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
Sampling location	pH	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
Sampling location	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 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