Screening cassava genotypes in two agroecological zones of Nigeria using tuberous root poundability

RÉSUMÉ A KPAROBI , S. O.: Despitage de génotype de manioc en deux zones agroécologiques du Nigéria utilisant la méthode de la qualité de pilonnage de racine tubéreuse. Douze génotypes de manioc étaient évalués dans deux zones agroécologiques (Ibadan : 25 ± 5 o C et Jos: 18 ± 5 o C), pour déterminer la qualité de pilonnage de la racine tubéreuse à 3, 6, 9 et 12 mois après la plantation (MALP). Les résultats montraient qu’il n’y avait pas des différences ( P < 0.05) considérables dans la qualité de pilonnage de racine tubéreuse entre les deux endroits et les deux années (1994 à 1996) partout dans les périodes d’échantillonage. En outre les différences génotypiques ( P < 0.05) n’ étaient pas observées parmi les génotypes de manioc pour la qualité de pilonnage de la racine tubéreuse soit à travers soit à l’intérieur d’ endroits. Isunikankiyan, TME 1, TMS 50395 et TMS 30572 donnaient les plus faibles valeurs de qualité de pilonnage de racine tubéreuse de 1.2, 1.3, 1.2 et 1.4 respectivement pour 3, 6, 9 et 12 MALP. Les différences génotypiques ( P < 0.05) étaient observées parmi les génotypes mis à l’essai pour le rendement par hectare de racine tubéreuse sèche totale. Les plus élevés de rendement par hectare de racine tubéreuse étaient produits par TMS 30572, TMS 50395, TMS 91934 et TME 1. Les résultats de cette étude ABSTRACT Twelve cassava genotypes were evaluated in two agroecological zones (Ibadan: 25 ± 5 o C and Jos: 14 ± 5 o C) to determine the tuberous root poundability at 3, 6, 9 and 12 months after planting (MAP). The results showed that there were no significant differences ( P <0.05) in tuberous root poundability between the two locations and years throughout the sampling periods. Also, genotypic differences ( P <0.05) were not observed among the cassava genotypes for tuberous root poundability either across or within locations. Isunikankiyan, TME I, TMS 50395 and TMS 30572 produced the lowest values for tuberous root poundability of 1.2, 1.3, 1.2 and 1.4 for 3, 6, 9 and 12 MAP, respectively. Genotypic differences ( P <0.05) were observed among the tested genotypes for total dry tuberous root yield per hectare. The highest tuberous root yields per hectare were produced by TMS 30572, TMS 50395, TMS 91934 and TME 1. The results of this study suggest that TME 1, TMS 50395 and TMS 30572 were poundable and also had high tuberous dry root matter. It is recommended that these varieties be made available for farmers in farm testing and also be used for further breeding programmes for incorporation of the poundability characteristics.


ABSTRACT
Twelve cassava genotypes were evaluated in two agroecological zones (Ibadan: 25 ± 5 o C and Jos: 14 ± 5 o C) to determine the tuberous root poundability at 3, 6, 9 and 12 months after planting (MAP). The results showed that there were no significant differences (P<0.05) in tuberous root poundability between the two locations and years throughout the sampling periods. Also, genotypic differences (P<0.05) were not observed among the cassava genotypes for tuberous root poundability either across or within locations. Isunikankiyan, TME I, TMS 50395 and TMS 30572 produced the lowest values for tuberous root poundability of 1.2, 1.3, 1.2 and 1.4 for 3, 6, 9 and 12 MAP, respectively. Genotypic differences (P<0.05) were observed among the tested genotypes for total dry tuberous root yield per hectare. The highest tuberous root yields per hectare were produced by TMS 30572, TMS 50395, TMS 91934 and TME 1. The results of this study suggest that TME 1, TMS 50395 and TMS 30572 were poundable and also had high tuberous dry root matter. It is recommended that these varieties be

Introduction
Cassava tubers form one of the major staple foods in the world (FAO, 1996;Akparobi, Ekanayake & Togun, 2002). Cassava will continue to assume greater importance with time as a major source of Ghana Jnl agric. Sci. 41, 145-149 carbohydrate for human consumption in the tropics and sub-tropics where the low per capita income will not permit a change in dietary habits (Carter et al., 1992;CIAT, 1993).
The two broad consumption patterns for cassava are in either the fresh or dry form (Hahn & Keyser, 1985;Sanni, 1994;Odogola, 1994). In the fresh form, cassava may be eaten raw in small quantities as snack, and may be boiled and pounded into 'fufu'. The dry form involves peeling of the roots, chipping, slicing, and pounding to obtain cassava meal called 'fufu'. Poundability of cassava roots is a primary factor in the choice of cassava by farmers and consumers (Cock, 1985;Dixon, Asiedu & Hahn, 1994). Poundability of the tuberous root is also of economic importance (Cock, 1985;Dixon et al., 1994;Nweke, 1996). It is, therefore, essential to incorporate traits such as poundability of roots in developing cassava varieties. Traits such as poundability are evaluated using subjective estimates (Dixon et al., 1994). This study investigated screening of cassava genotypes in two contrasting agroecological zones of Nigeria for changes in biochemical parameter of cassava tuberous roots using poundability.

Experimental design
Twelve cassava genotypes (six improved IITA genotypes: TMS 30001, TMS 91934, TMS 4(2) 1425, TMS 30572, TMS 50395, TMS 30555; four landraces [local genotypes] commonly grown in southwestern Nigeria: TME 1, TME 11, Isunikankiyan and Oko-Iyawo; and two landraces [local genotypes] adapted to mid-altitudes: Danduala and Danwaru). Cassava stem cuttings of 0.20 m length were collected from 12-monthold mother plants at the middle part of the stem and were immersed in 0.05 per cent of fungicidal benlate (a.i.=methyl 1-(butyl carbatomyl)-2benzimidazole carbamate) solution. The experiments were set up in each location in a completely randomized block design with three replications. Each plot had 6 rows, 10 m long, and spacing was l m between rows and 0.8 m within a row. Each plot contained 72 plants. Fields were kept free of weeds by regular hand-weeding.

Data collection and analyses
Harvesting was at 12 MAP. Cassava tuberous roots were brought to the laboratory immediately after the harvest. For each genotype, three healthy-looking tuberous roots were selected and treated as one sample. In genotypes with large tuberous roots (>5 cm in diameter), sampling was applied. Three discs were sampled per root, one each from each end (within 5 cm of the end), and the other from the middle of the root. The three root discs from each root were combined and treated as one sample. The samples were peeled and used to determine poundability. The samples were assigned labels and later put in cloth bags and cooked for 2 h at 100 o C. The sample was pounded in crucible.
Poundability was determined using 1-3 scale, where 1 = very poundable, 2 = poundable, 3 = not poundable. Statistical Analytical System (SAS, 1996) programme was used for data analyses. Analysis of Variance and Duncan's Multiple Range Test were used to evaluate significant differences in data collected.

Results and discussion
The results showed that there were no significant differences (P< 0.05) in tuberous root poundability between the two locations and years throughout the sampling periods (Fig. 1). No significant differences were observed in environmental effects, showing that cassava genotypes responded similarly to variation in environmental conditions concerning some biochemical changes like poundability. Similar results have been reported on cassava genotypes (Cock, 1985;Bueno, 1986;Akparobi et al., 2002) that environmental factors such as temperature, rainfall, solar radiation, and soil conditions sometimes have little influence on the biochemical and physiological processes of a cassava tuberous root. It seems there might be no need for testing at multiple locations over time for changes in biochemical parameters of cassava tuberous roots using poundability.
Genotypic differences (P<0.05) were not observed among the cassava genotypes for tuberous root poundability either across locations (Table 1) or within locations (Table 2). Isunikankiyan, TME 1, TMS 50395, and TMS 30572 produced the lowest values for tuberous root poundability of 1.2, 1.3, 1.2 and 1.4 for 3, 6, 9 and 12 MAP, respectively (Table 1). This study implies that no significant differences exist among the genotypes, but some had lower values for poundability. These ones can be exploited by breeders by incorporating the traits for future breeding programmes, because many people Ibadan) on tuberous root poundability of 12 cassava genotypes at 3, 6, 9 and 12 MAP. Bar represents LSD at 5% level of significance.
The results of this study suggested that three genotypes, TME 1, TMS 50395 and TMS 30572, were found to be  Means in the same column with the same letter (s) and within the same MAP are not significantly different (P < 0.05), using DMRT. MAP = months after planting. Means in the same column with the same letter (s) and within the same MAP are not significantly different (P < 0.05), using DMRT. MAP = months after planting.
poundable and also had high tuberous root dry weight, and should be made available to farmers for 'on-farm testing'. These identified genotypes should be used for further breeding programmes, so that the trait would be incorporated.