Dry-season sorghum is a type of sorghum whose establishment ends at the end of the rainy season and its development takes place during the dry and cold harmattan period. Its root system is particularly well developed with deep penetration for water withdrawal. This study was conducted to assess the level of genetic diversity present among dry-season sorghum in Chad’s Sudanese zone using phenotypic traits, and to identify new sources of drought tolerance that could be used in sorghum breeding programs. A high variability in qualitative traits was observed except for the botanical race which showed that all cultivars were of durra race. It was also observed that most cultivars had compact panicles (66.67%), mostly black glumes (66.67%), glume hairiness (58.33%) and did not have aristation (91.67%). Most qualitative traits showed a coefficient of variation of less than 30%, and the analysis of the variance showed that at 0.1% probability, there were significant differences between cultivars for all traits except botanical race. It was observed that the potential productivity of dry-season sorghum of this collection was strongly related to their staygreen characteristic; a trait of enormous importance in breeding for postflowering drought tolerance in sorghum. Plant height was highly heritable (91.9%), followed by the peduncle length (90.2%), panicle length (87.5%) and the internodes number (86.5%). Structuring of diversity separated the cultivars into four statistically distinct groups; with group 2 clustering cultivars with panicle productivity, early maturity and high staygreen, and other traits that contribute to the performance of cultivars. The findings will help to enhance the selection and production of dry-season sorghum in Chad and also provide alternative sources for staygreen introgression into the larger sorghum breeding community.

Cassava is a considerable source of food and income for the rural community of the south of Chad. Despite the importance of the diversity of cultivars in situ, their morphological traits and agronomic performance are under investigated. The aim of this study is to characterize and analyze the variability structure of the cassava's germplasm. Fifty nine cultivars collected from five main cassava growing regions, were evaluated by forty five agro-morphological descriptors in a Fisher design replicated three times. Data were collected at three, six, nine and twelve months after planting. High phenotypic variability was shown within the collection for the color of apical leaf, vein leaf, petiole, roots and pulp. The same case was observed for the root peduncle, the shape of the central leaflet and the root, the cortex root thickness and the texture of root epidermis. Significant to highly significant differences were observed for all the quantitative traits. High variability were shown for the size of the leaf lobe, petiole length, plant height, root number and length, harvest index, aboveground biomass and fresh root weight. Positive correlations were found between the leaflet and leaf lobe number. Fresh root weight was also positively correlated to the root number, length and diameter. Principal component analysis (PCA) on quantitative variable revealed four groups with two * Corresponding author. D. Nadjiam et al. 480of them containing performant cultivars: Group II with small root, high potential yield but less leaflet and leaf lobe and group III characterized by some cultivars with high productivity, more leaflet and leaf lobe, more and bigger roots. At regional level, significant differences were shown within cultivars which were discriminated in relation to their origin region by the number of the leaf lobes. The better cultivars and the interesting traits could be used to improve cassava production in Chad.

REMERCIEMENTS Nous adressons nos sincères remerciements aux responsables de l'ITRAD, au PRASAC et à l'UE pour la bourse qui nous a été accordée pour ce travail. RESUMEDans les petites exploitations familiales, les paysans détiennent un nombre important de cultivars de manioc inexploités par la recherche. L'objectif de cette étude est d'évaluer le niveau de la diversité du manioc et d'en analyser les pratiques locales de gestion. Une enquête suivant une approche participative avec des questionnaires a été conduite auprès de 636 paysans dans 43 villages. Une importante diversité variétale a été révélée par l'indice de Shannon (3,38). Soixante-quinze noms vernaculaires ont été inventoriés. Des différences hautement significatives ont été observées pour le nombre de cultivars qui varie de 2 à 12 par village (6 en moyenne). La variation entre ménages est faible, 1 à 4 cultivars (2 en moyenne). Le nombre de cultivars disparus varie de 1 à 14 (3,81 en moyenne) par village. La perte de la diversité est en moyenne de 18,20% et varie entre 11% et 50% selon les villages. Les paysans identifient les cultivars à partir des feuilles et tiges. La productivité, le goût et la grosseur des tubercules sont les critères prioritaires de sélection. Les échanges des boutures se font entre paysans locaux (60,84%) et par des introductions individuelles (37,43% Farmer management of cassava cultivars (Manihot esculenta Crantz)in the South of Chad D. NADJIAM et al. / Int. J. Biol. Chem. Sci. 10(3): 1098-1113, 2016 1099 ABSTRACTFarmers possess in their fields, many cassava cultivars which are unexplored by the research. The aim of this study is to assess their diversity and to analyze their traditional management. A total of 636 farmers selected from 43 villages, were surveyed using questionnaire and participatory rural appraisal. ShannonWeaver diversity index (H) revealed an important level of diversity of 3.38 in the study zone. Seventy-five (75) vernacular names were recorded. Highly significant differences were observed for the number of the cultivars that ranges from 2 to 12 per village (6 on average). At household level, the variation is low and ranged from 1 to 4 cultivars (2 on average). The number of disappeared cultivars range from 1 to 14 (3.84 on average) per village. The average rate of diversity loss is 18.20% and ranging from 11% to 50% per village. Farmers use leaves and stems to identify cultivars. High yield root, taste and large sized rate were the farmer preferred criteria. The exchanges of the stems are done among local farmers (60.84%) and by individual initiatives (37.43%). This knowledge will be integrated in the breeding program.

In Chad, despite the multiple culinary uses of cassava leaves and tubers, their nutritional values are untapped. In this study, the physicochemical compositions and structure of nine cultivars were assessed. The proteins were obtained by Kjeldahl's method. Total sugars were determined according to the Luff-Schoorl method. For starch content, the polarimetric method of Earle and Milner was used. Mineral elements were carried out using an atomic absorption spectrophotometry. The cyanide was evaluated by the method of Williams and Edwards. Significant variability has been demonstrated in the leaves and dry tubers except for water content and dry matter. Analysis of the variances of the components of the tubers reveals that the water contents of the cultivars vary from 5.01% to 5.86%. The ash contents vary from 4.23% (cultivar DVA2) to 8.32% (cultivar DVL2). For total sugars, the values are between 53.63% (cultivar DVL2) and 57.99% (cultivars DVL12 and KA0303). The fiber contents are lower and vary from 1.74% (cultivar DVL12) to 1.92% (cultivars SB1366, DVA2, TL0101 and PG1314). The starch content varies from 28.93% (cultivar DVL12) to 31.05% (cultivar SB1366). The variations in mineral constituents of the tubers in mg/100g are Ca (145.21-250.08), Mg (83.89-165.22), P (147.34-360.78), K (1534.50-3064.09), Zn (0.75-0.82) and Mn (0.78-0.89). Iron concentrations are from 7.72 mg/100g (cultivar BA0909) to 60.62 mg/100g (cultivar DVA2). Analysis of the variances of the leaf constituents reveals high contents of Calcium for SB1366 (2108.41 mg/100g), of iron (Fe 54.26 mg/100g) and potassium (K 1866.86 mg/100g) for DVL12, of phosphorus for TL0101 (471.87 mg/100g), of phosphorus (470.36 mg/100g

The integration of local plant genetic resources into the breeding program is an asset for research. The objective of this study is to assess the diversity and analyze the management practices of cultivated sorghum. A questionnaire following a participatory approach was submitted to 675 producers in 45 villages. The cultivars collected were characterized using 9 qualitative descriptors. In total, 151 accessions and 191 names were inventoried. On average, 25.17 accessions per department and 3.36 accessions per village. Local taxonomy is based on many criteria expressed in different local languages. The most common method of naming is that to the word sorghum is added either the color of the grain, the precocity, or any element deemed relevant by the farmers. Significant variability in grain and panicle traits was observed within the collection, except the color of the endosperm. The rate of diversity loss is 11.52% and red grain sorghums are the most threatened with extinction. Five accessions groups are differentiated by the presence or absence of awns, the color of glumes, and amount of grain covered by glumes, grain plumpness, and form. Based on productivity, precocity, plant size, seed shape, and color, the farmers identified seven promising accessions. This potential will be preserved and developed in the sorghum varietal improvement program in Chad.