March 15, 1999
Compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967

DISEASE TOLERANCE IN VEGETABLES is one of the most effective and least expensive means of controlling plant diseases. Here are descriptions of new developments in disease resistant or tolerant hybrids that are available for vegetable growers.

Disease Resistance in Squash: Breeders have been working on resistance for many viruses. For zucchini, resistance/tolerance to viral infections was developed by Novartis/Rogers and is available in Dividend and Revenue with resistance/tolerance to infection by zucchini yellows mosaic virus (ZYMV), watermelon mosaic virus II (WMV-2) and cucumber mosaic virus (CMV). Harris Moran has also worked on resistance to viral infections and developed Tigress with resistance/tolerance to ZYMV and WMV-2, Puma with resistance/tolerance to ZYMV, WMV-2 and papaya ring spot virus (PRSV), and Onyx with resistance/tolerance to ZYMV, WMV-2, CMV and powdery mildew (PM). Good news for summer squash growers is ZYMV and PRSV tolerance developed by Harris Moran in their new HMX 7705 hybrid. HMX 7705 also has the precocious yellow gene that resists greening caused by CMV and WMV-2. Many yellow straight?neck squash now have the precocious yellow gene that resists greening of tissue caused by many cucurbit viruses such as ZYMV, CMV, WMV-2, and PRSV, BUT remember this will last for only a short period of time. The only crookneck with the precocious yellow gene that resists greening of tissue caused by these viruses is Superset from Harris Moran.

Transgenic resistance (provided by a single gene inserted from another species) yields more complete resistance to some strains of a pathogen but is subject to pathogen variation and environment, etc. Asgrow was the first to develop a truly transgenic zucchini. Independence II and Declaration II are resistant to ZYMV and WMV-2. A transgenic yellow crookneck currently available from Asgrow is Prelude II, with resistance to ZYMV and WMV-2; in addition it has powdery mildew tolerance. Asgrow hopes to release Liberator III, a new transgenic yellow straight neck hybrid with resistance to CMV, WMV-2 and ZYMV this season. Asgrow should have other new transgenic hybrids available in the near future. These are Destiny III, a yellow crookneck, and Freedom III, a semi-crookneck; both are resistant to CMV, WMV-2 and ZYMV.

Powdery mildew tolerance is available from Harris Moran in their black zucchini Onyx. Powdery mildew tolerance in yellow straight neck squash was introduced by Peto (Seminis Seeds) with Sunray. Observed field tolerance to downy mildew has also been noticed with Sunray. General Patton, from Asgrow, has powdery mildew tolerance. Remember that Prelude II, Asgrow's transgenic yellow crookneck, also has powdery mildew tolerance.

Disease Resistance in Pumpkins: Often the problem with any breeding program is trying to get disease resistance while maintaining quality. This breeding problem is particularly true in the case of pumpkins. However, a new development for pumpkins is disease resistance/tolerance to powdery mildew. Harris Moran was the first to come out with powdery mildew tolerance in a cultivar now called Merlin. This is a 115 day, 15-25 pound pumpkin. Magic Lantern, from Harris Moran, is a midseason, 17-24 pound pumpkin with powdery mildew tolerance. HMX-6689 from Harris Moran looks promising in variety trials in Kentucky for both yield and powdery mildew tolerance. New from Asgrow is XPH-2837, a Howden type pumpkin (23-25 lb) with intermediate tolerance to powdery mildew. RWS?6260 from Novartis Seeds/Rogers Brand is a new small pie pumpkin like Baby Pan or Small Sugar that has powdery mildew tolerance. Lil' Ironsides, from Harris Moran, is a mini, 2-3 pound pumpkin with tolerance to Fusarium and Phytophthora.

Disease Resistance in Cabbage: A new development for cabbage is disease resistance/tolerance to black rot. Many hybrids are now available for both the fresh and processing markets. For green fresh markets Bronco, Fresco, Gideon, and Ramada have tolerance to black rot. Blue-green fresh and processing types with black rot tolerance include Atlantis, Augusta, Blue Bayou, Blue Gem, Blue Thunder, Blue Vantage, Emblem, Fortress, Green Cup, Lynx, Pacifica, Quisto, Royal Vantage, Sure Vantage, Talisman, Tenacity, Vantage Point, and Pruktor. Red types are Red Dynasty and Super Red 77. Both red types Regina and Super Red 80 have a low tolerance to black rot. Most cabbage hybrids mentioned also have resistance to Fusarium yellows.

Disease Resistance in Pepper: New developments in disease resistance for pepper hybrid varieties are resistance/tolerance to bacterial leaf spot races 1, 2, and 3, tolerance to Phytophthora, and tolerance to cucumber mosaic virus (CMV). Many hybrids have resistance to bacterial leaf spot (BLS) races 1 and 2, but several new hybrids also have resistance to race 3. Green-Red sweet peppers with resistance/tolerance to BLS races 1, 2, and 3 include Boynton Bell, Brigadier, Commandant, Enterprise, PS334094, Sentry, X3R Camelot, X3R Wizard and Yorktown. Green?yellow types are Early Sunsation, Gold Coast, and X3R Aladdin. Pageant is the new name for RPP4277-F1, a sweet banana pepper from Novartis Seeds/Rogers Brand. Pageant has resistance/tolerance to bacterial leaf spot races 1, 2, and 3. Phytophthora tolerance is available in Harris Moran's Emerald Isle and in Novartis Seeds/Rogers Brand's pepper named Paladin. Emerald Isle also has some CMV tolerance. Breeders ask that growers realize that breeding for resistance to Phytophthora and CMV is much more complex than for bacterial leaf spot because there are many more strains of these pathogens and they effect many more crops.

Disease Resistance in Tomato: New developments in disease resistance for tomato varieties are resistance/tolerance to Fusarium races 1, 2, and 3, bacterial speck, and early blight. Many tomato hybrids have resistance/tolerance to Fusarium races 1 and 2. However, Fusarium resistance/tolerance to races 1, 2, and 3 (F1, 2, 3) and Verticillium race 1 (V1) is now available in Floralina, developed by NC State, University of Florida and Peto Seeds. Floralina is available through Rupp Seeds and Seedway (and others). Peto Seeds also has a hybrid variety called Captiva that has resistance to Fusarium races 1, 2, and 3, V1, Alternaria stem canker (ASC), and gray leaf spot (GLS). Floralina and Captiva are fresh market, determinate varieties. Bacterial speck resistance/tolerance is available on many saladette or plum type tomatoes such as Aztec, Puebla, Spectrum 882, Supra and Yaqui. XPH?10089, a new hybrid from Asgrow, has resistance/tolerance to V1, Fusarium races 1, 2, and 3, ASC, and GLS, but this year it is available only on a limited basis as seed for trials. Mountain Fresh and Plum Dandy have tolerance to early blight.

Asgrow has two other new hybrids available. SunShine which will replace Sunstart; it has V1, F1, 2, ASC, and GLS disease resistance/tolerance. SunShine has the same maturity as Sunstart, but has a smoother fruit, it doesn't weather check, and has better foliage cover. Sun chief which will replace Sunrise has a larger fruit, and V1, F1 and 2, ASC, and GLS disease resistance/tolerance. (Adapted from Illinois Extension, contactt Loretta Ortiz 217-333-1845;

RESISTANCE OF BOTRYTIS (GRAY MOLD) to two major fungicides has been reported in S. Carolina and could well be prevalent in the trade throughout the northeast. This explains a lot of failures in botrytis control programs that depend too heavily on fungicides rather than good management. Research conducted using 35 isolates collected in commercial greenhouses in South Carolina showed that 69% were resistant to vinclozolin and 81% were resistant to
thiophanate?methyl, based on media tests. When the resistant and sensitive isolates were inoculated onto fungicide treated plants, percent disease incidence due to the resistant  isolates was in the 90's for both fungicides. Publication of this research, conducted by Len Yourman and Steve Jeffers, will be out in Plant Disease soon. (From Alan Gotleib, UVM)


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SWEET CORN AND POTATO IPM MEETING will be held on Tuesday April 6 in Lewiston, Maine at the Ramada Inn, located at 490 Pleasant St, just off exit 13 of the Maine Turnpike. The morning session starts at 9 am and will cover insect and weed managament in sweet corn. The afternoon session starts at 1pm and will cover insect, disease and weed management in potatoes. Registration is $20 at the door and includes lunch. Five pesticide applicator recertification credits will be offered. For more information call Dave Handley at (207) 933-2100