@article{shekoofa_sinclair_2020, title={Abscisic Acid and Sulfate Offer a Possible Explanation for Differences in Physiological Drought Response of Two Maize Near-Isolines}, volume={9}, ISSN={["2223-7747"]}, DOI={10.3390/plants9121713}, abstractNote={The hypothesis was tested that differences in response to water-deficits between low osmotic potential (LOP) and high osmotic potential (HOP) maize (Zea mays L.) near-isolines were associated with differences in transpiration rate sensitivity to abscisic acid (ABA) and/or sulfate. In a series of four experiments, decreases in transpiration rate (DTR) of whole plants and fully expanded leaves were measured in response to treatments of 1.0 µM ABA and 15 mM MgSO4 singly and in combination following long (2 day) and short (180 min) exposures. There was little evidence that intact plants grown on soil were responsive to the treatments. For hydroponically grown plants subjected to long exposure, there was similarly no response to treatments. Further, the short exposure of hydroponically grown plants to solely ABA or a combination of chemicals resulted in no sensitivity in DTR for either of the near-isolines. On the other hand, when these plants were fed sulfate, the transpiration was stimulated by about 20% for the LOP and 60% for the HOP. Detached leaves proved to be the most sensitive to treatment. Treatment with the two chemicals singly caused essentially equivalent DTR in the two near-isolines. However, treatment with ABA plus sulfate resulted in different DTR between the two near-isolines with values of 65% for the LOP and 16% for the HOP near-isoline. Overall, these results showed that the short exposure treatment of hydroponically grown plants or detached leaves supported the hypothesis of different transpiration rate sensitivities of the near-isolines in response to ABA and sulfate treatments.}, number={12}, journal={PLANTS-BASEL}, author={Shekoofa, Avat and Sinclair, Thomas R.}, year={2020}, month={Dec} }
 @article{beseli_shekoofa_ali_sinclair_2020, title={Temporal water use by two maize lines differing in leaf osmotic potential}, volume={60}, ISSN={["1435-0653"]}, DOI={10.1002/csc2.20062}, abstractNote={Abstract Two lines of maize which had different levels of expressions of leaf osmotic potential (OP) under water‐deficit conditions in the field were previously found to differ in leaf area duration and water extraction at soil depths greater than 0.80 m. In the current study, the hypothesis was explored that the difference in leaf OP between the two lines was associated with differences in transpiration rate which in turn had a major effect on the temporal dynamics of soil water use. The line with the lowest (most negative) OP in the early stages of the soil drying cycle was found to have the greatest transpiration rate and delayed wilting which was consistent with the original field observations. However, with further soil drying, the line with higher OP was able to sustain transpiration over a longer time period and actually reached the end point of transpirable soil water at a later date. The results of these experiments highlighted the necessity of accounting for temporal dynamics when interpreting crop water use in response to soil drying, particularly when comparing genotypes with differing OP.}, number={2}, journal={CROP SCIENCE}, author={Beseli, Amber L. and Shekoofa, Avat and Ali, Mujahid and Sinclair, Thomas R.}, year={2020}, pages={945–953} }
 @article{pradhan_shekoofa_sinclair_2019, title={Temperature effect on peanut (Arachis hypogaea L.) transpiration response to vapor pressure deficit and its recovery}, volume={33}, ISSN={["1542-7536"]}, DOI={10.1080/15427528.2018.1552900}, abstractNote={Partial stomata closure under high atmospheric vapor pressure deficit (VPD) has been identified as a means to conserve soil water to allow sustained crop physiological activity late in the growing season, especially during reproductive growth. This trait has been identified as potentially being particularly important in peanut (Arachis hypogaea L.) since peanut is commonly grown on sandy soils under variable rainfall conditions. While 11 peanut genotypes had been previously identified as expressing limited-transpiration trait (TRlim) at 32°C, there is no information on their response to VPD at higher temperatures to which peanut may be exposed. This study documented the response of these 11 genotypes to VPD when subjected to increasing temperatures at 2°C intervals from 32°C to 38°C. Nine of the 11 genotypes lost expression of the TRlim trait within this temperature range. Only two genotypes (N013042ol and G644) were able to sustain the TRlim trait at 38°C. Recovery of expression of the TRlim trait following the loss of the trait at high temperature also varied among genotypes. Three genotypes that lost expression of TRlim at 36°C were returned to 32°C to determine the ability to recover the trait. Two genotypes showed full recovery of TRlim within 1 or 2 days, whereas the third showed no recovery across 3 days. This study provides useful information on genotypic variability in transpiration response to VPD under high temperatures that can be applied in developing cultivars that are better suited to water-limited conditions.}, number={2}, journal={JOURNAL OF CROP IMPROVEMENT}, author={Pradhan, Deepti and Shekoofa, Avat and Sinclair, Thomas R.}, year={2019}, month={Mar}, pages={177–186} }
 @misc{shekoofa_sinclair_2018, title={Aquaporin Activity to Improve Crop Drought Tolerance}, volume={7}, ISSN={["2073-4409"]}, DOI={10.3390/cells7090123}, abstractNote={In plants, aquaporins (AQP) occur in multiple isoforms in both plasmalemma and tonoplast membranes resulting in regulation of water flow in and out of cells, and ultimately, water transfer through a series of cells in leaves and roots. Consequently, it is not surprising that physiological and molecular studies have identified AQPs as playing key roles in regulating hydraulic conductance in roots and leaves. As a result, the activity of AQPs influences a range of physiological processes including phloem loading, xylem water exit, stomatal aperture and gas exchange. The influence of AQPs on hydraulic conductance in plants is particularly important in regulating plant transpiration rate, particularly under conditions of developing soil water-deficit stress and elevated atmospheric vapor pressure deficit (VPD). In this review, we examine the impact of AQP activity and hydraulic conductance on crop water use and the identification of genotypes that express soil water conservation as a result of these traits. An important outcome of this research has been the identification and commercialization of cultivars of peanut (Arachis hypogaea L.), maize (Zea mays L.), and soybean (Glycine max (Merr) L.) for dry land production systems.}, number={9}, journal={CELLS}, author={Shekoofa, Avat and Sinclair, Thomas R.}, year={2018}, month={Sep} }
 @article{sinclair_shekoofa_isleib_balota_zhang_2018, title={Identification of Virginia-Type Peanut Genotypes for Water-Deficit Conditions Based on Early Decrease in Transpiration Rate with Soil Drying}, volume={58}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2018.05.0293}, abstractNote={Early decrease in transpiration rate as soil progressively dries allows soil water conservation for sustained crop physiological activity as water deficit continues to increase. This trait is likely to be particularly useful for peanut ( Arachis hypogaea L.), which is often grown on sandy soil where water deficit can develop quickly. This study was undertaken to identify peanut genotypes that express this water conservation trait and to determine if it confers a yield advantage. Three approaches were taken. (i) Two populations of peanut were tested in controlled environments during progressive soil drying. Especially high thresholds of soil water content for initiation of decrease in transpiration rate were identified in three lines in each of the breeding populations. (ii) Nine genotypes were identified for field observation of leaf wilting under rain shelters and in the open field. There was a correspondence between the early decrease in transpiration rate with soil drying and delayed wilting. (iii) Yield trial data for three genotypes were examined to identify those lines that consistently had higher yields than the commercial check cultivar ‘Bailey’, particularly at low yield levels commonly associated with drier conditions. When expressing total seed yield in monetary return, these breeding lines had yield values that were consistently superior to Bailey below the US$2000 ha −1 threshold. Based on the three experimental approaches, N12006ol consistently expressed a desired response of early decrease in transpiration rate with soil drying, delayed wilting in the field when soil water deficit developed, and greater yield value than Bailey in low‐yield environments.}, number={6}, journal={CROP SCIENCE}, author={Sinclair, Thomas R. and Shekoofa, Avat and Isleib, Thomas G. and Balota, Maria and Zhang, Hao}, year={2018}, pages={2607–2612} }
 @article{sinclair_pradhan_shekoofa_2018, title={Inheritance of limited-transpiration trait in peanut: an update}, volume={32}, ISSN={["1542-7536"]}, DOI={10.1080/15427528.2017.1420000}, abstractNote={Peanut (Arachis Hypogeae L.) is commonly grown on sandy soil and in environments with intermittent rainfall, both of which can lead to soil water-deficit. Limited transpiration (LT) under elevated vapor pressure deficit (VPD) can result in water conservation, allowing sustained physiological activity later in the season during reproductive development. The objective of this study was to expand the number of progeny lines phenotyped for expression of the LT trait from the mating of Tifrunner (LT trait not expressed) × NC 3033 (LT trait expressed) to allow a preliminary examination of inheritance. Half of the 24 phenotyped lines expressed LT with their VPD threshold ranging from 2.16 to 3.38 kPa. Six of the 12 genotypes expressing LT had a threshold at 2.65 kPa or less, which is the range likely to be relevant in most peanut environments. These results, indicating epistatic inheritance, are supportive of LT expression in progeny lines at a reasonable frequency for relevant use in cultivar development for water-deficit conditions.}, number={2}, journal={JOURNAL OF CROP IMPROVEMENT}, author={Sinclair, Thomas R. and Pradhan, Deepti and Shekoofa, Avat}, year={2018}, pages={281–286} }
 @article{shekoofa_sinclair_aninbon_holbrook_isleib_ozias-akins_chu_2017, title={Expression of the limited-transpiration trait under high vapour pressure deficit in peanut populations: Runner and virginia types}, volume={203}, ISSN={["1439-037X"]}, DOI={10.1111/jac.12204}, abstractNote={Abstract Drought can be a critical limitation on peanut yield. A physiological trait that may help to ameliorate drought is limited transpiration ( TR lim ), defined as a limitation on further increases in transpiration rate ( TR ) under high vapour pressure deficit ( VPD ) conditions. The advantage of the TR lim trait is that it allows plant water conservation to increase soil water availability for use during late‐season drought. While this trait has been identified in peanut, there is no information of how readily the trait may be transfer to progeny lines. The objective of this study was to obtain preliminary information on the expression of the TR lim trait in two peanut progeny populations. One population was runner type of 88 RIL s derived from the mating of Tifrunner × NC 3033. The second set was selected for the virginia‐type phenotype of large pods obtained from mating of PI 585005 ( ICGV 86015) and N0808ol JCT , both of which expressed the TR lim trait. A two‐tier screen was applied to both populations. The initial screen was based on exposure of de‐rooted shoots to silver ions. Fifteen runner type and 12 virginia type were selected for direct measures of transpiration response to varying VPD . The results from each of the two populations showed that an effective expression of the TR lim trait occurred in about 30% of the progeny in each population. While these results do not offer a definitive index of inheritance, they do indicate that there appears to be a strong possibility of transferring the TR lim trait to progeny genotypes.}, number={4}, journal={JOURNAL OF AGRONOMY AND CROP SCIENCE}, author={Shekoofa, A. and Sinclair, T. R. and Aninbon, C. and Holbrook, C. C. and Isleib, T. G. and Ozias-Akins, P. and Chu, Y.}, year={2017}, month={Aug}, pages={295–300} }
 @misc{sinclair_devi_shekoofa_choudhary_sadok_vadez_riar_rufty_2017, title={Limited-transpiration response to high vapor pressure deficit in crop species}, volume={260}, ISSN={["1873-2259"]}, DOI={10.1016/j.plantsci.2017.04.007}, abstractNote={Water deficit under nearly all field conditions is the major constraint on plant yields. Other than empirical observations, very little progress has been made in developing crop plants in which specific physiological traits for drought are expressed. As a consequence, there was little known about under what conditions and to what extent drought impacts crop yield. However, there has been rapid progress in recent years in understanding and developing a limited-transpiration trait under elevated atmospheric vapor pressure deficit to increase plant growth and yield under water-deficit conditions. This review paper examines the physiological basis for the limited-transpiration trait as result of low plant hydraulic conductivity, which appears to be related to aquaporin activity. Methodology was developed based on aquaporin involvement to identify candidate genotypes for drought tolerance of several major crop species. Cultivars of maize and soybean are now being marketed specifically for arid conditions. Understanding the mechanism of the limited-transpiration trait has allowed a geospatial analyses to define the environments in which increased yield responses can be expected. This review highlights the challenges and approaches to finally develop physiological traits contributing directly to plant improvement for water-limited environments.}, journal={PLANT SCIENCE}, author={Sinclair, Thomas R. and Devi, Jyostna and Shekoofa, Avat and Choudhary, Sunita and Sadok, Walid and Vadez, Vincent and Riar, Mandeep and Rufty, Thomas}, year={2017}, month={Jul}, pages={109–118} }
 @article{sinclair_manandhar_shekoofa_rosas-anderson_bagherzadi_schoppach_sadok_rufty_2017, title={Pot binding as a variable confounding plant phenotype: theoretical derivation and experimental observations}, volume={245}, ISSN={["1432-2048"]}, DOI={10.1007/s00425-016-2641-0}, number={4}, journal={PLANTA}, author={Sinclair, Thomas R. and Manandhar, Anju and Shekoofa, Avat and Rosas-Anderson, Pablo and Bagherzadi, Laleh and Schoppach, Remy and Sadok, Walid and Rufty, Thomas W.}, year={2017}, month={Apr}, pages={729–735} }
 @article{shekoofa_rosas-anderson_carley_sinclair_rufty_2016, title={Limited transpiration under high vapor pressure deficits of creeping bentgrass by application of Daconil-Action (R)}, volume={243}, ISSN={["1432-2048"]}, DOI={10.1007/s00425-015-2417-y}, number={2}, journal={PLANTA}, author={Shekoofa, Avat and Rosas-Anderson, Pablo and Carley, Danesha S. and Sinclair, Thomas R. and Rufty, Thomas W.}, year={2016}, month={Feb}, pages={421–427} }
 @article{shekoofa_sinclair_messina_cooper_2016, title={Variation Among Maize Hybrids in Response to High Vapor Pressure Deficit at High Temperatures}, volume={56}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2015.02.0134}, abstractNote={ABSTRACT Temperature and vapor pressure deficit (VPD) are two important environmental factors influencing stomatal conductance and transpiration. A limited transpiration rate (TR lim ) trait expressed under high VPD has been shown to offer an approach to increase crop yield in water‐limited areas. The benefit of the TR lim trait is that it lowers the effective VPD under which plants lose water and so conserves soil water to support crop growth for use during drought periods later in the growing season. Previous studies at moderate temperatures (32°C and lower) identified 12 maize ( Zea mays L.) hybrids that express the TR lim trait. A critical question is whether the TR lim trait is also expressed by these hybrids under temperatures up to 38°C, which are relevant in environments where maize may be grown. Five hybrids failed to express the TR lim trait at 38°C but seven hybrids had sustained expression of the trait at 38°C. The loss of expression of the TR lim response in the five hybrids was found to occur in the very narrow range of temperature increase from 36 to 38°C. The genetic differences in water use among these maize hybrids could be useful in selecting hybrids that are especially well adapted for temperature conditions in a targeted production area.}, number={1}, journal={CROP SCIENCE}, author={Shekoofa, Avat and Sinclair, Thomas R. and Messina, Carlos D. and Cooper, Mark}, year={2016}, pages={392–396} }
 @article{shekoofa_rosas-anderson_sinclair_balota_isleib_2015, title={Measurement of Limited-Transpiration Trait under High Vapor Pressure Deficit for Peanut in Chambers and in Field}, volume={107}, ISSN={["1435-0645"]}, DOI={10.2134/agronj14.0570}, abstractNote={Drought is one of the most important environmental factors that limit crop production. Based on controlled‐environment studies, it has been hypothesized that a limited‐transpiration (TR lim ) trait under high vapor pressure deficit (VPD) is a mechanism for water conservation leading to yield increase under water‐deficit conditions. The current research objective was to compare expression of TR lim in peanut ( Arachis hypogaea L.) observed by whole‐plant measurements in controlled environments and by leaf gas exchange measurements on plants grown in the field. Six peanut genotypes with different breeding backgrounds, that is, wild‐type, commercial cultivars, and advanced breeding lines were studied. Differences were observed among genotypes in their expression of TR lim with increasing VPD in the controlled environment at 31/26°C. Within each breeding background, one genotype showed a linear increase in transpiration with increasing VPD while the other expressed the TR lim trait. In a second set of controlled environment experiments at 36/26°C, none of the six genotypes expressed the TR lim trait. In the field, again none of the genotypes expressed the TR lim trait. The temperature to which the plants were exposed between the two controlled environments and field trial appeared critical in the expression of the TR lim trait of three of the genotypes.}, number={3}, journal={AGRONOMY JOURNAL}, author={Shekoofa, Avat and Rosas-Anderson, Pablo and Sinclair, Thomas R. and Balota, Maria and Isleib, Thomas G.}, year={2015}, pages={1019–1024} }
 @article{shekoofa_emam_shekoufa_ebrahimi_ebrahimie_2014, title={Determining the Most Important Physiological and Agronomic Traits Contributing to Maize Grain Yield through Machine Learning Algorithms: A New Avenue in Intelligent Agriculture}, volume={9}, ISSN={["1932-6203"]}, DOI={10.1371/journal.pone.0097288}, abstractNote={Prediction is an attempt to accurately forecast the outcome of a specific situation while using input information obtained from a set of variables that potentially describe the situation. They can be used to project physiological and agronomic processes; regarding this fact, agronomic traits such as yield can be affected by a large number of variables. In this study, we analyzed a large number of physiological and agronomic traits by screening, clustering, and decision tree models to select the most relevant factors for the prospect of accurately increasing maize grain yield. Decision tree models (with nearly the same performance evaluation) were the most useful tools in understanding the underlying relationships in physiological and agronomic features for selecting the most important and relevant traits (sowing date-location, kernel number per ear, maximum water content, kernel weight, and season duration) corresponding to the maize grain yield. In particular, decision tree generated by C&RT algorithm was the best model for yield prediction based on physiological and agronomical traits which can be extensively employed in future breeding programs. No significant differences in the decision tree models were found when feature selection filtering on data were used, but positive feature selection effect observed in clustering models. Finally, the results showed that the proposed model techniques are useful tools for crop physiologists to search through large datasets seeking patterns for the physiological and agronomic factors, and may assist the selection of the most important traits for the individual site and field. In particular, decision tree models are method of choice with the capability of illustrating different pathways of yield increase in breeding programs, governed by their hierarchy structure of feature ranking as well as pattern discovery via various combinations of features.}, number={5}, journal={PLOS ONE}, author={Shekoofa, Avat and Emam, Yahya and Shekoufa, Navid and Ebrahimi, Mansour and Ebrahimie, Esmaeil}, year={2014}, month={May} }
 @article{shekoofa_balota_sinclair_2014, title={Limited-transpiration trait evaluated in growth chamber and field for sorghum genotypes}, volume={99}, ISSN={["1873-7307"]}, DOI={10.1016/j.envexpbot.2013.11.018}, abstractNote={Sorghum [Sorghum bicolor (L.) Moench] is commonly grown in water-limited environments throughout the world. Plant traits could be useful allowing for early-season water conservation so that more water is available for use later in the season when drought is most likely to develop. One trait that might result in early-season water conservation is the expression of a limited-transpiration trait defined as a limitation on further increases in transpiration rate (TR) under high vapor pressure deficit (VPD) conditions. The objective of this study was to compare the expression of the limited-TR trait measured for nine sorghum genotypes under both controlled chamber and field conditions. In the growth chamber, plant TR was measured over a range of imposed VPD to provide a direct measure of plant transpiration under high VPD. In the field, stomatal conductance (gs) was measured over the daily cycle, which resulted in a range of ambient VPD. A decrease in gs under high VPD was evidence of the limited-TR trait. This study identified three sorghum genotypes (DKS 36-06, DKS 44-20, and DKS 54-00) that did not show any limitation on water loss at high VPD in either the greenhouse or field. On the other hand, four genotypes (BTX 2752, SC 599, SC 982, and B 35) exhibited the limited-TR trait in the growth chamber with breakpoints in response to VPD at values of 2.33 kPa and above. These four genotypes also expressed a breakpoint in gs in response to increasing VPD in the field. Two genotypes (TX ARG 1, TX 436) that differed between the growth chamber and field showed consistency in response on close examination of the field results. The overall general correspondence within genotypes between the controlled chamber and the field in expression or lack of expression of a breakpoint in response to increasing VPD demonstrated the possibility of selecting genotypes for the TRlim trait under differing environmental conditions.}, journal={ENVIRONMENTAL AND EXPERIMENTAL BOTANY}, author={Shekoofa, A. and Balota, M. and Sinclair, T. R.}, year={2014}, month={Mar}, pages={175–179} }
 @article{shekoofa_devi_sinclair_holbrook_isleib_2013, title={Divergence in Drought-resistance Traits among Parents of Recombinant Peanut Inbred Lines}, volume={53}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2013.03.0153}, abstractNote={ABSTRACT Peanut ( Arachis hypogaea L.) is often grown in climates of intermittent drought on sandy soils. Plants expressing water‐conservative traits would minimize exposure to end‐of‐season, severe drought. Two traits resulting in conservative transpiration rates (TRs) are limitations on TR with soil drying and with increasing vapor pressure deficit (VPD). This study focused on parents of existing recombinant inbred line (RIL) populations as sources of divergent expression of these two traits. If divergence is found, their derived RIL population could be used in identifying genetic markers. Since both water‐conservation traits are laborious to document, a key extension of this study was to explore the possibility of using aquaporin inhibitors as practical tools in marker identification. Tifrunner had a lower soil water threshold for a decline in TR than NC 3033 and N08082olJCT. Tifrunner also had a higher VPD breakpoint than three genotypes, including NC 3033 and N08082olJCT. The difference between Tifrunner and these other two genotypes extended to their response to aquaporin inhibitors. The decrease in TR of Tifrunner when exposed to aquaporin inhibitors was much larger than NC 3033 when treated with silver and N08082olJCT when treated with zinc. This study indicates that an effort to develop drought markers in peanut RIL population should focus on Tifrunner × NC 3033 using the silver inhibitor and/or Tifrunner × N08082olJCT using the zinc inhibitor.}, number={6}, journal={CROP SCIENCE}, author={Shekoofa, Avat and Devi, J. Mura and Sinclair, Thomas R. and Holbrook, Corley C. and Isleib, Thomas G.}, year={2013}, pages={2569–2576} }
 @article{choudhary_mutava_shekoofa_sinclair_prasad_2013, title={Is the Stay-Green Trait in Sorghum a Result of Transpiration Sensitivity to Either Soil Drying or Vapor Pressure Deficit?}, volume={53}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2013.01.0043}, abstractNote={ABSTRACT Persistence of green leaves during seed fill, referred to as a stay‐green trait, has been investigated in sorghum [ Sorghum bicolor (L.) Moench] as an approach to increasing yields under water‐limited conditions. An hypothesis to explain the observation of stay green in some sorghum genotypes and not in others is that the genotypes expressing the trait employ mechanisms to increase availability of soil water during seed fill. In this study, the expression of two mechanisms resulting in soil water conservation to allow greater water availability during seed fill was explored among 12 sorghum genotypes. One mechanism is an earlier decrease in transpiration with soil drying so that the rate of soil water loss is decreased earlier in the soil drying cycle. The second mechanism is a limitation on transpiration rate at high vapor pressure deficit (VPD) so that soil water is conserved on days when midday VPD is high. Field studies were undertaken to identify seven genotypes that consistently expressed the stay‐green trait and five genotypes that did not exhibit this trait. The range of the threshold for the decrease in transpiration rate with soil drying was similar among the two sets of genotypes. Similarly, the expression of the limited transpiration rate under high VPD was found for both sets of genotypes. There was no evidence in these studies that the stay‐green trait was closely linked with either mechanism of water conservation.}, number={5}, journal={CROP SCIENCE}, author={Choudhary, Sunita and Mutava, Raymond N. and Shekoofa, Avat and Sinclair, Thomas R. and Prasad, P. V. Vara}, year={2013}, pages={2129–2134} }