Effects of Different Paclobutrazol Concentrations on Growth and Tuber Development of Sweet Potato (Ipomoea batatas L.)
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Abstract
Sweet potato is a nutritionally important crop with increasing consumer demand; however, its productivity in Thailand remains relatively low, particularly during the rainy season when excessive vegetative growth limits storage-root formation. The application of plant growth regulators such as paclobutrazol (PBZ) may offer a practical approach to suppress vegetative growth and enhance assimilate accumulation in storage roots. This study aimed to evaluate the effects of PBZ on growth and yield of sweet potato cultivar ‘Beniharuka’. The experimental design was arranged in randomized complete block design of 4 PBZ foliar-application treatments; 0 (control), 100, 200, and 300 mg L-1, applied at 45 days after planting with four replications. The experiment was conducted at the experimental field of the Department of Agronomy, Faculty of Agricultural Production, Maejo University. The results showed that PBZ application significantly affected the vegetative growth and yield components of sweet potato. Foliar application at 200 and 300 mg L-1 effectively suppressed vine elongation at 60 days after planting. While SPAD Chlorophyll Meter Reading (SCMR) increased across all PBZ-treated treatments. Moreover, PBZ applied at 200 mg L-1 produced the highest tuber number and yield per rai, with 13,776.92 roots/rai and 1,607.32 kg/rai, respectively, and significantly increased tuber diameter and length. Analysis of size‑class distribution further revealed that PBZ applied at 200 mg L-1 promoted the highest and most uniform proportion of medium‑sized roots (2 - 5 cm), which aligns with market preference and commercial value. Thus, PBZ application, particularly at 200 mg L-1, exhibited the highest potential for suppressing vegetative growth and enhancing sweet potato yield. However, further research is recommended to determine the optimal timing and frequency of PBZ application, as well as its effects on tuber quality.
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