Soil and Foliar Applications of Glycinebetaine Ameliorate Salinity Effects on Squash Plants Grown under Bahraini conditions

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1 Middle East Journal of Agriculture Research ISSN Volume : 6 Issue : 2 April-June 17 Pages: Soil and Foliar Applications of Glycinebetaine Ameliorate Salinity Effects on Squash Plants Grown under Bahraini conditions Abdel-Mawgoud Ragab Abdel-Mawgoud Vegetable Research Dept., National Research Center (NRC), Dokki, Cairo, Egypt. Received: 12 March 17 / Accepted: 13 April 17 / Publication date: 15 April 17 ABSTRACT This work was carried out during the growing seasons of October-February of and in order to ameliorate salinity negative effects on squash plants. Seedlings of squash (Cucurbita pepo ) hybrid INX 146 F1 were irrigated with desalinized (>1. ds/m) or saline water (6. ds/m). In each irrigation treatment, plants were supplied with.5 l of glycinebetaine solution in concentration of mm (GB) or. mm (NGB). Application of GB took place three times during the growing season with two weeks interval. During growing season, GB solution was applied as soil application meanwhile it was applied as foliar application during Data revealed that salinity deteriorated all plant growth aspects such as stem length, petiole length, number of leaves and fresh and dry weights. Fruit yield was also reduced by about 25% under saline irrigation. However, GB treatment significantly improved plant growth and production to a comparable level with control. Moreover, soil application of GB proved to be more effective than foliar application. Key words: Salinity, glycinebetaine, Squash, growth, yield. Introduction Salinity is a major constrain to agricultural development. The United Nations estimates that salinity affects crops on about million acres (8 million hectares) of arable land and not just in developing countries, but areas in developed countries as well. The problem is aggregated especially in the irrigated arable lands due to misuse of irrigation water and/or fertilizers. Qadir et al. (14) reported more than % of world irrigated soils are affected by salinity. Due to rare rain fall, considerable areas of cultivated soils in the Middle East and Northern Africa have been also affected by salinity. This leads to a reduction in growth and production of cultivated crops and probably to limit the number of cultivable crops in salt affected areas. The negative effects of salinity on plants have been widely documented (Li, ; Abdel-Mawgoud et al., 4; Tantawy et al, 9 & 13 & 14). The degree of impact on different plant growth aspects differs according to plant tolerance which is genetically determined by plant species. Plants are grouped according to their degree of salinity tolerance ranging from very sensitive to highly tolerant species (Hill and Koenig, 1999). However, salinity tolerance is not without a limit. Therefore investigations were conducted to improve plant growth and production beyond that limit. For instance, manipulated greenhouse climate was used in order to ameliorate salinity effects on tomato (Li, ) and sweet pepper (Abdel-Mawgoud et al., 4). Also, application of plant growth regulators and amino acids (Tantawy et al, 9), humate (Abdel-Mawgoud et al., 1) or nutrient supplements (Tantawy et al., 13 & 14) were used successfully to improve plant growth and production of some vegetable crops grown under saline conditions. Other trails using food processing byproducts such as sugar molasses was successfully used to improve tomato growth and production under saline conditions (Tantawy, 7). The effect of molasses was due to its contents of glycinebetaine. Glycinebetaine is a well-known compatible solutes that accumulate in a number of plants grown under stress conditions where it acts as a potential osmoprotectent. Glycinebetaine, known also as trimethylglycine, plays different roles in plant metabolism (Ashraf and Foolad, 7). It has been applied successfully to many crops such as maize (Nawaz et al., 1), soybean (Agboma et al, 1997), rice (Naidu, 4), tomato (Tantawy 7) and sunflower (Iqbal et al., 5). However, not any data was found about applying glycinebetaine to any Corresponding Author: Abdel-Mawgoud Ragab Abdel-Mawgoud, Vegetable Research Dept., National Research Center (NRC), Dokki, Cairo, Egypt. Current Address: Agric. Affairs and Marine Res.,- Min. Works, Muni. Affairs and Urban Planning, Kingdom of Bahrain. dr_abdelmawgoud@yahoo.com 315

2 of cucurbitaceae such as squash. Squash is a salt mid-tolerance vegetable crop and can be severely damaged when grown in saline conditions. Therefore, this work was carried out in order to investigate the effect of applying glycinebetaine to squash plants irrigated with saline water. Materials and Methods Seeds of squash (Cucurbita pepo) hybrid INX146 F1 were sawn in trays in the nursery of agricultural affairs and marine resources, Budayia (26 12 N; 5 27 E), Northern governorate, Kingdom of Bahrain in October 15 and 16. At four leaf stage, plants were transplanted to the open field in the experimental farm in Budayia where the experiments took place during the period November- February growing seasons of and Soil was sandy loam type and organic manure was added to it during preparation before planting. Drip irrigation lines were set 75 cm apart and seedlings were transplanted at 5 cm between each other. Fertilization was carried out using recommended doses of fertilizers and plants were irrigated daily as needed. Treatments: In the beginning of both seasons, transplanted plants were irrigated for ten days using desalinized water (EC > 1. ds/m). Plants were then divided into two groups receiving two levels of salinity treatments namely control to be irrigated with desalinized water, and saline irrigation with a saline water (EC = 6. ds/m) until the end of the growing season. Under each irrigation treatment, plants were either treated or non-treated with glycinebetaine (GB). This resulted in four treatments as follow: Control (desalinized water irrigation with no GB treatment), control-gb (desalinized water irrigation with GB treatment), Salt-NGB (saline irrigation with no GB treatment), and Salt-GB (saline irrigation with GB treatment). In the growing season of 15-16, each plant treated or not treated with GB received a manual application of.5l of glycinebetaine solution in a concentration of mm or. mm glycinebetaine respectively for three times with a two weeks interval. Meanwhile in the growing season of 16-17, the application of glycinebetaine was as foliar spray in concentrations of mm or. mm for GB-treated or non-gb-treated respectively and was repeated three times with two weeks interval. In each treatment, fruit yield on all plants were harvested twice a week when it reached a marketable stage where weight and number of fruits were recorded. Average weight of individual fruit was calculated using total weight and number of harvested fruits in each treatment. By the end of the growing season, three plants in each treatment were randomly chosen to measure stem length, petiole length, number of leaves, and fresh and dry weights of areal parts. A random samples of marketable harvested fruits were chosen to determine fruit quality such as dry matter content, and total protein, N, P and K contents. The experiment was designed as a complete randomized block design. Recorded data were statistically analyzed using ANOVA with three replicates and Least Significant Difference (LSD) at 5% was calculated. Results In both growing seasons, there were detrimental effects of salinity on the overall growth parameters of the squash plants. Irrigation with saline water negatively affected stem length (Fig. 1) as well as number of leaves (fig. 2). Not only number of leaves was negatively affected by saline irrigation but also the length of petioles were shorter than those of control plants (Fig. 3). On the other hand, GB-treated plants showed improvements in such parameters and there was no significant differences between salt-gb-treated plants and control treatment. Moreover, desalinized water irrigated-plants treated with GB showed higher values in almost all growth parameters compared to control. 316

3 7 6 Stem length (cm) Fig. 1: Stem length of squash plants as affected by saline irrigation and treated (GB) or nontreated Number of leaves/plant Fig. 2: Number of leaves of squash plants as affected by saline irrigation and treated (GB) or nontreated 5 Petiol length (cm) Fig. 3: Petiole length of squash plants as affected by saline irrigation and treated (GB) or nontreated 317

4 Plant fresh weight was also negatively affected by saline irrigation and the reduction was significantly different compared to control treatment. However, the application of GB ameliorated that negative effect and there was no significant difference between control and salt-gb-treated plants (fig. 4). Consequently, dry weight also improved under GB treatment compared to control (fig. 5). 25 Total plant fresh weight (g) Fig. 4: Fresh weight (g) of squash plant as affected by saline irrigation and treated (GB) or nontreated 25 Total plant dry weight (g) Fig. 5: Dry weight of squash plant as affected by saline irrigation and treated (GB) or non-treated Salinity reduced fruit yield in terms of number (Figure 6) and weight (figure 7) compared to control, meanwhile they were improved as GB was applied compared to untreated plants. Fruit quality in terms of average individual fruit weight also increased in GB treated plants compared to untreated ones (Fig. 8). Fruit dry matter content increased under saline irrigation treatment as well as under GB treatment compared to control (Fig. 9). Although they were not significantly different, the nutritional quality of the fruits tended to be improved under GB treatment as revealed by the chemical analysis of total protein, total nitrogen, total phosphorus and total potassium (Data not shown). The three later parameters showed an increment by 6%, 3.5% and 2.6% compare to control treatments. 318

5 6 Total number of fruits/plant Fig. 6: Total fruit number/plant of squash plants as affected by saline irrigation and treated (GB) or nontreated Fruit yield (g/plant) Fig. 7: Total fruit yield (g/plant) of squash plants as affected by saline irrigation and treated (GB) or nontreated A v e r a g e in d iv id u a l fru it w e ig h t (g ) Fig. 8: Average individual fruit weight (g) of squash as affected by saline irrigation and treated (GB) or non-treated 319

6 1 Fruit dry matter content (%) Fig. 9: Fruit dry matter content (%) of squash as affected by saline irrigation and treated (GB) or nontreated Discussion Most of irrigated arable lands in the Middle East are suffering of salinity either in the soil or in the irrigation water. This problem has a strong impacts on countries with limited natural resources of lands and water such as Bahrain. Such a problem is forcing Bahraini growers to change their crop patterns to more saline tolerant ones or to different agricultural systems such as soilless cultures. Both alternatives are either not economic and/or limited to a certain number of crops. Therefore, this study aimed to find alternatives for the growers to extended their crop patterns under saline irrigation conditions. The obtained results showed clearly the negative effects of salinity on all plant growth aspects. The negative effects of salinity must be brought about by the osmotic effects of salts on the water status of the plants (Abdel-Mawgoud et al., 4) which ends by deterioration of growth parameters. The shorter stem length of the plant under saline conditions is a result of smaller cell size and/or smaller number of internodes (Li, ). The observed smaller number of leaves under saline conditions confirms the smaller number of internodes. Smaller number of leaves means also smaller area that intercepts light hence smaller amount of photoassimilate production. The latter is reflected on smaller plant fresh and dry weights. Fresh weight is also negatively affected by salinity as water flow into the plant is limited because of the osmotic effects of salinity in the root zone. All the above explanations have been interpreted into smaller fruit yield as was recorded. With a threshold of 3.9 ds/m, Amacher et al., () has reported a reduction of 25% in yield of squash as salinity increased to 5.9 ds/m and this what has been confirmed by our results. On the other hand, the application of glycinebetaine (GB) ameliorated these negative effects and plant growth and production improved. Similar positive results have been reported on different crops as a result of application of glycinebetaine (Tantawy, 7). As GB works as an osmoprotectant, GB-treated plants could absorb water more than untreated ones and this led to more elongated cells hence longer stem length and petioles. Although not measured in this study, stomatal conductance must have been higher in GBtreated plants (Mäkelä et al., 1998). Therefore, plants had higher fresh and dry weights which indicate higher photoassimilate production. This higher photoassimilate production means higher source-sink ratio which increases the chance of higher fruit set and reflects on higher growth rate of the fruits and finally higher fruit number and weight. The recorded higher fruit number indicates clearly that there was higher fruit set in GB-treated plants compared to saline irrigated plants with no GB application. Higher fruit number and weight must have been reflected on fruit quality expressed as individual fruit weight and dry matter content. The tendency for higher contents of N, P, K in GB- treated plants compared to untreated ones under saline conditions indicate that GB-treated plants could absorb more nutrients compared to untreated ones and this reflected on overall plants growth. Moreover, GB is an amino derivative compound which contributes to higher production of protein in GB-treated plants. 3

7 Despite the fact that under saline conditions in both seasons GB-treated plants showed positive response compared to GB-untreated ones, plants received GB by irrigation responded more than those treated with foliar application. This can be explained by two reasons. First, GB-irrigated plants maybe received higher amount of GB-solution compared to foliar sprayed ones hence the accumulated amount of GB were probably higher in the first group compared to the second one. Secondly, GBirrigated plants probably had the chance to accumulate GB faster in the root cells compared to the foliar treated plants, hence the effect of GB was faster in the first group compared to the second one. Mäkelä et al., (1998) mentioned that tomato foliage treated with glycinebetaine showed a negligible increase in the total leaf sap osmotic potential and suggested that glycinebetaine may have been accumulated in specific cells or cellular compartments. Conclusion Application of glycinebetaine has a positive effect on improving growth and production of squash plants grown under saline conditions. Our results indicated more positive response when glycinebetaine is applied to the root zone compared to the foliar application. Acknowledgment This work was conducted during a contracting period with Ministry of Works, Municipalities Affairs and Urban Planning- Agriculture Affairs and Marine Resources, Kingdom of Bahrain, Sincere thanks to H.E. Shikh Khalifa Bin Isa Al Khalifa, Undersecretary for Agriculture and Marine Resources for his continuous support and facilitating all administrative works. Thanks is extended to the technical staff of vegetable farming group for helping in field work. References Abdel-Mawgoud, A.M.R., C. Stanghellini, M. Boehme, A.F. Abou-Hadid and S.O. El-Abd, 4. Sweet pepper crop responses to greenhouse climate Manipulation under saline conditions. Acta Hort., 659: Abdel-Mawgoud, A.M.R., M.A. El-Nemr, A.S. Tantawy and Hoda A. Habib, 1. Alleviation of salinity effects on green bean plants using some environmental friendly materials. Journal of Applied Sciences Research, 6(7): Agboma, P.C., T.R. Sinclair, K. Jokinen, P. Peltonen-Sainio and E. Pehu, An evaluation of the effect of exogenous glycinebetaine on the growth and yield of soybean: timing of application, watering regimes and cultivars. Field Crops Research, (54): Amacher, J., R. Koenig and B. Kitchen,. "Salinity and Plant Tolerance". All Archived Publications. Paper Ashraf, M., M.A. Foolad, 7. Improving plant abiotic-stress resistance by exogenous application of osmoprotectants glycine betaine and proline. Environ. Exp. Bot., 59: Hill, R. and R.T. Koenig, "Water Salinity and Crop Yield". All Archived Publications. Paper Iqbal, N., M.Y. Ashraf and M. Ashraf, 5. Influence of water stress and exogenous glycinebetaine on sunflower achene weight and oil percentage. Int. J. Environ. Sci. Tech., 2(2): Li, Y.L.,. Analysis of greenhouse tomato production in relation to salinity and shoot environment. Thesis, University of Wageningen, The Netherlands. Pp96. Mäkelä, P., 4. Agro-industrial uses of glycinebetaine. Sugar Tech, 6(4): Mäkelä, P., R. Munns, T.D. Colmer, A.G. Condon and P. Peltonen-Sainio, Effect of foliar applications of glycinebetaine on stomatal conductance, abscisic acid and solute concentrations in leaves of salt- or drought-stressed tomato. Australian Journal of Plant Physiology, 25(6): Naidu, B.P., 4. Seed treatment and foliar application of osmoprotectants to increase crop establishment and cold tolerance at flowering in rice. A report for the Rural Industries Research and Development Corporation. RIRDC Publication No 4/4. RIRDC Project No CST-2A 321

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