Drought, Low Nitrogen Stress, and Ultraviolet-B Radiation Effects on Growth, Development, and Physiology of Sweetpotato Cultivars during Early Season

Abstract

Drought, ultraviolet-B (UV-B), and nitrogen stress are significant constraints for sweetpotato productivity. Their impact on plant growth and development can be acute, resulting in low productivity. Identifying phenotypes that govern stress tolerance in sweetpotatoes is highly desirable to develop elite cultivars with better yield. Ten sweetpotato cultivars were grown under nonstress (100% replacement of evapotranspiration (ET)), drought-stress (50% replacement of ET), UV-B (10 kJ), and low-nitrogen (20% LN) conditions. Various shoot and root morphological, physiological, and gas-exchange traits were measured at the early stage of the crop growth to assess its performance and association with the storage root number. All three stress factors caused significant changes in the physiological and root- and shoot-related traits. Drought stress reduced most shoot developmental traits (29%) to maintain root growth. UV-B stress increased the accumulation of plant pigments and decreased the photosynthetic rate. Low-nitrogen treatment decreased shoot growth (11%) and increased the root traits (18%). The highly stable and productive cultivars under all four treatments were identified using multitrait stability index analysis and weighted average of absolute scores (WAASB) analyses. Further, based on the total stress response indices, ‘Evangeline’, ‘O’Henry’, and ‘Beauregard B-14’ were identified as vigorous under drought; ‘Evangeline’, ‘Orleans’, and ‘Covington’ under UV-B; and ‘Bonita’, ‘Orleans’, and ‘Beauregard B-14’ cultivars showed greater tolerance to low nitrogen. The cultivars ‘Vardaman’ and ‘NC05-198’ recorded a low tolerance index across stress treatments. This information could help determine which plant phenotypes are desirable under stress treatment for better productivity. The cultivars identified as tolerant, sensitive, and well-adapted within and across stress treatments can be used as source materials for abiotic stress tolerance breeding programs.

Low- and High-Temperature Phenotypic Diversity of Brassica carinata Genotypes for Early-Season Growth and Development

“…Furthermore, individual genotype stress response index of the shoot, root, and physiological parameters or cumulative temperature response index was used to identify potential low- and high-temperature tolerant carinata genotypes ( Figure 6 ), similar to other recent studies ( Bheemanahalli et al, 2021 ; Reddy et al, 2021 ; Ramamoorthy et al, 2022 ). Among the genotypes studied, genotype AX17009 recorded a superior root system (no change in roots between low and optimum temperatures) coupled with shoot and physiology responses than the sensitive genotype (AX17010) at the early vegetative stage.…”

“…Cumulative low-temperature response index (CLTRI) and cumulative high-temperature response index (CHTRI) values were calculated using the standardized vigor index ( Wijewardana et al, 2015 ; Ramamoorthy et al, 2022 ). Initially, the individual stress response index (ISRI) for low temperature was calculated as the value of a parameter (P l ) for a given genotype at the low temperature divided by the value of the same parameter at the optimum temperature (P o ; Equation 1).…”

“…Several studies used variations in morpho-physiological and yield responses to evaluate stress tolerance in oilseed crops: canola ( Elferjani and Soolanayakanahally, 2018 ), peanut ( Arachis hypogaea L.) ( Kakani et al, 2002 ), and cotton ( Gossypium hirsutum ) ( Reddy et al, 2020 ). In addition, to shoot traits, root traits have been used to investigate crop responses to a range of stresses, including drought ( Raju et al, 2014 ), low temperature ( Reddy et al, 2021 ), high temperature ( Alsajri et al, 2019 ), nutrient ( Jia et al, 2022 ), salinity ( Kakar et al, 2019 ), waterlogging ( Walne and Reddy, 2021 ), and UV-B ( Ramamoorthy et al, 2022 ). These studies identified morpho-physiological traits enabling the selection of superior stress-tolerant genotypes at the early growth stage in rice ( Kakar et al, 2019 ; Reddy et al, 2021 ), corn ( Zea mays ) ( Wijewardana et al, 2015 ), sweet potato ( Ipomoea batatas ) ( Ramamoorthy et al, 2022 ), and cotton ( Brand et al, 2016 ).…”

“…In addition, to shoot traits, root traits have been used to investigate crop responses to a range of stresses, including drought ( Raju et al, 2014 ), low temperature ( Reddy et al, 2021 ), high temperature ( Alsajri et al, 2019 ), nutrient ( Jia et al, 2022 ), salinity ( Kakar et al, 2019 ), waterlogging ( Walne and Reddy, 2021 ), and UV-B ( Ramamoorthy et al, 2022 ). These studies identified morpho-physiological traits enabling the selection of superior stress-tolerant genotypes at the early growth stage in rice ( Kakar et al, 2019 ; Reddy et al, 2021 ), corn ( Zea mays ) ( Wijewardana et al, 2015 ), sweet potato ( Ipomoea batatas ) ( Ramamoorthy et al, 2022 ), and cotton ( Brand et al, 2016 ). Likewise, variations in stress tolerance among carinata genotypes have been reported ( Angadi et al, 2000 ; Gesch et al, 2019 ; Zoong Lwe et al, 2021 ).…”

Multiple Facets of Nitrogen: From Atmospheric Gas to Indispensable Agricultural Input

“…Reports have demonstrated that NUE is controlled genetically, and this complex trait allows optimizing the use of N available to the plant. NUE is equally important when plants experience nutrients shortage or unavailability caused by environmental stresses, such as drought [ 153 , 217 , 218 ], salinity [ 219 ], heat stress [ 220 ], or heavy-metal toxicity, whereby the acquisition of N is either restricted or impaired. In addition to the well-characterized NO 3 or NH 4 transport- and assimilation-related genes [ 221 ], N remobilization (one of the components of NUE) from NO 3 stored in the vacuole regulated through a process known as autophagy carries the potential to salvage poor N supply or transport within the plant, and it offers an alternative for balanced plant productivity and reduced GHG emissions [ 220 , 222 , 223 , 224 ].…”