Arkansas Agricultural Research Articles

Registration of Arkot 1202, Arkot 1207, Arkot 1208, and Arkot 1214 cotton germplasm lines

AbstractArkot 1202 (Reg. no. GP‐1143, PI 702793), Arkot 1207 (Reg. no. GP‐1144, PI 702794), Arkot 1208 (Reg. no. GP‐1145, PI 702795), and ‘Arkot 1214’ (Reg. no. GP‐1146, PI 702796) are conventional cotton (Gossypium hirsutum L.) germplasm lines released by the Arkansas Agricultural Experiment Station in June 2023. Arkot 1202, Arkot 1207, and Arkot 1208 lines share ‘UA48’ (PVP 201100041) as a common parent. The second parent for Arkot 1202 and Arkot 1207 was MD25‐87Y and ‘Columbia’, respectively. The second parent for Arkot 1208 was the F1 of a double cross of F1 (Ark 0219‐15 crossed with LA063071653) and F1 (Arkot 0222 crossed with Ark 0203‐11). Arkot 1214 was derived from a four‐way cross of two double crosses: F1 (MD25‐26ne crossed with Arkot 0113) and F1 (Arkot 0114 crossed with ‘UA222’). In replicated field tests at four Arkansas sites over 5 years, the four lines produced more lint yield than UA48 and UA222. Wide adaptation of the lines was indicated by high lint yields of lines in 2020 regional tests. All four lines displayed high resistance to bacterial blight and Fusarium wilt race 1. Plant (leaf, stem, and bract) trichomes and tarnished plant bug response of Arkot 1202 and Arkot 1214 were equal to UA48, but Arkot 1207 and Arkot 1208 were equal to UA222. Yield component values of the four lines were equal to or better than UA222. The maturity and fiber quality of Arkot 1202 approached that of UA48 while the other three were similar to UA222.

Registration of Arkot 1102ne cotton germplasm line

AbstractArkot 1102ne (Reg. no. GP‐1142; PI 702558) is a conventional, nectariless cotton (Gossypium hirsutum L.) germplasm line released by the Arkansas Agricultural Experiment Station in October 2022. The germplasm line represents an ongoing effort to develop improved genotypes with enhanced yield, yield components, seed traits, earliness, host plant resistance, and fiber properties. Arkot 1102ne was compared to ‘UA48’ and ‘UA222’ over 5 years and four test sites in Arkansas. Across all the test sites, lint yields of Arkot 1102ne were 7.9% and 20.8% higher than those of UA222 and UA48, respectively, due to its higher lint percentage, seed per area, and fiber density. Arkot 1102ne produced the highest average yield of 21 genotypes over 10 locations in the 2019 Regional Breeders’ Network Test (RBTN). Arkot 1102ne produced the highest oil and protein percentages at four 2019 RBTN locations where seed were evaluated. Host plant resistance traits that have been measured on Arkot 1102ne include bacterial blight resistance and Verticillium wilt tolerance. Leaf pubescence and bract trichome density of Arkot 1102ne were intermediate between UA48 and UA222, but stem pubescence was lower. This combination of host plant resistance and yield components should lead to more stable yield production over contrasting environments. The fiber quality of Arkot 1102ne was lower than UA48 and was similar to that of UA222.

Registration of R16‐45 as a flood‐tolerant, high‐yielding soybean germplasm line

AbstractR16‐45 (Reg. no. GP‐526, PI 704118) is a high‐yielding soybean [Glycine max (L.) Merr.] breeding line with flood tolerance at early reproductive stages released as germplasm by the Arkansas Agricultural Experiment Station in 2023. It is an F2 selection from the cross between the flood‐tolerant breeding line R07‐6669 and the high‐yielding Arkansas cultivar ‘UA 5612’. R16‐45 is a conventional (non‐genetically modified) soybean with a relative maturity of 5.6. Plants have determinate growth habit, white flower color, and buff hilum color. It has gray pubescence, tan pod wall at maturity, and yellow cotyledons with a dull yellow seed coat. R16‐45 showed high yield potential and broad adaptability across 17 environments in Arkansas and other southern states, with an average of 4145 kg ha−1 (95.3% of the checks’ mean). Six years of field evaluations for flooding tolerance showed that R16‐45 is consistently tolerant to 8‐to‐10‐day flooding stress at the R1/R2 growth stages (average flood damage score of 3.6, compared with 6.0 from the reference checks). In addition, R16‐45 is resistant to stem canker. Given substantial yield losses associated with flooding stress and stem canker, R16‐45 is a valuable germplasm source for public and private soybean breeding programs attempting to incorporate novel genetic diversity into their breeding pipeline.

Registration of Arkot 1112, Arkot 1114, and Arkot 1115 cotton germplasm lines

AbstractArkot 1112 (Reg. no. GP‐1139, PI 702559), Arkot 1114 (Reg. no. GP‐1140, PI 702560), and Arkot 1115 (Reg. no. GP‐1141, PI 702561) are conventional cotton (Gossypium hirsutum L.) germplasm lines released by the Arkansas Agricultural Experiment Station in November, 2022. The three lines share Arkot 0306 (PI 671966) as a common parent. The second parents for Arkot 1112, Arkot 1114, and Arkot 1115 were ‘UA222’ (US patent no. 8,859,862), Arkot 0309 (PI 669969), and Arkot 0316 (PI 669970), respectively. The three lines were compared with ‘UA48’ and UA222 in replicated field tests at four Arkansas sites over 5 years. Over these tests, each of the three lines produced about 11 and 25% higher lint yields than UA48 and UA222, respectively. Lint yields of Arkot 1115 exceeded those of Arkot 1112 and Arkot 1114. Over 10 locations of the 2019 Regional Breeders Testing Network test, lint yields of Arkot 1112, Arkot 1114, and Arkot 1115 were equal to each other and ranked third, fourth, and fifth, respectively, out of 22 genotypes, indicating that the lines have wide adaptation. Leaf pubescence, stem pubescence, and bract trichome density of the lines were higher than UA48 and similar to UA222. All three lines displayed high resistance to bacterial blight. The lines were more resistant to tarnished plant bug than UA48 but were more susceptible to tarnished plant bug than UA222. Fiber quality of Arkot 1115 approached that of UA48 (excellent fiber quality), whereas Arkot 1112 and Arkot 1114 was similar to UA222 (good fiber quality).

Registration of soybean germplasm line R14‐1422 with high yield and moderate resistance to southern root knot nematode

AbstractR14‐1422 (Reg. no. GP‐523, PI 702562) is a mid‐maturity group (MG) V (relative maturity 5.4), determinate growth habit, high‐yielding, conventional soybean [Glycine max (L.) Merr.] germplasm line developed and released in 2021 by the Arkansas Agricultural Experiment Station. R14‐1422 is an F4 selection from the cross between ‘R06‐4433’, a cultivar released by Arkansas, and the Missouri cultivar ‘S05‐11482’. Trial results of over 74 environments in Arkansas and other southern states showed that R14‐1422 is well adapted and provides high‐yielding performance. R14‐1422 is a MG V (5.4), line with determinate growth habit, white flowers, gray pubescence, and a tan pod wall at maturity. Seed of R14‐1422 has yellow cotyledon, yellow seed coat, and buff hilum color. R14‐1422 has high yield potential and moderate resistance to southern root‐knot nematode and is a chloride excluder.

Registration of ‘ARoma 22’, an aromatic long‐grain rice cultivar

AbstractThe University of Arkansas System Division of Agriculture's Arkansas Agricultural Experiment Station released the cultivar ‘Aroma 22’ (Reg. no. CV‐157, PI 701903) in February 2022. ARoma 22 is a high‐yielding, mid‐season, jasmine‐type aromatic long‐grain rice (Oryza sativa L.) cultivar derived from the cross ‘Jazzman’//‘Drew’/PI 637517/3/‘Taggart’ made at the Rice Research and Extension Center, Stuttgart, AR, in 2012. ARoma 22 has a milling yield of 62/69 (% whole:% total), has an average plant height of 97 cm and reaches 50% heading at 90 days in Arkansas Rice Performance Trials. The aromatic line, ARoma 22, offers a jasmine‐type rice adapted to Arkansas growing conditions for rice producers who wish to serve the aromatic rice consumer market.

Registration of RU9601099 short‐grain rice germplasm

AbstractThe University of Arkansas System Division of Agriculture Arkansas Agricultural Experiment Station released the germplasm of a short‐grain rice (Oryza sativa L.) known by its experimental designation RU9601099 (Reg. no. GP‐150, PI 701904). The line originated from the cross ‘Koshihikari’/’Mars’ (cross no. 900625), made at the Rice Research and Extension Center, Stuttgart, AR, in 1990. The RU9601099 line has an average yield of 7698 kg ha−1, excellent milling yield of 62/71 (% head rice/% total rice), and greater straw strength than either of its parents. The RU9601099 line provides a high‐yielding, lodging resistant, Japanese‐quality short‐grain rice line that is agronomically adapted to Arkansas growing conditions. These characteristics make this line beneficial for mid‐South producers to market rice to Japan.

Registration of Arkot 0902 cotton germplasm line

AbstractArkot 0902 (Reg. no. GP‐1130, PI 700940) is a conventional cotton (Gossypium hirsutum L.) germplasm line released by the Arkansas Agricultural Experiment Station in May 2022. Arkot 0902 was derived from a cross of ‘GA 230’ (PVP 201500309) and Arkot 0012. Over 5 yr and four test sites in Arkansas, Arkot 0902 produced 10 and 20% higher lint yields than ‘UA222’ and ‘UA48’, respectively. The high lint yield of Arkot 0902 was attributed to producing more (and smaller) seed per area than UA222 or UA48. Arkot 0902 possesses leaf and stem pubescence similar to UA48 (smooth leaf) but has higher density of marginal bract trichomes. Arkot 0902 displayed high resistance to bacterial blight and was similar to UA222 and UA48 in their response to other diseases. Arkot 0902 was more resistant to tarnished plant bug than UA48 and equal to UA222. Most fiber quality traits of Arkot 0902 approached those of UA48, a high fiber–quality cultivar.

Registration of Arkot 1005, Arkot 1015, and Arkot 1019 cotton germplasm lines

AbstractArkot 1005 (Reg. no. GP‐1127, PI 700852), Arkot 1015 (Reg. no. GP‐1128, PI 700853), and Arkot 1019 (Reg. no. GP‐1129, PI 700854) are conventional cotton (Gossypium hirsutum L.) germplasm lines released by the Arkansas Agricultural Experiment Station in April 2022. The lines were compared with UA48 and UA222 (check cultivars) in replicated field tests at four Arkansas sites over 5 yr. Over these tests, lint yields of the three lines did not differ from each other and were greater than UA48. Lint yield of Arkot 1015 was greater than UA222, while lint yields of Arkot 1005 and Arkot 1019 were equal to UA222. Performance in regional tests indicates that the lines have wide adaptation. The lint yields of Arkot 1015 and Arkot 1019 were attributed to producing more (and smaller) seed per area and less lint per seed (lint index) than UA222. Arkot 1005 produced higher lint index than the other two lines and the two check cultivars. Seed per area for Arkot 1005 was higher than UA48, equal to UA222, and lower than Arkot 1015 and Arkot 1019. Leaf pubescence, stem pubescence, and bract trichome density of the three lines were intermediate between UA222 and UA48. All three lines displayed high resistance to bacterial blight and were similar to UA222 and UA48 in their response to other diseases. Arkot 1015 was more resistant to tarnished plant bug (TPB) than Arkot 1005, Arkot 1019, and UA48, but all were more susceptible to TPB than UA222. Compared with the other lines and check cultivars, Arkot 1005 and Arkot 1019 displayed higher and lower, respectively, resistance to seed deterioration. Fiber quality of Arkot 1019 was superior to UA48, UA222, and the other lines. Fiber quality of Arkot 1005 and Arkot 1015 was superior to UA222.

Arkansas producers value upload speed more than download speed for precision agriculture applications

While access to broadband services has increased in recent years, many agricultural producers remain without access or are served by an inadequate connection. As many precision agriculture applications rely on data transfer through broadband networks, the expansion of broadband into rural areas has become critical for farm modernization. This study recruited Arkansas agriculture producers to complete a choice experiment on their willingness-to-pay (WTP) for a broadband connection. We examine factors influencing producers’ WTP for broadband upload and download speed using a conditional logit model. In the evaluation of WTP for broadband, producers were willing to pay on average $1.07 to $1.34 per Mbps (megabits per second) of upload speed, compared to $0.02 to $0.03 per Mbps of download speed. Producers also placed a premium on the reliability of the connection. These results suggest that producers value a symmetrical data flow for production operations to support precision agriculture applications.

Registration of two Arkot 0912 sister cotton germplasm lines

AbstractArkot 0912‐18 (Reg. no. GP‐1098, PI 697032) and Arkot 0912‐41 (Reg. no. GP‐1097, PI 697031) are conventional cotton (Gossypium hirsutum L.) germplasm lines released by the Arkansas Agricultural Experiment Station in December 2020. Both lines were derived from crossing ‘UA48’ and ‘UA222’. They produced higher lint yields than their parents over 5 yr and at four test sites in Arkansas. Both produced similar lint yields at each test site. Over test sites, the lines produced about 13 and 24% higher lint yields than UA222 and UA48, respectively. Arkot 0912‐18 produced the highest lint yield of all entries evaluated in the 2017 Regional Breeders Network Test. Over all locations of the 2017 Regional High Quality Test, lint yields of Arkot 0912‐41 ranked fourth out of 20 genotypes (second‐highest of 11 conventional genotypes) and equaled the lint yields of DP 1646 B2XF (U.S. patent no. 9,961,845) and PHY 444 WRF. Both lines produced higher lint percentage and lint index and were taller than either parent. Leaf pubescence, stem pubescence, and bract trichome density of each line exceeded both parents. Visual ratings of Verticillium wilt for Arkot 0912‐18 exceeded those of UA48. Both lines displayed high resistance to bacterial blight and were similar to UA222 and UA48 in their response to other diseases. The lines were more resistant to tarnished plant bug than UA48 but were more susceptible to tarnished plant bugs than UA222. Measurements of fiber quality for the two lines were intermediate between that of UA48 (excellent fiber quality) and UA222 (good fiber quality).

Registration of three Arkot 0908 cotton germplasm lines

AbstractArkot 0908‐52 (Reg. no. GP‐1091, PI 697035), Arkot 0908‐56 (Reg. no. GP‐1090, PI 697034), and Arkot 0908‐60 (Reg. no. GP‐1089, PI 697033) are conventional cotton (Gossypium hirsutum L.) germplasm lines released by the Arkansas Agricultural Experiment Station in October 2020. The lines are high performing, early maturing germplasm derived from parents (‘GA 230’ and ‘UA222’) having contrasting backgrounds and maturity. The lines produced higher lint yields than UA222 and ‘UA48’ over 5 yr and at four test sites in Arkansas, producing similar relative lint yields across all test sites and about 15 and 25% higher than lint yields of UA222 and UA48, respectively. Additionally, they had smaller seed while producing more seed per area and more or equal amount of lint per seed than UA222 or UA48. Arkot 0908‐52 and Arkot 0908‐60 performed well in the 2017 Regional High Quality Test and the 2017 Regional Breeders Network Test, respectively. Leaf pubescence and bract trichome density of Arkot 0908‐56 were greater than Arkot 0908‐52, Arkot 0908‐60, and UA48. Stem pubescence density of Arkot 0908‐52 and Arkot 0908‐56 was similar to UA48 and UA222 but greater than Arkot 0908‐60. All three lines displayed high resistance to bacterial blight and were similar to UA222 and UA48 in their response to other diseases. Arkot 0908‐56 and Arkot 0908‐60 were more resistant to tarnished plant bug than Arkot 0908‐52 and UA48, but all were more susceptible to tarnished plant bug than UA222. Fiber quality of Arkot 0908‐52 and Arkot 0908‐56 was similar to UA48, while fiber quality of Arkot 0908‐60 was similar to UA222.

Registration of Arkot 0822 cotton germplasm line

AbstractArkot 0822 (Reg. no. GP‐1088, PI 697030) is a conventional cotton (Gossypium hirsutum L.) germplasm line that was released by the Arkansas Agricultural Experiment Station in October 2020. In 2008, ‘UA48’ was crossed with Arkot 0016 with the goal of developing lines having fiber quality of UA48 but with improved yields and broadened adaptation. Arkot 0822 is a sister line to ‘UA248’. Over 5 yr of Arkansas tests at four locations, lint yields of Arkot 0822 were 15.9% higher than UA48 and equal to UA248. Fiber quality of Arkot 0822 approaches that of UA48. In most tests, fiber length, length uniformity, and strength of Arkot 0822 were equal to UA248 and exceeded most entries except UA48. Micronaire of Arkot 0822 is comparable to UA48 and coarser than UA248. Arkot 0822 is an early‐maturity cultivar. It displays high resistance to bacterial blight and is equal to UA248 and ‘DP 393’ in its response to other diseases and to tarnished plant bug. Arkot 0822 combines fiber quality traits comparable to UA48 and UA248 with enhanced ability to yield.

Registration of Clearfield ‘CLL15’ southern long‐grain rice

Abstract‘CLL15’ (Reg. no. CV‐154, PI 692952) is a high‐yielding, very early maturing, short‐stature Clearfield (BASF) long‐grain rice (Oryza sativa L.) cultivar with improved disease package developed by the University of Arkansas Rice Research and Extension Center in Stuttgart, AR, and approved for release by the Arkansas Agricultural Experiment Station, University of Arkansas System Division of Agriculture in January 2019. It was selected from the cross of RU1302048/RU1302045 made in summer 2013. CLL15 was initiated as a F4 bulk of a single progeny row in the winter nursery near Lajas, Puerto Rico, in spring 2015. From 2016 to 2019, CLL15 was evaluated in 47 multilocation trials. Clearfield cultivars ’CL151’, ‘CL153’, and ‘CL172’ served as checks. Grain yield of CLL15 was 9.33 t ha−1 across all trials compared with 9.50 t ha−1 for ‘CL151’, 8.74 t ha−1 for CL153, and 8.74 t ha−1 for CL172. However, in the multilocation trials in Arkansas—Arkansas Rice Performance Trial and Producer Rice Evaluation Program—CLL15 consistently produced the highest grain yield, ranging from 8.80 to 10.31 t ha−1. Plant height of CLL15 was 97 cm, which is 2 cm taller than CL172, but shorter than 101 cm for CL151 and 99 cm for CL153. CLL15 reached 50% heading in 83 d, which was similar to CL151 and 2 d earlier than both CL153 and CL172. CLL15 is moderately resistant to blast and susceptible to sheath blight, bacterial panicle blight, kernel smut, and false smut.

Registration of ‘R13‐13997’ soybean cultivar

Abstract‘R13‐13997’ (Reg. no. CV‐539, PI 695314) is an early Maturity Group V (relative maturity 5.4), determinate, conventional soybean [Glycine max (L.) Merr.] cultivar developed and released by the Arkansas Agricultural Experiment Station in 2020. R13‐13997 was evaluated across 62 environments in Arkansas and other southern states and yielded higher than the check cultivars in most test environments. Across the 62 test environments, R13‐13997 yielded on average 4,371 kg ha−1 compared with 4,243 kg ha−1 for the check mean. It has white flowers, tawny pubescence, and tan pod walls at maturity. Seeds of R13‐13997 have yellow cotyledons with dull yellow seed coats and black hila. Seeds average 408 g kg−1 protein and 226 g kg−1 oil, on a dry‐weight basis. R13‐13997 is resistant to stem canker and frogeye leaf spot; moderately susceptible to soybean cyst nematode races 2, 3, and 5 and peanut root‐knot nematode; and susceptible to southern root‐knot nematode. The high yield potential, broad adaptation, and adequate disease resistance package make R13‐13997 an appealing choice for southern soybean growers and breeders.

Registration of ‘UA248’ cotton cultivar

Abstract‘UA248’ (Reg. no. CV‐145, PI 693756) is a conventional cultivar of cotton (Gossypium hirsutum L.) that was released by the Arkansas Agricultural Experiment Station in March 2020. In 2008, UA48 was crossed with Arkot 0016 with the goal of developing a line having fiber quality of UA48 but with improved yields and broadened adaptation. Over 5 yr of Arkansas tests, lint yields of UA248 were 10–15% higher than UA48 at four locations. Fiber quality of UA248 approaches that of UA48. In most tests, the fiber length, length uniformity, and strength of UA248 exceeded most entries except UA48. Micronaire of UA248 is comparable to DP 393 and finer than UA48. UA248 is an early maturity cultivar but matures slightly later than UA48. UA248 displays high resistance to bacterial blight and is equal to DP 393 in response to other diseases. UA248 combines fiber quality traits comparable to UA48 and enhanced yielding ability.

Timing and Application Rate for Sequential Applications of Glufosinate are Critical for Maximizing Control of Annual Weeds in LibertyLink® Soybean

Preserving the utility of glufosinate in both LibertyLink soybean and other glufosinate-resistant crops is critical for managing herbicide-resistant weeds. An experiment with a two-factor factorial arrangement was conducted at the Arkansas Agricultural Research and Extension Center in Fayetteville, AR, in 2015, 2016, and 2017 to evaluate the efficacy of glufosinate in single and sequential applications at various rates on 8–32 cm tall Palmer amaranth, barnyardgrass, and broadleaf signalgrass. Herbicide treatments consisted of glufosinate applied at 454, 595, 738, and 882 g ai ha−1 (Factor 1) with either no sequential application or a sequential application occurring 7, 10, 14, or 21 days after the initial application (DAI) (Factor 2). For treatments that contained a sequential application, the same rate used in the initial application (e.g., 451 g ai ha−1) was also used in the sequential. Regardless of species and rate, sequential applications were always superior to single applications. Palmer amaranth control 3 weeks after the final treatment (WAF) was 8% greater when the sequential application occurred 10 DAI compared to 21 DAI, averaged over glufosinate rates. When at least 595 g ai ha−1 glufosinate was used in a treatment, no differences between the 7-, 10-, 14-, and 21-day sequential application intervals were observed for barnyardgrass or broadleaf signalgrass control, 3 WAF. Soybean yields were greater when the glufosinate applications occurred 7 or 10 d apart compared to 21 d, averaged over glufosinate rates. When large weeds are present in the field, these data suggest that glufosinate should be applied sequentially with a 7- to 14-day interval between applications. If sequential applications of glufosinate are used in combination with a comprehensive weed control management program, the value of the LibertyLink technology should be preserved by mitigating the risk of glufosinate resistance.

Resistance of Inzen™ grain sorghum to multiple PRE- and POST-applied acetolactate synthase–inhibiting herbicides

AbstractA non-GMO trait called Inzen™ was recently commercialized in grain sorghum to combat weedy grasses, allowing the use of nicosulfuron POST in the crop. Inzen™ grain sorghum carries a double mutation in the acetolactate synthase (ALS) gene Val560Ile and Trp574Leu, which potentially results in cross-resistance to a wide assortment of ALS-inhibiting herbicides. To evaluate the scope of cross-resistance to Weed Science Society of America Group 2 herbicides in addition to nicosulfuron, tests were conducted in 2016 and 2017 at the Lon Mann Cotton Research Station near Marianna, AR, the Arkansas Agricultural Research and Extension Center in Fayetteville, AR, and in 2016 at the Pine Tree Research Station near Colt, AR. The tests included ALS-inhibiting herbicides from all five families: sulfonylureas, imidazolinones, pyrimidinylthiobenzoics, triazolinones, and triazolopyrimidines. Treatments were made PRE or POST to grain sorghum at a 1× rate for crops in which each herbicide is labeled. Grain sorghum planted in the PRE trial were Inzen™ and a conventional cultivar. Visible estimates of injury and sorghum heights were recorded at 2 and 4 wk after herbicide application, and yield data were collected at crop maturity. In the PRE trial, no visible injury, sorghum height reduction, or yield loss were observed in plots containing the Inzen™ cultivar. Applications made POST to the Inzen™ grain sorghum caused visible injury, sorghum height reduction, and yield loss of 20%, 13%, and 35%, respectively, only in plots where bispyribac-Na was applied. There was no impact on the crop from other POST-applied ALS-inhibiting herbicides. These results demonstrate that the Inzen™ trait confers cross-resistance to most ALS-inhibiting herbicides and could offer promising new alternatives for weed control and protection from carryover of residual ALS-inhibiting herbicides in grain sorghum.

Registration of soybean germplasm lines R10‐2436 and R10‐2710 with drought tolerance traits and high yield under moderate water stress

AbstractSoybean [Glycine max (L.) Merr.] lines R10‐2436 (Reg. no. GP‐439, PI 692971) and R10‐2710 (Reg. no. GP‐440, PI 692972) are high‐yielding and drought‐tolerant conventional germplasm released by the Arkansas Agricultural Experiment Station in February 2017. R10‐2436 and R10‐2710 have a relative maturity of 5.6 and 5.8, respectively. R10‐2436 is an F4–derived line from the cross R01‐52F × R02‐6268F, and R10‐2710 is an F2–derived line from R01‐52F × ‘USDA‐N7002’. In 6 yr of testing, R10‐2436 and R10‐2710 significantly outyielded the maturity group 5 check mean under moderate water‐deficit stress in Stuttgart, AR (2,893, 2,889, and 2,506 kg ha−1, respectively) and were on a par with the checks under full irrigation in Stuttgart (4,644, 4,511, and 4,613 kg ha−1, respectively) and in five additional irrigated Arkansas environments. The water‐deficit treatment consisted of normal irrigation until blooming, after which irrigation was suspended for the rest of the season. In greenhouse pot studies, both releases exhibited sustained nitrogen fixation during a dry‐down cycle. This trait was presumably inherited from their ancestor ‘Jackson’. R10‐2436 also exhibited slow wilting in multiple drought‐stressed environments in Arkansas and North Carolina, likely inherited from PI 416937. Because of their yield potential under drought and irrigation, as well as their good agronomic characteristics, R10‐2436 and R10‐2710 can be easily incorporated in applied breeding programs to transfer drought tolerance into elite high‐yielding cultivars.

Antagonism in mixtures of glufosinate + glyphosate and glufosinate + clethodim on grasses

AbstractProper management of glufosinate in glufosinate-resistant crop technologies is needed to mitigate the likelihood of resistance evolution. Antagonism may result from mixtures of glufosinate and other commonly used POST herbicides in soybean and cotton. Two experiments were conducted at the Arkansas Agricultural Research and Extension Center in Fayetteville, AR, in 2015 and 2016 to evaluate mixtures of glufosinate + clethodim and glufosinate + glyphosate on barnyardgrass, broadleaf signalgrass, johnsongrass, and large crabgrass. Furthermore, droplet spectra analyses were conducted to determine if droplet size was associated with identification of herbicide interactions. Antagonism was dependent on the herbicide rates and the weed species. For barnyardgrass and large crabgrass control 4 wk after treatment, glufosinate + glyphosate was antagonistic at all rates evaluated. When large crabgrass was evaluated, some mixtures (e.g., 595 g ha–1 glufosinate + 76 g ha–1 clethodim) had a significant reduction in control relative to one of the herbicides applied alone. Glufosinate (451 and 595 g ai ha–1) + glyphosate (867 and 1,735 g ae ha–1) was antagonistic at all four possible rate combinations for broadleaf signalgrass control. Fewer instances of antagonism were observed for seedling johnsongrass control than for other species, but certain treatments were identified as antagonistic (e.g., glufosinate at 451 g ai ha–1 + clethodim at 76 g ai ha–1). Overall, antagonism was less likely and greater control was observed when the highest rates of both herbicides in a given mixture were used. The addition of glyphosate or clethodim to glufosinate can increase the volume median diameter and decrease the percentage volume of fines, compared to glufosinate alone. The droplet spectra analyses indicate that the glufosinate performance may be negatively affected by the addition of glyphosate or clethodim.