A b s t r a c t. The purpose of this study was to evaluate growth, chlorophyll content, and photosynthesis in Jatropha at different levels of soil moisture. Plants were cultivated in containers and the treatments of the soil water content evaluated were: 0% (without watering), 20, 40, 60, and 80% soil water content. Plant height was statistically similar for all treatments, but the number of leaves differed significantly. Total dry matter and chlorophyll at 40, 60, and 80% soil water content were statistically similar, but different from 0 and 20% soil water content. Leaf area at 40, 60, and 80% soil water content was statistically different from 0 and 20% soil water content. The photosynthetic rate, transpiration and stomatal conductance at 60 and 80% soil water content were statistically similar but different from 0 and 20% soil water content. Water stress affected growth, chlorophyll content, photosynthetic rate, transpiration, and stomatal conductance.K e y w o r d s: Jatropha, water stress, biodiesel, photosynthesis, Mexico
Background and Aims Jatropha curcas (jatropha) is an oil crop cultivated in (sub)tropical regions around the world, and holds great promise as a renewable energy source. However, efforts to fully commercialize jatropha are currently hampered by the lack of genetic diversity in the extant breeding germplasm, and by the toxicity of its seeds meaning that its seed cake cannot be used as a protein source in animal feed, among other constraints. In Mexico, the species’ native range, there are jatropha plants whose seeds are used to prepare traditional meals. This non-toxic jatropha ‘type’ is considered to harbour low genetic variation due to a presumed domestication bottleneck and therefore to be of limited breeding value; yet, very little is known regarding its origin and genetic diversity. Methods Using genotyping-by-sequencing (GBS), we extensively genotyped both indigenous toxic and non-toxic jatropha collected along roads and home gardens throughout southern Mexico. Key Results Single nucleotide polymorphism diversity in non-toxic jatropha is relatively high, particularly in northern Veracruz state, the probable origin of this germplasm. Genetic differences between toxic and non-toxic indigenous genotypes are overall quite small. A a genome-wide association study supported a genomic region (on LG 8, scaffold NW_012130064), probably involved in the suppression of seed toxicity. Conclusions Conservation actions are urgently needed to preserve this non-toxic indigenous, relatively wild germplasm, having potential as a fuel feedstock, animal feed and food source among other uses. More generally, this work demonstrates the value of conservation genomic research on the indigenous gene pool of economically important plant species.
En México existen poblaciones silvestres y domesticadas de Carica papaya; sin embargo, los estudios relacionados con su variación in situ han sido limitados en número tanto de ejemplares como de zonas geográficas. El objetivo del presente estudio fue caracterizar in situ la variación morfológica de ejemplares de C. papaya nativos de México. Se evaluaron 12 características morfológicas (seis cuantitativas y seis cualitativas) de frutos recolectados de 222 ejemplares de papayos nativos provenientes de 10 estados de las vertientes del Pacífico y Golfo de México. Se realizaron análisis de varianza, de componentes principales (ACP) y de agrupamiento jerárquico con distancias euclidianas. De acuerdo con el análisis de varianza, todas las características morfológicas entre recolectas presentaron diferencias significativas (P ≤ 0.01). El ACP reveló que las características de mayor contribución a la variación entre los ejemplares analizados fueron volumen comestible, diámetro de cavidad central, longitud, diámetro, grosor de pulpa, forma del extremo peduncular y forma del fruto. El análisis de conglomerados formó tres grupos fenotípicos estadísticamente diferentes (P ≤ 0.01) y detectó continuidad con base en dimensiones y forma del fruto. Ambos análisis multivariados diferenciaron entre tipos silvestres y domesticados recolectados en huertos familiares. La alta variabilidad morfológica entre C. papaya es apropiada para establecer un programa nacional de conservación de germoplasma de genotipos con disimilitud genética para usarse en programas de mejoramiento genético.
Resumo -Avaliou-se o efeito do anelamento de ramos sobre o florescimento e frutificação de lichieiras 'Bengal' com 17 anos de idade. Os tratamentos constaram de anelamento em ramos ou pernadas principais e ramos de 6; 4 e 2 cm de diâmetro, além do controle. O delineamento utilizado foi em blocos casualizados, com cinco repetições. As avaliações quanto à floração foram: percentagem de floração e comprimento de inflorescências por quadrante e árvore; quanto à frutificação, avaliaram-se: vingamento de frutos maduros por panícula, massa, diâmetros longitudinal e equatorial dos frutos, sólidos solúveis totais, época de colheita e rendimento. O anelamento nos ramos principais induziu maior florescimento, sem alterar as características das inflorescências; não houve diferenças no vingamento de frutos, mas o aumento na floração incrementou o rendimento por árvore, com significativa antecipação da colheita. Termos para indexação: Litchi chinensis, pegamento de fruto, produção. FLOWERING AND FRUITING OF LYCHEE TREES IN RESPONSE TO GIRDLING OF BRANCHESAbstract -The effects of girdling of branches on flowering and fruiting of 17 years old 'Bengal' lychee trees were evaluated. The treatments consisted of girdling of main branches, and branches with 6, 4 and 2 cm of diameter and the control. The experiment was conducted in a randomized block design, with 5 replicates. The evaluations in relation to flowering were: flowering per tree and per quadrant and length of flower panicles; in relation to fruiting were: fruit set per panicle, fruit weight, longitudinal and equatorial diameters, soluble solids, harvest time and production. The girdling in the main branches induced larger flowering, without influence on the flower panicles characteristics, there were no differences in the fruit set, but with an increasing in the flowering, it increased the production, with significant anticipation of the harvest.
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