ASSESSMENT OF SWEETPOTATO (Ipomoea batatas (L.) Lam) SEED SYSTEM AND THE EFFECT OF VINE CUTTING PORTIONS ON PERFORMANCE OF SELECTED VARIETIES

Abstract

Sweetpotato is an important subsistence crop with high food and nutrition security significance in Southern Ethiopia including Sidama Region. The productivity of sweetpotato in Ethiopia is very low compared to the global average. The low productivity of sweetpotato in Ethiopia is often linked to multitude of factors, but mainly ascribed to seed vine inaccessibility, lack or less adoption of improved varieties and use of sub-optimal agronomic practices, particularly related to seed vines. The present study was conducted with the objective of assessing sweetpotato seed system and evaluation of the performance of selected varieties established from different vine cutting portions in Sidama Region, Ethiopia. The seed system assessment was conducted in 2018/2019 involving 120 sweetpotato growing households from four Kebeles of Boricha and Dale woredas while the field experiment was done at Hawassa University research field. Survey results revealed that sweetpotato production in Sidama mainly occurs in smallholder settings on average farm size of ≈ 0.15 ha under variable socio-economic contexts. The highest average number of planted sweet potato seed vines (6855.53) per household was reported from Debub Mesenkele whereas the lowest (1704.03) was reported from Hanja Chafe. Most farmers used vine with middle cutting portions and medium seed age in studied area. Farmer’s meet their seed needs from multiple sources including own-saving, free purchasing, institutional donations, and exchange with relatives and fellow farmer friends across the community, but they heavily rely on their own stocks and on immediate circle of relatives and friends. The field experiment consisted three cutting portions (apical, basal and middle) combined with four selected varieties (Awassa-83, Alamura Hawassa -09 and Kabode) arranged in factorial-RCBD using three replications. The result revealed that from the 20 examined response parameters, only three including marketable root yield (ton/ha), root dry weight (g) and leaf area (cm 2 ), were significantly affected by vine cutting portions and varietal interaction effects. The remaining 17 parameters showed only main effect factors either for vine cutting portion, variety or both. The apical vine portion with total root yield of 38.5 ton/ha produced almost twice as high as basal cutting portion (19.8 tone/ha). Similarly, for marketable root yield (ton/ha), taking vines from older basal portion instead of the tender terminal apical regions of vines can decrease total marketable root yield by up to 51.43 %, depending on varieties. Variety Hawasa-09 out-performed the other three varieties for yield and yield component traits including total root yield (49.6 ton/ha), total root number and marketable root number. In the inter-trait correlation analysis, significant (p < 0.05) and negative correlations showed that early bud sprouting (r = -0.51) and crop maturity (r = - 0.49) did not favor for higher marketable root yields. Overall, sweetpotato production in Sidama is constrained severely by limited access to the required quantity of good quality seed-vines. From our experiment, regardless of varietal differences, apical seed-vine portions out-performed for important yield and yield component traits. We recommend evaluation of more number varieties accompanied by GXE multi-locations trials for evaluation of vine cutting portion for use as planting materials.