Evaluation of Bell Peppers for Resistance to Phytophthora Blight

M. Babadoost, S. Z. Islam, and M.D. Hurt

Department of Crop Sciences, University of Illinois, Urbana, IL 61801

Introduction

Approximately 1,000 acres are planted to peppers in Illinois. Phytophthora blight, caused by Phytophthora capsici, has become a serious threat to pepper production in Illinois. During 1999-2001, yield losses caused by P. capsici in pepper fields were as high as 100%. The objective of this study was to evaluate available cultivars and lines of bell peppers for resistance against P. capsici.

Materials and Methods

Fifty-six cultivars/lines of bell pepper (Table 1) were evaluated for resistance against P. capsici in the greenhouse and field.

Greenhouse trial. Four seedlings were grown in each 4.5-inch pot containing a soil mix (soil:peat:perlite; 1:1:1) in a greenhouse with 64 to 77EF. Eight-week-old seedlings were inoculated with P. capsici by adding 2 ml of zoospore suspension in sterile-distilled water (10⁵ spores/ml) at the base of each seedling. Control seedlings were treated with only sterile-distilled water. Four pots (a total of 16 plants) were included in each treatment.

The pots were watered before inoculation to keep the soil wet. After inoculation, the pots were watered three times per day. Beginning the 4th day after inoculation, seedlings were evaluated for development of Phytophthora lesions on the lower section of stems, losing leaves, wilting, and death of the seedlings. The evaluation of disease development on the seedlings was continued until 24 days after inoculation, when no more infection was observed.

Field trial. Seven cultivars and lines, Abbot-1, Abbot-2, Abbot-13, Emerald Isle, Paladin, Reinger, and Syngenta-7326, found resistant to P. capsici in the greenhouse trial, were selected for field evaluation. Also California Wonder, a susceptible pepper cultivar to P. capsici, was included in the field study, as a check.

Seedlings of the above-mentioned cultivars/lines were grown in the greenhouse. Eight-week-old seedlings were kept outside the greenhouse for 5 days, then transplanted in a commercial field in Shawneetown, Illinois, naturally infested with P. capsici. The seedlings were transplanted on June 11. The experiment was performed in a completely randomized block design with four replications, each with 10 plants. The seedlings in each plot were planted in two staggered rows with plants spaced 12 inches apart within and between rows. The plots were spaced 36 inches apart. Weeds were controlled by hand weeding. Plants received daily drip irrigation. Disease incidence was determined as percent wilted and dead plants on July 25, August 6, August 15, and September 2.

Results and Discussion

Greenhouse trial. Brown lesions were observed on the crown and at the base of stems of inoculated seedlings 5 days after inoculation. Seven days after inoculation, most of the susceptible plants developed symptoms. Shedding leaves, wilting, and death of the seedlings followed by development of lesions on the crown and lower section of the stems. Twenty-four days after inoculation, almost all of the infected plants were dead. The results of the evaluation of the incidence of Phytophthora blight of plants are presented in Table 1. Three cultivars, Emerald Isle, Paladin, and Reinger, and four lines, Abbot-1, Abbot-2, Abbot-13, and Syngenta-7326 were found resistant to P. capsici.

Field trial. The results of field study are presented in Table 2. All three cultivars and four lines of bell pepper, found resistant to P. capsici in the greenhouse trial, proved to be resistant to Phytophthora blight in the field too. These cultivars and lines can be grown commercially, if the yield and quality are satisfactory. They may also be used in breeding programs for developing commercially acceptable bell pepper cultivars resistant to P. capsici.

In this study, we inoculated the seedlings by adding zoospore suspension onto the crown section of the seedlings. This procedure appeared to be a reliable method for screening the bell pepper cultivars for resistance against P. capsici.

Table 1. Evaluation of bell pepper cultivars/lines for resistance to

Phytophthora capsici in greenhouse.

Cultivar/line	Seed source*	Disease development following inoculation of plants on April 12**
		Infected plants (%)		Plants with no symptom (%)
		April 17	April 19	(May 4)
Abbott – 1	AC	0	0	100
Abbott – 2	AC	0	25	58
Abbott – 3	AC	0	100	0
Abbott – 4	AC	0	100	0
Abbott – 5	AC	40	100	0
Abbott - 6	AC	0	100	0
Abbott - 7	AC	0	100	0
Abbott - 8	AC	0	100	0
Abbott - 9	AC	0	100	0
Abbott - 10	AC	8	82	0
Abbott - 11	AC	0	100	0
Abbott - 12	AC	0	100	0
Abbott - 13	AC	0	10	80
Abbott - 14	AC	0	100	0
Abbott - 15	AC	0	100	0
Abbott - 16	AC	0	100	0
Abbott - 17	AC	10	100	0
Abbott - 18	AC	0	100	0
Abbott - 19	AC	0	100	0
Abbott - 20	AC	0	100	0
Bell Boy	JWJ	0	100	0
Bianca	JWJ	0	100	0
Big Bertha	JWJ	0	100	0
Blushing Beauty	JWJ	0	100	0
Boynton	CS	0	100	0
Brigadier	NV	0	100	0
California Wonder	SOS	14	100	0
Camelot	JS/JSS	0	100	0
Choco	JWJ	0	100	0
Colossal	NV	0	100	0
Commandant	NV	0	100	0
Corona	JS/JSS	8	100	0
Crusader	NV	0	100	0
Diego	EZ	0	100	0
Emerald Isle	HR	0	0	91
Fat & Sassy	JWJ	0	100	0
Giapponese	NES	0	100	0
HMX 3640	CS	0	100	0
HMX 9646	CS	0	100	0
Inia	JWJ	0	100	0
Jingle Bell	JWJ	0	100	0
Jupiter	NV	0	100	0
Labrador	JS/JSS	0	100	0
Lafayette	NV	0	100	0
Legionaire	NV	8	100	0
North Star	JWJ	0	100	0
Orion	EZ	0	100	0
Paladin	NV	0	18	64
Perfection	JS/JSS	0	100	0
Queen Hybrid	JWJ	0	100	0
Reinger	JS/JSS	0	0	100
Sentry	NV	0	100	0
SPP 7117	SK	0	100	0
Syngenta – 7326	SG	0	0	100
Tequila	JWJ	0	100	0
Valencia	JS/JSS	0	100	0

* AC = Abbott and Cobb; EZ = Enza/Zaden; HR = Harris Seeds;

JS/JSS = Johnny’s Selected Seeds; JWJ = J. W. Jung;

NES = New England Seed; NV = Novartis; SK = Sakata Seed America;

SOS= Sow Organic Seed; SG = Syngenta.

** Plants were 8 weeks old at the time of inoculation on April 12.

Table 2. Evaluation of bell pepper cultivars/lines for resistance to Phytophthora

capsici in the field.

Cultivar/line	Seed source*	Plant stand(%)**
		July 25	August 6	August 15	September 2
Abbott – 1	AC	100	83	83	83
Abbott - 2	AC	76	76	65	53
Abbott - 13	AC	83	75	75	75
Emerald Isle	HR	93	93	93	90
Paladin	NV	97	97	97	93
Reinger	JS/JSS	97	97	97	93
Syngenta - 7326	SG	93	93	93	93
California Wonder	SOS	87	53	37	13

* AC = Abbott and Cobb; HR = Harris Seeds; NV = Novartis; JS/JSS = Johnny’s Selected

Seeds; SG = Syngenta; SOS = Sow Organic Seed.

** Seedlings were transplanted on June 11.