Genetic Variation of Postharvest Physiological Deterioration in a Cassava Gerplasm.

Postharvest physiological deterioration (PPD) nature of cassava root is reducing the crop's suitability for processing and general consumer acceptability. The Genetic Gain Collection of International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria, accumulated over years was assessed for natural perishability of the root. PPD was measured as the proportion of root surface covered with streak in ratio (0/4, ¼, ½, ¾, 4/4), and values were converted to decimal (0.00, 0.25, 0.50, 0.75, l.00). Streak was observed at the proximal, distal, and the middle portion of roots at 2, 4, 6, and 8 days after harvest. The values for streak at the three parts were averaged and its percentage was taken as mean PPD of a root. The estimated mean PPD was used for ranking the clones in descending order using rank-sum analysis in SAS package. The clones were grouped into 10 classes in reaction to PPD. The PPD varied highly significantly among assessed clones of cassava (p<0.0001) with mean values that ranged from 0.0 to 80.6%. with an average of 18.1 (±0.01). Of the total clones assessed, 14.6% were in very highly resistant class, 19.7% highly resistant plus, 26.6% highly resistant, 18.3% resistant, 13.0% moderately resistant, 3.3% moderately susceptible, 2.5% susceptible, 0.7% highly susceptible, 0.7% highly susceptible plus, and 0.5% very highly susceptible. The results obtained in the present study will be useful to designing breeding objectives for PPD in cassava.

Key Words: Cassava roots, Postharvest physiological deterioration, and Streak.