Varietal data from 27 crop species from five continents were drawn together to determine overall trends in crop varietal diversity on farm. Measurements of richness, evenness, and divergence showed that considerable crop genetic diversity continues to be maintained on farm, in the form of traditional crop varieties. Major staples had higher richness and evenness than nonstaples. Variety richness for clonal species was much higher than that of other breeding systems. A close linear relationship between traditional variety richness and evenness (both transformed), empirically derived from data spanning a wide range of crops and countries, was found both at household and community levels. Fitting a neutral “function” to traditional variety diversity relationships, comparable to a species abundance distribution of “neutral ecology,” provided a benchmark to assess the standing diversity on farm. In some cases, high dominance occurred, with much of the variety richness held at low frequencies. This suggested that diversity may be maintained as an insurance to meet future environmental changes or social and economic needs. In other cases, a more even frequency distribution of varieties was found, possibly implying that farmers are selecting varieties to service a diversity of current needs and purposes. Divergence estimates, measured as the proportion of community evenness displayed among farmers, underscore the importance of a large number of small farms adopting distinctly diverse varietal strategies as a major force that maintains crop genetic diversity on farm.

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The high diversity of chili pepper (Capsicum annuum L.) in Mexico offers an excellent alternative to search for wild and semi-domesticated genotypes as sources of resistance to the complex Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae)-Begomovirus, which has caused enormous losses in commercial production of various horticultural crops. The goal of the present work was to characterize ex situ 18 genotypes of C. annuum from southern Mexico through 47 morphological descriptors, and to evaluate its response to the B. tabaci-Begomovirus complex. Morphological characterization showed the variables calyx annular constriction (CAC), number of branch bifurcation (NBB), and calyx pigmentation (CP) had the highest variation. Principal components analysis (PCA) of 47 morphological characteristics showed that 12 components were selected as meaningful factors. These components explained 94% of the variation. Cluster analysis showed three major clusters and seven sub-clusters. On the other hand, evaluation of the response to B. tabaci-Begomovirus showed that the genotypes have differential susceptibility to this vector-pathogen complex. Genotypes 'Chawa', 'Blanco', 'Maax' and 'X´catic' were into the low susceptibility to B. tabaci and low severity of viral symptoms. Surprisingly, the genotype 'Simojovel' showed high susceptibility to whitefly, but was grouped into genotypes with low symptom severity. This study shows the potential of native germplasm of pepper to explore sources of resistance to the B. tabaci-Begomovirus complex.

Bemisia tabaci Genn. biotype B is a widely distributed plant pest that represents one of the major constraints for horticultural crop production. The purpose of the present work was to evaluate the oviposition preference, survivorship, and development of B. tabaci biotype B on semi-cultivated genotypes of Capsicum annuum from southeast Mexico. In free-choice experiments to evaluate the oviposition preference, lower number of eggs laid by B. tabaci biotype B was observed in the genotypes Maax and Xcat´ik relative to that in the commercial genotype Parado. Egg hatchability was significantly lower in Pico Paloma, Bolita, Blanco, Chawa, Payaso, and Xcat´ik than in the rest of the genotypes, including the commercial genotype Jalapeño. Likewise, survivorship of nymphs was significantly lower in Pico Paloma, Bolita, and Blanco than in the remaining genotypes. Nymph developmental time and the period of development from egg to adult were the shortest in Amaxito. Therefore, sources of resistance to B. tabaci biotype B by antibiosis (accumulation of plant defense compounds) might be found in the semi-cultivated genotypes Pico Paloma, Bolita, and Blanco.

In this paper we develop new indicators and statistical tests to characterize patterns of crop diversity at local scales. Households growing a large number of species or landraces are known to contribute an important share of local available diversity of both rare and common plants but the role of households with low diversity remain little understood: do they grow only common varieties-following a nestedness pattern typical of mutualistic networks in ecology-or do 'diversity poor' households also grow rare varieties? This question is pivotal in ongoing efforts to assess the contribution of small farmers to global agrobiodiversity at local scales. We develop new network-based approaches to characterize the distribution of local crop diversity at the village level (species and infra-species) and validate these approaches using meta-data sets from 10 countries. Our results highlight the sources of heterogeneity in the local crop diversity. We often identify two or more groups of households based on their different levels of diversity. In some datasets, 'diversity poor' households significantly contribute to the local crop diversity. Generally, we find that the distribution of crop diversity is more heterogeneous at the species than at the infra-species level. This analysis reveals the absence of a general pattern of crop diversity distribution independent of agro-ecological and socio-cultural context.

El chile habanero (Capsicum chinense Jacq.) es distintivo de la Península de Yucatán, México; sin embargo, los estudios de diversidad genética a nivel molecular en este cultivo son escasos. El presente trabajo se planteó con el objetivo de caracterizar la diversidad genética del germoplasma de chile habanero, mediante marcadores ISSR. El material genético consistió en 60 poblaciones criollas de chile habanero recolectadas en los estados de Yucatán, Campeche, Quintana Roo y Tabasco, México, las cuales fueron genéticamente analizadas con tres loci ISSRs. El ADN fue extraído por el método de CTAB y los fragmentos se amplificaron por la reacción en cadena de la polimerasa (PCR). Los datos se analizaron con los programas POPGENE V 1.31 y NTSYS V 2.0 mediante un análisis de componentes principales y las relaciones entre las poblaciones se obtuvieron con un análisis jerárquico de conglomerados usando el método UPGMA. Se detectaron un total 32 bandas y 98 % de ellas fueron polimórficas. Los resultados indican que la diversidad genética en poblaciones de chile habanero es alta, en donde el 95.5 % de la variación observada se encuentra dentro de las poblaciones y sólo el 4.5 % entre ellas. Se detectó un alto flujo génico entre las poblaciones. Los resultados de los análisis multivariados sugieren que gran cantidad de germoplasma de chile habanero se ha dispersado del estado de Yucatán a los estados de Campeche, Quintana Roo y Tabasco. El patrón de distribución de la diversidad genética de chile habanero no se asoció con el lugar de origen de las poblaciones analizadas.

ResumenLos problemas de crecimiento poblacional, escasez de alimentos, sobreexplotación y contaminación de los recursos naturales, así como el desempleo y bajo nivel de ingresos en el medio rural obligan a considerar la importancia del traspatio como unidad de producción de subsistencia y ahorro. En el presente trabajo se describen y analizan las condiciones socioeconómicas asociadas al manejo y aprovechamiento del traspatio, cuya diversidad de especies vegetales y animales son base de estrategias de vida de la unidad doméstica campesina en relación con su subsistencia y bienestar. La información se obtuvo en 2013 a través de una encuesta por muestreo estadístico en la localidad de Nolo, municipio de Tixkokob, ubicada en la ex zona henequenera de Yucatán, mientras que en el análisis del traspatio se le consideró como un agro-ecosistema y su análisis se basó en las teorías del desarrollo rural. Los resultados obtenidos permitieron concluir que las condiciones de riqueza y abundancia de las especies vegetales y animales en el traspatio le confieren a éste el papel de proveedor complementario de alimentos durante todo el año, al igual que el acceso a las plantas medicinales, ocupación e ingresos eventuales, así como banco de conservación del germoplasma de especies vegetales y animales. Se concluye que la agro-biodiversidad en el traspatio permite la disponibilidad de los recursos destinados al consumo y al mercado, garantizando así la autosuficiencia alimentaria rural.Palabras clave: agroecosistema, desarrollo rural, producción familiar, subsistencia. IntRoduccIónE n la actualidad las familias del medio rural de Yucatán, como la mayoría de las asentadas en zonas conurbadas o periféricas de las centros AbstRActThe problems of population growth, food scarcity, overexploitation and contamination of natural resources, as well as unemployment and low income level in rural areas force us to consider the importance of the backyard as a production unit for subsistence and savings. In this study, the socioeconomic conditions associated with management and exploitation of backyards, whose diversity of plant and animal species are the basis for life strategies in the peasant domestic unit related to their subsistence and wellbeing, are described and analyzed. The information required was obtained in 2013 with a survey by statistical sampling in the location of Nolo, municipality of Tixkokob, located in a former henequen zone in Yucatán, while the backyard was considered as an agro-ecosystem for its analysis, which was based on the theories of rural development. The results obtained allowed concluding that the wealth and abundance conditions of plant and animal species in the backyard give it the role of complementary food supplier throughout the year, as well as access to medicinal plants, occasional occupations and income, and a conservation bank of plant and animal species' germplasm. It is concluded that agro-biodiversity in the backyard permits the availability of resources destined to consumption and the market, thus gu...

The whitefly Bemisia tabaci (Gennadius, 1889) is a major plant pest of horticultural crops from the families Solanaceae, Fabaceae and Cucurbitaceae in Neotropical areas. The exploration of host plant resistance and their biochemical mechanisms offers an excellent alternative to better understand factors affecting the interaction between phytophagous insect and host plant. We evaluated the survival of B. tabaci in landrace genotypes of Capsicum annuum L., and the activity of plant defense-related enzymes (chitinase, polyphenoloxidase, and peroxidase). The landrace genotypes Amaxito, Tabaquero, and Simojovel showed resistance to B. tabaci, as we observed more than 50% nymphal mortality, while in the commercial susceptible genotype Jalapeño mortality of B. tabaci nymphs was not higher than 20%. The activities of plant defense-related enzymes were significantly different among pepper genotypes (P < 0.05). Basal activities of chitinase, polyphenoloxidase and peroxidase were significantly lower or equal in landrace genotypes than that of the commercial genotype Jalapeño. The activity of plant enzymes was differential among pepper genotypes (P < 0.05). For example, the activity of chitinase enzyme generally was higher in non-infested plants with B. tabaci than those infested. Instead polyphenoloxidase ('Amaxito' and 'Simojovel') and peroxidase enzymes activities ('Tabaquero') increased in infested plants (P < 0.05). We conclude that basal activities of plant defense-related enzymes could be act through other mechanism plant induction, since plant defense-related enzymes showed a different induction response to B. tabaci. We underlined the role of polyphenoloxidase as plant defense in the pepper genotype Simojovel related to B. tabaci.