Wild Cassava Species Research Articles

Culture media for the multiplication of wild Manihot species

ABSTRACT The cassava propagation system is slow and favors disease transmission through successive generations. Micropropagation is an alternative to overcome the aforementioned limitations, besides allowing the generation of a larger number of pest- and pathogen-free plants. Therefore, the aim of the present study is to investigate the effect of culture media on the multiplication in vitro of five wild Manihot species. The experiment followed a completely randomized design, at factorial arrangement 5 (wild Manihot species) x 6 (culture media), with 11 repetitions. Explants consisted in nodal segments (91 cm long and one lateral bud) of species Manihot flabellifolia, M. tristis, M. caerulescens, M. chlorosticta and M. jacobinensis, which were extracted in vitro from the collection of wild cassava species. One segment was placed in each test tube added with 10 mL of MS media 0.01, 17N, 12A3, 4E, 8S and WPM, and kept for 90 days in growth room under 30 μmol m-2 s-1irradiance, temperature 27 ± 1 °C and 16h photoperiod. Variables plant height (cm), number of green leaves, number of senescent leaves, number of shoots, number of microcuttings, fresh and dry shoot mass, fresh and dry root mass (mg) and callus mass (mg) were analyzed. Our results showed that the culture medium 12A3 was not responsive to any of the species; however, if one takes into consideration variables plant height and number of microcuttings, this medium can possibly be used in the micropropagation of other wild species belonging to genus Manihot.

First Report of Colletotrichum theobromicola and C. siamense Causing Anthracnose on Cultivated and Wild Cassava Species in Brazil

Cassava is an important staple food crop in Brazil. Surveys were conducted during three seasons (2014 to 2016) to collect symptomatic stem and leaf samples of cultivated cassava in the Reconcavo Region of Bahia, northeastern Brazil. Additionally, samples from 10 germplasm accessions of wild cassava species were also collected. Symptomatic tissues were disinfested with 70% ethanol (30 s), 0.5% sodium hypochlorite and then washed with sterilized distilled water three times, plated on PDA and incubated at 24 °C for 7 days, (12h photoperiod). A total of 94 isolates of Colletotrichum sp. were obtained from cultivated cassava and 15 from wild species. The genetic diversity of the isolates was accessed by rep-PCR (Mahuku and Riascos, 2004), with the formation of three groups: ‘group 1’ with 101 isolates closely related with C. gloeosporioides and C. fructicola and groups ‘2 and 3’ with no correspondence with previous reported species, with five and three isolates, respectively. Four isolates (PPAM 08, PPAM 15, A...

First Report of Colletotrichum tropicale Causing Anthracnose on the Wild Cassava Species Manihot dichotoma and M. epruinosa in Brazil

First Report of <i>Colletotrichum tropicale</i> Causing Anthracnose on the Wild Cassava Species <i>Manihot dichotoma</i> and <i>M. epruinosa</i> in Brazil

English

Cassava (Manihot esculenta) is a vital food security crop and staple in Africa, yet cassava brown streak disease (CBSD) and cassava mosaic disease result in substantial yield losses. The aim of this study was to identify genes that have undergone positive selection during adaptive evolution, from CBSD resistant, tolerant and susceptible M. esculenta varieties and inter-specific hybrids, as well as a wild cassava species. Transcriptomes of 13 genotypes were sequenced and three genes with strong positive selection were detected (designated as EG2771, EG964 and EG5651).&nbsp; Sequence variation for candidate genes in 18 different cassava genotypes was examined in relation to known response to CBSD and whitefly infection. Although, we cannot ascribe a selection pressure that was responsible for the observed positive selection with complete certainty at this stage, given the congruence of the pattern of particular alleles of our positively selected genes and the pattern of disease resistance of the cassava varieties we examined, it is likely that some protein variants coded by alleles of EG2771 and EG964 may be associated with CBSD and whitefly resistance responses. This warrants further investigation. Other alleles of our positively selected genes were likely influenced by domestication or some other unknown selective pressure. &nbsp; Key words: Cassava, cassava brown streak disease (CBSD), resistant, tolerant, susceptible.

English

Cassava leaves are largely consumed as vegetable in African, but contain a toxic compound, cyanide. To ascertain their safety and contribution to human nutrition, after a number of pre-treatments preceding their boiling in water, cyanide, vitamin C, β-carotene, crude protein, iron, calcium, phosphorus, potassium and zinc contents were assessed in leaves from bitter, sweet and wild cassava species, boiled for 15 and 30 min after differently processed by: (1) pounding un-dried (UND), (2) drying before pounding (DBP) and (3) drying after pounding (DAP). Blanching headed drying was done in a tunnel solar dryer. Results showed that cassava species, processing procedures, and boiling time significantly (p < 0.05) reduced cyanide and the nutrients. However, except vitamin C, eliminated to almost nil, other nutrients were retained at considerable levels. Sensibly decreased by drying and/or boiling, cyanide levels ranged from 32 - 50 mg HCN/kg (dry matter basis) after boiling for 30 min. These levels, above the recommended level (10 mg HCN/kg) for foods, were safe with regard to cyanide toxicity based on the fact that the vegetable is served in small quantities as side food. consumed quantities of relishes as side foods. Nevertheless, it was advisable not to make them the everyday foods, especially to lower body weight such as children, and to extend time of cooking. Key words: Cassava leaves, cassava species, processing procedures, cyanide and nutrients, Rwanda.

Biological parameters of Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae) on Jatropha gossypiifolia, commercial (Manihot esculenta) and wild cassava (Manihot flabellifolia and M. carthaginensis) (Euphorbiaceae)

Bemisia tabaci (Gennadius) is one of the most important pests of cassava in Africa and several countries of Asia due to the damage caused by direct feeding, the excretion of honeydew, and its capacity as a vector of cassava mosaic geminivirus. There is a general consensus that B. tabaci is a complex of morphologically indistinguishable populations with different biotypes. In the Americas, the polyphagous biotype B does not appear to feed on cassava. Recent studies indicate that it is possible, however, for biotype B to gradually adapt to cassava using phylogenetically related hosts. Therefore, the possibility that some wild species of cassava constitute intermediate hosts in the adaptation process may lead to the establishment of biotype B on commercial varieties of Manihot esculenta. In here, we evaluated Jatropha gossypiifolia, two wild species of cassava (Manihot flabellifolia and M. carthaginensis) and a commercial cassava variety (MCol 2063) as hosts of biotype B. The highest oviposition rate (2.7 eggs /two days) occurred on M. esculenta, although the development time (44 d) was the longest when compared to M. carthaginensis and J. gossypiifolia. About 60% of the population could reproduce on the wild cassava species vs. 55% on J. gossypiifolia and 27.5% on the commercial variety. Our data suggest that J. gossypiifolia is a suitable host and the wild species M. carthaginensis can constitute a potential intermediate host in the adaptation of biotype B to commercial varieties of cassava.

Introgression of genes for dry matter content from wild cassava species

Cassava cultivars often have poor resistance to biotic stresses and lack good quality traits. Wild species of cultivated crops have frequently been used as an important source of genetic diversity. Cassava breeders are becoming increasingly interested in incorporating genes of wild relatives. In 2000 the International Center for Tropical Agriculture (CIAT) initiated a programme to introgress genes for several root yield and quality traits from wild cassava relatives into its germplasm collection. The objectives of this study were to evaluate one resulting inter-specific cross with high variability for dry matter content (DMC) and to assess the effect of such a cross on other yield related traits. Crossing of the elite cultivar MTAI 8 to the wild relative Manihot tristis increased the percentage DMC above the normal average of about 35%, with percentage DMC ranging from 34.39 to 42.73. The crosses, however, were accompanied by some detrimental effects, most noticeable the reduction in harvest index (HI). It is apparent that when selecting for DMC, caution should be taken and HI and fresh root yield should be monitored. Regression analysis singled root weight, percentage DMC and fresh root yield out as the most important contributors to dry root yield. Principal component analysis indicated that root weight, roots per plants and DMC contributed most to storage root yield.

Wild manihot species do not possess C4 photosynthesis.

Cultivated cassava (Manihot esculenta) has a higher rate of photosynthesis than is usual for C3 plants and photosynthesis is not light saturated. For these reasons it has been suggested that cultivated cassava could be derived from wild species possessing C4 photosynthesis. The natural abundance of 13C and activities of phosphoenolpyruvate carboxylase and phosphoglycolate phosphatase were measured in leaves of 20 wild cassava species to test this hypothesis. All the species studied, including M. flabellifolia the potential wild progenitor of cultivated cassava, clearly exhibited C3 not C4 characteristics.