1 International Peer Reviewed Journal Vol. 21 · June 2015 Print ISSN 2012-3981 • Online ISSN 2244-0445 DOI: http://dx.doi.org/10.7719/jpair.v21i1.324 Journal Impact: H Index = 2 from Publish or Perish JPAIR Multidisciplinary Research is produced by PAIR, an ISO 9001:2008 QMS certified by AJA Registrars, Inc. Effect of Different Levels of Paclobutrazol on the Yield of Asha and Farmers’ Variety of Peanut MARY GRACE B. GATAN http://orcid.org 0000-0002-6083-0060 mbgatan.mgbg@gmail.com Pampanga State Agricultural University Magalang, Pampanga VIRGILIO DM. GONZALES http://orcid.org 0000-0002-7476-4703 virgon3000@gmail.com Pampanga State Agricultural University Magalang, Pampanga ABSTRACT Peanut (Arachis hypogaea) is commonly grown during the dry season and most farmers used the native variety. Growth retardants such as paclobutrazol (PBZ) was found to increase yield of some important crops. A study was conducted to determine the effect of different levels of paclobutrazol on the peanut yield of Asha and Farmers’ variety during the wet season. The experimental area was laid out using Randomized Complete Block Design (RCBD) factorial. Treatments were replicated thrice. Data were analyzed by Analysis of Variance (ANOVA) and the Honest Significant Difference (HSD) test was used to compare treatment means. The increasing level of PBZ increased the number of pods of Asha by 29.97% while the most number of seeds was obtained from farmers’ variety. Applied PBZ Asha at 150mg/L recorded the highest shelling percentage that is 16.19% higher when compared to the untreated. Paclobutrazol application 2 JPAIR Multidisciplinary Research significantly increased seed yield of Asha and farmers’ variety by 43.34% and 20.86% at 150mg/L and 75mg/L, respectively. The increase in yield was due to the observed reduction in plant height and stem growth which possibly enhanced assimilate partitioning to pods. Asha applied with PBZ at 150mg/L obtained the highest seed yield of 4.2 tons/ha. Keywords — Agriculture, yield, peanut, paclobutrazol, experimental design, Pampanga, Philippines INTRODUCTION About 95% of the peanut areas in the country are planted with the native low yielding variety. In the country, farmers are concern in finding means on how to increase peanut production. Paclobutrazol, a plant growth retardant is usually applied to some important crops to reduce unwanted shoot growth without lowering plant productivity. Plant growth regulators play a vital role in many physiological processes associated with growth and development of plants (P. S. Thakur & A. Thakur, 1993). Paclobutrazol was discovered in 1976 and is a member of the triazoles, which are the most highly active class of growth retardants. Paclobutrazol is commonly known as PP333TM, cultarTM,pacloTM, and Bonzi. It is effective on a wide range of plants species, including several bulbous and woody plants, which are not proved sensitive to other retardants (Purohit, 1985). Paclobutrazol is a xylem-mobile, and, therefore, effective retardation relies primarily on uptake of the chemical via the roots. Because triazoles chemicals can be transported in the xylem, they may be absorbed by the leaves, but cannot be moved out of the leaves to other parts of the plant. The most consistent effect of paclobutrazol on growth retardation is that it can induce additional effects such as an increase in ear or grain number or modification in canopy structure. Paclobutrazol have been reported to reduce the sterol levels of plant tissues. The functional role of sterols in membranes and the regulatory properties of the brassinosteroids may contribute to the spectrum of effects that these growth retardants can exert under certain conditions. Because of this, paclobutrazol is very active at low rates it is applied at the rate of 2 to 90 ppm. Paclobutrazol is a post-emergence growth regulator and is applied anytime after the emergence of target plants. Effects may not be noticeable for up to eighteen months. Growth retardants such as paclobutrazol are sometimes called anti gibberellins because 3 International Peer Reviewed Journal they inhibit gibberellin biosynthesis which reduces gibberellin levels and causes a decrease in shoot growth (Hartmann, Kester & Davies Jr. 1990). Paclobutrazol reduce plant growth by inhibiting the microsomal oxidation of kaurene, kaurenol, and kaurenal, which is catalyzed by kaurene oxidase, a cytochrome P-450 oxidase (Davis, Steffens, Sankhla, 1988;Izumi, Kamiya, Sakurai, Oshio & Takahashi, 1985). In addition to blocking gibberellin biosynthesis, paclobutrazol have been shown to inhibit sterol biosynthesis (Haughan, Burden, Lenton & Goad, 1989), reduce ABA (Wang, Sun, Ji & Faust, 1987), ethylene (Sauerbrey, Grossman & Jung, 1988) and indole – 3–acetic acid ( Law & Hamilton, 1989); an increase cytokinin content (Izumi et al., 1988). The effects of triazoles particularly the paclobutrazol on hormonal changes, photosynthetic rate, enzyme activities and yield components was reported by Zhou and Ye (1996). Paclobutrazol is an inhibitor of endogenous gibberellin synthesis by preventing the oxidation of ent-kaurene to ent-kaurenol, a precursor of gibberellic acid. Paclobutrazol applied with 100-200 ppm at the early pod filling of the peanut stage showed the greatest increase in pod and seed yields compared to that of untreated or with 400 ppm paclobutrazol. The number of pods m-2pod reached 370g/m2 that is due to the gain in podding rates during the early flowering stage resulting in the alteration of the distribution of assimilates from the foliage to the pods. In addition, photosynthetic potentials, such as chlorophyll contents, efficiencies of photosystem II and CO2 assimilation rates, were improved by the paclobutrazol treatment (Senoo & Isoda, 2003). In 2011, XiuMei et al., stated that the paclobutrazol treatment reduced pod number, productivity per plant and yield of peanuts relative to the control. According to Chen et al., (2010), paclobutrazol also reduced the peanut plant height and lateral branch while increasing the number of branches and number of pod per plant, rate of filled pod and oil content of seed. In addition, reported that peanut applied with paclobutrazol resulted in the reduction of stem length. Paclobutrazol at 150 mg/L applied at blossoming stage inhibited the growth of the main stems and branches. However, the number of pods per plant and percentage of filled pods were increased resulting to increase in yield (Ming-hui, 2009). The application of paclobutrazol at blooming stage of peanut inhibited the height of a plant and promoted the pod filling percentage, hence increased the yield and income. The optimum amount of paclobutrazol was 500g/m-2(Liang, Senlin, Zhizhong & Zheng Chen, 1995). Zheng (2008) reported that 15% 4 JPAIR Multidisciplinary Research paclobutrazol could effectively inhibit the growth of peanut plants and promote more pods and mature pods leading to high yield. The 15% paclobutrazol effectively controlled the growth of above-ground part of peanut plants and led to the highest yield. The spray concentration of 50 mg/kg of paclobutrazol can produce high pod yield (4518 kg/m-2), compared with 3756 kg/m-2 in CK (Tao, Zhang, Chen & Zhang, 2000). Soaking the seeds with different concentrations of paclobutrazol delayed germination of seeds, decreased germination rate and plant height of peanut. At harvest, the number of pods, the rate of plump pod and the yield of peanut were higher in the paclobutrazol treatment than that in the control. The highest peanut yield was found in 150mg/L paclobutrazol, which reached 3806.3 kg/m-2 and 12.6% higher than the control (Runmei, Li & Chen, 2004). Moreover, Qiankai, Huashou, Jianzhang and Shuiyuan (2010) reported that paclobutrazol solutions applied at a rate of 75-100mg/L at blossoming stage, significantly inhibited the main stems and branches while the number of pods per plant and filled pods increased. The frequent paclobutrazol application could decrease the number of pods per plant, the rate of filled pods and yield, and it could also increase the number of young and the unfilled pods (Hailing, 2011). Low yield is one of the problems encountered by farmers during wet season planting because the upper portion of peanut is prioritized at the expense of pod formation. One possible solution to this problem is through the use of paclobutrazol. The PBZ is believed to improve yield thereby increasing farmers production and profit. In addition, research particularly on the effect of various levels of PBZ on different varieties of peanut is limited. Thus, this study was conducted. OBJECTIVES OF THE STUDY The study was conducted to determine the effect of different levels of paclobutrazol to peanut varieties particularly on yield. Specifically, it aimed to determine the days to flower and maturity; pod number per plant; seed number/ pod; weight of 100 seed; shelling percentage and seed yield/hectare. MATERIALS AND METHODS The study was conducted during the wet season planting of peanut, May to October 2013 in Pampanga, Philippines using Asha and Farmers’ variety of 5 International Peer Reviewed Journal peanut. The following are the characteristics of the varieties used. Asha is a variety developed by ICRISAT. The seed yield averaged 3.0-3.5t/ha and is harvested 121-122 days after planting. Its plant height ranged from 55.9- 74.15cm with a shelling percentage of 71.9% during wet season and 74.2% in the dry season. The weight of 100 seeds is 71.9-74.2g. It is large seeded variety with pink seed color. Farmers’ Variety was developed by BPI and is also known locally as “Kalbo”. Days to flower is from 23-20 days after planting, and its plant height ranged from 41-64cm. The seed yield averaged 1.0-1.5 t/ha. It is harvested 80-90 days after planting depending on the season. It is small seeded variety, having three seeds per pod with red seed color. The experimental area was laid out following the procedure in three-factor Factorial Randomized Complete Block Design (RCBD) factor-factorial. Each treatment combination was replicated three times. The following were the two factors involved in the study. Factor A (Peanut Variety) T1 –Asha T2 –Farmers variety Factor B (Levels of Paclobutrazol, PBZ) L1 – Control (pure water) L2 – 75mg PBZ per Liter of water L3 – 150mg PBZ per Liter of water L4 – 225mg PBZ per Liter of water A total area of 342m2 was used in conducting the experiment having eight treatment combinations including the border plants. Each plot measures 2m in width and 5m in length comprising of four rows spaced 0.5 m apart. An alleyway of one meter between replications was provided for ease in placing stakes, plot tags, data gathering, weeding, and harvesting. Border Ridge was provided to prevent seepage in case rains occur after paclobutrazol application. The area was thoroughly prepared by plowing two times alternately followed by two harrowing to obtain fine tilth that is essential to achieve good germination. After the final harrowing, the field was furrowed at a distance of 50cm. Soil samples were collected before the conduct of the experiment as the basis of fertilizer application. The soil samples were pulverized; air dried and mixed 6 JPAIR Multidisciplinary Research thoroughly to make a composite soil sample, and this was brought to the Soils Laboratory at San Fernando, Pampanga for soil analysis. Based from the result, the type of soil is sandy loam. Calcium nitrate at the rate of 0.645g/hill that is equivalent to 12.9g/m2 was applied basally prior to planting. In addition to Calcium nitrate, organic fertilizer was also applied at a rate of 50g/m2. Both organic fertilizer and Calcium nitrate were applied uniformly along the rows and was covered with 2-3 cm layer of soil. Peanut seeds were inoculated with Rhizobium at the rate of 100g/50kg of seeds. Inoculation was done by coating the seeds with inoculant using water at least two hours before planting. Two seeds were planted per hill. Thinning was done ten days after planting. Ten plants were maintained per linear meter. The distance between hills is 10cm and 50cm between furrows. Plants were watered immediately after sowing to enhance gernmination. Watering was provided three times throughout the experimental period so that soil will not be too dry and prevent wilting of the plants. Hilling-up was done only during the flowering stage to cover the shallow pegs. Weeding was also done manually and regularly until the flowering stage. Paclobutrazol was applied following the different levels specified in the treatment. The solution was sprayed to the plants during the peak of flowering that is about 30-40 days after planting for the Asha variety and 25-30 days after planting for the farmers’ variety. Harvesting of peanut depended on the maturity indices of each variety used. Peanut were harvested when the leaves show signs of maturity by the change of color from green to slightly yellow and more than 75% of the pods per plant have ridges and when the inner side of the shell have dark venations. The Asha and Farmers’ variety were harvested 120DAP and 90DAP, respectively. Harvesting was done manually. Sun drying was done immediately after harvesting. Peanuts were exposed to sunlight for five days depending on the weather condition. Data Collection and Computation 1. Days to flower. This was counted and recorded as the number of days from emergence to that day when 50% of the plants in a row have produced their first open flower. 2. Days to maturity. This was counted and recorded as the number of days from emergence, and at least 75% of the pods show signs of maturity (dark brown pods with deep ridges) for peanut. 7 International Peer Reviewed Journal 3. Number of pods per plant. This was determined by the average number of pods per plant at harvest using the ten randomly sample plants. 4. Number of seeds per pod. This was counted as the number of seeds obtained from 10 randomly selected mature pods from the 10 sample plants. 5. Weight of 100 seeds. This was done by selecting at random 100 seeds from each plot, and it will be recorded the weight in grams. 6. Shelling percentage. This was obtained by weighing 100-gram unshelled pod samples from each plot. Shell the sample pods and weight the cleaned seeds. Shelling percentage is the weight of shelled beans from the 100- gram pod sample. 7. Seed yield/hectare. The clean seed yield from 1m2 of each plot was weighed and recorded, and the computed final seed yield from one m2 served as a basis for computing the seed yield in tons/ha. Statistical Analysis All data were subjected to statistical analysis to Analysis of Variance (ANOVA). Honest Significant Difference (HSD) test was used to compare treatment means. RESULTS AND DISCUSSION Days to Flower As shown in Table 1, a noticeable difference in days to flower was observed. Farmer’s variety produced flowers approximately five days earlier compared to Asha. Early flowering is one of the distinct characteristics of an early maturing variety such as the farmers’ variety. Neither paclobutrazol (PBZ) levels nor the method of paclobutrazol application influenced the number of days to flower. 8 JPAIR Multidisciplinary Research Table 1. Days to flower of asha and farmers’ variety of peanut in relation to levels of paclobutrazol application. Variety Mean T1– Asha 28.38 b T2 – Farmers’variety 23.58 a *Means within the column followed by a common letter is not significantly different at 5% HSD level. Days to Maturity Significant variations were noted among treatments. Asha exhibited the longest day to mature. Its maturity is longer (120DAP) when compared to farmers’ variety (90DAP) simply because its pod filling period is longer, and it is large seeded. Late maturing is one of the distinct characteristics of Asha. There is no effect of PBZ levels on days to maturity across varieties. Number of Pods per Plant at Harvest Paclobutrazol application significantly affected the number of pods per plant of the two varieties of peanut (Table 2a). Asha evidently produced 46% more pods compared to farmers’ variety. Figure 1a. Farmers’ variety during flowering stage Figure 1b. Asha during flowering stage 9 International Peer Reviewed Journal Table 2a. Number of pods per plant of asha and farmers’ variety of peanut in relation to the levels of paclobutrazol application. Variety Mean T1– Asha 29.16 b T2 – Farmers’ variety 19.75 a *Means within the column followed by a common letter is not significantly different at 5% HSD level. Paclobutrazol treatments increased the number of pods per plant in two varieties of peanut. (Table 2b). At least 75mg/L of PBZ is needed to increase the number of pods per plant. In other studies, application of paclobutrazol effectively inhibit peanut growth but can produce more pods resulting in high yield (Zheng, 2008). This increased in pod number is due to PBZ application that could shorten basal internodes. The shortened basal internodes should result to early emerging pegs proximal to ground penetration for pod formation. Table 2b. Number of pods per plant applied with different levels of paclobutrazol across types of peanut application. Levels of Paclobutrazol Mean L1– Control (Pure water) 20.82 b L2– 75mg/L of water 26.17 a L3– 150mg/L of water 27.06 a L4– 225mg/L of water 23.76 ab *Means within the column followed by a common letter is not significantly different at 5% HSD level. Table 2c. Number of pods per plant at harvest as affected by different levels ofpaclobutrazol across varieties of peanut. Levels of Paclobutrazol Mean** L1– Control 20.82 B L2– 75mg/L of water 26.17 A L3– 150mg/L of water 27.05 A L4– 225mg/L of water 23.76 AB * Means having the same letter are not significantly different at 5% HSD level. 10 JPAIR Multidisciplinary Research Number of Seeds per Pod at Harvest There was varietal variation in the number of seeds per pod across levels of PBZ application (Table 3). Asha is two seeded per pod while farmers’ variety is approximately three seeded. The findings confirm with the agronomic characteristics of the varieties used that Asha is two-seeded while farmers’ variety is three seeded. Table 3. Number of seeds per pod at harvest of asha and farmers’ variety of peanut in relation to levels paclobutrazol application Variety Mean T1– Asha 2.00 b T2 – Farmers’ variety 2.80 a *Means within the column followed by a common letter is not significantly different at 5% HSD level. Weight of 100 Seeds Asha produced the heavier weight, more than two folds than the farmers’ variety (Table 4). This can be possibly attributed to the longer pod filling period of Asha resulting to larger seed. On the other hand, farmers’ variety obtained the lightest seed mass due to its small size and shorter filling period, as farmers’ variety is an early maturing genotype (90 days vs. 120 days in Asha). Table 4. Weight of 100 seeds at harvest of asha and farmers’variety of peanut in relation to levels of paclobutrazol application Variety Mean T1– Asha 80.08 a T2 – Farmers’ variety 35.42 b *Means within the column followed by a common letter is not significantly different at 5% HSD level. Shelling Percentage The shelling percentage of Asha and farmers’ variety showed significant difference (Table 5a). Asha obtained shelling percentage heavier than the farmers’ variety. 11 International Peer Reviewed Journal Table 5a. Shelling percentage of asha and farmer’s variety of peanut in relation to levels and methods of paclobutrazol application. Variety Mean T1– Asha 77.21 a T2 – Farmers’ variety 72.59 b *Means within the column followed by a common letter is not significantly different at 5% HSD level. Table 5b showed an interaction effect among varieties of peanut and paclobutrazol application. Asha applied at 150mg/L of PBZ obtained the highest shelling percentage. Regardless of PBZ levels, farmers’ variety attained low shelling percentage and were comparable with the untreated. Table 5b. Shelling percentage of peanut as affected by varieties of peanut of paclobutrazol application. Variety of Peanut Level of Paclobutrazol Mean Asha L1- Control 74.50 B L2- 75mg/L 76.33 AB L3- 150mg/L 80.00 A L4- 225mg/L 78.00 AB Farmers’ Variety L1- Control 73.00 B L2- 75mg/L 73.33 B L3- 150mg/L 72.67 B L4- 225mg/L 71.33 B *Variety and level means having the same letter (A-B) are not significantly different at 5% HSD level. Computed Seed Yield per Hectare Levels of paclobutrazol significantly increased the seed yield of the two varieties of peanut (Table 6). Application of PBZ in Asha at any rate considerably increased yield but highest when applied at the rate of 150mg/L. In farmer’s variety, it appears that seed yield tended to increase yield at 75mg/L. It is believed that peanut applied with paclobutrazol altered dry matter distribution towards the growth seed resulting in increased yield. The photosynthetic potentials such 12 JPAIR Multidisciplinary Research as chlorophyll contents, efficiencies of photosystem II and CO2 assimilation rates were improved through PBZ application at the proper concentration (Senoo & Isoda, 2003). Table 6. Seed yield (ton/ha) of asha and farmer’s variety type of peanut in relation to levels of paclobutrazol. Level of Paclobutrazol Variety of Peanut Mean**Asha Farmer’s variety L1– Control 2.93 BC 2.78BC 2.86b L2– 75mg/L of water 3.62 AB 3.36ABC 3.49a L3– 150mg/L of water 4.20 A 2.65C 3.42a L4– 225mg/L of water 3.52 AB 2.61C 3.07ab *Level means having the same letter (A-C) are not significantly different at 5% level under HSD. **Variety and level means with the same letter (a-b) are not significantly different at 5% level CONCLUSION The increasing level of PBZ increased number of pods of Asha. The most number of seeds was obtained from farmers’ variety. Asha applied with PBZ at 150mg/L recorded the highest shelling percentage. Paclobutrazol application significantly increased seed yield of Asha and farmers’ variety at 150mg/L. TRANSLATIONAL RESEARCH At present, the country is 60-70% import-dependent on peanut and this is because of the limited supply and availability of improved peanut varieties that known to be high yielding, large seeded and resistant to major fungal diseases. Through this study, the production yield of peanut is enhanced through appropriate levels of PBZ application. As a result, this will lead to a sufficient and continuous supply of peanut in the country that will also provide additional income to farmers and peanut growers. 13 International Peer Reviewed Journal ACKNOWLEDGMENTS The authors expressed their sincerest thanks to the Pampanga State Agricultural University and Agricultural Training Institute – Region III, Philippines for providing financial assistance to this research endeavor. LITERATURE CITED Chen, H. L., Huang, J. T., Li, Q. H., Qiu, G. Q., Li, S. P., & Xie, Z. Q. 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