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. 2024 Feb 16;13(4):537.
doi: 10.3390/plants13040537.

Safe Farming: Ultrafine Bubble Water Reduces Insect Infestation and Improves Melon Yield and Quality

Jo-Chi Hung  1   2 , Ning-Juan Li  3 , Ching-Yen Peng  3 , Ching-Chieh Yang  3 , Swee-Suak Ko  1   2
Affiliations

Safe Farming: Ultrafine Bubble Water Reduces Insect Infestation and Improves Melon Yield and Quality

Jo-Chi Hung et al. Plants (Basel). .

Abstract

Melon pest management relies on the excessive application of pesticides. Reducing pesticide spraying has become a global issue for environmental sustainability and human health. Therefore, developing a new cropping system that is sustainable and eco-friendly is important. This study found that melon seedlings irrigated with ultrafine water containing H2 and O2 (UFW) produced more root hairs, increased shoot height, and produced more flowers than the control irrigated with reverse osmosis (RO) water. Surprisingly, we also discovered that UFW irrigation significantly reduced aphid infestation in melons. Based on cryo-scanning electron microscope (cryo-SEM) observations, UFW treatment enhanced trichome development and prevented aphid infestation. To investigate whether it was H2 or O2 that helped to deter insect infestation, we prepared UF water enrichment of H2 (UF+H2) and O2 (UF+O2) separately and irrigated melons. Cryo-SEM results indicated that both UF+H2 and UF+O2 can increase the density of trichomes in melon leaves and petioles. RT-qPCR showed that UF+H2 significantly increased the gene expression level of the trichome-related gene GLABRA2 (GL2). We planted melons in a plastic greenhouse and irrigated them with ultrafine water enrichment of hydrogen (UF+H2) and oxygen (UF+O2). The SPAD value, photosynthetic parameters, root weight, fruit weight, and fruit sweetness were all better than the control without ultrafine water irrigation. UFW significantly increased trichome development, enhanced insect resistance, and improved fruit traits. This system thus provides useful water management for pest control and sustainable agricultural production.

Keywords: jasmonate; muskmelon; nanobubbles water; pest damage; trichome; yield.

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Conflict of interest statement

Authors Ning Juan Li, Ching Yen Peng, and Ching Chieh Yang, were employed by the company Season Agricultural Technology Co., Ltd., Tainan, Taiwan. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Ultrafine water affected seed germination and rooting of melons. (A) Effects of ultrafine water (UFW) on melon seed germination. Four melon varieties, each with 40 seeds, were germinated in Petri dishes containing RO water and UFW. Arrows show the presence of root hairs on the root at 1 day after seed germination. (B) Germination rate of melon seeds at 7 days after germination. (C) Melon seedlings grown in plug trays containing peat moss at 7 days after sowing (DAS). Arrows show vigorous root development.
Figure 2
Figure 2
UFW irrigation affected the growth of melon seedlings. (A) The phenotype of melon potted plants at 14 days after transplantation (DAT). Red arrows indicate the fresh flowers, blue arrows indicate the wilting flowers. Bars, 10 cm. (B) Plant height of melons. Error bars represent the standard error of the mean (n = 10–21 per treatment). (C) Scatter plot of flower number per plant at 14 DAT. Horizontal lines indicate mean values (n = 10–21). *, significant differences between CK and UFW treatment were determined using Student’s t-test at p < 0.05 (B,C).
Figure 3
Figure 3
UFW irrigation affected aphid infestation on melon seedlings. (A) Phenotype of melon leaves attacked by aphids 14 days after transplantation. Scale bars, 2 mm. (B) Scatter plot of aphid infestation rating. A rating of 0 indicates no aphids were observed, and 9 indicates a high aphid density. Horizontal lines indicate mean values (n = 10–21). *, significant differences between CK and UFW treatment were determined using Student’s t-test at p < 0.05. (C) Aphids attacked the young flower buds of melon (arrowhead). Trichomes development after UFW treatment (arrow). (D) Cryo-SEM showed aphid infestation on flower buds of CK (D) and UFW (E). The arrowheads point to the aphids. Scale bars, 500 µm (D,E).
Figure 4
Figure 4
Hydrogen-rich or oxygen-rich ultrafine water irrigation affected the development of trichomes in melon cv. “Camilla”. (A) Dissecting microscope observation of the development of trichomes in melon petioles after irrigation with ultrafine water enrichment of hydrogen (UF+H2), oxygen (UF+O2), and RO water (Ck), respectively. Bars, 2 mm. (B) Cryo-scanning electron microscope (cryo-SEM) showing trichomes on the midribs of the melons. Blue arrows indicate the presence of granular trichomes. Bars, 500 µm. (C) Cryo-SEM showed the development of trichomes on the abaxial of newly established young leaves of melon (red arrows). Bars, 500 µm. (D) Trichome density in melon petioles irrigated with RO water, UF+H2, and UF+O2, n = 3 to 6. (E) RT-qPCR showed GLABRA2 (GL2) gene expression patterns in young melon leaves irrigated with UF+H2, UF+O2, and RO water control (CK). *, significant differences between CK and UFW treatment were determined using Student’s t-test at p < 0.05 (D,E).
Figure 5
Figure 5
Melon irrigated with hydrogen- and oxygen-rich ultrafine water altered jasmonic acid (JA) and methyl-JA (MeJA) contents, and gene expression patterns. (A) JA content. (B) MeJA content. (C) The gene expression level of JASMONATE ZIM DOMAIN PROTEIN (JAZ) and JA carboxyl methyltransferase (JMT). The gene expression level was normalized to two housekeeping genes: Actin (MELO3C023264) and ADP ribosylation factor 1 (ADP, MELO3C023630). Error bars represent the standard error of the mean (n = 3). Student’s t-test was used to find the significant difference between CK and UF+H2 or UF+O2 treatment. *, p < 0.05; ns, not significant.
Figure 6
Figure 6
Ultrafine water irrigation affected the photosynthesis capacity of melons. (A) Chlorophyll content in melons. The SPAD value was measured on the 4th leaf at the late stage of fruit maturity. n = 4 plants. The Li600 Porometer/Fluorometers meter detected the photosynthesis parameters of (B) stomatal conductance (gsw); (C) ΦPSII, the quantum yield of PSII calculated from fluorescence; and (D) the electron transport rate (ETR) of L1 melon leaves. Student’s t-test was used to find the significant difference between UFW and the regular tap water (CK). *, p < 0.05. Error bars represent the standard error of the mean (n = 4).
Figure 7
Figure 7
UFW irrigation affected fruit weight and sweetness of melon cv. “Camilla”. (A) Melons were planted in a greenhouse. Photo taken 42 days after pollination. Bars, 20 cm. (B) Root morphology at harvest stage. (C) Root fresh weight of each plant. (D) Root dry weight per plant. (E) Melon fruits at 5 days after harvest. (F) Average fruit weight of melon. (G) The sweetness of melon fruits. UF+H2, hydrogen-rich ultrafine water irrigation. UF+O2, oxygen-rich ultrafine water irrigation. CK, irrigated with tap water. Bars, standard deviation of 22 plants. Student’s t-test was used to find significant difference between CK and UF+H2 or UF+O2 treatment. *, p < 0.05.
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