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Effect of Sowing Date on the Incidenceand Severity of Okra Mosaic TymovirusM. D. Alegbejo aa Department of Crop Protection , Institute for Agricultural Research,Ahmadu Bello University , P.M.B. 1044, Zaria, NigeriaPublished online: 22 Oct 2008.

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Study of Some Qualityand Quantity Factors of Tomato(Lycopersicon esculentumMill.)in Responce to Sowing Dates

Under Plastic TunnelsGh. Peyvast

ABSTRACT. Two sowing dates (26 Sept. and 16 Oct.) were evaluatedfor yield and some morphological and quality factors of two hybridtomato cultivars (‘E 338’ and ‘GC 774’) under plastic tunnel conditionsin Guilan province, Iran. The early sowing had a significant positiveeffect (p = 0.01) on the yield and the number of fruits of both cultivars.The early sowing had also a significant effect (p = 0.05 and p = 0.01) onthe plant height until development of the first inflorescence in ‘GC 774’and on the distance between two inflorescences in ‘E 338’ (p = 0.01).Sowing date and genotype had no effect on the number of flowers in thefirst inflorescence and on the amount of soluble solids in tomatoes. Theamount of organic acids in the fruits differed significantly (p = 0.05) inthe early sowing only by ‘E 338’ cultivar. Vitamin C concentration wassignificantly different for different sowing date (p = 0.01), but weresimilar between the two cultivars. [Article copies available for a fee fromThe Haworth Document Delivery Service: 1-800-342-9678. E-mail address:<getinfo@haworthpressinc.com> Website: <http://www.HaworthPress.com>E 2001 by The Haworth Press, Inc. All rights reserved.]

KEYWORDS. Lycopersicon esculentum, yield, sowing date, cultivars

INTRODUCTION

Benifits of plastic tunnels to extend the production period and growth ofvegetables out-of-season are well documented (Sims and Smith, 1984, Gerb-

Gh. Peyvast is affiliated with the Department of Horticulture, Faculty of Agriculture,P.O. Box 3179, The University of Guilan, Rasht, Iran (E-mail: gpeyvast@agr.gu.ac.ir).

Journal of Vegetable Crop Production, Vol. 7(1) 2001E 2001 by The Haworth Press, Inc. All rights reserved. 15

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er et al. 1988). Research on out-of-season production of tomato (Lycopersi-con esculentumMill.) and cucumber (Cucumis sativus L.) under plastic tun-nels has been more extensive than on any other vegetables (FAO, 1990,1994). This system of production started nearly two decates ago in Iran andthe protected cultivation under glasshouses and plastic tunnels now occup-pies about 500 ha (Iran Statistical Sources, 1998). Growing of tomatoesunder plastic tunnels increased rapidly, specially in the north of Iran, whereuntil recently only outdoor tomatoes were grown. Research such as deter-mination of sowing date may help farmers grow tomatoes in plastic tunnelsfor higher yield and better quality. In this experiment tomato was selectedbecause it has proved to be the most suitable vegetable crop for plastic tunnelcultivation in northern Iran (Peyvast, 1998).Low concentration of 2,4-D (2,4-dichlorophenoxyacetic acid) herbicide has

been used under greenhouse condition for vegetables such as pepper (Capsi-cum annuum L.), tomato, and cucurbits because of its hormonal effect toflower induction and an increase of fruit weight (Mehta et al. 1991 andTafasoli et al. 1998). Synthetic auxines are also used in some cold frames toincrease fruit set and fruit weight (Cuartero et al. 1987). Minimal concentra-tion of 2,4-D and 2,4-dichlorphenoxy dimethylamin under plastic tunnelconditions for production of tomato are recommended (Jordaan et al. 1992).Extensive research on greenhouse tomato cultivars has been conducted to

determine the morphological characters such as flower numbers, place offlower set, number of inflorescence on the main stem and first, second, third,and fourth lateral axis, distance between two inflorescences, number of fruits,and fruit weight (Chirinos et al. 1997). Investigation on 6 cultivars of Incatomato hybrids (‘Inca 3-A’, ‘Inca 9-1’, ‘Inca 13-9’, ‘Inca15’, ‘Inca 17’, and‘Inca-53’) have shown that the ‘Inca 9-1’ hybrid had a maximum inflores-cence, maximum fruits on the inflorescence, highest percent of fruit set,maximum fruit weight and yields (Domini et al. 1997). An experiment withfive tomato cultivars (‘Local’, ‘Queen’, ‘VF’, ‘Super Marmande’, and ‘Spe-cial Back’) was conducted to evaluate the performance of tomato cultivars.The results indicated that ‘Local’ gave highest early yield and had highestpercentage of TSS in fruits, while ‘Special Back’ had the greatest plant dryweight and titrable acidity (TA) of the fruits, compared to the other cultivars.‘Super Marmande’ and ‘VF’ were superior in plant height, while ‘Queen’gave the largest total fruit yield of the two cultivars. No significant differenceamong the cultivars was observed in fruit firmness (Mohammed, E.S. andMohammed, A.R.S., 1991).The objective of this study was to determine the effects of two different

sowing dates on two different tomato hybrid cultivars under plastic tunnel inGuilan province in Iran.

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Gh. Peyvast 17

MATERIALS AND METHODS

Two different cultivars of greenhouse tomato were compared for morpho-logical and quality factors in a plastic tunnel at the College of Agriculture,University of Guilan, Rasht, Iran in 1995-1996. The experiment was ar-ranged in compeletely randomized block design with two treatments (twotomato hybrid cultivars, namely ‘E 338’ and ‘GC 774’, and two sowing dates(26 Sept. and 16 Oct.) with three replications. The seeds of two cultivars weresown on 26 Sept. and 16 Oct. 1995 in seed trays, which contained equalproportion of composted manure, silty textured soil and sand. Seedlings ofthe tomato cultivars were grown in trays in a greenhouse. Six-week-oldtransplants were placed in a space of 60 × 60 × 100 cm3 under a plastictunnel on 1 Nov. and 14 Nov. 1995. Each plot contained 20 plants in doublerows. The tunnel was a round arch tunnel with steel construction, 2.5 m high,9.0 m wide and 57 m long and covered with PE plastic films of 60 mthickness. The tunnel had a natural ventilation, a hot-air oil heater and achimeny to exhaust the burned gasses. The temperature in plastic tunnel waskept at 24_C during the days and 15_C at nights. The relative humidity wasmaintained at 67%. Soil samples were taken prior to planting and analyzedfor pH, available P, and exchangeable K, Ca, and Mg (Brupbacher et al.1968). Soil chemical analysis respectively were: 6.0 pH, 87 P, 99 K, 495 Ca,and 67 Mg (in mg.kg−1 soil). Nitrogen (urea), phosphorus (superphosphate),potassium (potassium nitrate), and micronutrients were incorporated with thesoil before and after planting of tomato seedlings according to recommenda-tion (Faustzahlen, 1980 and Orellana, A. and M. Wilson, 1996). The plotswere prepared with a rotary tiller cultivator and the fertilizer was applied.Tomato plants were staked with rope for support. Insect and disease controlpractices were in accordance with Guilan province recommendations. Nineharvests of pink maturity stage for the first sowing date, and five harvests ofpink maturity stage for the second sowing date were made between 18 Febru-ary and 30 April 1996. Fruits were counted, weighed and recorded. Plantheight was measured at initial flowering stage in first harvest. The lateralaxises were pruned for both cultivars in same levels and the flowers weresprayed with 2 ppm concentration of 2,4-D for fruit set.The vitamin C ascorbic acid content was measured 6 times for different

cultivars by indolphenol method (Tooley, 1975). Fruit caps and seeds wereremoved and the remaining pericarp tissue was sliced and blended with 10 mlof distilled water. To each 5 ml of the extract, 45 ml acetic acid and ortho-phosphoric acid reagent were added and titrated by 2,6-dichlorophenolindo-phenol in the presence of 2-3 drops of phenol phetalein. The amount ofvitamin C of each sample was determined in extracts in mg per 100 g freshweight of fruit pericarp tissue. Thin Layer Chromatography was used fordetermination of organic acids. The solvent was 95% ethanol. A mixture of

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reagent 0.04 g bromotymolblue in 100 ml of 0.01 mol/l NaOH sprayed overthe chromatogram (Aeinehchi, 1979). Standard methods were used for thesoluble solids (A.S.T.M, 1980). One hundred milliliter of tomato extractswere filtered in a vacuum and the filtrate dried at 104_C for half hour and thedifferences between the weight of filtrate before and after drying were re-ported as total soluble solids. The resultant data were subjected to analysis ofvariance using a MSTAT-C statistical program (Michigan State University).Means were separated by LSD values at 5 and 1% level.

RESULTS

The earlier sowing date increased yield significantly (p = 0.01). However,the yield difference between cultivars was not significant. ‘E 338’ showed thehighest yield (7.85 kg/ m2) at the first sowing date (Table 1).As shown in Table 1, the fruit weight of two cultivars was statistically

significant (p = 0.05) at second sowing date and the ‘GC 774’ showed heavier

TABLE 1. Effect of sowing date on yield, fruit weight and fruit number of tomatocultivars in plastic tunnel

Cultivars Sowing date

Sept. 26 Oct. 16 Mean

Yield (kg/m2)

E 338 7.85 a 3.65 b 5.75GC 774 7.03 a 4.20 b 5.61

Mean 7.44 3.93LSD 1% = 2.499

Mean fruit wt. (g)

E 338 123.25 ab 114.32 b 118.78GC 774 140.75 ab 153.25 a 147.00

Mean 132.00 133.79LSD 5% = 27.06

No. of fruit (per m2)

E 338 95.00 a 45.75 bc 70.38GC 774 59.75 b 32.00 c 45.88

Mean 77.38 38.88LSD 1% = 23.22

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Gh. Peyvast 19

fruits by 23.7%. The results indicated that the difference in fruit numbersbetween cultivars was statistically significant (p = 0.01) only at the firstsowing date. The first sowing date brought 50% more fruits than the secondsowing date. The mean fruit numbers between two cultivars at differentsowing dates showed that the ‘E 338’ had 35%more fruits than the ‘GC 774’,while the sowing date had no effect on the fruit weight but the increase in themean values was as a result of the fruit numbers.The plant height until the first inflorescence of ‘GC 774’ cultivar was

affected significantly (p = 0.05) by the first sowing date. The mean plantheight until the first inflorescence was measured at the first and secondsowing dates were 31.07 and 25.85 cm, respectively. The plant height untilthe first inflorescence of ‘E 338’ was significantly (p = 0.05) higher than the‘GC 774’ (Table 2).The first sowing date had a significant (p = 0.01) effect on the distance

between two inflorescences on ‘E 338’. Between cultivars, the distance be-tween two inflorescences of ‘E 338’ was significantly (p = 0.01) higher thanthe ‘GC 774’ for the first sowing date. The results of analysis of variance

TABLE 2. Effect of sowing date on some morphological factors of tomatocultivars under plastic tunnel

Cultivars Sowing date

Sept. 26 Oct. 16 Mean

Plant height until the first inflorescence (cm)

E 338 33.60 a 28.65 a 31.12GC 774 28.53 a 23.05 b 25.79

Mean 31.07 25.85LSD 5% = 5.397

Distance between two inflorescences (cm)

E 338 43.28 a 23.00 b 33.14GC 774 25.58 b 25.65 b 25.62

Mean 34.43 24.33LSD 1% = 10.87

No. of flowers by the first inflorescence

E 338 7.75 a 7.55 a 7.65GC 774 6.45 a 6.33 a 6.39

Mean 7.10 6.94LSD 1% = 23.22

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indicated that genotype and sowing date had no effect on the number offlowers by the first inflorescence and soluble solids of tomato (Table 3).Between tomato cultivars the organic acid content (0.52%) of ‘E 338’ was

significantly (p = 0.05) higher than ‘GC 774’ at the first sowing date. It isevident that the second sowing date had a significant effect (p = 0.01) onvitamin C content of both cultivars.

DISCUSSION

The results indicated that the first sowing date increased the yield of bothtomato cultivars significantly. This increase was 54% for ‘E 338’ as 40% for‘GC 774’ in number of fruits. The number of fruits and fruit weight of twocultivars deffered. The increase in yield of ‘GC 774’ was related to the fruitweight whereas the increase in yield of ‘E 338’ related to the number offruits. While the increase in yield was due to fruit number, it is evident thatthe ‘E 338’ was prefered to ‘GC 774’ cultivar at the first sowing date.

TABLE 3. Effect of sowing date on some quality factors of tomato cultivarsunder plastic tunnel

Cultivars Sowing date

Sept. 26 Oct. 16 Mean

Soluble solid (%)

E 338 5.18 a 4.52 a 4.85GC 774 3.95 a 4.40 a 4.18

Mean 4.57 4.46LSD 5% = 2.543

Organic acid (%)

E 338 0.52 a 0.47 ab 0.50GC 774 0.34 b 0.40 ab 0.37

Mean 0.43 0.44LSD 5% = 0.16

Vitamin C (mg/cc)

E 338 19.38 b 35.50 a 27.43GC 774 12.28 b 32.40 a 22.33

Mean 15.83 33.95LSD 1% = 8.714

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Gh. Peyvast 21

Increase in yield of ‘E 338’ was due to plant height which brought betterair circulation and number of flowers in the first inflorescence. The result wasin agrement with Sims and Smith (1984) and Ruiz and Romero (1998). Thedistance between two inflorescences of ‘GC 774’ which were shorter than the‘E 338’ had no effect on the yield increase. That ‘E 338’ cultivar showed ahigher amount of soluble solids, organic acid, and vitamin C concentration ascompared with ‘GC 774’ may be due to genotype.It can be concluded that between cultivars, ‘E 338’ showed higher yield

and better quality at the first sowing date under plastic tunnels. Therefore‘E 338’ was recommended for plastic tunnel culture.

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Aeinehchi, Y. 1979. The new analytical methods of plants. Teheran University Press,Teheran, Iran.

A.S.T.M. 1980. American Standard Methods for the Examination of Water andWastewater, 11.ed. APHA. AWWA. WPCF.

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Chirinos, Dt., Geraud, F., Vergara, Ja. and M. Marin. 1997. Development of thetomato plant, Lycopersicon esculentum Miller, cv. Rio Grand en la zona del rioLimon del Estado Zulia, Venezuela. III. Arquitectura de la planta. Revista de laFaaculta de Agronomia, Universidad del Zulia, 13: 25-34.

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Mehta, A.K., Singh, R.P. and G. Lal. 1991. Effect of concentrations and methods ofapplication of 2,4 dichlorophenoxy acetic acid on yield, fruit quality and seedquality of tomato (Lycopersicon esculentum Mill.). Vegetable Science, 1989, 16:1-8.

Mohammed, E.S. and A.R.S. Mohammed. 1991. Growth, yield and quality of sometomato cultivars under the condition at Hammam Al-Alil. National AgriculturalDocumentation Center, Baghdad, Iraq.

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