1 Vegetative growth and monitoring of diseases and pests of cassava (Manihot esculenta Crantz) hybrids N’Zué B., Essis B.S., Dibi K.E.B., Kouakou A.M., Yéo N.C. et Zohouri G.P Côte d’Ivoire Research in root and tuber crops value chain: The hope for food security in the ECOWAS sub region May 1-7, 2016, CSIR-CRI, Fumesua, Ghana Centre National de Recherche Agronomique

2 Outline Introduction Material et methods Results and discussion Conclusion

3 Introduction

4 Importance of cassava Cassava, 2nd food crop in CI after yam with a production of 4.2 millions tons in 2014 (FAOSTAT, 2015) Cassava is produced on the all territory with the main production in South, West and Center. Cassava is both subsistence and cash Crop for the producers Products are diversified (attiéké, placali, foutou, toh, flour, starch, gari, etc.) Products destined to all the social strata and to market.

5 Potential market of cassava products Various local cassava meals Cassava tuberous root to be used by women for processing Cassava semi-industrial processing

6 Constraints Grown varieties are low yielding and sensitive to pests and diseases High soil pressure Irregularity of rains Low national yield (8.4 t/ha) (FAOSTAT, 2015) + 90% of cultivated cassava areas are for white varieties and only -10% for colored varieties Colored varieties are rich in provitamin A and white varieties are poor Food low in vitamin A, may expose people to skin diseases, blindness, digestive disorders, nervousness, abnormal embryo, dental caries, etc.. (Shrimpton, 1989 et WHO (OMS), 1995)

7 Objective Overall objective: To create new cassava varieties rich in provitamin A and multipurposes Specific objective: To select cassava hybrids through a preliminary assessment on station

8 Material and methodes

9 Experimental site Research carried out Research Station on Food Crops (7° 4’ N and 5° 2’ W) of CNRA at Bouaké, in the Center of Côte d’Ivoire Ferrallitic soils moderately desaturated dominate the region Rainfall regime is limited to two rainy seasons (March to July and September to October) and two dry seasons (August and November to February) : annual average 1100 and 1200 mm

10 Plant material 195 seeds obtained from controlled (manual) crossings and seeds obtained from free crossings between 15 colored cassava varieties and 13 white cassava varieties.

11 Methods used Immersion test of seeds The test consisted of soaking the seeds in a bucket of water. Seeds that have floated have been unfit for germination. They were therefore rejected. The seeds that remained submerged, an amount of 23762, were selected for direct sowing in the field.

12 Experimental design The Fisher design with a single block was used. The block was split into two bands. Each band was sub-split into five (5) sub-bands. After plowing and picket the soil, the seeds were sown directly into the depth of 5 cm planting holes at the rate of one seed in per hole The spacing was 0.4 m between plants, 0.6m between rows,1.5 m between sub-bands and 2 m between bands.

13 Observations and measures per family of full-sib and half-sib Sprouting : counting of sprouted hybrids 30 days after sowing. Number of viable hybrids (vegetative vigor). Diseases (virus disease, 3 months after sowing) and pests (mites, during dry season). Type of vegetative growth: counting of number of hybrids with a linear growth or in zigzag growth

14 Observations and measures Observations and measures (‘d and end) Morphological characteristics related to color and shape of the aerial organs were observed ( stems, leaves, petioles, apex, habit plants) Tuberous roots conformation (shape, skin color, texture) at harvest: the desired traits are regular forms of tuberous roots, non pedunculate slightly fibrous, little wet matter and colored flesh

15 Statistical analyses The averages of the observed variables were calculated using Excel software. The graphics were created with the same software

16 Results and discussion

17 Rate of sprouting With a total of sown seeds, sprouting rate was 62% against 43% with seeds sown in pots ( Ndubuisi et al. (2015) ). Also according to Njoku et al. (2014) and Ceballos et al. ( 2004), the sprouting rate is low.

18 Figure 1 : Sprouting rate of seeds derived from controled and free crossings between traditional and improved varieties Taux issus de variétés améliorées Taux issus de croisements contrôlés Parents Rate from traditional varieties

19 Vegetative vigor of plants Figure 2 : Vegetative vigor of cassava hybrids from free and controlled crossings between improved and traditional varieties

20 green or purple apex about 76% of large leaves and 24% of narrow leaves green, bicolor and purple young apical stem red, green, bicolor (red dominant and green dominant) petioles blackish, green, yellowish and orange stem spread, semi-erect and erect habit linear or zigzag growth : more than 13,400 hybrids with a linear growth against 8 hybrids with zigzag growth. Aerial morphological traits observed The morphological variability in hybrid is similar to that observed in the collection of CNRA in Côte d’Ivoire (N’Zué, 2007)

21 Virus disease : upon a total of 13,456 hybrids, 223 hybrids presented symptoms of the disease, an incidence of 1.7%. Whiteflies (Bemicia tabaci) are the only viruses vectors of transmission on hybrids since they derived from seeds. In addition, the impact of viruses on hybrid from traditional female parents was greater than that observed on hybrid derived from improved female parents Mites: More than 5000 hybrids were attacked by mites. These pests cause enormous damage from year to year on cassava plant in Côte d’Ivoire ; very few improved varieties or traditional resist to it. Diseases and pests

22 Characteristics of selected hybrids Upon a total of 13,456 hybrids harvested, 1126 hybrids have been selected, a selection rate of 8%. Controlled crossings recorded the highest selection rate, reaching 67%, while those of hybrids derived from free crossings fluctuated between 4% and 10 %. The selected hybrids are composed of 224 genotypes with orange flesh, 364 dark yellow flesh, 332 light yellow flesh, 152 cream flesh and 54 white flesh.

23 Conclusion

24 A total of 1126 hybrids were selected on the basis of tolerance to pests and diseases, the vegetative vigor, the flesh color and conformation of tuberous roots The hybrids from controlled crossings or improved female parents were stronger and were less prone to viruses than those from free crossings Promoter hybrids will be submitted to a series of clonal evaluations in stations and will undergo selection at each cycle

25 Thank you for your attention