Sweetpotato Injury Research Articles

Safety and efficacy of linuron with or without an adjuvant or S-metolachlor for POST control of Palmer amaranth (Amaranthus palmeri) in sweetpotato

AbstractField studies were conducted to evaluate linuron for POST control of Palmer amaranth in sweetpotato to minimize reliance on protoporphyrinogen oxidase (PPO)-inhibiting herbicides. Treatments were arranged in a two by four factorial in which the first factor consisted of two rates of linuron (420 and 700 g ai ha−1), and the second factor consisted of linuron applied alone or in combinations of linuron plus a nonionic surfactant (NIS; 0.5% vol/vol), linuron plus S-metolachlor (800 g ai ha−1), or linuron plus NIS plus S-metolachlor. In addition, S-metolachlor alone and nontreated weedy and weed-free checks were included for comparison. Treatments were applied to ‘Covington’ sweetpotato 8 d after transplanting (DAP). S-metolachlor alone provided poor Palmer amaranth control because emergence had occurred at applications. All treatments that included linuron resulted in at least 98% and 91% Palmer amaranth control 1 and 2 wk after treatment (WAT), respectively. Including NIS with linuron did not increase Palmer amaranth control compared to linuron alone, but it resulted in greater sweetpotato injury and subsequently decreased total sweetpotato yield by 25%. Including S-metolachlor with linuron resulted in the greatest Palmer amaranth control 4 WAT, but increased crop foliar injury to 36% 1 WAT compared to 17% foliar injury from linuron alone. Marketable and total sweetpotato yields were similar between linuron alone and linuron plus S-metolachlor or S-metolachlor plus NIS treatments, though all treatments resulted in at least 39% less total yield than the weed-free check resulting from herbicide injury and/or Palmer amaranth competition. Because of the excellent POST Palmer amaranth control from linuron 1 WAT, a system that includes linuron applied 7 DAP followed by S-metolachlor applied 14 DAP could help to extend residual Palmer amaranth control further into the critical period of weed control while minimizing sweetpotato injury.

Impact of tank mixing plant hormones with bentazon and mesotrione on sweetpotato injury and weed control

AbstractDue to excessive crop damage, currently, there are no selective postemergent (POST) herbicides registered for sweetpotato [Ipomoea batatas (L.) Lam] to control broadleaves and nutsedge species. Expansion of bentazon and mesotrione herbicide labels to include sweetpotato would be beneficial for growers. Two experiments were conducted. The first evaluated the dose response of sweetpotato cultivars Beauregard and Covington to bentazon (514, 1,028, and 1,542, g a.i. ha–1) and mesotrione (105, 210, and 315 g a.i. ha–1) when melatonin, 24‐epibrassinolide, or ascorbic acid (AsA) were included in the tank mix. The second experiment evaluated the efficiency of bentazon and mesotrione for control of yellow nutsedge (Cyperus esculentus L.) and Palmer amaranth (Amaranthus palmeri S. Wats.), when different doses of melatonin, 24‐epibrassinolide, or AsA were added to each herbicide. In the first experiment, when treated with herbicide alone, Beauregard exhibited injury levels lower than Covington for both herbicides. No injury was observed when plants were treated with plant hormones or AsA alone. At the lowest dose of bentazon and mesotrione, the addition of AsA or plant hormones in the tank mix significantly reduced percentage injury and increased plant tolerance, requiring higher doses of herbicide to cause 10, 20, and 30% injury. In the second experiment, the addition of plant hormones and AsA in the tank mix had no antagonistic effect on herbicide effectiveness, exhibiting similar levels of injuries as herbicides application alone. These results suggest that the use of plant hormones and AsA could improve sweetpotato tolerance to POST applications of bentazon and mesotrione without reducing herbicide effectiveness.

In Vitro Safening of Bentazon by Melatonin in Sweetpotato (Ipomoea batatas)

Weed competition is a main factor limiting sweetpotato [Ipomoea batatas (L.) Lam] production. Yellow nutsedge (Cyperus esculentus L.) is a problematic weed to control due to its ability to quickly infest a field and generate high numbers of tubes and shoots. Compounding this is the lack of a registered herbicide for selective postemergence control of yellow nutsedge. Research was conducted to evaluate the bentazon dose response of two sweetpotato cultivars and one advanced clone and to evaluate the plant hormone melatonin to determine its ability to safen bentazon post emergence. Bioassays using Murashige and Skoog (MS) media supplemented with melatonin (0.232 g a.i./L and 0.023 g a.i./L) and bentazon (0.24 g a.i./L) were conducted to evaluate the effect of bentazon on sweetpotato and to determine the interactive response of the Beauregard cultivar to bentazon and exogenous applications of melatonin. Beauregard swas the most tolerant cultivar and required dosages of bentazon that were two-times higher to cause the same injury compared with other cultivars. MS media containing melatonin and bentazon showed fewer injuries and higher plant mass than plants treated with bentazon alone. These results indicate that sweetpotato injury caused by bentazon may be reduced by melatonin.

Consumer Perception of Skinning Injury in Sweetpotatoes and Implications for Marketability: An Experimental Auction

Skinning of sweetpotato (Ipomoea batatas) storage roots is one of the greatest concerns of sweetpotato producers. Although skinning injury is very common, the severity of the injury can vary widely. At an undefined threshold, sweetpotatoes with skinning injury are no longer sold for fresh consumption. The objectives of this study were to examine how skinning injury influences consumers’ willingness-to-pay (WTP) for sweetpotatoes and to identify differences in valuations when the extent of skinning injury is labeled. Image analysis was used to quantify skinning injury and then an incentive-compatible, nonhypothetical laboratory experimental auction was conducted to collect data on consumers’ WTP for five categories of sweetpotatoes: 0% to <1% skinning injury, 1.0% to 3.0%, 3.1% to 5.0%, 5.1% to 7.5%, and 7.6% to 10.0%. On average, consumers were willing to pay the most for sweetpotatoes with 0% to <1% skinning injury (up to $1.51/lb to $1.67/lb) and the least for sweetpotatoes with 7.6% to 10% (up to $0.76/lb to $0.85/lb), yet mean WTP values were nonzero for all skinning levels. Moreover, when the extent of skinning was labeled (relative to when they bid blindly), consumers were willing to pay price premiums for sweetpotatoes with low skinning injury levels (0% to 5%) and discounted sweetpotatoes with the highest skinning injury level (7.6% to 10.0%), suggesting that skinning levels of 7.6% and above may not be acceptable by consumers.

Response of Palmer Amaranth and Sweetpotato to Flumioxazin/Pyroxasulfone

AbstractStudies were conducted to determine the tolerance of sweetpotato and Palmer amaranth control to a premix of flumioxazin and pyroxasulfone pretransplant (PREtr) followed by (fb) irrigation. Greenhouse studies were conducted in a factorial arrangement of four herbicide rates (flumioxazin/pyroxasulfone PREtr at 105/133 and 57/72 g ai ha–1,S-metolachlor PREtr 803 g ai ha–1, nontreated) by three irrigation timings [2, 5, and 14 d after transplanting (DAP)]. Field studies were conducted in a factorial arrangement of seven herbicide treatments (flumioxazin/pyroxasulfone PREtr at 40/51, 57/72, 63/80, and 105/133 g ha–1, 107 g ha–1flumioxazin PREtr fb 803 g ha–1S-metolachlor 7 to 10 DAP, and season-long weedy and weed-free checks) by three 1.9-cm irrigation timings (0 to 2, 3 to 5, or 14 DAP). In greenhouse studies, flumioxazin/pyroxasulfone reduced sweetpotato vine length and shoot and storage root fresh biomass compared to the nontreated check andS-metolachlor. Irrigation timing had no influence on vine length and root fresh biomass. In field studies, Palmer amaranth control was≥91% season-long regardless of flumioxazin/pyroxasulfone rate or irrigation timing. At 38 DAP, sweetpotato injury was≤37 and≤9% at locations 1 and 2, respectively. Visual estimates of sweetpotato injury from flumioxazin/pyroxasulfone were greater when irrigation timing was delayed 3 to 5 or 14 DAP (22 and 20%, respectively) compared to 0 to 2 DAP (7%) at location 1 but similar at location 2. Irrigation timing did not influence no.1, jumbo, or marketable yields or root length-to-width ratio. With the exception of 105/133 g ha–1, all rates of flumioxazin/pyroxasulfone resulted in marketable sweetpotato yield and root length-to-width ratio similar to flumioxazin fbS-metolachlor or the weed-free checks. In conclusion, flumioxazin/pyroxasulfone PREtr at 40/51, 57/72, and 63/80 g ha–1has potential for use in sweetpotato for Palmer amaranth control without causing significant crop injury and yield reduction.

Sweetpotato Response to Simulated Glyphosate Wick Drip

Field studies were conducted in 2009 at Clinton, NC and 2014 at Pontotoc, MS to determine the influence of simulated glyphosate drip on sweetpotato yield and quality. Treatments consisted of three glyphosate solution (140 g ae L–1) drip volumes (0.16, 0.32 and 0.48 ml) by four application timings [(4 wk after transplanting (WAP); 6 WAP; 8 WAP; and 4 WAP followed by (fb) 6 WAP fb 8 WAP]. A non-treated check was included for comparison. Visual sweetpotato injury consisted of chlorosis at the shoot tips approximately 1 wk after treatment fb necrosis and stunting. At 6 WAP and 8 WAP, sweetpotato injury following glyphosate applied 4 WAP was 71 and 65%, respectively. Injury from glyphosate applied 4 WAP fb 6 WAP was 78%. Injury from glyphosate applied 6 WAP was 26% at 8 WAP. In 2009, jumbo, no. 1, canner, and marketable yield of the non-treated check were two to three times greater than glyphosate treatments (0.16, 0.32, 0.48 ml). Likewise, yield of the non-treated check was substantially greater than those treated with 0.16 to 0.48 ml glyphosate solution in 2014. In 2009 and 2014, sweetpotato yield of all grades increased as glyphosate application timing was delayed. In 2009, no. 1 yield from glyphosate 8 WAP (8,210 kg ha–1) was similar to the non-treated check. In 2009, there were no cracked storage roots in the non-treated check. However, sweetpotatoes receiving 0.16 to 0.48 ml glyphosate solution displayed 8 to 17%, 11 to 18%, 5 to 13%, and 11 to 16% cracking (by weight) in jumbo, no. 1, canner, and marketable storage roots, respectively. Compared to the non-treated check, glyphosate applied 4 WAP, 6 WAP, or 4 WAP fb 6 WAP fb 8 WAP had a greater percentage of cracked marketable sweetpotato storage roots.

Rate and Application Timing Effects on Tolerance of Covington Sweetpotato to S-Metolachlor

Field studies were conducted in 2011 and 2012 at the Horticultural Crops Research Station near Clinton, NC, to determine ‘Covington' sweetpotato tolerance to S-metolachlor rate and application timing. Treatments were a factorial arrangement of four S-metolachlor rates (0, 1.1, 2.2, or 3.4 kg ai ha−1) and six application timings (0, 2, 5, 7, 9, or 14 d after transplanting [DAP]). Immediately following application, 1.9 cm of irrigation was applied to individual plots. Sweetpotato injury was minimal for all treatments (≤ 10%). No. 1 grade sweetpotato yield displayed a negative linear response to S-metolachlor rate, and decreased from 25,110 to 20,100 kg ha−1 as S-metolachlor rate increased from 0 to 3.4 kg ha−1. Conversely, no. 1 sweetpotato yield displayed a positive linear response to S-metolachlor application timing and increased from 19,670 to 27,090 kg ha−1 as timing progressed from 0 to 14 DAP. Total marketable sweetpotato yield displayed a quadratic response to both S-metolachlor application rate and timing. Total marketable yield decreased from 44,950 to 30,690 kg ha−1 as S-metolachlor rate increased from 0 to 3.4 kg ha−1. Total marketable yield increased from 37,800 to 45,780 kg ha−1 as application timing was delayed from 0 to 14 DAP. At 1.1 kg ha−1S-metolachlor, sweetpotato storage root length to width ratio displayed a quadratic relationship to application timing and increased from 1.87 to 2.23 for applications made 0 to 14 DAP. At 2.2 kg ha−1 of S-metolachlor, sweetpotato length to width ratio displayed a quadratic response to application timing, increased from 1.57 to 2.09 for 0 to 10 DAP, and decreased slightly from 2.09 to 2.03 for 10 to 14 DAP. Application timing did not influence length to width ratio of sweetpotato storage roots for those plots treated with S-metolachlor at either 0 or 3.4 kg ha−1.

Herbicide-Based Weed Management Programs for Palmer Amaranth (Amaranthus palmeri) in Sweetpotato

Studies were conducted in 2010 and 2011 to determine the effect of herbicide-based Palmer amaranth management systems in ‘Covington' sweetpotato. Treatments consisted of three herbicide application times. Pretransplant applications were flumioxazin at 107 g ai ha−1, fomesafen at 280 g ai ha−1, flumioxazin at 70 g ha−1plus pyroxasulfone at 89 g ai ha−1, or no herbicide. A second herbicide application was applied within 1 d after transplanting (DAP) and consisted ofS-metolachlor at 800 g ai ha−1, clomazone at 630 g ai ha−1, or no herbicide. Two weeks after planting (WAP) plots receivedS-metolachlor at 800 g ha−1, metribuzin at 140 g ai ha−1, a tank mix ofS-metolachlor at 800 g ha−1plus metribuzin at 140 g ha−1, hand-weeding followed by (fb)S-metolachlor at 800 g ha−1, or no herbicide. Crop tolerance, Palmer amaranth control, and sweetpotato yield in systems containing fomesafen pretransplant were similar to flumioxazin-containing systems. Systems containing flumioxazin plus pyroxasulfone pretransplant resulted in increased crop stunting and decreased sweetpotato yield in 2010, compared with systems containing flumioxazin or fomesafen, but were similar to systems with flumioxazin or fomesafen in 2011. In 2010, systems containingS-metolachlor applied within 1 DAP resulted in increased sweetpotato injury, similar Palmer amaranth control, and reduced no. 1, jumbo, and total sweetpotato yield, compared with systems with clomazone. In 2011, systems containing clomazone were more injurious to sweetpotato than systems receivingS-metolachlor, but Palmer amaranth control and sweetpotato yield were similar. Systems containing metribuzin 2 WAP resulted in increased sweetpotato injury and Palmer amaranth control (in 2010) but similar no. 1 and total sweetpotato yields, compared with systems containingS-metolachlor at 2 WAP. Hand-weeding fbS-metolachlor provided greater Palmer amaranth control and no. 1 sweetpotato yield than did systems ofS-metolachlor without a preceding hand-weeding event in 2010.

Identification and Expression of Skinning Injury-responsive Genes in Sweetpotato

Skinning injury in sweetpotatoes (Ipomoea batatas) is responsible for significant postharvest loss resulting from storage diseases and weight loss. Unfortunately, there is no report on the genes involved in wound healing of sweetpotato and a better understanding will facilitate improved breeding strategies. An annealing control primer (ACP) system was used to identify genes expressed after skinning injury of sweetpotato cultivar LA 07-146 storage roots. Using 20 ACPs, 63 differentially expressed genes (DEGs) were identified. Functional annotation of the DEGs revealed that genes previously shown to respond to dehydration, those involved in wounding response, and the lignin and suberin biosynthesis pathways were induced in response to skinning. Expression analysis of 18 DEGs through quantitative reverse transcription–polymerase chain reaction (PCR) showed that DEGs involved in lignin and suberin pathways were up-regulated after 8 and 12 hours of skinning. Other genes showed up- or down-regulation in their transcript abundance depending on the time the storage root was sampled after intentional skinning. The genes up-regulated in response to skinning may be useful to identify expression markers for screening sweetpotato lines tolerant to skinning injury in breeding programs.

Efficacy and Tolerance of Flumioxazin on Sweetpotato (Ipomoea batatas)

Experiments were conducted at three locations in Louisiana in 2002 and 2003 to evaluate flumioxazin (36, 72, or 109 g ai/ha) applied pretransplant (PRE) or post-transplant (POST) to sweetpotato. All treatments were applied immediately before or after sweetpotato transplanting to weed-free beds. PRE applications caused 4% or less injury with any rate of flumioxazin at 9 or 18 d after transplanting (DATr) compared with 18 to 20% injury at 9 DATr and 6 to 14% at 18 DATr with 72 or 109 g/ha POST, respectively. Injury from PRE applications of flumioxazin were not different from injury with clomazone (840 g ai/ha) applied POST. Injury at Chase, LA, in 2002 was 8% and less with flumioxazin PRE, but 35 to 83% with flumioxazin POST and appeared to be due to the use of greenhouse-grown cuttings instead of field-grown cuttings, which were used in the other two experiments. There was no interaction between experiments for sweetpotato yield. Plots treated with flumioxazin PRE or 36 g/ha POST yielded greater than sweetpotato treated with clomazone for U.S. No. 1 and 2 grade yield as well as total marketable yield. No differences were observed in yellow nutsedge control with any rate of flumioxazin. At 34 or 50 DATr, flumioxazin controlled yellow nutsedge 73 to 85% with 72 or 109 g/ha applied PRE or POST. Flumioxazin, regardless of application timing or rate, controlled carpetweed and spiny amaranth at least 86%. A similar experiment in Mississippi evaluated tank-mixes of flumioxazin (36, 72, or 109 g/ha) and clomazone (840 g/ha) applied PRE or POST. No sweetpotato injury was observed with flumioxazin PRE. However, injury from flumioxazin POST increased with increased rates (18 to 50% at 18 DATr and 16 to 93% at 25 DATr). Weed control was greater than 80% with all treatments.

Sweet Potato (Ipomoea batatas) Clones Differ in Response to Ethyl-Metribuzin

Six commercial sweet potato clones were evaluated in field and greenhouse studies for the ethylthio analog of metribuzin (ethyl-metribuzin) tolerance. ‘Southern Delite’ was most tolerant in field studies and ‘Cordner’ the most tolerant in the greenhouse. ‘White Delite’ was the most susceptible clone in the field and greenhouse. Considering the rates used in this study, all the sweet potato clones generally were tolerant to ethyl-metribuzin. When averaged over all clones, sweet potato injury increased as the ethyl-metribuzin rate increased from 1.6 to 3.2 kg/ha but injury decreased as the season progressed and was minimal in late season. Ethyl-metribuzin did not reduce marketable yields at Clayton, NC. At Clinton, NC, ethiozin PRE, POST, or PRE followed by POST at 3.2 kg/ha or PRE at 1.6 kg/ha reduced yield.

Sweet Potatoes (Ipomoea batatas) Differ in Response to Bentazon

Selected sweet potato clones were evaluated in greenhouse and field trials to identify clones with superior tolerance to bentazon. ‘Julian’ and NC 1519 were the most tolerant in the greenhouse. ‘Sweet Red’ exhibited foliar injury in the field, but yields were not reduced. The clone 79-BM-17 was equally tolerant in the field as Sweet Red, but in the greenhouse exhibited only intermediate tolerance. ‘Jewel,’ a widely grown commercial cultivar, was sensitive to bentazon in both the greenhouse and field. When averaged over all clones sweet potato injury increased as bentazon rate was increased from 1.1 to 2.2 kg ai ha-1, but it decreased as the season progressed. Bentazon did not reduce marketable yields at Clayton, NC. Bentazon as a split or late application at the 2.2 kg ha-1rate, reduced yields at Clinton, NC. Percent culls among bentazon treatments did not differ at either location.

Mechanism of Chilling Injury in Sweet Potatoes

1. The ratio of the unsaturated C16, C18 and C20 fatty acids to total fatty acids was higher in the crude mitochondrial fraction from chilling-stored sweet potatoes 4 days after transfer to 0°C than from healthy sweet potatoes; and, the difference became greater at periods of 7, 10, and 14 days. However, this difference was shown to be mainly due to the decrease during chilling storage in contamination with lauric acid, isopalmitic acid (presumable) and erucic acid (presumable) contained in the latex body fraction.2. There were no significant changes in the composition and amounts of fatty acids in the 0 ~ 700 × g fraction, the microsomal fraction, and the supernatant fraction, when sweet potatoes were given a chilling treatment.3. The ratio of C16, C18 and C20 unsaturated fatty acids to total fatty acids in the pure mitochondrial fraction from sweet potatoes was not changed significantly as a result of chilling storage. However, the ratio of lipid-phosphorus (lipid-P) to acid insoluble nitrogen (acid ins...

Mechanism of Cold Injury in Sweet Potatoes

The biochemical mechanism of cold injury occurring in sweet potatoes stored at 0°C was studied. Oxygen uptake and RC ratio of mitochondria from sweet potatoes kept at 0°C for about 15 days declined when succinate or malate was used as substrate. As sweet potatoes suffered slight cold injury, a decrease in the respiratory rate of state 3 of mitochondria was observed. This decrease could be restored approximately to the level of that of healthy sweet potato mitochondria by the addition of cytochrome c when succinate was used as substrate. When sweet potatoes suffered severe damage, only partial recovery was observed with cytochrome c. While it was found that the respiratory rate in state 3 of mitochondria from chilled sweet potatoes was less inhibited by cyanide than that of healthy sweet potato mitochondria, the inhibition could be restored to that of healthy sweet potato mitochondria by the addition of cytochrome When malate was used as substrate, no effect of cytochrome c and NADH2 was observed. There was no difference between chilled and healthy sweet potato mitochondria in enzyme activities of the electron transport system except for malate dehydrogenase.

Mechanism of Chilling Injury in Sweet Potatoes

1. Both amounts of lipid phosphorus and acid-insoluble nitrogen in the mitochondrial fraction from chilling-injured sweet potatoes (var. Okinawa 100) were larger than in the fraction from healthy sweet potatoes. The N-amount appeared to be increased more by chilling-injury than the P-amount.2. Sweet potato, a tropical plant, showed lower value of the degree of unsaturation of fatty acids in mitochondrial fraction than white potato, a temperate-zone plant.3. The amount of unsaturated fatty acids of C16, C18 and C20 as percentage of the total fatty acids was higher in mitochondrial fractions from chilling-injured sweet potatoes (var. Okinawa 100 and var. Norin 1) than in mitochondrial fractions from healthy sweet potatoes. However, in the case of white potato mitochondrial fraction no detectable difference was observed between storage at 0~1°C and at 10~14°C.

Biochemical Studies of Chilling Injury in Sweetpotatoes.

Biochemical Studies of Chilling Injury in Sweetpotatoes.