The effect of seed treatment using plant growth promoter rhizobacteria (PGPR) on the germination process of chili (Capsicum annum L.)

Chili is one of the leading horticultural commodities that has high economic value and still requires serious handling, especially in increase production both in quality and quantity.The research was conducted at the Laboratory of Seed Science and Technology, Department of Agrotechnology, Faculty of Agriculture, Syiah Kuala Darussalam University, Banda Aceh. The research was conducted from April 2023 to June 2023.The design used in this study was a 7 x 2 Factorial Completely Randomized Design (CRD) with 3 replications, so there were 14 treatment combinations and 42 experimental units, each treatment consisting of 3 plants so that 126 plants were obtained. The results showed that the effect of rhizobacterial treatment on the germination process had a significantly increased effect on maximum growth potential, germination, vigor index and growth simultaneity compared to no treatment (control). Almost all rhizobacteria can increase the rate of seed germination. At the variable maximum growth potential, germination capacity, vigor index and growth simultaneity, there are two isolates that have the potential to be candidates for plant growth promoting rhizobacteria agents (PGPR) and these isolates, namely AD 7/1 and LABA F1 varieties significantly provide an increase in seed vigor and viability.


Introduction
Chili is one of the leading horticultural commodities that has high economic value and still requires serious handling, especially to increase production both in quality and quantity.Chili plants can grow and develop in Indonesia, both in the highlands and lowlands.Chilies contain high-value substances such as vitamins A, C, K, B6, calcium, iron, zinc, and capsaicin which make chilies spicy and useful as anti-cancer and antioxidants [1].National chili production in 2020 reached 2.77 million tons.While the potential can reach 183.96 thousand tonnes or 7.11% compared to 2019 [2].Efforts to increase chili productivity reached be carried out by spelling the factors that can cause a decrease in the quality and quantity of chili production including inefficient plant cultivation techniques, planting chili cultivars that are not resistant to pests and diseases put coma using inferior seeds [3].Quality seeds of superior varieties are the main key to the success of a farming business.Seed 1297 (2024) 012010 IOP Publishing doi:10.1088/1755-1315/1297/1/012010 2 quality concerns genetic, physical, physiological and pathological quality ies [4].Improving the quality of seeds and seedlings can be done through seed treatment (seed treatment).One of the goals of seed treatment is to improve seed germination and protect seeds from pests and diseases.Seed treatment using biological agents (biological seed treatment agents) is an alternative as a substitute for synthetic chemicals [5].We know that plant protection is an inseparable part of an overall agricultural ecosystem management system, so controlling plant-disturbing microorganisms by utilizing biological resources (biocontrol agents) is a top priority at this time.Therefore, this research is directed to find effective biological control methods for controlling seed-borne diseases.

Tool sterilization
The tools used, such as Erlenmeyer, test tubes, petridish, spatulas, are washed first using detergent, then dried in an electric oven for 15-20 minutes, after drying the tools are sterilized first before being used for research , all the tools are wrapped using newspaper and then put in an electric oven for ± 4 hours until it reaches a temperature of 121 0 C. The tools that have been sterilized are then waited until they reach room temperature.

Preparation of planting medium
The soil to be used is entisol soil or river sediment soil.Then the soil used is refined by sifting using a 12 mesh sieve.Then the entisol soil is sterilized using basamide G (12 grams) with the aim to sterilize the soil.The sterilization process was carried out for 14 days, by mixing Basamide G according to the required dose in the soil medium on black polyprophylene plastic.Then it is watered until it reaches field capacity and covered with black polypropylene plastic and placed in a place that is not exposed to direct sunlight.The sterilized soil must always be moist.Then the sterile soil was put into a plastic container with a diameter of 22 cm and a height of 6 cm.

Suspension Preparation and Inoculum Density Calculation
The rhizobacteria used were isolates from exploration results in plantations in the village of Pantan Musara (Central Aceh).Rhizobacteria were isolated from soil taken from healthy chili plant roots.In this study, 14 rhizobacterial isolates were used which had been tested in vitro as potential biocontrol agents.Rhizobacteria were rejuvenated on SPA (Sucrose Peptone Agar) media until the rhizobacterial colonies grow.Furthermore, the rhizobacteria suspension was made using 50 ml of sterile distilled water by slowly taking the rhizobacterial colonies without knowing the growth medium.Next, the density of the rhizobacteria suspension solution was calculated using a spectrophotometer up to 109 cfu ml-1 or equivalent to reading the absorbance value OD600 = 0.192.

Seed treatment and planting
The seeds used were the Laba and Laju varieties of chili seeds as many as 840 seeds.Before the seeds were treated, the seeds were cleaned by soaking in 70% alcohol for 3 minutes.Then the seeds were washed using sterile distilled water three times.Then air-dried in laminar air flow.Furthermore, the seeds were given immersion treatment with a total of 60 seed treatments.The immersion treatment consisted of 12 treatments using 50 ml of rhizobacterial suspension and 1 seed soaking treatment carried out for 1 x 24 hours.The seeds were planted according to the treatment on the paper using the UAK (Inter-Paper Test) method and observed every day until a radicle (prospective root) appeared on the seed.After the radicle appeared 3 days after planting, the seeds were transplanted into plastic containers filled with sterile soil.

Observed parameters and data analysis
Parameters observed included maximum growth potential, germination rate, vigor index, growth simultaneity, relative growth speed and time needed to reach 50% germination.The collected data were analyzed using ANOVA.The results of the F test showed a significant effect followed by (Duncan) at the 5% level.

Effect of rhizobacteria on seed viability and vigor
The indigenous rhizobacteria treatment on seed viability and vigor had a very significant effect on rhizobacteria but had no significant effect on variety and an insignificant effect on seed viability and vigor.The average values of maximum growth potential, germination, vigor index, growth simultaneity, relative growth speed, and time needed to reach 50% germination are presented in Table 1.The results of variance or F test showed that the treatment of indigenous isolate e rhizobacteria very significant effect on the parameters of seed viability and vigor.Relatively higher maximum growth potential was found in the treatment using AD 7/1 rhizobacteria which was 90.00% and higher germination was found in the treatment using AD 7/1 rhizobacteria with a value of 90.00%.The vigor index was higher in the treatment using AD 7/1 rhizobacteria, namely 81.67%.
The average percentage of simultaneous growth was higher in chili sprouts using AD 7/1 rhizobacteria, namely 76.67%.Growth speed was relatively higher in the treatment using rhizobacteria AD 7/1 with a percentage value of 44.21%.The time required to achieve 50% germination was found to be faster in the treatment using control rhizobacteria, namely 4,39 days and tended to be longer in the treatment using AD 7/1 rhizobacteria, namely 6.03 days, but it did not have a significant effect on the variety.The results of this study are relevant to the results of previous studies which reported that a mixture of endophytic bacteria and rhizobacteria was capable increase seed viability and vigor [6].The increased viability and vigor of chili seeds is thought to be caused by the ability of endophytic bacteria to produce IAA hormones [7].This is presumably because the seeds that were treated with biopriming first experienced imbibition (water absorption process) compared to seeds without treatment or control.This statement is in line with the results of research [8] which states that the increase in vigor value can be seen in the percentage of seed vigor index using rhizobacteria.

Table 1 .
The average value of maximum growth potential, germination, vigor index, simultaneity of growth, relative growth speed, and time needed to reach 50% germination on the viability and vigor of red chili varieties