Research Article

Influence of 4-CPA Growth Regulator for Enhancing Yield of Tomato During Low Night Temperature Stress

Saeed Ahmed Shah Chishti1, Saba Aleem1*, Iram Sharif2, Kashif Nadeem1, Nusrat Parveen1 and Muhammad Najeebullah1

1Vegetable Research Institute, Ayub Agricultural Research Institute, Faisalabad, Pakistan; 2Cotton Research Station, Ayub Agricultural Research Institute, Faisalabad, Pakistan.

Received | April 21, 2019; Accepted | March 21, 2020; Published | April 20, 2020

*Correspondence | Saba Aleem, Vegetable Research Institute, Ayub Agricultural Research Institute, Faisalabad, Pakistan; Email: sabaaleem22@gmail.com

Citation | Chishti, S.A.S., S. Aleem, I. Sharif, K. Nadeem, N. Parveen and M. Najeebullah. 2020. Influence of 4-CPA growth regulator for enhancing yield of tomato during low night temperature stress. Pakistan Journal of Agricultural Research, 33(2): 217-223.

DOI | http://dx.doi.org/10.17582/journal.pjar/2020/33.2.217.223

Keywords | 4-Chlorophenoxy acetic acid, Low night temperature, Parthenocarpy, Tomato, Yield

Introduction

At the flowering stage tomato (Solanum lycopersicum L.) is very prone to both high and low temperatures. Studies conducted to find the relationship between daily temperature and reproductive stage of tomato have found that day temperatures of 21–28°C and night temperatures of 15-20 °C are optimal for proper fruit setting and size development in tomato (Rahman et al., 2015). Any increase or decrease from optimum temperature results in premature drop of tomato fruit (Pramanik et al., 2017). Night temperature also plays an important role in the setting and development of the fruit, as night temperature below 10 °C significantly affects the fruit set in tomato (Karapanos et al., 2008). Adam et al. (2001) while evaluating the impact of temperature on growth and development of tomato fruit, reported that temperature below 14°C greatly reduces the tomato growth and causes the development of small and parthenocarpic tomatoes. Low temperature mainly reduces the pollen viability, pollen release and also delays germination of pollen on stigma, pollen tube development in style that leads to poor pollination and delays the fertilization process which are the prerequisite for proper fruit setting and development in tomato (Fernandez-munoz et al., 1995; Pressman et al., 2007).

Plant growth regulators are extensively being practiced in tomato for improving crop yield in temperature stress conditions. The impact of synthetic auxins and gibberellins to boost the production of tomatoes by setting parthenocarpic fruits has been acknowledged by many researchers (Tiwari et al., 2014; Pramanik et al., 2017). 4-Chlorophenoxy acetic acid is a synthetic auxin whose application has been reported to increase fruit set and size of tomato in temperature stress conditions (Picken and Grimmett, 1986; Ramin, 2003).

Many studies tested the growth hormones applications to improve tomato crop yield during high-temperature stress. There are few studies that check its effectiveness in low-temperature stress. However, investigations regarding 4-CPA test for low night temperature conditions are limited. In the present study effects of different 4-CPA levels were assessed in response to two minimum temperature conditions. In the first condition, different 4-CPA levels were tested during October to November when minimum night temperature was ranging between (12.5°C-23°C) and secondly the same levels of 4-CPA were tested in December- January when the minimum temperature at night was ranging between (2°C-7.5°C). The ultimate goal of the study was to find the best suitable level of 4-CPA growth regulator that could improve the fruit set and yield of the tomato crop during minimum nigh temperature conditions.

Materials and Methods

The experiment was conducted at the research area of Vegetable Research Institute Faisalabad, Pakistan, located at 31°23’52.8”N and 73°02’56.9”E during August 2017 to April 2018. Two indeterminate tomato hybrids Saandal and Sahel were used in this study. Both these varieties are being used commercially in normal planting season. Sandals give early production, but Sahel’s fruit size is larger than sandals. During the last week of August 2017, seeds of both varieties were sown in vermicompost filled trays and seedlings of each variety were transplanted on both sides of the two beds in the last week of September in the high tunnel with the dimension of (100ft×30ft×15ft). Two-factor randomized complete block design with five replications was used to design the experiment and a flower cluster with 3 opened flowers was treated as an experimental unit. All the recommended cultural practices were followed during the conduction of this experiment.

The spray of 4-CPA treatments was performed five times with a one-week interval from October to November (18th Oct- 15th Nov) when minimum night temperature was ranging between (12.5°C-23°C). Secondly, the same experiment was repeated in December- January (28th Dec to 26th Jan) when the minimum night temperature was ranging between (2°C-7.5°C). Seven 4- chlorophenoxy acetic acid (4-CPA) levels i.e. T1= 00 ppm (control), T2 = 25 ppm single spray, T3= 50 ppm single spray, T4= 75 ppm single spray, T5= 25 ppm double spray, T6= 50 ppm double spray, T7=75 ppm double spray were used to access the effect of different levels of 4-CPA. In single spray treatments selected clusters were sprayed only one time while in double spray treatments, clusters were sprayed twice.

To collect data regarding tomato yield, all ripened fruits of each treatment were harvested separately. To collect data for fruit per cluster, all the marketable size ripened fruits were counted. On average five fruits from the center of the cluster of each treatment were used for data collection for fruit weight, fruit diameter, and the number of seed per fruit.

Analyses of variance for all the characters were performed using Statistix software. Means of all the treatments were calculated and the significance of differences between the pairs of means was tested by using the least significant difference test at 5 % level of significance. Percentage increase and decrease by the use of dose (double spray 75 ppm) that give more increase in traits over control was also calculated to get a more clear picture of the effect of 4-CPA.

Results and Discussion

Yield per plant

Yield per plant is a complex trait and is highly correlated with other traits such as fruit weight, fruit diameter and the number of fruit set per cluster. In the present study, yield per plant was significantly improved when minimum night temperature was between 2°C -7.5°C by the application of growth regulator 4-CPA. A comparison of means showed significant differences in response to the different levels of 4-CPA. During cooly nights when the temperature was between 2°C -7.5°C, highest yield per plant (7.08 kg) was recorded by the use of 75 ppm dose twice in a week (Table 3). 87 % more yield was recorded in double sprayed 75 ppm treatment than control (Table 1). In single spray treatment, 75 ppm produced the highest yield (5.91 kg) as compared to other treatments i.e 25ppm (4.18 kg) and 50 ppm (4.35 kg). Control treatment (0 ppm) showed the minimum yield (3.78 kg) as compared to other treatments (Table 3). Both varieties also showed significant differences regarding yield per plant. Saandal variety showed more yield per plant (4.74 kg) than the Sahel (4.30 kg) when night temperature was 2°C -7.5°C.

When the temperature was between 12.5-23°C, then again the application of growth regulator was found effective. Yield per plant was increased by the use of growth regulator 4-CPA in this condition. The interaction effects of variety into 4-CPA levels were found non-significant and indicated that the main effects of variety and 4-CPA levels are more important. Differences in varieties in respect of yield per plant were non-significant when minimum night temperature was 12.5-23°C. Significant differences in means of different 4-CPA levels indicated that to improve the yield of tomato use of 4-CPA is effective when night temperature was between 12.5-23°C. Highest yield per plant was recorded with 75 ppm double spray treatment and minimum was found in control. In single spray treatment, 75 ppm (10.51 kg) was found more effective than other treatments i.e. 25 ppm (7.53 kg), and 50 ppm (8.22 kg). Double spray treatment of 25 ppm (8.46 kg) and 50 ppm (9.69 kg) showed more yield than single spray treatment 25 ppm (7.53 kg) and 50 ppm (8.22 kg) (Table 3). Increase yield per plant was mainly due to the increase in fruit set and fruit growth of tomato. Picken and grimmett, 1986 found a small increase in yield by the application of 4-CPA at the rate of 0.02 gl-1 and β napthoxy acetic acid 0.0075 gl-1 in tomato. They found that β napthoxy acetic acid is effective at 16°C and 4-CPA at 13°C minimum night temperature. Further, the effect of both these growth regulators was questionable when minimum night temperature was 11°C. Our results varied from their findings as we recorded an increase of 87 % in yield when minimum night temperature was 2°C -7.5°C. This increase in yield was may be due to the use of higher concentration 75 ppm (0.075 gl-1) and twice spray in a week.

Tomato yield in both temperature conditions was significantly increased by the application of plant growth regulator 4-CPA. This increase in yield was mainly due to an increase in the number of fruits set on a cluster, fruit weight, and fruit diameter. 75 ppm double spray treatment in both temperature conditions 12.5°C -23°C and 2°C -7.5°C produced more yield per cluster as compared to control (0 ppm). An overall 163-300 % increase in yield was recorded in sprayed clusters over control in both temperature conditions (12.5°C -23°C and 2°C -7.5°C) (Table 1). The highest yield of 1.12 kg and 0.58 kg per cluster was recorded respectively, for both minimum night temperature conditions (12.5°C -23°C and 2°C -7.5°C) when the genotypes were sprayed with 75ppm twice while lowest yield was observed in control (0.42 kg, 0.14 kg) as presented in Table 3. In single spray treatment,

Table 1: Percentage increase/decrease in 75 ppm double sprayed treatmetnt over control in respect of different studied parameters.

Table 2:Performance of different tomato varieties in low night temperature stress.

Table 3: Impact of different 4-CPA levels on different yield contributing characters of tomato during low night temperature.

75 ppm produced the highest yield (0.49 kg) as compared to other treatments i.e. 0 ppm (0.14 kg), 25ppm (0.26 kg), and 50 ppm (0.36 kg) when crop faced the temperature of 2°C -7.5°C at night time (Table 3). Control treatment (0 ppm) showed the minimum yield per cluster (0.14 kg) as compared to other treatments. Double sprayed treatments also showed more yield per cluster than single spray when minimum night temperature was between 2°C -7.5°C. Significant differences were also observed between varieties regarding yield per cluster. Saandal hybrid (0.35 kg) gave more yield per cluster than Sahel (0.35 kg). The performance of the varieties under different treatments showed that the variety Saandal is more responsive to the different levels of 4-CPA than Sahel (Table 4).

Table 4: Comparison of interaction effects of 4-CPA levels and varieties in respect of different yield contributing characters of tomato during low night temperature stress.

When minimum night temperature was 12.5°C-23°C then the double spray of 75 ppm caused more gain in yield per cluster (1.12 kg) than other treatments especially control (0.42). Double spray treatment of 25 ppm (0.70 kg) and 50 ppm (0.80 kg) showed more yield than the single spray treatment of 25 ppm (0.54 kg) and 50 ppm (0.68 kg). Single spray of 75 ppm (0.87 kg) was found more effective than other single spray treatments to increase yield per cluster i.e. 25 ppm (0.54 kg), and 50 ppm (0.68 kg). It was noted that in the sprayed cluster mostly fruits were formed by bypassing the regular fruit development process in which pollination and fertilization are the main requirements for fruit set. An increase in yield by the application of growth regulators under the cool season was also observed by Abad and Guardiola (1985). Gemici et al. (2006) and Ramin (2003) reported that parthenocarpic fruits development, increase in fruit weight and fruit size (fruit diameter) were the main reasons for more yield of plants that were treated with 4-CPA.

Number of fruits per cluster

The number of fruits per cluster is an important parameter that contributes to yield. As more the number of fruit sets per cluster more will be the yield of the plant. During cool nights when minimum night temperature was 2°C -7.5°C, the interaction effects of variety into 4-CPA levels were non-significant indicating that the main effects of variety and 4-CPA levels are more important in respect of the number of fruit per cluster. Double sprayed treatments set more number of fruits per cluster than single spray when minimum night temperature was between 2°C -7.5°C. More number of fruits (6.00) was set by applying double spray of 75 ppm (T7) while fewer fruits per cluster (2.5) were set in control clusters on which no chemical dose was sprayed (Table 3). In single spray treatment, by applying 75 ppm concentration more number of fruits (5.90) were sets as compared to other treatments i.e 25ppm (3.80), and 50 ppm (4.70) when crop faced the temperature of 2°C -7.5°C in the night (Table 3). Saandal variety was able to set 10.5% more fruits (4.85) per cluster as compared to Sahel (4.34) when night temperature was ranged between 2°C -7.5°C (Table 2).

When minimum night temperature was 12.5°C-23°C, double spray treatment of 75 ppm (6.80) showed more number of fruit per clusters than other double spray treatments i.e. 25 ppm (4.90) and 50 ppm (5.40). However, these double sprayed treatments did not show significant differences in comparison with single spray treatment 25 ppm (4.50) and 50 ppm (5.30). In single sprays, 75 ppm was found more effective than other treatments to increase the number of fruits per cluster i.e. 25 ppm (4.50), and 50 ppm (5.30). More number of fruits in treated clusters were mainly due to parthenocarpy that bypassed the process of natural pollination and fertilization which are two major processes required for proper fruit setting through sexual processes.

Fruit weight

In cooly nights when the temperature was 2°C -7.5°C at night time, Sahel hybrid (51.37 g) shows more reduction in fruit weight than Saandal (65.22) as compared to nights when the temperature was between 12.5°C-23°C in which Sahel fruit weight was 112.40g and Saandal was 114.18 g. An increase in fruit weight by the application of different doses of 4-CPA was observed in both temperature conditions. During cool nights when minimum night temperature was 2°C -7.5°C, interaction effects of variety into 4-CPA levels were significant indicating that the response of different 4-CPA levels was highly dependent on varieties. With a double spray of 75 ppm, Sahel hybrid (96.79) depicted more gain in fruit weight than Saandal (95.55). Overall 46.9% increase in Sahel (96.79 g) and 31.74% in Saandal fruit weight (95.55g) occurred with a double spray of 75 ppm (Table 4). Mean comparison of single and double sprayed treatments regarding fruit weight showed that double sprayed treatments were more effective in increasing fruit weight than single spray

treatments in both varieties. An experiment performed by Gemici et al. (2006) also showed congruent results with our studies and reported an increase in fresh as well as dry fruit weight of the plants that were treated with 4-CPA.

Fruit diameter

An increase in fruit diameter by the application of 4-CPA over control in both temperature conditions was recorded. Highest fruit diameter (67.46 mm, 61.26 mm) was observed by the use of 75 ppm concentration two times in a week in both temperature conditions 12.5°C -23°C and 2°C -7.5°C, respectively. Similarly, minimum fruit diameter (52.38 mm, 45.71 mm) was found in control (0 ppm) in both temperature conditions 12.5°C -23°C and 2°C -7.5°C, respectively (Table 3). Both varieties showed different responses towards different 4-CPA levels but maximum fruit diameter was recorded in both varieties when treated with 75 ppm twice in a week (Table 2). The results of this study are in agreement with the findings of Halder et al. (2003) who reported the application of 4-CPA increased the fruit length as well as fruit diameter of summer tomato. Gemici et al. (2006) also observed an increase in fruit diameter by the application of 4-CPA and on the basis of hormonal assay he linked this increase with the increase in the internal hormone Indol-3-acetic acid IAA of the sprayed plants.

Number of seed per fruit

Parthenocarpic fruit development is the main reason for increase fruit set per cluster and yield. The decrease in seed per fruit was observed with the application of growth regulators. Less seed formation in sprayed fruits indicates the effectiveness of hormone in parthenocarpic fruit development. The highest number of seeds (57.05, 39.50) was observed in fruits of the control cluster in which no spray occurred and the minimum number of seeds (20.70, 9.50) was found in the fruits that were treated with 75 ppm concentration twice in a week (Table 3). Karapons et al. (2008) reported the parthenocarpic fruit development in the fruit clusters that were treated with 4-CPA. Gemici et al. (2006) found 80% parthenocarpic fruits in the plants that were treated with 4-CPA. Moreover, they reported that these seedless fruits were formed in control as well as treated clusters as ovaries of these flowers did not wait for pollination and form fruit bypassing the process of pollination and fertilization.

As in the case of hormonal application, the ovary has not waited for signal receipt on account of natural fertilization to develop into fruit and fewer seeds in these fruits may be due to delayed or disturbance in pollen tube growth on account of ovary enlargement. Whereas in case of control treatment, stigma as well as pollen tube development has remained active for the large time, thus allowing natural fertilization even after prolonged time and resulted in more seed formation as compared to sprayed one.

Conclusions and Recommendations

Based on this study it may be concluded that increase in yield of winter tomato planting is possible during low temperature stress when minimum night temperature was ranging between 12.5°C -23°C and 2°C -7.5°C, by the use of growth regulator 4-CPA at 75 ppm two times in a week. A positive influence of 4-CPA describes above on tomato yield could be a tool for getting economical tomato yield in the low night temperature stress conditions.

Authors Contributions

Saeed Ahmed Shah Chishti, Saba Aleem, executed the whole experiment, collected and analyzed the data and also wrote the whole manuscript. Kashif Nadeem helped in data collection. Nusrat Parveen and Iram Sharif helped in data, analyzing and write-up of the manuscript. Muhammad Najeebullah monitored the whole experiment and provided technical help in performing the experiment

Conflict of interest

The author(s) declare(s) that there is no conflict of interest regarding the publication of this article.

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