Clemson Green Bean Variety Trial Report Spring 2023

Authors
Affiliation

Jenna Hershberger, Assistant Professor of
Vegetable Breeding and Genetics

Clemson Pee Dee Research & Education Center
2200 Pocket Rd,
Florence, SC 29506

Tyler Williams, Vegetable Research Technician

Clemson Pee Dee Research & Education Center
2200 Pocket Rd,
Florence, SC 29506

Introduction

Clemson’s 2023 Spring Green Bean Variety Trial included 19 round-podded and 4 flat-podded varieties from 5 participating companies. The purpose of the trial was to evaluate varieties for yield, quality, and heat tolerance characteristics in a once-over harvest situation.

Table 1: Spring 2023 varieties trialed
Name Entering company Pod type
Navajo Crites flat
857 Crites round
HM Peary Harris Moran round
HM Flavor Sweet Harris Moran round
HM LaSalle Harris Moran round
HM Bartram Harris Moran round
HM Caprice Harris Moran round
HM Byrd Harris Moran round
HM Valero Harris Moran flat
HM 4423 Harris Moran round
RR 7002 Pure Line round
WAV 75 Pure Line round
PL 0014 Pure Line round
PL0136 Pure Line round
PL0008 Pure Line round
PL 0070 Pure Line round
Usambara Seminis flat
SVGG1312 Seminis round
SVGF2123 Seminis round
Stonga Seminis flat
SB4824 Syngenta round
Greenback Syngenta round
SB4829 Syngenta round

Materials and methods

Location

The Clemson 2023 Spring Green Bean Variety Trial was performed in Field 22 at the Clemson Pee Dee Research and Education Center in Florence, South Carolina. The soil type in this field is Noboco loamy sand with a 0-2% slope. It is well-drained, but has a low organic matter content and nutrient holding capacity. This soil type also tends to be highly acidic. This trial was planted following corn.

Cultural practices

Experimental design

The green bean variety trial was planted on May 4, 2023. Varieties were planted in single-row plots with 38-inch inter-row spacing. Plots were 25 feet long and arranged in a randomized complete block design with four replications. Border rows of the standard variety ‘Caprice’ were planted surrounding the trial. The seeding rate was 7 seeds/foot, for an in-row spacing of ~1.7 inches.

Fertility

Standard soil tests were performed by the Clemson Soil Lab prior to planting. Pre-planting soil test results are reported in Table 2 and Table 3. Full soil testing results are available online under Lab ID Numbers 23032170, 23032171, and 23032172. The field was fertilized with 350 lb/acre of 0.7 ton 11-52-0, 0.2285 ton 46-0-0 Urea granular, 1.8210 tons 0-0-60 MOP granular, and 0.66 Ton Microsync pro 50 lb bag prior to planting. On May 9, 1,000lbs/acre of crushed lime were broadcast on the field. Plots were broadcast with 420lb of 15-11-14-11.5 on May 10. Calcium was applied on May 24 at a rate of 3qt/acre.

Table 2: Standard soil fertility test results
Sampling location pH lbs/acre
P K Ca Mg Zn Mn Cu B Na
22-1 5.4 86 160 794 112 5.6 21 0.6 0.7 10
22-2 5.5 60 113 463 60 4.2 16 0.6 0.6 6
22-3 5.6 58 118 324 47 3.2 11 0.6 0.5 2
Table 3: Soil ammendment recommendations
Sampling location lbs/acre
Lime N P2O5 K2O Ca Mg Zn Mn Cu B S
22-1 2600 70-1101 20 80 0 0 0 10 0 0 10
22-2 1600 70-1101 80 120 0 0 0 10 0 0 10
22-3 1100 70-1101 80 120 0 0 0 10 0 0 10
1 N recommendations in lb/acre: 25-50 preplant, 20 at planting, sidedress with 25-40
Weed, disease, and insect pest control

Pre-emergent herbicides were applied for weed control (Table 4). The trial was cultivated. Weed control on the trial was excellent.

The trial was sprayed weekly with fungicides (Table 4) following the identification of Alternaria leaf spot symptoms on May 31 (Figure 7). Despite these regular applications, Alternaria symptoms were again identified on the pods of most varieties at harvest. No other major disease symptoms were noted in the trial.

Three applications of insecticides were applied to the trial (Table 4).

Table 4: Pesticide applications
Chemical Class FRAC/IRAC Rate Application date Comments
Cruiser (Thiamethoxam) Insecticide 4A - - Seed treatment
Velum Fungicide/ nematicide 7 16 fl oz/acre 5/4 In-furrow at planting
Subtilex NG + HiStick L Rhizobial inoculant & biological fungicide 44 12.5 fl oz/acre 5/4 In-furrow at planting
Reflex Herbicide 14 1.5 pints/acre 5/5 Pre-emergence
Dual Magnum Herbicide 15 1.5 pints/acre 5/5 Pre-emergence
Roundup Herbicide 9 22 fl oz/acre 5/9 -
Crushed lime Soil amendment - 1000 lb/acre 5/9 -
Acephate Insecticide 1 8 fl oz/acre 5/25 -
Select (clethodim) Herbicide 2 12 fl oz/acre 5/25 -
Bravo (chlorothalonil) Fungicide M05 22 fl oz/acre 6/2 -
Quilt Xcel Fungicide 3&11 11 fl oz/acre 6/11 -
Dimethoate Insecticide 1B 6 fl oz/acre 6/11 -
Bracket 97 (acephate) Insecticide 1 8 fl oz/acre 6/17 -
Sysstem K Fertilizer/Fungicide 33 2-3 qts/acre 6/19 -
Fontelis Fungicide 7 18 fl oz/acre 6/26 -

Irrigation

The trial was overhead irrigated as necessary with a traveling linear system as needed (Figure 2).

Weather

Daily weather was recorded by the PDREC front compound weather station. Minimum and maximum temperatures for each day are presented in Figure 1 and rain accumulation in Figure 2.

Figure 1: Daily temperatures at the PDREC during the study period
Figure 2: Daily rain accumulation at the PDREC during the study period

Phenotyping

Pre-harvest

Stand counts were recorded as the number of germinated plants at two weeks after planting. Flowering time represents the date at which approximately 10% of the plants in a plot started flowering.

Harvest

To determine a variety’s maturity, the most mature pod was removed from each of ten random plants from a plot. The center seed from each of the ten pods was removed and lined up end to end. A variety was considered ready for harvest when the line of seeds measured 9-11.2 cm (i.e. average seed length of 9 to 11.2 mm).

Harvest of the trial began on June 29, 2023 (56 DAP) and was completed on July 11, 2023 (68 DAP). Plants were pulled from a random 3-foot section of each plot and all pods were removed by hand. When possible, this sample was taken from the middle third of each plot.

For round-podded varieties, pods were graded into three categories by sieve size; size three and under; size four, and size five. The total pod weight for each category was recorded. Additive center seed length of 10 size four pods was recorded for each plot.

For flat podded varieties, only seed length and total pod weight were measured.

Two images were taken at harvest for each plot: one of all harvested pods sorted into sieve sizes and one of a split bean next to ten seeds lined up end to end on a ruler. These images are available on Google Drive.

Results

Stand counts, flowering time, and yields are reported separately by pod type in Table 5 and Table 6. Stand counts are presented in Figure 6 and flowering date is shown in Figure 4.

Figure 3 shows mean yields for each variety of both pod types, with sieve size proportions indicated for round-podded varieties. The correlation between stand count and yield was 0.1.

Table 5: Round-podded harvest phenotypes
Variety Stand count Days to flowering Seed length (mm) Yield (lbs/acre) Sieve size 3 and under (lbs/acre) Sieve size 4 (lbs/acre) Sieve size 5 (lbs/acre)
SB4824 213.5 a 36 h 11.45 bcd 3278.64 abcde 1860.76 a 1300.54 bcdef 117.33 e
SB4829 193.25 ab 36 h 13.15 a 3110.23 bcdef 1093.5 bcd 1465.32 abcd 551.41 cde
Greenback 178.25 bc 36.25 gh 12.35 ab 3240.43 bcde 819.28 cdef 1509.62 abcd 911.53 bcd
HM Caprice 168 cd 38.5 abcde 12.15 abc 2924.7 bcdefg 522.78 ef 1414.06 abcde 987.86 bcd
WAV 75 165.25 cde 39 abc 9.93 d 1845.09 h 1231.5 bc 584.87 hi 28.72 e
RR 7002 155.25 def 37.5 defg 13.18 a 3805.86 ab 934.66 cdef 1775.29 ab 1095.92 bc
HM Peary 154.25 def 36.25 gh 11.32 bcd 3493.22 abc 585.8 def 1480.06 abcd 1427.36 ab
SVGG1312 154.25 def 38 bcdef 10.57 cd 3485.85 abc 942.37 cdef 1635.42 abc 908.06 bcd
HM Byrd 153 defg 36 h 12.22 abc 3059.57 bcdef 745.66 cdef 1437.02 abcd 876.88 bcd
HM 4423 146.25 defgh 38 bcdef 12.53 ab 2163.79 fgh 707.29 cdef 899.93 efghi 556.58 cde
SVGF2123 143.25 efghi 38.75 abcd 11.3 bcd 3354.71 abcd 1075.54 bcde 1448.12 abcd 831.05 bcd
PL0008 142.5 fghi 36.25 gh 11.45 bcd 4267.01 a 702.8 cdef 1847.04 a 1717.17 a
HM LaSalle 140.25 fghi 39.25 ab 13.28 a 2478.59 defgh 920.94 cdef 1167.37 cdefg 390.28 de
PL 0070 140 fghi 37 fgh 11.25 bcd 2575.76 cdefgh 1538.59 ab 996.76 defgh 40.41 e
HM Bartram 136.25 fghi 36.25 gh 13.47 a 1937.69 gh 867.91 cdef 869.43 fghi 200.35 e
HM Flavor Sweet 131 ghi 39.5 a 11.32 bcd 1974.62 gh 1598.83 ab 375.8 i 0 e
PL 0014 130.5 ghi 37.75 cdef 11.2 bcd 2343.47 efgh 962.79 cdef 1189.06 cdefg 191.63 e
857 125.5 hi 37.25 efgh 12.32 ab 2757.05 cdefgh 486.94 f 1309.36 bcdef 960.75 bcd
PL0136 121.5 i 36 h 10.57 cd 1992.41 gh 1139.42 bcd 738.46 ghi 114.53 e
Mean 152.21 37.34 11.86 2846.77 986.18 1233.87 626.73
Coefficient of variation 10.51 2.57 10.07 24.85 40.6 30.54 68.75
Fisher's LSD1 22.68 1.36 -2 1002.28 567.33 533.98 610.55
p-value 0 0 0 0 0 0 0
1 Means followed by the same letter are not significantly different according to Fisher’s LSD.
2 LSD cannot be calculated for an unbalanced dataset.
Table 6: Flat-podded harvest phenotypes
Variety Stand count Days to flowering Seed length (mm) Yield (lbs/acre)
Usambara 134.5 a 36 b 10.73 ab 5796.12 a
Stonga 133.25 a 36 b 11.38 ab 4281.41 ab
Navajo 128 a 36 b 12.5 a 3439.6 bc
HM Valero 82 b 37.75 a 9.32 b 2499.94 c
Mean 119.44 36.44 11 4004.27
Coefficient of variation 13.41 2.16 14.93 25.45
Fisher's LSD1 25.24 1.24 -2 1605.79
p-value 0 0.02 0.12 0.01
1 Means followed by the same letter are not significantly different according to Fisher’s LSD.
2 LSD cannot be calculated for an unbalanced dataset.
Figure 3: Mean yield with sieve size composition
Figure 4: Date at 10% flowering
Figure 5: Mean seed length at harvest (mm)
Figure 6: Stand count at two weeks after planting

Discussion

The trial had good emergence and stand establishment for most varieties. Stand counts were above the expected number of seeds planted (n = 175) in 12 of the plots in this trial. Because the seeds were packed by individual companies and sealed until planting, the number of seeds was not verified by Clemson prior to planting. Assuming the number of seeds in each packet was consistent at 175, the increased stand count is most likely due to planter error with spillover from one plot to the next. If this is the case, the ends of the plots are most likely to contain seeds from the previous plot, so only the middle third of each plot was phenotyped.

Stand count and yield were not highly correlated in this trial (\(r = 0.1\)).

Florence experienced an abnormally cool spring during this trial.

The round-podded variety with the highest yield was PL0008 (4267 lb/acre), but the yield of this variety was not significantly different from that of RR 7002 (3806 lb/acre), HM Peary (3493 lb/acre), or SVGF2123 (3355 lb/acre). PL0008 was the only variety with a total yield significantly above that of standard variety HM Caprice.

The flat podded variety with the highest yield was Usambara (5796 lb/acre), but the second highest-yielding variety, Stonga (4281 lb/acre), was not significantly different (Table 3). The small number of flat podded varieties limits the ability to provide further insight.

Many pods were marked with small brown dots at harvest (Figure 8). In many cases, every bean within a plot was affected despite regular fungicide applications. A sample of these pods was sent for examination by the Clemson Plant Disease Diagnostic Clinic, who identified it as Alternaria leaf and pod spot (ALPS) caused by the fungal pathogen Alternaria alternata. According to a factsheet from the University of Florida, high humidity and cool temperatures like those experienced at the PDREC this spring are ideal conditions for ALPS. Beans under nutritional stress are particularly susceptible to this disease. Given the low pH of the soil for this trial, it is likely that the beans were not able to take up the nutrients provided by the fertilizer applications and were therefore under considerable nutrient stress. Earlier soil amendment with lime will likely help with future management of ALPS by encouraging improved nutrient update.

Acknowledgements

The authors gratefully acknowledge:

  • Participating seed companies

  • Stewart Higgins for organizing entry selection and shipping logistics and providing management decision support

  • Chuck Parker and the PDREC farm crew for trial management advice and assistance

  • Bruce McLean, Clemson Area Commercial Horticulture Extension Agent, for pesticide spray plan recommendations

  • Clemson PDREC vegetable breeding program employees

Photos

Figure 7: Foliar disease symptoms, likely Alternaria leaf spot, on May 31, 2023
Figure 8: Pod with symptoms identified as Alternaria leaf and pod spot
Figure 9: Seed company visit on June 27, 2023