Early-season Soil Moisture Deficit Reduces Sweetpotato Storage Root Initiation and Development

Abstract

<jats:p>Sweetpotato [<jats:italic>Ipomoea batatas</jats:italic> (L.) Lam.] storage root formation is a complex developmental process. Little quantitative information is available on storage root initiation in response to a wide range of soil moisture levels. This study aimed to quantify the effects of different levels of soil moisture on sweetpotato storage root initiation and to develop functional relationships for crop modeling. Five levels of soil moisture, 0.256, 0.216, 0.164, 0.107, and 0.058 m<jats:sup>3</jats:sup>·m<jats:sup>−3</jats:sup> soil, were maintained using sensor-based soil moisture monitoring and semiautomated programmed irrigation. Two commercial sweetpotato cultivars, Beauregard and Evangeline, were grown in pots under greenhouse conditions and treatments were imposed from transplanting to 50 days. Identification of storage roots was based on anatomical, using cross-sections of adventitious roots, and visual features harvested at 5-day intervals from 14 to 50 days after transplanting (DAT). Recorded time-series storage root numbers exhibited sigmoidal responses at all soil moisture levels in both cultivars. Time to 50% storage root initiation and maximum storage root numbers were estimated from those curves. Rate of storage root development was determined as a reciprocal of time to 50% storage root formation data. Time to 50% storage root initiation declined quadratically from 0.05 to 0.15 m<jats:sup>3</jats:sup>·m<jats:sup>−3</jats:sup> soil moisture and increased slightly at the higher soil moisture levels in both the cultivars. Cultivars differed in time to 50% storage root initiation and the storage root developmental rate. Soil moisture optima for storage root initiation were 0.168 and 0.199 m<jats:sup>3</jats:sup>·m<jats:sup>−3</jats:sup> soil, equivalent to 63% and 75% field capacity for cultivars Beauregard and Evangeline, respectively. The data and the inferences derived from the functional algorithms developed in this study could be used to advise growers to schedule irrigation more precisely, make planting decisions based on available soil moisture, and to develop sweetpotato crop models for field applications.</jats:p>

Genotype × Environment Interactions for East African Orange‐Fleshed Sweetpotato Clones Evaluated across Varying Ecogeographic Conditions in Uganda

“…The low yields obtained at Namulonge Season 2 are probably a result of poor rains at the beginning of the season. Enough soil moisture is critical for sweetpotato vine establishment and initiation of storage root forming roots (Gajanayaka et al, 2013). Overall, except for Mobuku, rains were normal and higher during the first season than the second season for all the sites.…”

S-metolachlor and rainfall effects on sweetpotato (Ipomoea batatas L. [Lam]) growth and development

“…The transformation of adventitious roots into storage roots starts around 2 weeks after transplanting of slips in the field (Togari, 1950;Lowe and Wilson, 1974;Firon et al, 2009;Villordon et al, 2010). Thus, adverse environmental factors such as moisture stress (Gajanayake et al, 2013), unfavorable temperature and management including application of herbicides for the control of weeds during this stage may have detrimental effects on final sweetpotato SR quantity and quality. In recent years, attempts have been initiated to develop gene transfer technology to improve environmental stress tolerance of sweetpotato crop plants and thereby reducing the loss of crop production due to adverse climatic and soil conditions (Kasukabe et al, 2006).…”

Quantifying Storage Root Initiation, Growth, and Developmental Responses of Sweetpotato to Early Season Temperature

“…Therefore, any decline in storage root initiation, growth, and foliage growth could not be expected due to shortage of N in the plants. In other experiments where N or water deficits are variables, storage initiation and subsequent bulking were affected (Villagarcia et al, 1998; Gajanayake et al, 2013, Villordon et al, 2013).…”

“…[1]; Fig. 1) using SigmaPlot 11.0 (Systat Software, Inc., San Jose, CA) as described by Gajanayake et al (2013). …”