The 1997 trials included several cultivars from 1996 and several new entries as well. The 1997 trials appear to have cleared up some of the bolting problems and extended our knowledge base about production and pungency of a number of sweet onion cultivars. Trials were conducted in Buellton and Arroyo Grande in 1997 and we did not see bolting at either site. Bolting is related to the intensity of cold temperatures and the size of the onion plant at the time the cold temperatures come. Also, some cultivars bolt more than others at a given temperature. We planted 30 days later in 1997 than in 1996 and used somewhat smaller transplants and these changes appear to have eliminated the bolting problem. We did not see bolting in 1997 from plants seeded November 15 to December 1 and transplanted in early February. All of these transplants were grown in trays (512 cells) in an unheated greenhouse, and plants were slightly less than pencil size when planted in the field.
The trade-off with planting smaller transplants relatively late with short-day cultivars is that the plants may not have time to size up. This is because they receive the bulbing signal as daylengths reach 12-13 hours in mid-to late March and are usually ready for harvest about June 1.
We did not observe sizing problems generally and particularly in the Arroyo Grande plots where the cooperator transplanted single lines per bed, the harvested onions often exceeded 80% jumbo sizes. This is important because it means that these short-day cultivars may be transplanted at least as late as February 15 on the Central Coast and still have time to size up. Management of cultural practices is also critical to onion sizing.
| CULTIVAR | |||||
| Encino | 32.0 | 65-74 | 15.6 | 3-27 | |
| Linda Vista | 40.0 | 88-93 | 19.8 | 35-50 | |
| Granex 429 | 46.8 | 72-96 | 15.7 | 15-37 | |
| Excaliber | 30.2 | 75-86 | n/a | n/a | |
| Granex 33 | 41.0 | 64-88 | 15.6 | 23-31 | |
| Monsoon | 32.2 | 57-86 | 16.8 | n/a | |
| TX1015 | 43.8 | 74-94 | 16.5 | 17-36 | |
| MrMax | 39.3 | 57-76 | 12.4 | 15-27 | |
| Sunsweet | 43.9 | 77-86 | 16.6 | n/a | |
| Daybreak | 43.4 | 80-93 | 17.4 | 44 | |
| Ringer | 43.5 | 81-88 | 14.3 | 17-33 | |
1The two locations are not comparable. Plot size and plant density were different between sites.
Replicates incomplete at Buellton.
The results show that all of the cultivars have the potential to produce a high percentage of jumbo sizes even when relatively small transplants are planted in early February. All of the cultivars evaluated will produce commercially acceptable yields, and cultivar selection will now be driven more by specific management preferences and requirements of the market.
Marita Cantwell, Vegetable Crop Post Harvest Specialist at UC Davis, collaborated again this season to evaluate harvest quality and pungency of the onion cultivars. We evaluated pyruvic acid development (PAD), which is a laboratory test which has been inversely related to mildness or "sweetness." In other words, a high PAD value is a sign of a more pungent onion and, thus, less desirable as a sweet onion. Onions produced in a range of environments are generally acceptable to consumers as "sweet" onions when the PAD is below 5.0. The lower the PAD, the "sweeter" or milder the onion. A standard, "storage type" onion will typically have PAD levels in the 9 -12 range.
It is important to note that sugar content has not been consistently related to mildness or "sweetness" in taste panel evaluations.
All of the short-day onion cultivars we have evaluated in two seasons have thus far generally shown PAD values in the range of acceptability for sale as sweet onions. There has been some variation between growing sites, and other factors such as soil sulfur levels and the growing environment have been shown to affect pungency. The PAD and sugar content at harvest for the different cultivars are presented in Table 2.
| CULTIVAR | |||||
| Encino | 3.16 | 69.1 | 4.15 | 64.7 | |
| Linda Vista | 4.67 | -- | 4.18 | -- | |
| Granex 429 | 3.23 | -- | 4.82 | -- | |
| Excaliber | 3.32 | 40.6 | 2.87 | 61.7 | |
| Granex 33 | 3.18 | -- | 4.05 | -- | |
| Monsoon | 3.66 | 45.3 | 3.81 | 63.8 | |
| TX1015 | 3.73 | -- | 4.47 | -- | |
| MrMax | 3.07 | 61.5 | 3.79 | 58.4 | |
| Sunsweet | 3.16 | 54.9 | 2.98 | 75.2 | |
| Daybreak | 3.88 | 52.4 | 5.29 | 52.8 | |
| Ringer | 3.05 | 35.6 | 4.51 | -- | |
1 PAD expressed as mole pyruvate /g FM
2 Sugar concentration expressed as mg/g FM
Short-day onions typically are not stored for extended periods because the relatively high moisture content of these onions has traditionally made them unsuitable for extended storage. Sweet onions are occasionally stored in controlled atmosphere (CA) storage for up to four months to extend the sales season. Dr. Cantwell also evaluated the PADs, sugars, and quality of the different cultivars before and after storage. The results of the storage trials will be presented in the next issue of Central Coast Agriculture Highlights.
It may be possible to extend the sales season for these onions up to 90 - 120 days. Some preliminary observations during 1996 and 1997 showed that it may be possible to store short-day onion cultivars for as much as 60 to 120 days in cool dry storage with relatively little specialized storage infrastructure. We will be evaluating different types of storage options for short-day "sweet" onions during the 1998 season to see if it will be possible for growers to extend their marketing season for fresh sweet onions.
Growing heirlooms is not without drawbacks, however, even when flavor is exceptional. Often heirloom cultivars suffer from other fruit quality or plant vigor shortcomings. The plant or fruit may be more susceptible to diseases or fruit may show cracking, catfacing, or discoloration. A buyer looking for a typical tomato may be put off by the first site of many heirlooms. It is extremely important to get to know the market for prospective heirloom tomatoes. It is also important to be certain that the market knows what it is getting and there is adequate price compensation to adjust for potential production shortfalls.
San Joaquin County Farm Advisors Benny Fouche and Bob Mullen with grower Ted Viss and Technician Dawn Cutter evaluated a number of heirloom-type tomatoes and several modern tomato cultivars in field trials during the 1997 season. They also put several of the more productive cultivars into blind taste panel evaluations to determine which the tasters preferred.
Flavor and taste evaluations are generally very difficult. People have different preferences for tomato flavors; some like them sweet and light and others acidic and intense. And tasters often tire after a few samples, and the subsequent evaluations are unreliable. So it is important to note that taste panel evaluations often involve a great deal of variability.
I am including here a list of the heirloom tomato lines evaluated and some of the grower’s field notes from the trials. In Table 2 are results of taste panel evaluations on the cultivars which were sufficiently productive and attractive for the grower to feel that the cultivar has potential for commercial production. Cultivars not included in taste panel tests produced very low yields or very poor quality or both. As an example, the popular red Brandywine produced only 8.2 tons per acre in these trials in which a number of cultivars produced from 30 to more than 50 tons per acre. And Brandywine’s flavor was unremarkable by comparison to a number of other cultivars.
| CULTIVAR | OBSERVATIONS |
| Amish Paste | Slightly angular, moderate sunburn, good flavor |
| Arkansas Traveler | Long, pointed, meaty Roma type, severe pox, green shoulder, good flavor |
| Atomic | Severe nematode damage to vine, sunburn, ground rot |
| Aochka | Very large, rough, catfaced, flat, yellow fruit, severe rot, good acid flavor |
| Black Prince | Small, brownish red, egg-shaped |
| Brandywine | Very rough pink fruit, pox, severe cracking, ground rot, poor flavor |
| Caro Rich | Nice, orange fruit, good color, flavor, and quality |
| Celebrity | Green shouldered, moderate cracking, some rot, sunburn |
| Champion | Somewhat rough, soft fruit, green shoulders |
| Cherokee Purple | Large green shouldered pink/brown fruit, catfacing, ground rot, ugly |
| Dad's Sunset | Nice, orange, elongated fruit, good color, excellent flavor, late maturing |
| Daniela | Small, round, uniform shape, black mold, sunburn |
| Druzba | Green shoulder, variable shape, cracking, good flavor |
| Early Girl | Small, green shoulder, some black mold |
| Eva Purple Hall | Nice, round, soft, pink fruit, good flavor |
| Hawaiian | Nice, slightly pointed, angular, green shoulder |
| Hillbilly | Rough, ribbed, bi-colored, yellow, pink, fruit cracking, ground rot |
| Lemon Boy | Yellow, soft, good color, moderate cracking and pox, good flavor |
| Old German | Similar to Hillbilly |
| Oxheart | Pink, rough, irregular shaped, green shoulder, puffy, cracking and rot, bland flavor |
| Pruden's Purple | Rough, pink, variable shape and size, cracking and ground rot |
| Shady Lady | Sunburned, black mold, severe nematode damage |
| Sunbrite | Rough fruit, cracking, ground rot and sunburn |
| Tenerife | Small exposed fruit, severe sunburn |
| Yellow Brandywine | Catfacing, ground rot, pox, good acidic flavor |
Table 2. Taste panel. Evaluation of more productive fresh market tomato lines. San Joaquin County. 1997.
1 1 = very bad, 3 = average, 5 = best flavor.
CULTIVAR Taste Rating Tons/Acre W424 2.07 a 52.1 W436 2.36 ab 30.5 PSR 208795 2.50 ab 27.5 Daniela 2.50 ab 34.1 Lynx 2.64 ab 24.2 PSR 206195 2.64 ab 19.6 Arkansas Traveler 2.71 ab 21.8 Celebrity 2.86 abc 28.2 Early Girl 2.93 abc 34.9 Eva Purple Hall 3.00 abc 23.6 Hawaiian 3.56 bc 36.5 Dad's Sunset 3.50 bc 23.0 Lemon Boy 4.07 c 36.9
Mean ratings followed by the sample letter are not significantly different at the 5% level.
There are numerous other heirloom tomatoes, and the San Joaquin County group plans to extend the trials in the 1998 season. We may see very different results in other years. If you wish to receive a copy of the complete set of data from these trials, contact Benny Fouche at 209/468-2085.
Vermont Bean Seed Company has a new catalogue out called Totally Tomatoes with a special emphasis on tomato cultivars for special circumstances. They have devoted a special section to heirloom cultivars and overall offer well over 175 different tomato cultivars. You can reach them via telephone at 803/663-0016, or via fax toll-free at 888/477-7333.
