Growth and Water Content Responses of the Selected Cassava (Manihot esculenta Crantz) Genotypes to Drought and Salinity; and their Effects on Yield

Aims: To screen ten selected cassava genotypes for tolerance to drought and salinity using growth and yield attributes; and leaf relative water contents (LRWC) as screening tools.

Study design: The design was factorial consisting of ten cassava genotypes, three treatments (and control) with six replications laid out in a randomized complete block design(RCBD).

Place and Duration of Study: Department of Botany, University of Ibadan, between January and July, 2019.

Methodology: There were a total of 240 experimental units, 60 units in each group. It was a semi-field experiment. All plants were watered for 6 weeks before exposing them to the physiological stresses of drought (D), salinity (S) and their interaction (D×S). The designated plants were subjected to S by applying 100mM of NaCl solution, D by with-holding water for 2 weeks interval, (D×S) by combining the two stresses and the first block (the first 60 units) served as control.

Results: With respect to plant height, the least and most significantly affected by drought were IBA120008 (61.94 cm) and I098510 (32.77 cm); by salinity were IBA120008 (57.09 cm) and I920326 (35.24 cm) and by D×S were IBA120008 (67.45 cm) and I920326 (34.57cm), respectively. With respect to RWC at the final stage of growth, the most tolerant were TMEB419 (100.00%) under D, I980581 (100.00%) under S and I010040 (100.00%) under D×S while the most susceptible were TMEB693 (89.75%), IBA120008 (63.64%) and I070593 (55.56%) under D, S and D×S respectively. In all the three stresses, genotype I980581 was the least significantly affected with the tuber yield of 174.54g.

Conclusion: High shoot growth does not guarantee high yield. It can also be concluded that drought had more detrimental effects on cassava productivity than salinity and their combination.