INTRODUCTION

Kimchi Cabbage (Brassica rapa var. pekinensis (L.) belongs to the cabbage family and is cultivated year-round, with numerous cultivars bred for production across various growing season (Hirai et al., 2007). It is also known as Napa cabbage in other countries and Baechu in Korea, is a barrel-shaped dense-head with a firm, crunchy texture and milder flavor than traditional green head cabbage. This resembles Swiss chard in growth habit. The leaves are long, dark-green, and oblong or oval, and they do not form a solid head. It is also called Chinese mustard (Kalloo et al., 1993). Also known as Chinese cabbage, are eaten raw or lightly cooked by, for example, stir-frying. More than 90% of the Chinese cabbage harvested in Korea is used for making Kimchi, a fermented side-dish eaten throughout the year by virtually every family (Fordham et al., 2003).

Also known as napa, napa cabbage, pe-tsai, wong-bok, chihli. This is a vegetable of major importance in China (over 300 000 ha grown), Korea, Taiwan, and Japan. Grown as an annual crop, most cultivars are biennial and produce tight, compact, cylindrical heads. This vegetable has been cultivated in China for over 1600 years and accounts for a major fraction of the total vegetable consumption in certain (northern) areas of the country. In Korea, it is fermented to produce (preserved) Kimchi, which is thus a year-long, ubiquitous commodity in that country (Fahey, 2016).

In the Philippines, Kimchi Pechay is produced at an annual vloum exceeding 0.5 milion metric tons (Philippine Statistics Authority, 2019), but this kind of vegetable is mostly grown in the highlands because it requires cool temperature for optimum growth. In the lowland areas of the country, planting of this kind should be done during cool months usually from November to February. On the other hand, aiming the possibility to plant kimchi Cabbage in the lowland is being studied using hormones to assure leaf heading for optimum yield, thus this trial was conducted.

Diniconazole (Binnari) is a Korean brand triazole fungicide often used to control diseases caused by ascomycetes and basidiomycetes in banana, cereal and vine crops. It was also claimed that Diniconazole also regulates the inhibition of stem elongation and stimulation of root development (Journal of Bio-Environment Control, 2020). Diniconazole is a versatile fungicide used for disease control in various crops and ornamental plants. Its effectiveness against fungal pathogens makes it a valuable tool for agriculture and horticulture (https://sitem.herts.ac.uk/aeru/iupac/Reports/247. htm). One disadvantage of this product is the unavailability in the Philippines.

Diniconazole is a triazole fungicide. It has a low aqueous solubility and a low volatility. It tends to be persistent in both soil and water systems. Whilst available ecotoxicology data is limited, diniconazole is moderately toxic to birds, fish and honeybees. It also has a moderate oral mammalian toxicity (Lewis et al., 2016).

Diniconazole application increased firmness and cutting force compared with the control. Residues of diniconazole soon after application was detected but not at 40 days after application. As a result, the proper amount of diniconazole (5% original sum) to regulate excessive growth of Chinese cabbage during summer season without decreasing marketable yield seemed to be 50 mg/litre with application frequency of 1-2 times at 20 days after transplanting (Sun et al., 2002).

While, Paclobutrazol is also a fungicide that can regulate inhibition of plant growth. It has been mainly used in agriculture and horticulture to improve plant growth in the open field and in green house soils (https://www.science direct.com). Paclobutrazol is one of the members of triazole family having growth regulating property. The growth regulating properties of Paclobutrazol are mediated by changes in the levels of important plant hormones including the gibberellins (Gas), abscisic acid (ABA) and cytokinins (CK) (Soumya et al., 2017). It is also available in several brands in the Philippines.

There was another study performed on sandy-loam soil from a mango garden revealing that the community structure of soil bacteria was reduced by the presence of the paclobutrazol. With the paclobutrazol, the amounts of proteobacteria and planctomycetes were significantly augmented and those of actinobacteria and firmicutes were significantly reduced (Jin et al., 2019).

PBZ is a plant growth retardant, which is a compound used to reduce plant growth without changing developmental patterns or being phytotoxic. the group of Pbz is the largest group of plant growth retardants, which include chemicals antagonistic to gibberellins (the hormone of plant growth). Pbz also has some fungicidal activity because of its action as a triazole to inhibit sterol biosynthesis. Pbz may also induce many morphological changes in plant leaves including thicker leaves, smaller stomatal pores, increased the number of surface appendages and their size, and increased root density, which may support the plant tolerance against environmental stress and disease resistance as well (Abdalla et al., 2021).

MATERIAL AND METHODS

Evaluation of “Diniconazole (Binari, Dongbangagro Inc) and Paclobutrazol (Paclobutrazol PGR 25SC, S&P Enterprises, Inc.)” in Kimchi Cabbage was conducted in one of the experimental area of the Bureau of Plant Industry, Los Baños Laguna, Philippines from February 4 to April 13, 2024 using Kimchi Cabbage variety “Woori (Nongwoobio Inc)”. The field trial was arranged in Randomized Complete Block Design (RCBD) in three replications. The treatments used were as follows:

The different activities and treatment application were done within the duration of the trial (February 23 to April 13, 2024).

Seeds of KimchiCabbage, “Woori Variety” were sown in seedling trays. The seeds emerged in 2 days after sowing (DAS) 1 seedling per hole was maintained as shown in Fig. 3.

First application of treatments was done at 7 DAS using pressurized hand sprayer following the recommended rate of application for each treatment. Barrier was used during application to enclose during application (Fig. 4).

Transplanting of seedlings was done on February 23, 2024 at the 12^th day after the 1^st treatment application. One (1) x four (4) meter plots were used for the different treatments. The distance of planting was 0.5 m between rows x 0.25 m between hills (2-row plot) with thirty-two (32) seedlings were planted per plot. A total of 864 seedlings for the whole experiment were used. Re-planting on dead hills was done as necessary within 7 days after transplanting. Separate seedling trays were used based on the number of treatments (Fig. 5).

The second treatment application was done at 15 days after transplanting (DAT) in the field for Diniconazole (Binnari) and Paclobutrazol while side dressing of granular fertilizer were done at 15 DAT and 45 DAT (Fig. 6).

Data gathering were done at two (2), four (4), six (6) weeks after transplanting (WAT).and at harvesting (Fig. 7).

Observation at seedling stage (1 week after first treatment application) and photo documentation were done. Ten (10) tagged plants per plot were used during data gathering for plant height, number of leaves and growth diameter before transplanting, at 2, 4, 6, weeks after transplanting and at harvest. Data on fresh plant yield in 2 square meter area and computed yield in tons per hectare were gathered.

All data were subjected to Analysis of variance (ANOVA) while Duncan’s Multiple Range Test (DMRT) for treatment differences at 5% level of significance using Statistical Tool for Agricultural Research (STAR).

RESULTS AND DISCUSSION

Observation at seedling stage of kimchi cabbage

Seedlings were observed based on the color and initial plant height, number of leaves and plant diameter at 7 days after treatment application. Untreated seedlings (Treatment 1 and Treatment 2) were lighter green in color but with taller plant height of 7.6 and 7.9 centimeters, average of 5 leaves per plant and 9.5 and 7.5 centimeter plant diameter respectively. On the other hand, seedlings treated with Diniconazole (Binnari) (Treatments 3 and 4) gave the shortest plant height of 3.5 and 3.9 centimeters, but both with 6 leaves and narrowest plant diameter of 5.4 and 5.5 centimeters, respectively. While, seedlings treated with Recommended rate of Paclobutrazol (RR-PBZ) and ½ RR-PBZ (Treatments 5, 6 and 7) gave the average plant height of 4.2, 4.3 and 4.4 centimeters, all with 6 leaves and average diameter of 5.7, 7.9 and 6.5 centimeters, respectively (Fig. 8). Another general observation was, the untreated plants have soft and lanky stem while the treated plants have firmer plant stand (Fig. 9).

In terms of root development, it was observed that seedlings treated with PBZ have more and compact roots than plants treated with Diniconazole (Binnari) and untreated plants (Fig. 10).

PBZ increases the allocation of biomass to roots relative to shoots. This means that more resources are directed toward root development. It can lead to either reduced shoot growth or an absolute increase in root growth, especially fine roots near the soil surface (Desta et al., 2021).

Paclobutrazol are often referred as multi-stress protectants due to their innate potential of mitigating the negative effects of abiotic stresses had on plant growth and development, by regulating hormones level, enzymatic and non-enzymatic antioxidants and osmolytes (Kamran et al., 2018; Kuai et al., 2016).

Plant height before transplanting, 2,4,6 and 8 Weeks After Transplanting (WAT)

Fig. 11 shows the plant height in centimeters of Kimchi cabbagein different treatments before transplanting, 2, 4, 6, and 8 weeks after transplanting. It was observed that Treatment 2 (RR-G) took advantage in terms of plant height during the whole duration of the trial with 44.2 cm at harvest . No stunting effect on this treatment was observed because it was not sprayed by any foliar treatment.

Number of leaves of kimchi cabbage before transplanting, 2, 4, 6 and 8 WAT per treatment

In Fig. 12, significant increase in number of leaves was observed between 4 and 6 WAT among treatments. But at harvest which was 7 WAT, Treatment 6 (RR-G + RR PBZ) gave the significant number of leaves with a mean of 41 which was also comparable with Treatment 2 with 40 leaves. Other treatments ranged from 33 to 45 leaves per plant.

Plant diameter of kimchi cabbage before transplanting, 2, 4, 6 and 8 WAT per treatment

Fig. 13 shows the plant diameter in centimeters of Kimchi pechay in different treatments. Treatment 2 gave the widest plant diameter of 63.6 centimeters at harvest, but was comparable to treatments 3, 6 and 7 with 58.1, 57.9 and 54.9 centimeters, respectively.

Yield of kimchi cabbage per 2 square meter harvest area in kilograms (Kg)

Table 2 shows the yield in kilograms from 2 square meter harvest area. Treatment 6, Recommended Rate of Granular Fertilizer (RR-G) + Recommended Rate of Paclobutrazol (RR-PBZ) gave the yield of 13.0 Kg/ 2 square meter which was significantly higher than other treatments. While Treatment 7 (RR-G + ½ RR-PBZ) with 11.1 Kg/2 m² was comparable to Treatment 2 (RR-G only) with 11.0 Kg / 2 m².

6. Yield of kimchi Cabbagein tons per hectare

When converted to tons per hectare (t/ha), significant differences were still observed among treatments, as shown in Table 3. Still, Treatment 6, (RR-G + Recommended Rate of Paclobutrazol RR-PBZ) gave the highest significant yield of 64.9 t/ha. Treatments 2 and 3 were also comparable with each other with 54.9 and 55.3 t/ha respectively. On the other hand, plants treated with Diniconazole, Binnari (Trt. 4) and Paclobutrazol (Trt.5) alone were comparable to each other with 33.0 and 35.8 t/ha respectively but the latter, Treatment. 5 was also comparable to Treatment 3 (RR-G+ RR-B).

PBZ application has reduced plant height, improved stem diameter and leaf number, altered root architecture (Pal et. al., 2016) directly contributed to yield increase, and indirectly reduced the event of lodging (Syahputra et al., 2016).

Since Kimchi Cabbage is a semi-temperate crop and more adopted in the highlands, the high temperature in the lowland during the trial period (February 23 to April 13, 2024) greatly affected the growth performance of the plants especially on its heading stage. During March high temperature with an average of 32°C was recorded and even higher in April with an average of 35 °C based on “AccuWeather, historical data in Los Baños”. Lesser and looser leaves were observed in treatments with Diniconazole (Binnari) and Paclobutrazol alone and comparable to the untreated check, while with the addition of granular fertilizer, the head had more leaves and more compact (Fig. 13). Although Woori variety was known to be tight in heading especially during it’s growing season, it was also observed that heading of this variety was generally affected by the higher temperature in the Philippines during the trial thus the head are lesser compact as expected (Fig. 13).

In the Philippines, not all regions produce Chinese cabbage (KimchiCabbage) because of its climatic requirements and adaptability to the area. Just like cabbage, most of the Chinese cabbages are grown in CAR with a contribution of 75% (2,688.86 ha) to the area planted and 44,329.73 mt (86%) in 2020. Other than CAR, the regions with significant contributions to area and production are Regions VII, X, XI, and XII, totaling 98% and 99%, respectively in 2020 (https://www.da.gov.ph/wp-content/uploads/2023/ 05/Philippine-Vegetable-Industry Roadmap.pdf).

Plant growth regulators are chemical substances which govern all the factors of development and growth within plants. The application of plant growth regulators to crops modifies hormonal balance and growth leading to increased yield, enhanced crop tolerance against abiotic stress and improved physiological trait of crops (Desta et al., 2021).

On the other hand, infestation of cabbage web worm and diamond back moth (DBM) which are more prevalent during hot months affected the plant performance in all of the treatments, thus yield was also affected (Fig. 14).

적 요

배추는 배추과에 속하는 작물로 육종을 통해 연중재배가 가능하게 되었다. 필리핀에서도 매년 50만 톤 이상이 생산되 고 있으며 선선한 기후를 필요로 하는 작물 특성상 필리핀 북 부 고냉지에서 주로 생산되고 있다. 이에 착안하여 온도가 상 대적으로 높은 필리핀 루손섬 남부 지역에서도 배추 생산이 가능할 수 있도록 생장조절제 처리를 통한 결구 배추 생산 시 험을 진행하였고, 필리핀 루손섬 남부지역 최초로 이 가능성 을 확인하였다.

본 연구에서는 필리핀 현지 생장조절제(Paclobutrazol)를 이 용하여 배추의 웃자람을 억제하고 조직의 밀도를 높이는 방식 으로 필리핀의 남부 지역의 고온조건에서도 상품성 있는 결구 배추 재배가 가능한지 검증하고자 하였다. 공시 재료는 한국산 배추 품종(우리, 농우바이오)과 한국산 생장조절제 Diniconazole (빈나리, 동방아그로), 필리핀 현지 생장조절제 Paclobutrazol (Paclobutrazol PGR 25SC, S&P Enterprises, Inc.)로, 이를 이 용하여 생장조절제 시용 및 농도에 따른 배추 수량 및 원예학 적 특성을 비교하고자 2024년 필리핀 식물산업국(BPI, Bereau of Plant Industry)의 로스바뇨스 시험 포장에서 격리 상태로 3 반복 실험으로 진행되었다.

위 결과를 종합해보면 Paclobutrazol을 이용하면 열대성 해 양 기후인 필리핀 루손섬 남부 지역에서도 결구 배추 재배가 가능하며 수량성, 상품성 또한 가지고 있다 사료된다.