CROP SCIENCE, VOL. 57, NOVEMBER– DECEMBER 2017 WWW.CROPS.ORG 3145 RESEARCH B ambara groundnut ( Vigna subterranea Verdc.) is an indig- enous, leguminous food crop that originated in various locations across semiarid Africa (Hepper, 1963). Thus, it exhib- its diverse adaptations to diferent agroecological environments. The inheritance of the crop determines the pattern of growth and development, and environmental conditions alter the growth and developmental rates. As crop production is fundamentally sensitive to the variability in climate (Porter et al., 2014; Rosenz- weig et al., 2014), farmers who have survived by using traditional knowledge to adapt to varying weather and climate conditions are increasingly faced with severely unpredictable weather pat- terns that overwhelm traditional coping practices (World Bank, 2015). Studies on bambara groundnut landraces from semiarid African locations reported the highest yield at optimum tem- perature around 31°C, with further warming reducing yields (Karunaratne et al., 2015). The photothermal control of fower- ing, podding, seeding, and tuber formation is recognized as a very important crop adaptation, which is a very complicated phenom- enon (Summerfeld et al., 1991). Roberts and Summerfeld (1987) divided the time from sowing to frst fower into three phases: (i) a preinductive phase, Modelling Pod Growth Rate of Bambara Groundnut ( Vigna subterranea Verdc.) in Response to Photoperiod and Temperature S. Etemini Oseghale,* Samson U. Remison, Ester I. Otamere, Kevin E. Eifediyi, and Gerrit Hoogenboom ABSTRACT Photoperiod and temperature are important environmental factors that affect the adapta- tion of bambara groundnut (Vigna subterranea Verdc.) and other crops to hostile climates in the tropics. The use of the accumulation concept, in which the relative rate of progress towards podding sums up to one is a common method- ology. However, the lack of quantitative informa- tion, has resulted in poor decision making for crop management practices in relation to the time of optimum pod growth rate (R opt ). This study investigated modeling pod growth using an additive and interactive relation between pod growth rate, mean photoperiod, and tempera- ture during the pod inductive phase. The feld experiment was conducted at Ekpoma Nigeria. Ten bambara groundnut landraces from three different regions in Nigeria (Anyigba, Otukpo, and Nsukka) were sown on six dates from 15 June to 1 September during the successive growing seasons of 2010 to 2012, thus expos- ing the landraces to mean natural photoperi- ods of 12 h 23 min, 12 h 19 min, 12 h 14 min, 12 h 10 min, 12 h 5 min, 12 h, 11 h 55 min, 11 h 51 min, and 11 h 47 min during the pod induc- tive period. The observed optimum photoperiod and temperature for R opt were 12 h and 26°C, respectively, for all landraces. Allocation to pod growth began at the critical photoperiod (P c ) of 12 h 19 min for Otukpo landraces, whereas P c for Nsukka landraces was 12 h 14 min . How- ever, the P c for Anyigba landraces occurred ear- lier at 12 h 23 min . The pod growth model that was developed provided good predictions of pod growth for a natural range of photoperiods and temperatures. S.E. Oseghale and S.U. Remison, Dep. of Crop Science, Faculty of Agriculture, Ambrose Alli Univ., Ekpoma, Nigeria; E.I. Otamere, Dep. of Soil Science, Faculty of Agriculture, Ambrose Alli Univ., Ekpoma, Nigeria; K.E. Eifediyi, Dep. of Agronomy, Univ. of Ilorin, Ilorin, Nigeria; G. Hoogenboom, Institute for Sustainable Food Systems, Univ. of Florida, Gainesville, FL. Received 29 Aug. 2016. Accepted 21 Aug. 2017. *Corresponding author (oseghaleetemini@aauekpoma.edu. ng). Assigned to Associate Editor Hans-Werner Olfs. Abbreviations: BAMGRO, Bambara Groundnut Growth; DAS, days after sowing; P, photoperiod; P c , critical photoperiod; P opt , optimum photoperiod; P s , photoperiod sensitivity; R, pod growth rate; R opt , optimum pod growth rate. Published in Crop Sci. 57:3145–3155 (2017). doi: 10.2135/cropsci2016.08.0714 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. Published October 12, 2017