Development of Varieties with Enhanced Resistance to Common Scab Preliminary Results (2000-2005)

Félix Navarro1, Bryan Bowen2 Jiming Jiang3, Horia Groza4 and Jiwan Palta3 UW Breeding Program, Department of Horticulture

INTRODUCTION

Common Scab of Potato, a disease caused by the bacterium Streptomyces scabies continues to be a serious problem for growers in the north central and other potato producing regions of the United States. This disease adversely affects the marketable yield of potato crops, either through occasional reduction of gross yield, or more importantly, reducing the skin quality. The incidence and severity of scab varies with location and season. Cropping history, soil moisture, and soil texture are largely responsible for this variability (Haynes et al. 1997). Lowering the soil pH under 5.2 has been proposed to reduce scab problem, but this practice will greatly reduce the choices of crops that can be used in rotation with potatoes. Furthermore, other species, Streptomyces acidiscabies produces scab diseases at pH lower than 5.2 (Bonde and McIntyre, 1986; Lambert and Loria, 1989).

Another strategy to control common scab is maintaining the soil near field capacity during the 2-6 weeks following tuber initiation. However, in sandy soils like in the Central Sands of Wisconsin, this is difficult and may increase other disease problems (Pérombelon, 2002). Crop rotation does not provide an effective control to this disease because the bacterium S. scabies can survive for years in the absence of potatoes (Vrugging, 1976). Moreover, crop rotation makes consolidation of production fields difficult. Chemical control also has not provided reliable management tool.

Resistant varieties are the best option to manage common scab when available. Only a limited number of cultivars such as Russet Nugget and of russet type and the chipping cultivars Superior and Pike have shown acceptable resistance to this disease (Rieman, 1962; Holm et al., 1992; Loria et al. 1997; Jansky and Rouse, 2003). However, the standard chipping cultivars such as Atlantic as well as most recently released varieties (e.g. Snowden) are susceptible. Resistance to common scab has been detected in wild species. Results from scab evaluations by the Potato Germplasm Introduction Station indicate that out of 95 accessions that showed resistance to common scab, 48 corresponded to S. phureja subsp. phureja, 25 to S. tuberosum subsp. andigena, and 13 to S. chacoense subsp. chacoense. Breeding programs have included these species in the background of numerous breeding lines and some resistant varieties, e.g. Russet Nugget have resulted. Experimental strategies are needed to overcome the challenges posed by environment by location and year interactions in the evaluation of scab

1 Assistant Scientist- 4181 Camp Bryan Afon, Rhinelander, WI 54501. E-mail: [email protected]. 2 Researcher- 4181 Camp Bryan Afon, Rhinelander, WI 54501. E-mail:[email protected]. 3 Professor, Department of Horticulture, University of Wisconsin, 1575 Linden Drive, Madison WI 53706, Email: [email protected]. 4 Former University of Wisconsin Assistant Scientist. E-mail: [email protected]. resistance in breeding programs (Haynes et al. 1997; Bramwell et al. 1998; Bouchek- Mechiche et al., 2000; Jansky and Rouse, 2003). Starting in 2006 we have began anew effort in breeding for scab resistance. The objective of our study is to estimate the level of resistance in Wisconsin potato breeding lines and to use this information as a selection criterion to develop elite lines with future variety potential. We report here scab evaluation results from 2002 and 2005 seasons of investigation. In these two years it was possible to separate resistant and susceptible lines.

MATERIALS AND METHODS

The experiments were carried out during years 2000, 2002, 2004 and 2005 in a field with high scab potential at the UW-Rhinelander Agricultural Research Station. A randomized complete block design including 3 replications was used; plot size consisted of 8 hills 2000-2004, 4hills in 2005. Each year, 45 to 92 different lines as well as resistant and susceptible checks were evaluated. This included russets, reds and chipping lines. Line performance was evaluated by the incidence (% of tubers affected) and severity (% of lesion coverage) of scab. A combined, equally weighted scab index was developed from the incidence and severity values, where 1=no scab and 9 = worst scab (60-100 of tubers in a plot covered with pitted scab.

Statistical Analyses

The statistical model to study the variability among the lines was Yijk = µ + ri + varj(typek) + eijk. Scab index data were normalized using Box-Cox transformations. Best linear unbiased predictors (BLUP) for the line performance and their corresponding variances were estimated using REML in SAS. Data were transformed back to 1-9 scab index for reporting.

RESULTS

In years 2000 and 2002, scab pressure did not allow separation of resistant and susceptible lines and cultivars. In years 2003 and 2005 significant differences for scab performance separated resistant lines and cultivars from the susceptible ones.

The best scab resistance in the russet types was observed for Freedom Russet (W1836-3), W1879-1rus, W3132-1rus and W5785-5rus with equal or better scab resistance than Russet Burbank. (W1201) was one of the chipping varieties with outstanding scab resistance. Our results for MegaChip agree with results from the 2004 New Brunswick Chip variety trial, 2005 Michigan and Idaho (US Potato Board 2005-Snack) and 2005 National Scab Trial. Enhanced resistance to scab, in addition to high specific gravity and chip quality are important attributes of MegaChip. Of the red varieties tested, W2275-7, a sister line to Villeta Rose (W2275-3R) was the only one with better performance than Dark in 2003.

PROSPECTS FOR THE FUTURE

To be more efficient we need to develop a bigger number of lines that have scab resistance and good performance for yield and quality. Our plan to achieve that goal include the use of additional locations with high scab potential and the evaluation of a bigger number of progenies at earlier stages in the breeding scheme. Implementation of these should increase our chances of detecting more scab resistant lines that may be considered for release through SpudPro in the future.

Table 1. Scab performance of breeding lines, Rhinelander Agricultural Research Station, 2003. Breeding Scab P- Line 1-9 Value Comments from Yield Trials from WI and Out of State ROUND WHITE W2955-4 2.8 0.0006 Nice, midsize tubers, knobs, yellow flesh, variable size, gravity 1.074 W3002-2 2.8 0.0006 Nice, midsize, growth cracks, specific gravity 1.079, deep bud end W2492-3 4.2 0.0236 good size round, rough, growth cracks, specific gravity 1.082 W2033-8 4.4 0.0452 Excellent yield, color, nice smooth mid size tubers, specific gravity 1.091 W1201 4.6 0.0618 MegaChip, early bulk, good chip color from 45ºF, specific gravity 1.094 ND5822-C7 4.8 0.1005 Good size, ON, rough, med deep eyes, WI:NCRT03 MSH095-4 4.9 0.1261 Medium specific gravity, yield similar to Atlantic, Chip from 45ºF SFA03 W2143-1 4.9 0.1207 Flat, netting and smooth, specific gravity 1.086, some vascular discoloration W2889-1 5.1 0.1939 Pink eye, yellow skin, light netting, specific gravity 1.070 MSE221-1 5.3 0.2735 Nice, uniform: NCRT03, WI, flat oval, knobby 02 W2203-2 5.6 0.4705 Oval, smooth tubers that may become green, high specific gravity 1.092 V0056-1 5.7 0.5478 Some pink rot (ON), small tubers (WI): NCRT03 B0766-3 5.9 0.6788 Very nice: NCRT03, WI, NCRT01 W2768-3 5.9 0.6925 Flat, smooth, netting visible, specific gravity 1.084 W2982-1 6.0 0.7909 Oval shape, smooth, specific gravity 1.076 W2310-3 6.1 0.8993 Flat, too oval, Specific gravity 1.084 W2768-9 6.1 0.8404 Rough, flat, oval, specific gravity 1.076 W2114-5 6.2 0.9098 Low yield, medium spec. gravity, shatter-bruise W2615-2 6.3 0.9718 White color, specific gravity 1.078 W2962-2 6.3 0.9098 Flat, light netting, large tubers, specific gravity 1.082, vascular discoloration W2310-11 6.4 0.8721 Oval, small, like a prism, specific gravity 1.075 Norvalley 6.5 0.7974 Smooth tubers, variable size and shape:NCRT03 V0379-2 6.5 0.7772 Good size, uniform, not smooth: NCRT03, ON,WI W1443 6.6 0.6527 Atlantic type, early bulking, good yield & chips, net. NCRT04 W1773-7 6.6 0.6951 Fresh harvest chipping, good size, yield and quality, sg=1.087. SFA04 W5784-3 6.6 0.6736 Yellow skin, yellow flesh, smooth, light netting, sg 1.082 W2265-25 6.7 0.5833 Deep bud end, high specific gravity 1.090, some hollow hearts W3011-1 6.7 0.5741 Greens, small size tubers, specific gravity 1.089 Snowden 6.9 0.4032 Standard variety, deep eyes, small-mid size tubers: NCRT02, s. gravity 1.088 Note: P-values < 0.05 indicate that scab performance is statistically different to the overall mean. Scab scale 1=best, 9=worst. Scab performance of boldfaced lines was statistically better than the rest. NCRT= North Central Regional Trial. SFA=Snack Food Association/US Potato Board Chip Variety Trial.

Table 1 (Cont’d). Scab performance of breeding lines, Rhinelander Agricultural Research Station, 2003. Scab P- Breeding Line 1-9 Value Comments from Yield Trials from WI and Out of State ROUND WHITE (Cont’d) W2978-2 6.9 0.4446 Round, nice looking, deep stolon insertion, specific gravity 1.076 W2978-3 6.9 0.4504 Smooth, white, specific gravity 1.075 W2978-3 6.9 0.4504 Smooth, white, specific gravity 1.075 ND2470-27 7.0 0.3510 Very nice, good size, round: NCRT03, ON, WI. Folded bud end 99 W2438-3 7.1 0.2860 Yellow flesh, specific gravity 1.079, chipping quality, deep eyes W2499-12 7.1 0.3235 Smooth, flat-oval, specific gravity 1.078 W2660-2 7.1 0.2860 Nice, smooth, high specific gravity 1.094 W2133-1 7.2 0.2510 High yield, good internal quality, mid-large tubers. Chips from 45-50ºF W2233-2 7.2 0.2278 Low yield, poor size, tendency to shatter bruise W2656-5 7.2 0.2472 Some vascular discoloration and bruises, specific gravity 1.086 W2327-4 7.3 0.2161 Oval, smooth, specific gravity 1.087 W2717-5 7.7 0.0725 Good yield, specific gravity 1.092, remarkable fry color W5784-7 7.7 0.0676 Yellow skin, yellow flesh, high specific gravity 1.097 Atlantic 7.8 0.0512 Standard, large tubers, deep eyes, stolons NCRT02-04, s. gravity 1.094 W1980-1 7.8 0.0618 MSH031-5 8.0 0.0272 Good specific gravity, small and flat: NCRT03, WI W5785-2 8.2 0.0142 Nice round, specific gravity 1.086 RED W2275-7R 4.6 0.0664 Sister to Villeta Rose MN19525R 5.5 0.3820 Skins, bruises, very nice color: NCRT, MN2003. W2303-8R 5.7 0.5082 Mid-large tuber size, round shape, high yield, excellent color Dark Red Norland 6.5 0.8045 Standard variety. Oblong, uniform, fading color, NCRT01 ND3196-1R 7.0 0.3636 Skinning, med. deep eyes, medium red:NCRT02, Good color 00. W2275-3R 7.4 0.1646 Villeta Rose, dark red round tubers, 6-8 oz in size CV89023-2R 8.0 0.0346 Attractive & uniform: NCRT03, ON, Fading color WI-02 W2275-9R 8.0 0.0272 Sister to Villeta Rose, darker in color, 6-8 oz. Red Pontiac 8.5 0.0053 Standard variety. Round, good size, deep eyes: NCRT01 RUSSET/LONG MN18710 2.8 0.0005 Small-medium tubers, too short for French fries: NCRT02 W1836-3rus 2.8 0.0005 Freedom Russet, high yield, medium-dark net, specific gravity 1.071 W1879-1rus 2.8 0.0005 Good appearance, solids & processing quality, specific gravity 1.066 W5785-4rus 2.8 0.0005 Nice, big, dark russet, specific gravity 1.068, no internal defects A9014-2 4.2 0.0242 Short, dark netted: NCRT03, WI Russet Burbank 5.0 0.1747 Standard variety, specific gravity 1.072 MSE202-3rus 5.3 0.2897 Attractive, uniform, midsize, sprouts: NCRT03 Russet Norkotah 5.4 0.3543 Nice size & shape, attractive, uniform: NCRT03 MN, ON AC Stampede Russet 5.6 0.4489 Mid-large size, smooth, attractive:NCRT03 ON,WI Note: P-values < 0.05 indicate that scab performance is statistically different to the overall mean. Scab scale 1=best, 9=worst. Scab performance of boldfaced lines was statistically better than the rest. NCRT= North Central Regional Trial. SFA=Snack Food Association/US Potato Board Chip Variety Trial.

Table 1 (Cont’d). Scab performance of breeding lines, Rhinelander Agricultural Research Station, 2003. Scab P- Breeding Line 1-9 Value Comments from Yield Trials from WI and Out of State RUSSET/LONG (Cont’d) W5781-5rus 5.6 0.4220 Long white, blocky, specific gravity 1.076 MN15620Lrus 5.6 0.4195 Excellent size, shape, flesh, long, pink: NCRT03 W2466-5rus 7.0 0.3984 Long white, light russet, nice looking, specific gravity 1.071 W2466-9rus 7.1 0.3188 Long white, bulky, some pink rot, specific gravity 1.075 W2249-4rus 7.7 0.0732 Light russet, good appearance, yield, solids, frying W1151rus 7.8 0.0512 Very attractive blocky tubers, fresh market, low spec. gravity 96 MN18747rus 7.8 0.0512 Good russet, blocky, too short: NCRT03, long in MN-01 A90586-11rus 8.0 0.0280 Light net, very attractive, uniform: NCRT03, ON Pacific Russet 8.3 0.0087 Blocky, uniform, attractive (ON), short, oval (WI)

Table 2. Scab performance of breeding lines, Rhinelander Agricultural Research Station, 2005. Scab P- Breeding Line 1-9 Value Comments from Yield Trials from WI and Out of State ROUND WHITE W3157-2 5.0 0.0383 Deep eyes, good size, smooth, growth cracks, hollow heart, s. grav. 1.084 W4132-1 5.3 0.1201 Some small, uniform, may be resistant to late blight ARS1253-1 5.5 0.1288 Pre-breeding line W2128-8 5.6 0.2073 Lumpy, round-oval, skinning, need size. NCRT04. Good solids, cold chipper W2203-2 6.3 0.5636 Oval, smooth tubers that may become green, high specific gravity 1.092 ARS1253-2 6.3 0.5521 Pre-breeding line MN99380-1 6.3 0.5636 Minnesota line MSI152-A 6.3 0.5521 Round-oval, uniform, large, blocky: NCRT04 WTS1181-5 6.3 0.5521 Pre-breeding line WTS1181-1 6.5 0.7141 Pre-breeding line W2310-3 6.6 0.8167 Oval shape, netting, specific gravity 1.094 W3910-4 6.6 0.8167 Medium deep eyes, big, uniform, good yield, spec. gravity 1.074, hollow heart ARS1254-2 6.7 0.8889 Pre-breeding line ARS1255-1 6.7 0.8889 Pre-breeding line MN9460-21 6.7 0.8889 Minnesota line MN99380-1 6.7 0.8889 Round, light net, small-mid size, excel chipper: NCRT04 W2644-3 6.8 0.9750 Big tubers, medium deep eyes, specific gravity 1.084 W2841-1 6.8 0.9660 Smooth , oval tubers, nice looking, specific gravity 1.086 W3273-2 6.8 0.9660 Very nice looking, relatively small and yellow flesh Norvalley 6.8 0.9660 Smooth tubers, variable size and shape:NCRT03 W2301-1P 6.8 1.0000 Purple MN460-21 6.9 0.9188 Minnesota line W3255-2 7.1 0.6847 Very nice looking, specific gravity 1.074 Note: P-values < 0.05 indicate that scab performance is statistically different to the overall mean. Scab scale 1=best, 9=worst. Scab performance of boldfaced lines was statistically better than the rest. NCRT= North Central Regional Trial. SFA=Snack Food Association/US Potato Board Chip Variety Trial. Table 2 (Cont’d). Scab performance of breeding lines, Rhinelander Agricultural Research Station, 2005. Scab P- Breeding Line 1-9 Value Comments from Yield Trials from WI and Out of State ROUND WHITE (Cont’d) W4016-4 7.1 0.6847 Mid size, uniform, some netting, specific gravity 1.061, fries well W4113-5 7.1 0.6847 Very nice, white flesh, lenticels, large size, specific gravity 1.064 V0319-1 7.1 0.6847 Lumpy, knobs, small-large, round-oval , cracks. NCRT04 WTS1180-7 7.1 0.6847 Pre-breeding line W2133-1 7.2 0.5445 High yield, good internal quality, mid-large tubers. Chips from 45-50ºF. W3145-5 7.2 0.5977 Yellow flesh, high specific gravity (1.093), internal brown spot. W3291-4 7.3 0.5295 Specific gravity 1.085, some vascular discoloration NY126 7.3 0.5295 Nice yellow flesh, tuber appearance, table stock WTS1181-10 7.3 0.5295 Pre-breeding line Snowden 7.4 0.3738 Standard variety, deep eyes, small-mid size tubers: NCRT02, s. gravity 1.088 W2128-8 7.5 0.2982 Lumpy, round-oval, skinning, need size. NCRT04. Good solids, chips W2324-1 7.5 0.2982 Good yield potential and solids, good table stock W4113-3 7.5 0.2982 Hollow heart, 90% “A” tubers, specific gravity 1.073 F12246-6 7.5 0.2982 Canadian line MSH095-4 7.6 0.2767 Round-oval, flattened, stolons, long, rough: NCRT04. Good chips NSA03 W2154-1 7.9 0.1291 Good solids and chipping color from 44ºF. Medium yield. W2309-7 7.9 0.1291 Smooth & round, good chipper, specific gravity 1.092, no internal defects W3351-3 7.9 0.1291 Yellow flesh, no internal defects, 93.5 “A” tubers. W3747-14 7.9 0.1291 Smooth & large, round chipper, specific gravity 1.087, no internal defects. W3747-3 7.9 0.1291 High percentage of “A” tubers. Specific gravity 1.072 Atlantic 7.9 0.1291 Standard var. , large tubers, deep eyes, stolons NCRT02-04, s. gravity 1.094 F12486-2 7.9 0.1291 Canadian line MSJ461-1 7.9 0.1291 Uniform round tubers, low internal and chip defects. SFA04 WTS1181-9 7.9 0.1291 Pre-breeding line W3754-3 8.2 0.0468 93.5% “A” tubers, specific gravity 1.085. WTS1180-4 8.2 0.0468 Pre-breeding line RED W2275-4R 5.5 0.1288 Sister to Villeta Rose W2303-8R 5.6 0.2073 Mid-large tuber size, round shape, high yield, excellent color W2609-1R 5.6 0.2073 Good color, no internal defects, specific gravity 1.074 W2624-1R 6.3 0.5521 Medium size, light color to good color specific gravity 1.056 W3921-1R 6.3 0.5521 Smooth & small long red W3571-2R 6.5 0.6931 Nice color, smooth, small tubers, some vascular discoloration W3575-1R 6.8 0.9750 Round, blight on skin, some vascular discoloration and shatter-bruise Red Norland 7.0 0.8293 Standard variety. Oblong, uniform, fading color, NCRT01 Villeta Rose 7.1 0.6847 Good color, small-mid size, good yield: NCRT04 W3016-6R 7.2 0.5445 Nice, medium (good size), good color, specific gravity 1.071. W2799-1R 7.3 0.5295 Deep red color that holds in storage, mid-large oblong tuber, white flesh W3565-5R 7.3 0.5295 Fresh market, medium to late maturity Note: P-values < 0.05 indicate that scab performance is statistically different to the overall mean. Scab scale 1=best, 9=worst. Scab performance of boldfaced lines was statistically better than the rest. NCRT= North Central Regional Trial. SFA=Snack Food Association/US Potato Board Chip Variety Trial. Table 2 (Cont’d). Scab performance of breeding lines, Rhinelander Agricultural Research Station, 2005. Scab P- Breeding Line 1-9 Value Comments from Yield Trials from WI and Out of State RUSSET/LONG Red Pontiac 7.9 0.1291 Standard variety. Round, good size, deep eyes: NCRT01 W1879-1rus 4.3 0.0066 Good appearance, solids and processing quality W3132-1rus 4.3 0.0066 Nice, blocky, growth cracks, specific gravity 1.073 W3160-5rus 5.0 0.0833 Better than standards for late blight (lab & field) s. grav. 1.075 Russet Burbank 5.2 0.0630 Standard variety, specific gravity 1.072 V1102-1 5.2 0.0630 Oval-oblong, lumpy, mid-large, light russet, NCRT04 W3140-3rus 5.3 0.0824 Nice looking, light russet, large tubers spec. gravity 1.065 W2683-2rus 5.9 0.2751 Short tubers, rough, very big (Hancock), specific gravity 1.070. W4143-3rus 6.0 0.3455 Excellent yield, medium dark, growth cracks, spec. grav 1.072 W3533-8rus 6.1 0.3653 Medium dark, good color, uniform, blocky, spec. gravity 1.065 W3042-1Prus 6.3 0.5636 Purple russet W4146-1rus 6.6 0.8167 Nice shape, 95% “A” tubers, specific gravity 1.085 W3174-1rus 6.8 0.9660 Dark netting, short tubers, hollow hearts, some growth cracks Gemstar 6.8 0.9660 Nice shape & size, good specific gravity and French fries W2253-5rus 7.1 0.6847 No internal defects, specific gravity 1.063 W3059-1Yus 7.2 0.5977 Yellow flesh, light netting, specific gravity 1.085 AC Stampede Russet 7.2 0.5977 Mid-large size, smooth, attractive:NCRT03 ON,WI W2466-9rus 7.3 0.4824 Long white, bulky, some pink rot, specific gravity 1.075 W3059-2rus 7.4 0.3738 Light russet, lenticels, blocky--oval, spec. gravity 1.085 W4096-3rus 7.4 0.3738 Nice, specific gravity 1.073 Russet Norkotah 7.5 0.2982 Nice size & shape, attractive, uniform: NCRT03 MN, ON W3162-3rus 7.9 0.1291 Large russet, oval, specific gravity 1.077 YELLOW FLESH MN96013-1R 5.0 0.0833 Line from Minnesota MSI005-20 5.1 0.0435 Line from Minnesota W5784-1Y 5.3 0.0684 Very nice, yellow skin, yellow flesh, specific gravity 1.084 ARS1253-8 6.4 0.5969 Yellow flesh ARS1253-4 6.8 0.9650 Yellow flesh W5784-3Y 7.1 0.6847 Yellow skin, yellow flesh, smooth, light netting, sg 1.082 ARS1253-6 7.2 0.5445 Yelllow flesh W5787-4Y 7.9 0.1291 Yellow skin, yellow flesh, high specific gravity 1.097 W5784-7Y 8.2 0.0468 Yellow skin, yellow flesh, high specific gravity 1.097 Note: P-values < 0.05 indicate that scab performance is statistically different to the overall mean. Scab scale 1=best, 9=worst. Scab performance of boldfaced lines was statistically better than the rest. NCRT= North Central Regional Trial. SFA= National Snack Food Association Trial

REFERENCES

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