Breeding for CMV tolerance for bell peppers adapted for California production

2005 RESEARCH REPORT
California Pepper Improvement Foundation/
California Pepper Commission

Title: Breeding for CMV tolerance for bell peppers adapted for California production

Principal Investigator: Molly Jahn (mmj9@cornell.edu), Professor, Dept. of Plant Breeding & Genetics, Cornell University, Ithaca, NY 14853

Personnel: George Moriarty, Research Support Specialist

Duration: May 1, 2005 – April 30, 2006

Requested Funds: $25,000

At the request of the CPIF/CPC, we revived our breeding program focused in the improvement of tolerance to cucumber mosaic virus resistance in bell peppers adapted for open field production in California. We have used the two leading sources of CMV resistance (CMR): C. annuum 'French Perennial', a Perennial line obtained from INRA, France that compared favorably with other versions of Perennial for stability and uniformity of CMR and a selection from this source (CMR 3990); and C. frutescens 'BG2814-6'. At the direction of the CPIF, we are using ëBaroní as the recurrent parent in this phase of the breeding program. Our disease screening protocol involves a cotyledon stage mechanical inoculation followed by two or more subsequent inoculations on older leaves and rouguing of all symptomatic plants until after fruit set. Resistance or tolerance derived from both the C. annuum and the C. frutescens sources refers to the failure to develop symptoms. Although virus titer appears to be substantially reduced in tolerant genotypes relative to fully susceptible genotypes, virus is generally present at levels that are slightly higher than uninoculated controls. To reflect this, we refer to materials we are developing as "tolerant" to CMV. We still feel that the combination of Perennial and the C. frutescens sources gives the highest frequency of symptomless progeny.

We now routinely run F3 progeny screens in order to confirm the tolerance of F2 plants used for backcrossing, since selected tolerant F2 plants give occasionally give low percentages of tolerant offspring. We have virtually no escapes of susceptible check plants (a couple of plants out of many hundreds). We hypothesized that the relatively low numbers of resistant individuals from resistant F2 plants may be due to some incompletely penetrant tolerance to the disease (i.e., the tolerance may be exhibited in the F2 but may fail to be expressed in a genotypically similar plant). We also see incomplete penetrance of CMV tolerance in the C. frutescens source and occasionally in Perennial.

Bell

When notice came about the California pepper commissionís renewed interest in CMV resistance we already had a program in place for an early maturing red bell with CMV resistance for the Northeast. We were using King of the North and a selection from Early Red Sweet as recurrent parents. For this program, we used best material from the original work with CalPep in the 1990s which was planted and re-screened for resistance. The variety Baron was crossed into both the CalPep and the Northeast populations. Selections from both populations were sent to Bob Heisey for testing and crossing as well. The list of pedigrees for the newly generated populations is below.

Populations generated in 04-05 in Ithaca

Resistant plants X Baron

	Pedigree
pedigree 1 five F1s	K.O.N. X [Gad X (Ver X (Ver X (Jup X (14-6 X F.Per))-18)F2-4)F2-2]F2 X CMR3990)F4 X Baron
pedigree 2 one F1	[Gad X (Ver X (Ver X (Jup X (14-6 X F.Per))-18)F2-4)F2-4]F3] X K.O.N. F4 X BARON)F1
pedigree 3 Three F1ís	[Gad X (Ver X (Ver X (Jup X (14-6 X F.Per))-18)F2-4)F2-4]F2 X CMR 3990 F2 x KON Bc1F2) X BARON)F1
pedigree 4 Three F1s	K.O.N. X [Gad X (Ver X (Ver X (Jup X (14-6 X F.Per))-18)F2-4)F2-2]F2 X CMR 3990 F1)F2 X KON}Bc1 F2 X BARON)F1
pedigree 5 One F1	K.O.N. X [Gad X (Ver X (Ver X (Jup X (14-6 X F.Per))-18)F2-4)F2-4]F3)F4 X BARON)F1
pedigree 6 Eight F1s	K.O.N. X [Gad X (Ver X (Ver X (Jup X (14-6 X F.Per))-18)F2-4)F2-4]F3)F2 X E.R.S)F2. X BARON)F1
pedigree 7 Four F6s	K.O.N. X [Gad x (Ver X (Ver X (Jup X (14-6 X F.Per))-18)F2-4)F2-11]F2 X CMR 3990 F1) F2 X Yankee Bell)F2 X BARON)F1
pedigree 8 three F1s	[Gad X (Ver X (Ver X (Jup X (14-6 X F.Per))-18)F2-4)F2-4]F3] X K.O.N.) F2 X E.R.S.)F2 X BARON)F1
pedigree 9 Two F1í=s	[Gad X (Ver X (Ver X (Jup X (14-6 X F.Per))-18)F2-4)F2-4]F3] X K.O.N. F2 X KON X BARON)F1

All 31 F1 populations generated in Ithaca were planted in the field in 2005 without virus pressure and selected for earliness, habit and large blocky fruit. Out of these populations 29 individual plant selections were made for F2 populations to be tested in the 05-06 winter greenhouse plantings. Several of the Northeast breeding lines were also sent to Bob Heisey for testing and crosses to "Baron". The F1s were increased in the greenhouse and F2s were sent to Ithaca for winter virus testing.

Populations generated in 04-05 by Bob Heisey

	Pedigree
pedigree H1 36 F2s	K.O.N. X [Gad X (Ver X (Ver X (Jup X (14-6 X F.Per))-18)F2-4)F2-4]F3)F4 X Baron
pedigree H2 17 F2s	[Gad X (Ver X (Ver X (Jup X (14-6 X F.Per))-18)F2-4)F2-4]F3] X K.O.N. F4 X Baron

For the 05–06 winter screens 50+ seed of each of the F2 families (82 families total) were planted in seedling flats. All plants were inoculated the first time in the cotyledon stage and again one week later. Two weeks post-inoculation all plants were classified, symptomatic plants were discarded and all symptomless plants were transplanted to 72 cell trays for further development. Resistant individuals will be selfed and crossed to Baron to develop F3 and BC1 F1 populations. The F3 populations will be inoculated and transplanted to the field for selection. BC1 F1 lines will be planted without inoculation and selected for type. A few F1 populations between Baron and CMR3990 are being selfed to generate F2 populations that will be included in the spring screens and field plantings.

Initial results are below.

Row #	pedigree	# resistant	# susc	Total plants	% resistant
3060	H2	12	30	42	28.57%
3061	H2	16	52	68	23.53%
3062	H2	13	60	73	17.81%
3063	H2	15	53	68	22.06%
3064	H2	19	37	56	33.93%
3065	H2	10	67	77	12.99%
3066	H2	19	59	78	24.36%
3067	H2	10	49	59	16.95%
3068	H2	25	50	75	33.33%
3069	H2	8	69	77	10.39%
3070	H2	16	40	56	28.57%
3071	H2	37	44	81	45.68%
3072	H2	13	65	78	16.67%
3073	H2	38	37	75	50.67%
3074	H2	22	65	87	25.29%
3075	H2	19	33	52	36.54%
3076	H2	23	53	76	30.26%
3077	H2	20	78	98	20.41%
3078	H1	25	46	71	35.21%
3079	H1	32	61	93	34.41%
3080	H1	37	35	72	51.39%
3081	H1	0	0	0	#DIV/0!
3082	H1	23	47	70	32.86%
3083	H1	23	56	79	29.11%
3084	H1	18	49	67	26.87%
3085	H1	21	71	92	22.83%
3086	H1	36	45	81	44.44%
3087	H1	41	54	95	43.16%
3088	H1	36	58	94	38.30%
3089	H1	9	55	64	14.06%
3090	H1	10	50	60	16.67%
3091	H1	12	71	83	14.46%
3092	H1	17	46	63	26.98%
3093	H1	11	54	65	16.92%
3094	H1	20	44	64	31.25%
3095	H1	17	45	62	27.42%
3096	H1	11	54	65	16.92%
3097	H1	35	60	95	36.84%
3098	H1	14	49	63	22.22%
3099	H1	19	55	74	25.68%
3100	H1	12	52	64	18.75%
3101	H1	13	52	65	20.00%
3102	H1	4	61	65	6.15%
3103	H1	10	58	68	14.71%
3104	H1	25	37	62	40.32%
3105	H1	14	46	60	23.33%
3106	H1	18	34	52	34.62%
3107	H1	22	33	55	40.00%
3108	H1	31	34	65	47.69%
3109	H1	22	37	59	37.29%
3110	H1	15	38	53	28.30%
3111	H1	32	35	67	47.76%
3112	H1	29	42	71	40.85%

Populations developed in Ithaca (pedigrees 1–9) had to be restarted and inoculated due to virus culture contamination. These populations have not been classified yet.

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