Population structure and genetic diversity in sweet cassava accessions from South of Brazil

Cassava (Manihot esculenta Crantz) is a crop of high socioeconomic importance for several tropical and subtropical regions of the world. It is mainly present in small cultivated areas that unintentionally guard a large part of the species' germplasm. The present work aimed to evaluate the population structure and genetic diversity of 156 traditional sweet cassava accessions from the Western of Paraná and Midwestern regions of Santa Catarina using 29 microsatellite molecular markers. All loci included were considered polymorphic, ranging from 3.00 to 7.00, with an average of 3.93 alleles per locus, and the average value of heterozygosity (Ho) was 0.6185. The polymorphism information content (PIC) presented an amplitude that varied from 0.4887 (GA134) to 0.7041 (GA131), with an average of 0.6130, while the genetic diversity ranged from 0.5688 (GA134) to 0.7424 (GA131), with an average of 0.6751. Analysis of the population structure based on the 29 microsatellite loci demonstrate that the accessions can be separated into two distinct subpopulations - in Santa Catarina and Paraná - with some mixtures observed according to Delta K = 2 groups. The ideal number of groups was found at K = 3, a level in which accessions from Santa Catarina were divided into two subpopulations and accessions from Paraná were grouped into a unique subpopulation. The genetic variability found among the traditional sweet cassava cultivars evaluated was considered wide, and the most dissimilar groups were mostly the accessions from Toledo and Santa Catarina states, constituting a source of genes for the sweet cassava breeding programs and for the development of new sweet cassava cultivars.

Tuber yield, morphology, and chemical properties variability of sweet cassava germplasm

In Indonesia, the superior sweet cassava varieties are still limited due to the situation on which the majority of the superior varieties -bitter varieties- are used as industrial raw material until now. Therefore the availability of new high yielding of sweet cassava varieties is still needed. Assembling varieties requires the support of germplasm that has identified its superiority. The research objective was to evaluate tuber yield, morphology, and physico-chemical properties of cassava tuber from sweet cassava germplasm. A total of 75 accessions were characterized in Jambegede research station in February-November 2016, using Randomized Block Design. Variables observed included plant height, number of plants at harvest, harvest index, number and weight of tuber yield, and starch content. Physico-chemical analysis of tubers was carried out on 15 accessions with high tuber yields. Plant height at harvest was 393.2 cm in average. There were 10 accessions of sweet cassava with high fresh tuber yields ranging from 36.61 ton.ha-1 to 61.64 ton.ha-1, i.e MLG 10366, MLG 10365, MLG 10318, MLG 10197, MLG 10325, MLG 10341, MLG 10018, MLG 10279, MLG 10298, and MLG 10263. Physico-chemical analysis showed that the average of HCN content was 9.40 ppm, moisture content of 59.5 %, starch content of 28.8 % wb, and amylose content of 11.0 % wb. The bitter cassava with steamed tuber texture not cracked had relatively higher levels of HCN and water content, which was 82.88 ppm and 74.8 %, while the starch and amylose content was relatively lower (15.8 % wb and 5.5 % wb).

Reaction of Sweet Cassava Genotypes to Xanthomonas phaseoli pv. manihotis From Three Regions of Brazil

Xanthomonas phaseoli pv. manihotis (Xpm) is the causal agent of Cassava Bacterial Blight (CBB), one of the most important cassava diseases. The aim of this study was to evaluate the susceptibility of sweet cassava genotypes to strains of Xpm from three different geographic regions of Brazil in greenhouse conditions. The inoculation of 14 genotypes of cassava was made by cutting leaflets using scissors previously soaked in a bacterial suspension with 1 × 108 UFC ml-1 and also by inserting a soaked toothpick into the bud of the oldest leaf. The results showed significant differences when the cassava genotypes were individually evaluated in relation to the Xpm strains used; however, the relationship between cassava genotypes and Xpm strains was significant for wilt symptom. The UnB 1111 strain was more aggressive than the UnB 1386 strain based on the average value of the reaction grade, showing the variation that exists between the bacterial isolates from different regions. Considering the reaction of cassava germplasm’s resistance to the three strains used in the study, the BGMC 434 genotype was the only one classified as resistant based on the average reaction grade. The genotypes BGMC 753, BGMC 1289, BGMC 982 and the elite clones BRS 396, BRS 397, BRS 398, 259/08 and BRS 399 were classified as moderately resistant, which indicates the possibility of recommending them for disease favorable regions.

Culinary quality and sensory profile of cassava varieties harvested at different ages

Sweet cassava must be rapidly cooked and meet the sensory and technological requirements of consumers. The objectives of this study were to evaluate the culinary quality of sweet cassava varieties harvested at three ages and obtain the sensory profile of these varieties using the check-all-that-apply method (CATA). Roots of three cassava varieties released or recommended by Embrapa (BRS Aipim Brasil, BRS Dourada and Saracura) and the commercial variety Eucalipto, harvested at nine, 12 and 15 months of age, were evaluated for physical, chemical and sensory aspects. At nine months of age, the Saracura, BRS Aipim Brasil and BRS Dourada varieties did not differ in cooking time, averaging 41.62 min. The Eucalipto variety had similar cooking times at the three harvest ages, averaging 21.83 min. There was a difference between the four varieties at nine months, with Saracura exhibiting the lowest acceptance score (5.0) and differing from the Eucalipto variety, which showed an average score of 6.3. At 12 months of age, there was a significant increase in the acceptance of the Saracura and BRS Aipim Brasil varieties, which did not differ from Eucalipto and had an average score of 6.4. Consumers perceived differences between the sensory characteristics of the cassava varieties using CATA. The sensory terms “creamy”, “soft” and “sticky” can be associated with greater acceptance of cooked cassava roots, whereas terms such as “floury”, “slightly bitter”, “no taste”, “hard” and “fibrous” can be associated with less acceptance and are therefore undesirable from the consumer’s point of view. Principal component analysis showed that the age at which the roots were harvested had a great effect on the culinary quality of cassava, regardless of the evaluated variety. The commercial variety Eucalipto was well-accepted by the consumers irrespective of root age and can be harvested at any of the evaluated ages. For the Saracura, BRS Aipim Brasil and BRS Dourada varieties, harvesting is recommended at 12 or 15 months so that better quality roots are obtained.

Effect of the storage period on physical-chemical characteristics, microbiological composition and sensory acceptance of two varieties of frozen sweet cassava

Sweet cassava can be sold frozen, i.e., frozen food, to facilitate preparation and consumption. This study aimed to evaluate physical-chemical characteristics, cooking time, microbiological quality and sensory attributes regarding the varieties BRS Aipim Brasil and Eucalipto in frozen storage. The roots were washed in water, sanitized, cut into cylinders, peeled, sanitized, drained, packed in nylon/ low density polyethylene packages and stored at -18 °C, being evaluated every 30 days, approximately. The Eucalipto variety showed the lowest moisture (61.98%) and the highest pulp yield (71.41%) and starch content (33.45%). However, the BRS Aipim Brasil variety had lower color intensity (11.48) and greater color angle (97.45°) than Eucalipto. The two cassava genotypes showed no difference in terms of acidity, luminosity, soluble solids, total sugar content and pH. The Eucalipto variety showed the shortest cooking time (25 minutes) and moisture (62.92%) concerning the five storage times that were evaluated. This variety also had the highest starch content during storage, except at 31 days. The Eucalipto variety was more accepted for the color, aroma and overall impression attributes. Regarding flavor and texture, the two varieties were considered similar and were classified between the hedonic terms “like slightly” and “like moderately”. The sensory acceptance of the roots was not altered during storage and the grades attributed were above 6.0, which represents the minimum acceptance limit, for all evaluated attributes. Cassava frozen at -18 °C can be marketed for 120 days without microbiological risk, and without significant changes in its physical-chemical and sensory characteristics.

Desempenho agronômico de mandioca de mesa manejada com irrigação e uso de cobertura plástica do solo

Although cassava is recognized for its high tolerance to drought, irrigation is showing satisfactory results. However, few studies have been carried out to determine the effects of soil cover, irrigation and the combination of both on crop development. Theobjective of this study was to determine the influence of irrigation and plastic soil cover on the agronomic performance of sweet cassava. The planting was done in beds, in thedouble row system with the stem cutingsimplanted vertically, with 0.60m between rows and 0.80 m between plants. The following treatments were applied: naked non-irrigated bedding, bedding covered with non-irrigated black polyethylene plastic, naked bedding with irrigation and bedding covered with irrigated black polyethylene plastic. Irrigation wasperformedby conventional sprinkling, based on the daily soil water balance at the effective depth of the cassava root system in the different stages of crop development. The characters evaluated were: shoot weight, root yield, starch percentage in the roots and time for cooking. The expression of the characters shoot weight, root yield and starch percentage in the roots wassignificantly influenced by irrigation managementandsoil cover. The individual use of irrigation and plastic soilcover technologies led to increases in root yieldof 55% and 13%, respectively, and when used together, root yieldincreased by 89%.

Agronomic performance of sweet cassava cultivars

ABSTRACT Brazilian sweet cassava consumers are becoming more and more demanding in relation to sanitary conditions, organoleptic and nutritional characteristics of this vegetable products and their derivatives. Thus, more nutritious, early, productive, adapted to mechanized planting and good culinary quality sweet cassava cultivars were developed. This study aimed, therefore, to evaluate the performance of four sweet cassava cultivars in Uberaba, in Triângulo Mineiro region. The experiments were carried out in the experimental field of Faculdades Associadas de Uberaba (FAZU) during two harvest seasons. We adopted a randomized block design with three replicates, each plot consisting of four lines with ten plants. Trait averages were grouped by the Scott & Knott test. The results showed that cultivars BRS 399, BRS 397 and IAC 576-70 have potential to be grown in the region, since they showed root yield higher than 32 t ha-1 and up to 30-minute cooking time. BRS 399 stood out for its performance, showing root yield of 37 t ha-1 and 48 t ha-1 in 2015/2016 and 2016/2017 harvest seasons, respectively, with short-time cooking and presenting shoot productivities which allow its use even as animal feed.