Efecto de tres herbicidas pre-emergentes en el establecimiento en campo de plantas in vitro de yuca (Manihot esculenta Crantz)

Entre los principales problemas para el desarrollo del cultivo de la yuca (Manihot esculenta Crantz) en Venezuela esta la carencia de buen material de siembra. Tradicionalmente, la yuca se propaga por estacas, siendo esto una fuente importante en la diseminación de plagas y enfermedades. El uso de plantas in vitro permite obtener material de siembra sano y vigoroso; sin embargo, su adaptación en campo requiere mayor atención en el control de malezas o arvenses. El presente trabajo evaluó el efecto de 3 herbicidas, fluometurón, S-metolacloro, pendimetalín, en comparación con el desyerbe manual, durante el establecimiento en campo de plantas in vitro de yuca. Los ensayos se realizaron en San Pablo, Edo. Yaracuy. Se usó un diseño de bloques al azar con cuatro repeticiones. Aunque los resultados no mostraron diferencias significativas en el porcentaje de supervivencia de las plántulas, su crecimiento fue significativamente superior (p <0,05) en parcelas tratadas con fluometurón y S-metolacloro con respecto al control manual. No se encontró diferencias entre tratamientos en el control general de arvenses, pero el S-metolacloro mostró mejor control de especies de hoja ancha. Se recomienda usar S-metolacloro y fluometurón el mismo día del transplante para mejorar la competitividad de las plántulas

Starch determination, amylose content and susceptibility to in vitro amylolysis in flours from the roots of 25 cassava varieties

Cassava cultivars are classified following different criteria, such as cyanogenic glucoside content or starch content. Here, flours from the roots of 25 cassava varieties cultivated simultaneously in a single plantation, were characterized in terms of starch content (SC), amylose content (AC), alpha-amylolysis index (AI) and gel formation ability. Resistant starch content (RS) was measured in 10 of the samples. RESULTS: Cassava flours exhibited high SC, low AC and low AI values, with differences among varieties. Cluster analysis based on these parameters divided the cultivars in four groups differing mainly in SC and AC. AI and AC were inversely correlated (r = -0.59, P < 0.05) in 18 of the cultivars, suggesting AC as an important factor governing the susceptibility to enzymatic hydrolysis of starch in raw cassava. Differences in susceptibility to amylolysis, assessed by RS, were also recorded in the sample subset analyzed. Most flours yielded pastes or gels upon heating and cooling. Gels differed in their subjective grade of firmness, but none exhibited syneresis, confirming the low retrogradation proclivity of cassava starch. CONCLUSION: Some differences were found among cassava samples, which may be ascribed to inter-cultivar variation. This informationmay have application in further agronomic studies or for developing industrial uses for this crop. (C) 2011 Society of Chemical Industr

Genetic diversity characterization of a Venezuelan in vitro cassava (Manihot esculenta Crantz) collection with Simple Sequence Repeats (SSR)

Cassava (Manihot esculenta Crantz), is an important root crop in most Neotropical countries and is one of the richest carbohydrate sources for millions of people in the tropics. This crop has a diversity of different varieties and/or cultivars with a variety of morphological, agronomic and industrial characteristics. To elucidate the genetic differentiation in cassava varieties, recent progress has been made with the application of Simple Sequence Repeats (SSR). In the present study, we characterized the genetic diversity of an in vitro Venezuelan germplasm cassava bank, located at Instituto de Estudios Avanzados, using the SSR described by CIAT (Mba et al., 2001). A total of 20 SSR markers were amplified using genomic DNA isolated from fully in vitro plants of 100 cassava accessions. In preliminary analysis of 7 SSR (SSR 12, 51, 63, 102, 103, 105, 161) a total of 33 alleles (between 2 and 7 alleles per locus) were found with a high level of polymorphism. The genetic diversity value (H) was 0.68. The highest Polymorphism Information Content (PIC) was recorder by de SSR 12 (0.82) and the lowest PIC by SSR 102 (0.38), hence the SSR 12 was found to be highly informative followed by SSR 51 (0.78). With this preliminary study, we can confirm that SSR markers can contribute to a better understanding of the genetic diversity present in this Venezuelan collection of cassava in vitro plants