Participatory consumer evaluation of twelve sweetpotato varieties in Kenya

Eleven improved sweetpotato varieties; “Kemb10, SPK004, Mugande, Namaswakhe, K117, Polista, Bungoma, Odinga, 292-H-12, Zapallo” and “Nyathi Odiewo (improved) ”, were tested against four popular farmer varieties; “Nyathi Odiewo (local), Jayalo, Amina and Kuny kibuonjo” for consumer preference. The experiment was laid out in a randomized complete block design with 12 treatments replicated four times in mother and baby trial with farmers’ involvement. The study was conducted in farmers’ fields in four locations covering the major sweetpotato production Agro-Ecological Zones (AEZ ) of southwest Kenya namely; Kabondo AEZ, Upper Midland2 (UM2), Ndhiwa, Low Midland2 (LM2), Rangwe, Low Midland1 (LM1) and Kendu, Low Midland3 (LM3). The trials were planted in May and September 2005 both long and short rains, respectively. Ten participating and ten non-participating farmers per location formed a panel and evaluated the mother trial for consumer preference. Focused group discussions were held to determine farmers’ perception for evaluation. Data was collected on consumer preference: yield, taste, aroma, ease to cook and texture. There were differences in yield with variety “Mug and” yielding highest followed by “K117 Nyathi Odiewo, Namaswakhe” and “Kemb10” respectively across locations. Farmers’ preferred local varieties “Nyathi Odiewo” and “Kuny kibounjo” were comparable to the improved varieties. Variety “Zapallo” and the local varieties; “Jayalo” and “Amina” had lower yielding. “Odinga” was most preferred for consumption followed by “Nyathi Odiewo Kemb10, SPK004, Polista, 292-H-12” and the local checks. Farmers’ involvement is crucial in evaluation of preferred sweetpotato varieties for consumption. However, varieties “K117” and “Mugande” have potential to increase farmers production.


INTRODUCTION
Sweetpotato [Ipomoea batatas (L.) Lam] belongs to convolvulaceae family.Sweetpotato is the world's seventh major food crop after maize, wheat, rice, potato, barley and cassava (Gichuki et al., 2003).Sweetpotato is mainly grown for its edible roots which are high in dietary energy (Woolfe, 1992).
In Kenya, over 75% of production is concentrated in western, central and coastal areas of the country.Out of this, over 80% is grown in the Lake Victoria basin (Grũneberg et al., 2004).
In western Kenya, farmers grow landrace varieties that *Corresponding author.E-mail: kwachjk@yahoo.com.
are preferred locally but lack consumption appeal for distant market.Sweetpotato is an important food security crop in this region.The remedy is to involve the farmers through introduction, evaluation and selection of new varieties with superior preference (Mcharo et al., 2001;Keith et al., 2004).A participatory farmer approach of Mother-Baby trial (Snapp, 1999) was used to test a range of improved sweetpotato varieties.For each "mother" trial, there were eleven corresponding "baby" trials within a distance of 5 km.The mother trials were researcher and farmer group managed to evaluate the varieties under optimal management conditions.The trials were located at the centre of the identified farming community.The baby trials were farmer managed where each contained a subset of four sweetpotato varieties out of twelve varieties in the mother trials.The four subset treatments (varieties) were randomly assigned to each farmer (Snapp, 2004).
In addition to yield, other qualitative parameters that were considered by consumers include the roots taste, texture, aroma of the storage roots.All these influence consumer preference of sweetpotato (Woolfe, 1992;Kapinga et al., 2000;Opare-Obisaw et al., 2000;Marti, 2003).
In this study, potential consumer preference sweetpotato varieties have been identified by scientists from Kenya Agricultural Research Institute (KARI) and International Potato Centre (CIP) for consumer preference and acceptability.
These varieties had dry matter content of at least 27% were preferred by consumers due to their maeliness.The identified varietis are rich in β-carotene and may improve the nutritional status of the consumers (Hagenimana et al., 1999;Opare-Obisaw et al., 2000).Surplus production of these varieties will likely increase farmers' income and improve their livelihoods.
It has been found that consumers determine the adoption and acceptance of sweetpotato varieties therefore their preferences, fears and aspirations have to be taken into consideration before new varieties are released (Christopher et al., 1995;Martin and Rodriguez-Sosa, 1985).

MATERIALS AND METHODS
Four sets of experiments were undertaken in four agro-ecological zones (AEZs) for two seasons in 2005, the Long Rains (LR) and Short Rains (SR) in three locations; Kabondo Upper Midland2 (UM2), Ndhiwa Low Midland2 (LM 2) and Rangwe Low Midland1 (LM1).In the fourth location for one season during the Long Rains at Kendu Low Midland3 (LM3) that has a single cropping season (Andima et al., 2003;FAO/UNESCO, 1990;Jaetzold and Schmidt, 1982).In western Kenya Long Rains (LR) is the major rainfall season and usually starts in February and spreads to July while Short Rains (SR) is the minor rainfall season starts in August to October yearly.

Rainfall received during the crop growth
During the LR season crop growth period, Ndhiwa location received a total of 896.5 mms, Kabondo, 634.1 and Kendu, 476.2 mm.In the SR season, Ndhiwa received a total of 782.0mm and Kabondo, 316.5mm.Rangwe rainfall data was not available.

Experimental approach
A participatory Mother Baby approach involving four farmers groups; Kabondo Farmer Field School (Nyapalo), Ndhiwa Farmer Men's group (Ndonyo), Kendu Self Help group (Hocapo) and Community Health and Rangwe Agricultural workers group Kwach et al 1601 (Lwaho).Mother-baby trial approach (Snapp, 1999) was used to test a range of improved sweetpotato varieties for consumer preference.For each "mother" trial, there were eleven corresponding "baby" trials within a distance of 5 km.The mother trials were researcher and farmer group managed to evaluate the varieties under optimal management conditions.The trials were located at the centre of the identified farming community.The baby trials were farmer managed where each contained a subset of four sweetpotato varieties out of twelve varieties in the mother trials.The four subset treatments (varieties) were randomly assigned to each farmer (Snapp, 2004).Each group elected eleven participating farmers who planted the baby trials.There were no replications at individual farm.The baby trials were to make the participating farmers understand the sweetpotao varieties better before requesting them to select for preference in the mother trials at harvesting.

Experimental design
The mother trial of twelve varieties was set in a randomised complete block design (RCBD) replicated four times in each location.Each variety was planted in a 3.3 x 4.0 m 2 plot.Sweetpotato vines were spaced 1.0 m between ridges and 0.3 m within the row.The gross plot had four rows each with twelve plants resulting in 48 plants per plot.This was managed by the researcher who collected the data and analysed statistically.The baby trials were set in a completely randomized design with four treatments (varieties); three improved varieties and one local check variety, without replication.Spacing for baby trials was the same as mother trials.This was managed by the farmers while data was collected by researcher and analysed statistically (Data not reported).The plot sizes were 6.0 x 5.0 m 2 .The net plot harvested for root yield for both the mother and baby trials consisted of the two rows of each variety comprising of twenty plants (2 x 2.27) m 2 and was done 150 days after planting (CIP, 1999).

Data collected
Data collected during the experiment by the researcher at 90 days from planting (at vigorous vegetative stage) included number of plants planted, drought tolerance (those varieties which could not show any symptom of water stress after missing rains for one month), and early maturity (those varieties that form harvestable roots in 90 days) in the mother trials in all the four locations (data not reported).
At harvesting (150 days from planting) collected data on yield.During harvesting a sample weighing 200 gm per plot of root roots were picked at random cut into small cubes of 1 cm 3 , oven dried at 80 0 C for 24 h and dry matter content per variety determined as percentage of root dry weight to fresh weight (data not reported).Standard data collection procedures were followed according to the International Potato Centre (CIP, 1999).

Consumers' selection by the farmers
During the crop growth period in each season (three and five months) after planting at twenty farmers ten participating and ten non-participating (Table 1), per location evaluated the mother trial.Efforts were made to ensure the involvement of all gender (Table 1).Focused group discussions were held to determine farmers' perception for evaluating storage roots for consumer preference.The farmers set their own criteria (consumer preference, taste, aroma, market preference and overall acceptance) for evaluation.During the evaluation process, farmers evaluated two replications of all the twelve sweetpotato varieties per location.Each variety was scored according to the farmers' set criteria using a five point scale (5 = very good, 4 = good, 3 = satisfactory, 2 = poor and 1 = very poor).A mean score 3.0 and above was rated as acceptable while below 2.5 was rated as unacceptable.
After harvesting a coded sample of roots the twelve varieties were sealed in a clear polythene bag so as to retain its characteristics then cooked.The twelve varieties were each displayed on a plate after cooking without its name identification in to avoid any biasness.The cooked roots were cut into small pieces and taste by the farmers using a cocoa beverage as this was accepted in the locations where the experiment were conducted there were some (farmers) who are strong Seventh Day Adventist Church believers who could not accept other beverages such as coffee or tea for oganoleptic tests.Farmers rinsed their mouths after tasting each variety before tasting the next variety to reduce the lingering taste of the last tasted variety.All the twelve were all tasted.A five point scale (5 = very good, 4 = good, 3 = satisfactory, 2 = poor and 1 = very poor) was used.Each farmers involved in the taste filled in a score form independently. Lastly each the twenty farmers ranked the twelve for overall acceptability the best being ranked 1 and the least was ranked 12 (CIP, 1999).

Socio-characteristics of farmers who evaluation the twelve sweetpotato varieties
A total of twenty farmers (Table 1) per location were chosen by the themselves to represent them on the evaluation day at harvesting who formed the taste pannel members.The twenty farmers used a score forms for scoring the twelve sweetpotato varieties for analysis.They comprised of different age aductional level and gender (Table 1).The total number of farmers who were present on that day were more than 50 per location per season.

Data analysis
Consumer preference data was analysed using the Statisical Analysis for Scientists (SAS) statisical package version 8. General Linear Model (GLM) for the analysis of variance (ANOVA) and mean separation using LSD (p < 0.05) was applied to determine whether there were significant differences among the varieties (Gomez and Gomez, 1984;Virk and Witcombe, 2004).

Fresh root yields
Data for root yield was collected by the researcher.There were significant (P < 0.05) differences in fresh root yield among the varieties (Table 2).The variety "K117" had the highest fresh root yields at Ndhiwa of 27.8 tons ha -1 whilst the local check variety, "Jayalo" had the lowest yields of 3.0 tons ha -1 at Kendu during the long rains season.In the LR season Ndhiwa location had the highest mean fresh root yield of 20.6 tons ha -1 while Kendu had the lowest at 9.8 tons ha -1 .
In LR season at Kendu varieties "K117, Improved Nyathi Odiewo, Namaswakhe, Kemb10, Odinga, Zapallo and Polista" had root yields between 11.0 -14.9 tons ha -1 as compared with the local check "Jayalo" with root yields of 3.0 tons ha -1 and was the lowest The variety "K117" had the highest root yield of 14 tons ha -1 .The yield variation may be due to genetic potential of different varieties, climatic differences, such as amout of raifall recived by the crop during the growth period (Mcharo et al., 2001).
In short rains season, no data for Kendu was taken because it is a single season zone and Rangwe had crop failure due to drought.

Preference based on taste of cooked roots as scored by farmers
There were significant (P < 0.05) differences on taste preference of cooked roots among the varieties (Table 3).At harvest of mother trial in the LR season, the variety "Odinga" was the most preferred for taste at Kabondo and Kendu with a mean of 4.5 whilst the least preferred variety was "Jayalo" at Kendu with a score of 1.6.In SR variety "Odinga" had the highest mean score of 4.6 at Kabondo and Ndhiwa.The least preferred was "K117" with a mean of 2.9 at Kabondo.
In short rains season, no data for Kendu was taken because it is a single season zone and Rangwe had crop failure due to drought.

Preference based on the roots ease to cook as scored by farmers
There were significant (P < 0.05) differences on the roots Means followed by the same letter(s) in the same column are not significantly different as separated by Lsd p=0.05 ˇLocal check (s) varieties: Ndhiwa-"Kuny kibuonjo"; Kabondo-"Nyathi Odiewo"; Rangwe-"Amina"; Kendu-"Jayalo" ˇˇScored by 20 farmers per location per season: scale (5 = very good, 4 = good, 3 = satisfactory, 2 = poor and 1 = very poor) ease to cook among the varieties (Table 4).In the LR at harvest of the mother trials variety "Odinga" had highest score as the most preferred for ease to cooking at Ndhiwa with a mean score of 4.5 while the lowest was "Jayalo" at Kendu with a score of 1.5.The variety "Odinga" had the highest mean score of 4.7 at Ndhiwa whilst variety Kemb10 had the lowest with a mean score of 3.0 at Kabondo in the SR season.At Ndhiwa the varieties; "Odinga, Improved Nyathi Odiewo, Bungoma, Zapallo, Spk004, 292-H-12" and the local check variety "Kuny kibuonjo" were preferred for ease of cook in the LR season.In the SR season varieties; "Odinga, Improved Nyathi Odiewo, Bungoma, Zapallo, Mugande, K117, Spk004, 292-H-12", were selected while the local check variety "Kuny kibuonjo" was rated very low.At Kabondo varieties "Odinga, Improved Nyathi Odiewo; Polista, Zapallo, Spk004, K117" and the local check variety "Nyathi Odiewo" were preferred for ease to cook in the LR season.The varieties, "Odinga, Improved Nyathi Odiewo; Kemb10, Polista, Zapallo" and the local check variety "Nyathi Odiewo" were selected in the SR season.
In short rains season, no data for Kendu was taken because it is a single season zone and Rangwe had crop failure due to drought.

Based on preference on the aroma of cooked roots as scored by farmers
Sweet potato has different aromatic smell that varies with the variety.There were significant (P < 0.05) differences in preference on the aroma of cooked roots among the varieties (Table 5).In the LR the variety "Odinga" significantly scored the highest as the most preferred for aroma at Kendu with a mean of 4.3 while the least preferred for aroma was local check variety "Jayalo" at Kendu with a mean score of 1.7.In the SR season the variety "Odinga" significantly scored the highest as the most preferred for aroma at Kendu with a mean of 4.5 while the least preferred was variety the K117 with a mean score of 2.8 at Kabondo.Overall, variety "Odinga" led across the locations with a mean score of 4.0 and the less preferredvariety for aroma was "K117" with a mean score of 2.4.
In short rains season, no data for Kendu was taken because it is a single season zone and Rangwe had crop failure due to drought.

Preference based on cooked root texture as scored by farmers
There were significant (P < 0.05) differences on preference of cooked root texture among the varieties (Table 6).Variety "Odinga" was significantly scored the highest as the most preferred for texture in Kabondo with a mean of 4.6 while the less preferred texture was local variety Jayalo in Kendu with a mean score of 1.5.Overall "Odinga" led across the locations with a mean score of 4.2 and the less preferred for texture were K117 and Namaswakkhe with a mean score of 3.1.
In short rains season, no data for Kendu was taken because it is a single season zone and Rangwe had crop Means followed by the same letter(s) in the same column are not significantly different as separated by Lsd p = 0.05 ˇLocal check (s) varieties: Ndhiwa-"Kuny kibuonjo"; Kabondo-"Nyathi Odiewo"; Rangwe-"Amina"; Kendu-"Jayalo" ˇˇRanked by 20 farmers per location per season: scale 1 -12 (1 very highly accepted, -12 very poorly accepted).
failure due to drought.

Preference for overall acceptability as ranked by farmers
Overall the farmers ranked the twelve varieties giving the best as rank number 1 while the least preferred was ranked 12.There were significant (P = 0.05) differences on overall acceptability among the varieties (Table 7).Variety, "Odinga" most accepted ranked as with a mean of 1.6 in the LR season at Kendu and in the same location variety Jayalo was the least accepted ranked number 11.1.In SR season "Odinga" was significantly accepted, ranked number 1.4 at Kabondo whilst variety K117 was significantly least accepted, ranked 9.4 at Kabondo location.The two varieties were significantly different from each other In the LR season, at Ndhiwa varieties; "Odinga, Kemb10, Spk004, Improved Nyathi Odiewo, 292-H-12, Zapallo" and the local check variety "Kuny kibuonjo" were overally accepted.In the Short Rains season, varieties; "Odinga Kemb10, Spk004, 292-H-12, Zapallo" and the local check variety "Kuny kibuonjo" were accepted.
At Kendu, in the Long Rains season, varieties "Odinga, Kemb10, Improved Nyathi Odiewo, Polista, Spk004, 292-H-12 and Mugande" were accepted while the local check variety "Jayalo" was least acceptable due to its poor yields, taste and was also highly affected by viruses.Selection for market, preference for colour of root skin taste and aroma also vary with the locality.Martin and Rodriguez-Sosa (1985) on their work in Puerto-Rico on preference for colour, sweetness and mouth feel of sweetpotato reported that significance differences occur from one location to the other as some score one criteria high, the other very low they attributed this to individual differences, cultural affiliations and even sex differences amongst the groups.This might have been attributed to individual differences on taste and preferences, cultural affiliations, even sex differences amongst the groups, geographical locations.Similarly this study concurs with Hagenimana et al. (2001) who reported that some varieties differed in preferences than others of orange fleshed sweetpotato in western Kenya.Similarly Keith et al. (2004) reported that in rural communities in Africa are thought to be cautious about accepting foods substantially different in colour and taste from those they are used to in Tanzania.There were significant differences in colour, aroma, taste texture and yields.This could have led to differences in overall acceptability.The variety "K117" was ranked very high for consumption at Kendu and very low at Kabondo.This might have been attributed to the variety "K117" having high yields potential.Kendu, being a dry area with deficit in sweetpotato production, so any high yield variety could be accepted as opposed to Kabondo location which is a high potential zone and has a surplus producer consumption and commercial market."Zapallo" was ranked highly for ease to cook of other varieties.Overally, variety "Odinga" was most preferred variety across locations likely due to its taste, market, colour of skin and flesh while the least was K117 which is white skinned and less market preference Farmers used various criteria for selecting sweetpotato for consumption; taste, ease to cook, aroma, and root texture.The study showed that there were significant differences amongst the varieties across locations.There also variations per location.Farmers clearly selected variety "Odinga" as most preferred, varieties; "Kemb 10, Spk004, Polista" and local check varieties "Nyathi Odiewo and Kuny kibuonjo" were equally preferred for consumption, based on roots taste, ease of cook, aroma and texture.However, the varieties "K117, Zapallo, Namaswakhe and Bungoma" were less preferred because of poor taste, low dry matter and watery.Consitently six improved varieties "Odinga, Kemb10, Improved Nyathi Odiewo, Spk004, Polista Kuny kibuonjo and 292-H-12", were selected for consumption based on their preference for, taste, ease to cook, aroma and texture of the roots.The varieties "K117 and Mugande" led on yiled.thissuggests that the newly introduced varieties could be adopted by producers for consumer demand.
In short rains season, no data for Kendu was taken because it is a single season zone and Rangwe had crop failure due to drought.

Conclusions
Six improved varieties "Odinga, Kemb10, Improved Nyathi Odiewo, Spk004, Polista Kuny kibuonjo and 292-H-12",were selected for consumption based on their preference for, taste, ease to cook, aroma, and texture of the roots.However the varieties "K117, Zapallo, Namaswakhe and Bungoma" were less preferred because of roots poor taste, low dry matter and watery.Based on yields the farmers preferred, "Mugande, K117, Improved Nyathi Odiewo, Namaswakhe, Kemb10 and Odinga".A breeding program to incorporate the good consumer preference traits might increase preference to consumers.

Table 1 .
Socio-Characteristics of farmers who evaluated sweetpotato varieties mother trials at different locations during 2005 cropping seasons.

Table 2 .
Mean fresh root yields of twelve sweetpotato varieties mother trials at different locations during 2005 cropping seasons.

Table 3 .
Mean score by farmers of twelve sweetpotato varieties on cooked root taste at harvesting mother trials at different locations during 2005 cropping seasons.

Table 4 .
Mean farmers score for ease cooking the roots at harvesting mother trials at different locations during 2005 cropping seasons.

Table 5 .
Mean farmers score on aroma preference of cooked roots at harvest of mother trials at different locations during 2005 cropping seaseons.

Table 6 .
Mean farmers score on cooked roots texture preference at harvest mother trials at different locations during 2005 cropping seaseons.

Table 7 .
Mean farmers rank on cooked overall roots acceptability at harvest of mother trials at different locations during 2005 cropping