Abstract: In this study, relationships between number of stem and yield were investigated for some indeterminate tomato varieties. Two different stem applications (single and double-stem) and ten different indeterminate tomato varieties were used. Experiments were carried out at randomized blocks split plots experimental design with three replications during the years 2004-2005. Stem applications were applied in main blocks and varieties were applied in sub-plots. Plant total yield (kg plant-1), total number of fruit per plant (number plant-1), marketable plant weight (g) and marketable yield (t ha-1) were taken into consideration. Correlation and path analysis were carried out between marketable yield and the other plant characteristics. It was observed that plant total yield and number of fruit per plant had significant and positive effects but number of stem had negative effects on marketable yield of tomato. Then, it was concluded that varieties with higher total yield, total number of fruit and adaptation capability should be selected and single stem application should be implemented for higher and quality marketable yield in tomato.
INTRODUCTION
Tomato is a South-America originated vegetable and one of the most widely cultured plant over the world. There is a recent increase in tomato cultured lands and tomato yields (Anonymous, 2006). This increase may result from the development of new high-yield hybrid varieties and new culture techniques.
Temperature demand of tomato is between 15-28°C for the best growth. Proper growth also takes place at temperatures over 30°C and flowers are formed at these temperatures but fertilization problems and consequently yield decreases occur at high temperatures (Vural et al., 2000). Although tomato does not enjoy high air humidity, existence of always available water around the root zone provides proper and high yield conditions. Climate demands are important factors for variety selection in open-air culture.
Determination of variety characteristics in new-variety development studies constitutes the main objective of breeding programs. In these studies, adaptation capabilities of varieties for different regions, their resistance to plant diseases, fruit quality and etc. characteristics are investigated (Thomas, 1986). During the recent years, greenhouse indeterminate tomato varieties were successfully grown in open-air. Although controlled conditions are not provided in open-air; varieties have exhibited significantly high performance with regard to yield and fruit quality (Cuertero and Baguena, 1980; Saglam, 1994; Karatas et al., 2002). However, plant characteristics vary under various climate conditions; that brings the need for new studies to be carried out with tomato varieties in different regions.
Tomato has a direct respond to cultural techniques. Fruit size, plant yield and early rising increase with increasing land space per plant (Günay, 1981). Cuertero and Baguena (1980), Varis (1985), Tsambanakis (1987) and Stoica and Ilie (1990) reported yield changes with number of plant sown over per unit area. Proper fertilization has also a significant effect on tomato yield. Amount of fertilization and mineral material content are effective both on yield and fruit quality (Alan et al., 1992; Bagal et al., 1992; Ohta et al., 1993). Tomato producers usually prefer gravity irrigation methods. Recent studies about drip irrigation method for tomato indicated a better water utilization and fertilizer application (Rubeiz et al., 1990). Pruning methods applied in tomato culture vary and plant yield also varies with pruning methods. For instance, while double-stem pruning method carried out in spring season has negative effects on yield and quality; pruning has positive contributions on yield when carried out in fall season (Bas and Sevgican, 1990).
Researchers have reported significant linear correlations between yield and number of fruit per plant, mean fruit weight, fruit size, number of cluster per plant and number of sprouts per plant (Singh et al., 1990; Singh et al., 1993). Singh et al. (1990) determined that number of fruit, fruit size and fruit weight have direct impact on fruit yield.
Continuously new tomato varieties are introduced into markets by the companies trying to increase their market share. That is why; there is a need for performance determination of varieties in different regions. For an economical tomato culture, first of all, proper variety for the region and cultural techniques to be applied should be well-known.
In this study, relationships between number of stem and yield were investigated for some indeterminate tomato varieties.
MATERIALS AND METHODS
This study was carried out under Tokat-Turkey ecological conditions during the years 2004-2005. Tokat is located in the northern Turkey, which is generally known as Mid-Black Sea region. Astona Fi, Menhir Fi, Volare Fi, Sümela Fi-RN, Töre Fi, BT 131 Gülle Fi, Cemile Fi, Alida Fi, Diyansa Fi and Newton Fi indeterminate tomato varieties have constituted the plant material of the study.
Soils of study area have high pH values and low organic material content. Experiments were carried out under producer conditions. Producers have applied traditional fertilization programs in previous years without carrying out any soil analysis. That is why, significantly high levels of available phosphorus and potassium were observed in study area during the first year of the study (Table 1). A fertilization program proper for the soil analysis results was followed in this study.
During the study years of 2004 and 2005, all of the climate data were higher in the second year than the first year. Second year had higher temperatures, precipitation and relative humidity (Table 2).
Experiments were carried out at randomized blocks split plots experimental design with 3 replications; stem applications (single and double stem) were placed in main blocks and varieties were applied in sub-plots. Seeds were sown on 10 April 2004 during the first year and on 11 April 2005 during the second year of the study. Then the mature seedlings were planted over the experimental land on 24 May 2004 during the first year and on 15 May 2005 during the second year of the study. Row spacing was 75 cm and on-row spacing was 40 cm for single-stem culture and these values were 75 and 60 cm, respectively for double-stem culture. In each method, 10 plants were placed in each plot. Drip irrigation method was applied to meet the water requirements of the plants. Fertilizers were applied via drip irrigation method (Rubeiz et al., 1990). To terminate the plant growth, two leaves were left after the 8th cluster and by this way growing tip was broken-off and tip-taking was carried out (Campos et al., 1989). All the other maintenance works were also regularly carried out during the experiments.
In this study, plant total yield (kg plant-1), total number of fruit
per plant (number plant-1), marketable plant weight (g) and marketable
yield (t ha-1) characteristics were taken into consideration. Marketable
plant weight and marketable yield values were determined by summing the weights
of 1st and 2nd quality fruits specified by tomato standards of TSE (Turkish
Standards Institute), Bad and Sevgican (1990).
| Table 1: | Soil analysis results for study area |
| Table 2: | Climate data for study years |
| Source: Climate Records of Tokat Soil and Water Resources Institute | |
TARIST statistical software was used for variance analysis on experimental results and Duncan tests were run on statistically significant differences (Açikgöz, 1988).
RESULTS AND DISCUSSION
Single and double-stem applications and ten tomato varieties were taken into consideration in this study. Statistically significant changes were observed in total plant yield with regard to number of stem at 0.05 significance level during the first year and at 0.01 significance level during the second year of the study. Varieties have caused very significant changes on yield during both years of the study. A statistically significant change was not observed in number of stemxvariety interaction. During both years of the study, plant total yields were higher in double-stem (6.00 and 4.19 kg plant-1) than in single-stem (4.07 and 2.93 kg plant-1). Variety averages were 5.77-4.69 kg plant-1 for the first year and 4.05-3.05 kg plant-1 for the second year. The highest yields observed in varieties of Newton Fi and Volare Fi during the year 2004 and in Sümela Fi RN during the year 2005. The lowest yields were observed in Cemile Fi and BT 131 Gülle Fi during the first year and in BT 131 Gülle Fi during the second year (Table 3).
Stem applications caused statistically significant changes in total number of fruit per plant during both years of the study at 0.05 significance level and varieties caused significant changes at 0.01 significance level. Double-stem has provided higher number of fruit than single-stem during both years of the study (49.10-38.60, 31.62-26.13 fruit plant-1, respectively). Among the varieties, Volare Fi (48.22 fruit plant-1) yielded the highest number of fruit per plant for the first year and Sümela Fi (36.97 fruit plant-1) and Astona Fi (36.95 fruit plant-1) yielded the highest numbers for the second year. The lowest values were yielded by Alida Fi (33.33 fruit plant-1) in the year 2004 and by Newton Fi (28.87 fruit plant-1) and BT 131 Gülle Fi (27.75 fruit plant-1) in the year 2005.
As it can be seen from Table 3, statistically significant changes were observed among varieties with regard to marketable fruit weights at 0.01 significance level for both years. Average marketable weights of the varieties for the years 2004 and 2005 were between 142.39-113.66 and 120.23-104.84 g, respectively. During the first year of the study, Newton Fi and Alida Fi yielded the highest marketable fruit weights and Töre Fi and Menhir Fi yielded the lowest values. During the second year, while the highest values were obtained from Alida Fi and it was followed by Cemile Fi, the lowest values were obtained again from Töre Fi.
Statistically significant changes were observed among only varieties with regard to marketable yield in both years. For the first year, varieties of Newton Fi (152.75 t ha-1) and Volare Fi (152.46 t ha-1) had the highest and BT 131 Gülle Fi (123.52 t ha-1), Cemile Fi (123.85 t ha-1), Töre Fi (124.86 t ha-1) and Alida Fi (124.96 t ha-1) had the lowest marketable yields. During the second year, Sümela Fi (107.64 t ha-1) and Menhir Fi (103.55 t ha-1) had the highest and BT 131 Gülle Fi (80.39 t ha-1) had the lowest marketable yields (Table 3).
Double-stem application had statistically significant dominance over the single-stem with regard to plant total yield and total number of fruit per plant. Although a statistical significance was not observed in marketable fruit weight and marketable yield characteristics, in which fruit quality criteria were largely taken into consideration, numerical values were better in single-stem than double stem. Average values for all parameters obtained during the first year were rather higher than those obtained during the second year. Generally, high temperatures during the flowering period of tomato negatively affect the vigor of pollens. Also germination rates of pollens vary with plant genotypes (Çürük and Abak, 1995). When the climate data in Table 2 were evaluated, it can be seen that maximum temperatures during the second year of the study reached up to 37.8 and 38.3°C in July and August. This high temperature period was longer in the second year than the first year. This period coincide with the intensive cultural practices of the region. That is why, fertilization problems were experienced in most of the flowers formed at this period and that has caused the values of all parameters for the second year to be smaller than the first year.
Varieties have exhibited differences with regard to plant characteristics taken into consideration in this study. Genotype-dependent changes in plant characteristics were also emphasized in previous studies (Cuartero And Baguena, 1980; Saglam, 1994; Karatas et al., 2002).
During the first year of the study, marketable yield exhibited very significant
and positive correlations with plant total yield, total number of fruit per
plant and marketable plant weight (0.524**, 0.343** and 0.352**, respectively).
While positive but insignificant correlation was observed between marketable
yield and variety, insignificant but negative correlation was observed with
number of stem. For the second year, marketable yield exhibited very significant
positive correlations with plant total yield (0.424**) and significant positive
correlations with total number of fruit per plant (0.324*).
| Table 3: | Mean values for some plant characteristics with regard to different stem number and different varieties |
| SN: Number of Stem, V: Variety, *,**: Respectively 0.05, 0.01 significance level, ns: not significant, 1: Means indicated with the same later fall into same statistical group | |
Contrary to second year data, while very significant and negative correlations were observed between marketable yield and variety (-0.511**); positive but insignificant correlations were observed with marketable fruit weight. Also, insignificant but negative correlations were observed with number of stem (Table 4). These findings support the results of Singh et al. (1990 and 1993).
Since there are also indirect impacts among plant characteristics, correlation
coefficients were not able to fully indicate the relationship between characters.
| Table 4: | Correlation of marketable yield with number of stem, variety and plant characteristics |
| Table 5: | Results of path analysis on characteristics affecting marketable yield of tomato |
That is why path analyses were used to indicate the both direct and indirect impacts. Results of path analysis carried out over characteristics affecting the marketable yield were given in Table 5.
When the correlation coefficients in Table 4 were evaluated, it was seen that marketable yield exhibited significant and positive correlations with plant total yield and total number of fruit per plant in both years. However, plant total yield characteristic exhibited the highest positive direct impacts in both years. Indirect impacts of the same characteristic reazlied at the highest rate over stem application but coefficients of these impacts are negative. Number of fruit increases with increasing number of stem but plants are forced to feed more fruits and fruit weight and quality decrease. When the coefficients for the year 2004 were evaluated, it was seen that the highest secondary positive impacts came from marketable fruit weight. Linear positive impact rates of this characteristic (23.75%) were higher in the year 2005. The highest indirect impact of the same characteristic was realized positively over stem applications in both years. Number of quality fruits decreased with increasing number of stem but individual weights of marketable fruits increased. Again, based on correlation coefficients given in Table 4, it can be stated that a negative correlation existed between number of stem and marketable fruit weight in both years and a statistically significant relation was observed in the year 2004. Although number stem had a high rate of direct impact over marketable yield in both years (50.88 and 53.10%, respectively), these impacts had negative coefficients. While the indirect impacts of the same characteristic over plant total yield and total number of fruit per plant were positive, impacts over marketable fruit weight were negative. That indicates the existence of negative relations between the amount of market quality fruit and number of stem.
Observed significant and positive relations of marketable yield with plant total yield and total number of fruit per plant are in well-agreement with the findings of Singh et al. (1990).
CONCLUSIONS AND RECOMMENDATIONS
This study was carried out to determine the relationships between number of stem and yield for ten different indeterminate tomato varieties during the years 2004 and 2005. Following conclusions can be drawn from this study:
With regard to number of stem, although plant total yield and total number of fruit per plant characteristics were seen as statistically superior in double-stem application, it was observed that single-stem application was numerically superior in marketable yield and marketable fruit weight.
With regard to marketable yield, varieties exhibited changes with years. Relatively extreme temperatures arisen in the second year of the study and their duration has affected the performance of varieties. Average values for all characteristics were higher during the first year of the study. That brings a need to test the varieties under various climate conditions.
Following the correlation and path analysis, plant total yield and total number of fruit per plant had significant and positive contributions over marketable yield of tomato. Number of stem had negative effects on the same characteristic.
Finally, it was concluded that varieties with higher total yield, total number of fruit and adaptation capability should be selected and single stem application should be implemented for higher and quality marketable yield in tomato.