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Research Update

±'" 1990
:
FIRST IN RESEARCH UPDATE SERIES ON FRUITS AND VEGETABLES

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Native Bee Efficient Pollinator of Blueberries
Rabbiteye blueberries are generally not self-fertile and require insect visitation to achieve the 40-60 percent fruit set expected by growers. Studies have shown that only 4 percent of the flowers on a bush will produce fruit if insect access to the flowers is prohibited. I Bees are the most abundant floral visitors to rabbiteye blueberries, seeking nectar and sometimes pollen rewards. Among these bees, the southeastern blueberry bee, Habropoda laboriosa, shows remarkable fidelity and pollination efficiency for rabbiteye blueberry. This bee resembles a small worker bumblebee in appearance and is easily distinguished from the much larger queen bumblebees. The female blueberry bee lives solitarily, constructing well-concealed subterranean nests in sandy locations and producing only one generation of offspring a year in the spring. In Alabama and Georgia, females forage almost exclusively on species of wild and domestic blueberries for the pollen and nectar provisions needed to feed their offspring. Such fidelity can be important for pollination when there are other floral species blooming concurrently and competing for a pollinator's visits. One reason for the blueberry bee's pollination efficiency is its ability to buzz each visited flower. This audible buzzing vibrates the bloom and releases pollen. Bees that do not buzz flowers, such as the honeybee, gain little, if any, pollen from the rabbiteye blueberry flower. Experiments conducted by the AAES and at the USDA Fruit and Tree Nut Laboratories in Byron, Georgia, show that single floral visits by this bee can result in a 45 percent field fruit set on drip-irrigated commercial rabbiteyeblueberries. The resulting fruits are equivalent to those from open-visited flowers in size, maturation date, and number of viable seeds. Since flowers persist for 3-5 days and can be visited many times per day (females visit over 10 flowers per minute), the activities of the blueberry bee alone can be responsible for the entire fruit set on cultivated rabbiteye blueberries in the Southeast. Since no artificial management methods have been developed to replace or augment the activity of these efficient bees, farming practices that protect blueberry bee populations are critical for successful blueberry production.
J.H. CANE

This is the first fruit and vegetable
research report published in a new publication series entitled "Reseach Update," inaugurated in 1989 by the Alabama Agricultural Experiment Station (AAES). The new series is meant to promote timely reporting of research results dealing with a specific crop or commodity, with distribution to all producers of that particularcommodity, Inthiscase,thetarget audience is all Alabama farmers who grow fruits and vegetables as commercial crops. Today's highly competitive conditions make it doubly important that farme.s have available the latest scientific information. Publication of this new series is meant to help meet that need. Efforts will be made to maintain up-to-date mailing lists of each producer group so all Alabama producers will receive the appropriate report annually. Other information about fruit and vegetable production and latest recommendations are available from each county Extension Service office in Alabama.

A

LABAMA AGRICULTURAL EXPERIMENT STATION AUBURN ALABAMA LOWELL T. FROBISH, DIRECTOR AUBURN UNIVERSITY, UNIVERSITY

Super Sweet Corn Varieties Show Promise

Performance of Super Sweet Corn Varieties

Quality Yield/acre, Days Super sweet corn varieVariety dozen ears to maturity index' ties showed their potential for the commercial ast Gulf Co Substation market in 1989 AAES 4.5 SS7900 ..................... 1,7 6 1 sweet corn variety trials. 5.0 SS8000 ..................... 1 ,7 6 1 varieties difSuper sweet Showca se ................. 1,325 5.0 2 fer from traditional sweet How Sw It Is ....... 1,162 eet 5.0 SS7810 ..................... 1,067 4.9 corn varieties because they 5.0 Excell ........................ 1,252 sugar concentrapossess Crispin ,3weet ........... 1,470 4.9 tions as high as 35 percent Sunset ..................... 1,779 4.6 4.9 Sweet Belle .............. 1,888 and hold them much 5.0 Sweetie ..................... 1,220 longer in both field and storage conditions. Chilton Area Horticulture Substation Trials at the Gulf Coast sS7900 .....................76 1,234 4.1 Substation in Fairhope, the SS8000 .....................77 1,03 5 4.8 926 4.4 Showca se ................. 76 Chilton Area Horticulture 76 How Sweet It Is ........ 1,343 5.0 Substation in Clanton, and SS7810 .....................76 1,452 4.4 Excell ........................72 1,053 5.0 the North Alabama HortiSuper Sweet culture Substation in Cull76 Jubilee ..................... 1,476 5.0 man included 10 super Sunset ..................... 72 1,143 4.5 sweet varieties (9 yellow elle Sweet B .............. 1,470 76 4.9 1,688 4.6 Sweetie ..................... 76 and I white). Results from two locations are listed in 'Rating iindex: 5=excellent, 4=good, 3=fair, 2=poor, 1=very the table. Fertilizer was poor. 'White variety. applied according to soil test recommendations and pesticides and irrigation were applied as needed. All of the varieties rated good to and Crown Rots excellent on quality index. Good yielding varieties included Sweet Can Be Problem for Belle, Sweetie, Sunset, Jubilee, and possibly Summersweet 7900, and Kiwi Plants 8000 also showed promise for production in Alabama. Studies also Considerable interest has been showed that isolation of varieties or shown for production of kiwi as an manipulation of planting dates will alternative fruit crop. Prospects for keep super sweet varieties from cross such an Alabama enterprise appear pollinating with other corn types. quite lucrative since New Zealand, Cross pollination results in loss of the main source of kiwifruit, is losome of the super sweet characteriscated below the equator and thus tics. The studies indicate that super has a harvest season opposite of the sweet corn varieties germinate betUnited States. ter under warm soil conditions, AAES studies at several locations suggesting that the varieties may in the State have revealed some not perform as well if planted in potential production problems with cold soil. D.W. PORCH kiwi. One planting at the Wiregrass

Substation in Headland was made in 1986 on land previously used for long-time peanut production. During the first year of growth, heavy summer rains at the Substation promoted the development of a soilborne organism, Pythium ultimum, which caused root rot and killed more than 60 percent of the plants. A 1986 planting at the Gulf Coast Substation in Fairhope developed well and some plants bore fruit in the fall of 1988. However, rainy weather caused by hurricane activity in September of that year saturated kiwi plantings, resulting in asphyxiation and leaf drop from approximately one-third of the plants. Many of the kiwi plants failed to bud out" the following spring, and Pythium root rot and possible Phytophthora crown rots were found on nearly 30 percent of the plants during 1989. Further studies indicate that these soil-borne problems can be reduced if the kiwi plantings are made on well-drained, light-textured soils.
AJ. LATHAM AND W.A. DOZIER, JR.

Root

Soil Tests Accurately Predict Soil Fertility Needs of Sweet

Potatoes
Sweet potatoes grow well on the sandy, acid soils found in Alabama. However, little research has been done to evaluate sweet potato response on soils with different levels of residual fertility. Such information could enable the Soil Testing Laboratory to make more accurate fertilizer recommendations. To learn more about this issue, sweet potatoes were planted in 1988 and 1989 on existing, long-term soil fertility plots (since 1954) at three AAES locations: the Brewton and Prattville Experiment Fields and the

Sand Mountain in Substation The Crossville. purpose of the study was to determine yield and quality response of sweet potatoes to residual phosphorous (P) and potassium (K) and to rates of applied nitrogen (N), P, and K. In 1988, yields at Brewton were less than half those at the other tw o locations due to late planting, dry weather, and late m aturity. Yields at Prattville and Sand M ountain are presented in the table.

Yields of U.S. No. 1 Sweet Potatoes and Soil Test Ratings Under Different Levels of Long-Term N, P, and K Fertilization Prattville Soil test Yield/ acre rating1 Cwt. N rate 36 0 ............................ --70 2 0 .......................... ----70 40 .......................... 107 80 ................. --102 120 ........................ --1 60 ........................ --92

Sand Mountaiin
Soil test rating'

Treatment

eld/ ere 66 60 93

bloom of peach trees and provide frost protection. Three app!ications of 0,10, 50, and 100 parts per million (p.p.m.) GA 3, plus 0.2 percent BufferX surfactant were applied to 6-yearold Loring peach trees. The treatments were applied at monthly intervals to the point of run-off beginning in August. GA -treated trees retained their foliage later in the fall than the control trees. Trees treated with 50 and 100 p.p.m. made vegetative growth of 6 and 11 inches, respectively, in the fall as shown in the table. The treatments did not affect the number of flower buds that developed on the treated trees. However, 50 to 100 p.p.m. treatments delayed bloom in the spring, whereas the 10 p.p.m. treatment did not delay bloom. The 10 p.p.m. treatment resulted in a larger fruit set which required more fruit thinning. The highest yields were produced on trees treated with 10 p.p.m., resulting in a 39 percent increase in yield when compared to the control trees. The results of this experiment com-

Cwt

- -

1.81

14

05 77 80 98

0205 rate H 20 ...................... . H VH 40 ...................... .... .... VH 60...................... VH 100 .................... ....
K2 0 rate

86 14

14 At both locations, 2 44 No lime ............ 80poundsof N per acre (the current 'Soil test rating of plots based on residual level of plant n utrient: recommended N VL=very low; L=Ioy N;M=medium; VH=very high. Nitrogen do)es not pare favorably with an experiment rate) resulted in build up insoils an d therefore is not rated. 2 'rattville and 4.9 at Sand Mountain. that was conducted in 1986. A late pH was 5.0 at F highest yields and spring frost occurred after bloom quality of potatoes. that year and reduced the crop conThe application of siderably. As in the latest test, the achieved in several areas of Alabama P had a positive effect on yield at greatest yields were produced on and that using lime and fertilizer Prattville where even the "no P" plots recommendations based on soil tests trees treated with 10 p.p.m. GA 3. tested high in P after 35 years of The fall-applied GA 3 appears to results in highest marketable yields. cropping. Residual soil P at Sand both increase the cold hardiness of CC. MITCHELL AND C.E-EVANS Mountain ranges from low in the "no P" plots to very high where 100 the peach buds and delay bloom, and has potential as a method of pounds per acre of P20 are applied frost protection. annually. Here, additional direct P WA, DOZIER, JR., AA, POWELL, application even at the very high reAW. CAYLOR, WR. MCDANIEL, Fall-Applied sidual level benefited potato yields. AND E.L. CARDEN Sweet potatoes have a high K reGibberellic quirement and the current recomEffect of Fall Application of Gibberellic mended rate of application is 100 Acid Protects Acid on Loring Peaches pounds K20 per acre. At Prattville, Peaches this rate produced the highest yields of both No. l's and total potatoes Fruit thinned/ Yield/ Open Fall Gibberellic Against Frost m. shoot blossoms, 14 in. tree even though the soil on these plots acid, p p growth 3/14/89 shoot length already tested very high in K. The Results of an AAES In. Pct. No. Lb. very acid, no lime treatment reduced study initiated in 1988 3.7 85 0 ......................... 0 77 yields more at Sand Mountain than 75 6.1 138 10 ...........0 indicate that fall appliat Prattville. 50 ........................ 6 57 5.1 105 cationsof gibberellic acid Results of this test indicate that 46 5.0 115 100 ..................... 11 (GA 3) delay spring good sweet potato yields can be

0........................ 2 0 ...................... 40 ...................... H 60 ...................... H 80 ..................... H
10 0 ................... ..... VH

15 36

60 70
66

New Herbicides Control Broadleaf Weeds in Strawberries
Three new herbicides that have potential to control broadleaf weeds in strawberries were evaluated in the summer of 1988 and spring of 1989 by the AAES. A strawberry planting at the Chilton Area Horticulture Substation in Clanton was renovated after harvest in June 1988 by plowing the middles and barring off the beds leaving a 6-inch-wide strip of strawberry plants in the row. A mixture of broadleaf weed seed that contained prickly sida, coffee senna, morningglory, and sicklepod were evenly distributed on the plots to ensure a uniform population of weed species in each plot. The herbicides were applied broadcast over the top after the weed seedlings emerged. Lactofen and fomesafen herbicides were evaluated at 0.25

pound per acre and aciflurofen evaluated at 0.50 pound per act Slight foliar injury was evidc days after treatment applical however, within 3 weeks the pl developed new growth and thf jured foliage was not visible. E, lent control was achieved witl A.W. CAYLOR, W.A. DOZIER, JR., three herbicides of all weed spc J.A. PITTS, AND K.C. SHORT except sicklepod. The young sicklepod Effect of Herbicides on Strawberry Plant Performance and Weed Control plants that were present when the herbiHerbici de-rate/ Foliar Weed Runners/ Yield/ cides were applied acrre acre control 9 sq. ft. injury were killed; however, Pct. Pct. No. Lb. additional seedlings emerged. Lactofe n-0.25 lb. ............ 37,699 Fomes afen-0.25 Ib. ........ Lactofen reduced 31,435 Acifluor fen-0 50 Ib ...... 30,159 strawberry runner Hand-h,oed, weed-free development plots .. 100 106 26,984 slightly, while fome-

safen and aciflurofen severely reduced runner development. The effect on runner development resulted in substantial death to runners that were developing and growing when herbicides were applied. In the spring of 1989, all herbicidetreated plots produced greateryields than the hand-hoed check plots. Lactofen-treated plots produced the highest yields, about 28 percent greater than the check plots.

Summer Screening Provides Heat-Tolerant Tomato Selections
Research at the Wiregrass Substation in Headland was conducted to evaluate fruit production of tomato varieties and breeding lines during the hot days and nights of the summer months. Earlier results had shown that the predominant reason for lack of fruit formation during high temperature conditions was a decrease in pollen fertility. Lines exhibiting heat tolerance showed higher pollen fertility but were found to be smaller. Hybrids between the most heattolerant and heat-sensitive selections were analyzed and compared to parent lines and commercial variety performance. Populations derived from heat-tolerant parents outperformed their parents in fruitsetting ability as shown in the table. Of the recently released new heat-tolerant varieties, Heatwave and Solar Set, Heatwave showed promising results because it set large fruit under high temperatures. Selections were made in the best populations and will be used in the breeding program to combine the genetic capability to set high-quality fruit under high temperatures with resistance to root-knot nematode, mosaic virus, and fusarium wilt.
F.K. DANE AND O.L.CHAMBLISS Heat Set Ratings of Parent and F Lines of Tomatoes Line Parent lines and varieties Heatwave........................................................ AVRDC CL-5915-153-D4-3-3 ...................... Nagcarlan................................. Beaverlodge 6804 ....................................... Red Cherry ............. .............. Solar Set................. ........... Suncoast ..... ............. .............. Flora Dade...... .......... ................ F lines AVRDC CL-5915-153 x Beaverlodge ............ Beaverlodge x Nagcarlan ......................... AVRDC CL-5915-153 x Nagcarlan................. Nagcarlan x Red Cherry ............................... Beaverlodge x Red Cherry ............................ Flora-Dade x AVRDC CL-5915-153 ......... AVRDC CL-5915-153 x Red Cherry .............. Red Cherry x Suncoast............................... Flora-Dade x Nagcarlan......................... 0 = no fruit set; 5=abundant fruit set. Rating1 3.2 3.0 3.0 2.9 2.8 1.9 1.3 0.9 3.8 3.7 3.5 3.2 3.1 2.8 2.7 2.6 2.4

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Results of 1989 Tomato Variety Trials Released
Results of the 1989 tomato variety trials, conducted at the Gulf Coast Substation, Fairhope, and the Chilton Area Horticulture Substation, Clanton, have identified several tomato varieties with good production potential. Of the varieties tested, Sunny, Celebrity, Mountain Pride, Hayslip, and Pacific, all varieties with demonstrated commercial potential in Alabama, produced high yields in the 1989 trials, verifying the performance of these varieties as standards for commercial production. Better Boy and Bonnie Nematode Resistant, popular gardening varieties, also produced high yields, as shown in table. Four varieties introduced into the trials for the first time in 1989 performed exceptionally well, though further testing is needed before they are planted extensively. Solar Set, a heat-tolerant variety that has the ability to set fruit under high temperature conditions, had good fruit set during a hot period early in the season when other varieties had poor fruit set. It produces firm, shipping type fruit. Summit, a variety with a jointless pedicel which allows the stem to remain on the plant during harvest, also has firm fruit good for shipping and is a late season variety. Sunbelt, another new variety, produced an early yield of firm shipping-type fruit. Empire, the fourth new variety, produced very large Tomato Variety Trial Results s /fruit which may be too large for shipMarkettable yield/acre 5 x6 ping but has potenVariety Total tial for home use and direct marketCwt. Cwt. South Alabama, Fairhope ing. 690 375 Sunny VF2................................. Two other new 422 Hayslip V F2......................................... 670 entries in the trial 476 Celebrity VF2NTMV......................... 618 Pacific VF2..................... 616 have uniquely high 462 Bonnie Nematode levels of foliage disResistant V FN.................................. 604 226 ease resistance. The 416 Solar Set VF2.................................... 546 early blight resisMountain Pride VF2..........................520 272 516 Olympic VF2.................................. 374 tant lines (NCEBR277 Better Boy VFN.................................. 399 1 and -2) exhibited NCEBR-2 VF2............................... 386 220 Summit VF2.... ................. 360 almost no early 252 NCEBR-1 VF2................................. 348 64 blight symptoms at mid to late season when other entries Central Alabama, Clanton in the trial were Celebrity VF2NTMV................................. 822 449 showing severe 294 Sunny VF2..................................... .817 symptoms. HowEmpire VF2NTMV ..................... ....... 790 506 Pacific V F2.......................................... 763 409 ever,theselinesdid Mountain Pride VF2........................ 752 281 not rank among the 394 Summit VF2............................ .. .... 699 best entries for 334 Solar Set VF2................................... 699 Sunbelt V F2 ......................................... 698 353 yield. Better Boy VFN.................................... 681 316 P.B, STRNISTE AND Olympic VF2................. .................. 659 316 OL. CHAMBLISS 86 NCEBR-1 VF2.................. .............. 623 NCEBR-2 VF2................... ................ 599 192

Plant
Introductions Offer
Valuable Watermelon Germplasm Resource
Watermelon germplasm from many areas of the world has been evaluated at Auburn during the past 2 years in a cooperative research project with the U.S. Department of Agriculture. This material represents a wide range of characteristics, including sources of insect and disease resistance, which should prove valuable in developing improved varieties. Evaluations for resistance to gummy stem blight, anthracnose, androot-knot nematode were made during the 1988 growing season, with widely varying results noted. Ratings were made on a scale of 1 to 9 (1=resistant and 9=susceptible). An introduction from Venezuela rated best for anthracnose resistance with a rating of 2.19. This one also rated good in gummy stem blight resistance (2.77), but was intermediate or worse for nematode resistance with a rating of 5.00. The best rating for gummy stem blight resistance was 1.83 for an introduction from Zambia. This was combined with a rating of 4.00 for nematode resistance and 3.25 for anthracnose resistance. Less resistance was found for root-knot nematodes in all the germplasms tested. The best rating came from a Zambia plant which rated 3.44. This germplasm was fairly well balanced, with ratings of 2.71 for gummy stem blight and 2.96 for anthracnose resistance.
J. D. NORTON

1 Fruit size grade established by USDA, 5 x 6 lug arrangement for fruit diameter from 2 11/16 inches to 3 3/16 inches.

New Screening
Technique May Lead to Mosaic Virus Resistant Southernpea Varieties
Blackeye cowpea mosaic virus (B1CMV) is a prevalent virus that limits production of cowpeas (southernpeas) in the Southeast. Resistance to BICMV does exist in a limited number of cultivars, but needs to be expanded. For variety enhancement work to build on these B1CMVresistant sources, two hurdles must be cleared: development of a reliable method to screen plants and discovery of the genetic mechanism that governs BICMV-resistance. Hope for resistant varieties has resulted from AAES research that has developed an efficient virus screening method which utilizes the enzyme-linked immunosorbent assay (ELISA). Plants to be tested are mechanically inoculated with B1CMV, evaluated for symptoms, and assayed for the presence of viral particles. Because this process is fairly rapid, a large number of plants can be surveyed over the course of a

S

UPPORT FRUIT

& VEGETABLE

RESEARCH

Funds appropriated by the Alabama Legislature provide the major financial support for Alabama Agricultural Experiment Station research. Hatch funds from the U.S. Government also represent an important funding source. Since these funds are limited, however, many areas of research would go unsupported except for financial support from various granting agencies, commodity groups, and other friends of the Experiment Station. Contributions of these supporters to the AAES program of research are acknowledged with gratitude. Among these supporters of AAES research, the following are recognized and thanked for their contributions to research on fruit and vegetable production:

Abbott and Cobb, Inc. Abbott Laboratories, Inc. Agplast Co. Asgrow Seed Co. Ethyl, Inc. Ferry Morse Seed Co. Harris Morgan Seed Co. Hollar Seeds I.B. Chemical Co. ICI Americas, Inc. Pinebloom Limited, Inc. Roy Lee Smith Produce SKW Trostberg Ag. Tennessee Valley Authority USDA-ARS, SE

year. Screening to date includes part of the cowpea germplasm collection, AAES advanced breeding lines, and regional cooperative field trial entries.

Inheritance studies on BICMVresistant cultivars at the AAES have revealed that one gene confers B1CMV-resistance in cowpeas.
P.B. STRNISTE AND O.L. CHAMBLISS

EDITOR'S NOTE Mention of company or trade names does not indicateendorsement by the
Alabama Agricultural Experiment Station or Auburn University of one brand over another. Any mention of non-label uses or applicationsin excess of labeled rates of pesticides or other chemicals does not

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Alabama Agricultural Experiment Station Auburn University Auburn University, Alabama 36849-0520

NON-PROFIT ORG. POSTAGE & FEES PAID PERMIT No. 9 AUBURN, ALA.

constitute a recommendation. Such use in research is simply part of the scientific investigation necessary to fully evaluate materialsand treatments. Information contained herein is available to all persons without regard to race, color, sex, or national origin.

January 1990 3M