As estratégias de conservação on farm e as ameaças de erosão genética e do conhecimento associado às variedades crioulas de milho de agricultores familiares do município de Novo Horizonte – SC

Abstract

Agrobiodiversity is fundamental to food security and sovereignty and the development of agroecological systems. In Brazil, there is little research focused on the diversity conserved on farm, most of which are related to germplasm conserved ex situ and for use in breeding. Previous studies have indicated the presence of a high richness of corn varieties grown on farm by family farmers in the western region of Santa Catarina, Brazil. In order to identify, quantify and characterize the diversity, geographic distribution, selection and management of maize varieties in the municipality of Novo Horizonte, a Diversity Census of Zea mays L. was developed between 2011 and 2012 based on 398 semi-structured interviews with farmers in 21 communities. Between 2013 and 2014, a second diagnosis was carried out with 66 support families. The research identified 331 varieties being 241 of popcorn, 75 of field corn, 11 of farinaceous corn and 4 of sweet and sweetish corn. In addition, 14 populations of wild relatives were found coexisting with the different types of corns. The varieties were characterized based on the traditional knowledge of farmers and grouped into 42 morphological groups. The highest diversity of groups was popcorn, which is mostly kept by women (58%). The estimated values of the Shannon diversity index for popcorn were: grain color (1.2), grain size (0.85), grain shape (0.92) and morphologic group (1.84), and for field corn , farinaceous and sweet corn: grain color (0.98), endorperm type (1.03) ad morphologic group (0.78) indicated a high diversity regarding the phenotypic characteristics studied. The characteristics grain color, size and shape were the basis of local taxonomy used by the farmers for the characterization of the varieties. Fifteen selection criteria were identified, with highlights being better corn cobs, better seeds and cob and grain size. Access to knowledge about selection is mainly due to intra-generational transmission. The maintainers are mostly over 50 years of age and have a multiethnic origin, whose traditional knowledge is acting in the selection, use and conservation of this diversity. Seed interchange systems are dynamic and access to seeds is based on relationships of trust between relatives and neighbors. The vast majority of varieties (83.3% for field corn, farinaceous and sweet corn and 72.8% for popcorn) is been cultivated for almost 10 years, but 50 varieties can be considered old and are older than 20 years. The cultivation time for popcorn is significantly higher than that of field corn. The varieties showed gastronomic, adaptive, agronomic, economic, cultural, medicinal and handicraft values. The use of popcorn is given mainly in human food (93% for popcorn and 96.4% for field, farinaceous and sweet), in animal food (pasture) and also for aesthetic/handicraft. The elevated number of populations of different types of maize, high levels of diversity, richness of use and cultivation values, close coexistence with possibility of bilateral gene flow between maize and teosinte, and the socio-cultural aspects that act intensively in the use, in the generation and conservation of the diversity, accredit the municipality as part of the microcentre of diversity of Zea mays L. in the West of Santa Catarina. However, in the last years the loss of 75 varieties and the causes associated with the genetic erosion processes have occurred, the lack of seed multiplication and the drought account for 56% of the losses occurred. The practices of temporal and spatial isolation of crops to avoid bilateral gene flow between types of maize and wild relatives are insufficient in 76% of agricultural establishments. Geographic proximity, reduced size of farms, presence of teosinte, genetically modified (GM) maize and insufficient isolation are allowing gene flow between maize and GMs and between maize and teosinte. This situation could aggravate the genetic erosion of the varieties. This situation can generate new genotypes but also the loss of variety identity and genetic erosion of the varieties. Other reasons for this genetic erosion are internal to agroecosystems (reduced area size, aging of the guardians, lack of manpower and management), but aggravated by climatic change events, pollen pressure of large crops with GM maize and the lack of protective policies for farmers and their landrace varieties. These varieties, however, are fundamental to household food security, breeding programs and the development of agroecological production systems. The different indications of uses and the description of the intrinsic qualities demonstrated the importance of the traditional knowledge in the on farm conservation of corn germplasm. The high diversity of the varieties is associated with the selection and management dynamics of multi-ethnic farmers and their traditional use in food, based on innumerable intrinsic sociocultural values. The study emphasized the importance of deepening the research on maize landrace varieties conserved in the municipality and the urgency in the establishment of conservation strategies on farm

and ex situ in an integrated and systematic way. The information generated in this research should guide the establishment of integrated strategies and conservation on farm ande x situ at regional level that englobe participative genetic breeding programs, the establishment of OGMs free zones and public politics to estimulate conservation of landrace varieties and to maintain young people in rural areas and agriculture.