Evaluation of 16 Phytophthora capsici-tolerant Pepper Cultivars in Southwest Michigan

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1 Evaluation of 16 Phytophthora capsici-tolerant Pepper Cultivars in Southwest Michigan Dr. Ron Goldy and Virginia Wendzel Southwest Michigan Research and Extension Center Benton Harbor, Michigan Objective To evaluate performance of 16 Phytophthora capsici-tolerant pepper selections for adaptability to southwest Michigan growing conditions. Summary Differences were found between the 16 selections for all traits evaluated. Total yield ranged from 1,747 (ACR 285) to 1,368 ( Intruder ) bushels per acre and average number one fruit weight ranged from 176 grams (PS ) to 133 grams (ACX1003) per fruit. The best performing entries across several traits were ACR285, Aristotle, Karisma, HMX1649, Vanguard, and PS Color differences were also noted with some selections being lighter green in color. Growers are warned that, since there are multiple races of Phytophthora capsici, each selection may not be tolerant at all sites. Materials and Methods Fertilizer Prior to planting, , , 95% sulfur, and Granubor were broadcast and incorporated at 90, 250, 28 and 15 pounds/acre, respectively. After planting, nutrients were applied with Nitro Plus (18N-5Ca-1.5Mg and a proprietary growth regulator) or Ca. Nitro Plus at a rate of 15 gallons per acre was applied four times prior to fruit set from June 13 to July 5. After fruit set, Ca was applied weekly from July 12 to August 16 at a rate of 1 pound nitrogen/acre/day. Fumigation/Weed Control Beds were not fumigated and weeds were controlled using black plastic on the beds and cultivating and hoeing between the beds. Planting Plants were started in the greenhouse on April 2 and planted to the field on May 22. Plants were set on raised, black plastic mulched beds, 6 inches high, 22 inches wide at the top and 5.5-feet on center. Plants were set in double rows 14 inches between rows and 18 inches in the row (10,560 plants/acre). The trial was planted and analyzed as a completely randomized design with 16 plants per plot and four replications. Plots were separated by four guard plants. Plant Care Plots were irrigated as needed and pests were controlled using standard commercial practices. Harvest and Data Collection Harvest was conducted four times: August 3, 15, 28, and September 17, and graded into Jumbo, Extra Large, Large, Medium, Number Two, and Cull fruit. Each category was weighed and converted into bushels per acre.

2 Results and Discussion Statistical differences were found for all traits measured. Total yield was fairly uniform statistically with yields ranging from 1,747 to 1,368 bushels per acre (Table 1). ACR285 had the highest yield but it was not statistically different than 12 other entries. Only ACR294, Escalade, and Intruder had smaller total yield. Greater differences were found in other traits such as average number one fruit weight, which ranged from 176 to 133 grams per fruit. PS had the highest number one fruit weight at 176 grams. However, it was not significantly different than eight other entries (Table 1). ACX1003 and ACR294 had a significant amount of fruit in the large and medium categories and had the lowest average fruit sizes at 133 and 147 grams, respectively. The best performing entries across several traits were ACR285, Aristotle, Karisma, HMX1649, Vanguard, and PS Two selections, ACR285 and ACX1003, were more pale-green in color (Figures 1 and 2). Even though ACR285 was a top performer, the pale color may make it undesirable to growers and produce brokers. Figure 1 was taken from the first harvest and the amount of fruit shown is indicative of the 16 selections early yield potential. The three poorest early performers (ACR294, Escalade, and Intruder ) also were the three poorest performers for total yield. The 2012 growing season was a difficult year for peppers. There were 24 days above 90 o F and 10 nights above 70 o F. These temperatures could have contributed to blossom drop affecting fruit yield and blossom end rot affecting fruit quality. Blossom end rot was the main factor contributing to cull fruit. The reason for this trial was to compare Phytophthora capsici-tolerant bell peppers with each other. Usually pepper trials are a mix of tolerant and nontolerant entries and may not be a fair comparison. None of the selections were retested for tolerance to Phytophthora capsici. No plant or fruit symptoms of Phytophthora capsici were observed in any of the trial plants or the nontolerant border plants. Since there are several races of Phytophthora capsici, it is possible for a grower to plant a tolerant cultivar only to have it show symptoms. This would be indicative that the race present in the soil is not one the cultivar can tolerate. Therefore, it would be of value for growers to identify what race(s) they have and for seed companies to identify which race(s) their pepper is tolerant to so growers can intelligently plant the proper cultivar. Alternatively, they could fumigate or choose not to plant peppers on that site again since Phytophthora capsici is long lived in the soil.

3 Table 1. in bushels/acre and size grades of 16 Phytophthora capsici-tolerant bell peppers grown at the Southwest Michigan Research and Extension Center, Benton Harbor, Michigan, in Plant population was approximately 10,560 plants per acre. Entry Seed* Source Total Avg. No. 1 Fruit Wt.(gms) Jumbo Extra Large Large Med. No. 2 Cull ACR285 AC 1, FPP1814 SK 1, CSX32805 SK 1, Aristotle SM 1, Karisma HM 1, HMX1649 HM 1, Vanguard HM 1, Paladin SY 1, Lulton (ACX1003) SK 1, nn SY 1, PSO SM 1, nn SY 1, Archimedes SM 1, Enforcer (ACR294) AC 1, Escalade AC 1, Intruder SY 1, lsd *Seed Source: AC = Abbott & Cobb, SK = Sakata Seed, SM = Seminis, HM = Harris Moran, SY = Syngenta/Rogers Jumbo = >240 gm, Extra Large = gm, Large = gm, Medium (Med.) = <170 gm. Numbers in bold in the same column are not statistically different than the highest number.

4 Figure 1. Sixteen Phytophthora capsici-tolerant bell peppers grown at the Southwest Michigan Research and Extension Center, Benton Harbor, Michigan, in Front row (from left): FPP1814, ACR285, Enforcer (ACR294), Escalade. Second row (from left): Karisma, Vanguard, HMX1649, CSX Third row (from left): Lulton (ACX1003), PS , Aristotle, Archimedes. Back row (from left): nn030974, nn030627, Intruder, Paladin.

5 Figure 2. Color difference between Lulton (ACX1003) and PS Midwest Vegetable Trial Report for 2012