental gradient have been carried out. The results obtained show that, although exist in Cuba several previos investigations on R. solani as well as a methodology for the topic studied were available, the damages caused by this organism still persist. So, there is necessary to address new alternative methods of sampling and advanced analysis that may offer a more objective and detailed information of the behaviour of this pathogen, which should result in a new methodology for the evaluation. Also, it was verified that there was not information about the structure of the spatial distribution of R. solani in any the agricultural crop, neither at world-wide level nor in Cuba, following the literature review performed in this PH. D. thesis. It was also ascertained that not only R. solani but also the main soil pathogens associated to V. unguiculata crop (caupí bean) in the study areas showed percentages of frequency of apparition and distribution higher than 40%. This implies a wide genetic diversity of this pathogen, as well as a high pathogeny in the entities object of study. The structure of the spatial distribution of R. solani in the cultivation of Vigna unguiculata L. Walp (caupí bean) is reported for the first time, and denoted an aggregate type behavior of the populations of this pathogen within the evaluated areas, adjusting mainly to exponential and gaussian models. In addition, it was possible to establish specific areas of infestation, located on the edges of the plot, which is very useful to manage control measures towards those specific areas and thereby reduce economic and environmental costs. This study contributed to increase the knowledge on the influence that some abiotic factors exert on the studied organism, as well. It also helped in ranking these factors, which offer little and some restriction to his presence in the crop. The superiority of the method of systematic sampling was scientifically proved, focussing the method of diagonal sampling. Also, a new methodology has been proposed to characterise the structure of the spatial distribution of Rhizoctonia solani Kühn in the crop Vigna unguiculata (L.) Walp (caupí bean), based on the use of geostatistical techniques, a new method of systematic sampling and the application of statistical analyses to environmental gradients and concurrence of species along this gradient. This procedure should allow a deeper and detailed knowledge, of the behaviour of this pathogen in the areas evaluated. It also should help in the design of future management strategies of integrated control of the analysed pathogen.