Testing of Ethylene Stimulation to Enhance Latex Yield of Hevea Brasiliensis Clone RRIM 600 in Southern Thailand

Recently, latex price has continuously increased, This motivates rubber smallholders in southern Thailand to increase latex productivity. Then, ethylene stimulation has been introduced in tapping systems. Therefore, it needs to be tested before recommendation to the smallholder. An experiment was established at Thepa Research Station, Songkhla province. Rubber clone RRIM 600 (20 year-old) was used in the experiment. The experiment was designed as one-tree-plot design with 20 replicates. There was 6 treatments: 1) 1/3S­ 2d/3 (C), 2) 1/8S­ 1d/3, 3)1/8S­ 1d/3 + RRIMFLOW (RF), 4)1/8S­ 1d/3 + LET (LET), 5) 1/8S­ 1d/3 + Double Tex (DT) and 6) 1/8S­ 1d/3 + Ethyphon 5% (E). The experimental period was during June 2010 to February 2011. It was found that the RF treatment provided the highest rubber productivity (137.7 g/tree/tapping and 5.9 kg/tree/year), and it was significantly different from the remaining treatments. According to latex diagnosis, sucrose in the RF treatment trended to decrease, but inorganic phosphate and thiol trended to increase

A simple framework to analyze water constraints on seasonal transpiration in rubber tree (Hevea brasiliensis) plantations

Climate change and fast extension in climatically suboptimal areas threaten the sustainability of rubber tree cultivation. A simple framework based on reduction factors of potential transpiration was tested to evaluate the water constraints on seasonal transpiration in tropical sub-humid climates, according pedoclimatic conditions. We selected a representative, mature stand in a drought-prone area. Tree transpiration, evaporative demand and soil water availability were measured every day over 15 months. The results showed that basic relationships with evaporative demand, leaf area index and soil water availability were globally supported. However, the implementation of a regulation of transpiration at high evaporative demand whatever soil water availability was necessary to avoid large overestimates of transpiration. The details of regulation were confirmed by the analysis of canopy conductance response to vapor pressure deficit. The final objective of providing hierarchy between the main regulation factors of seasonal and annual transpiration was achieved. In the tested environmental conditions, the impact of atmospheric drought appeared larger importance than soil drought contrary to expectations. Our results support the interest in simple models to provide a first diagnosis of water constraints on transpiration with limited data, and to help decision making toward more sustainable rubber plantations

Using SPAD-502 to evaluate the total chlorophyll and nitrogen status in leaves of longkong (Aglaia dookkoo Griff.) and rambutan (Nephelium lappaseum L.)

Total chlorophyll and nitrogen status in leaves of longkong and rambutan were evaluated by using the SPAD-502 meter. Leaves of both species were sampled from 10 year-old trees grown in an experimental plot at Prince of Songkla University, Hat Yai campus. The relationship between SPAD-502 meter reading (SPAD) and total chlorophyll content analyzed in the laboratory was evaluated in longkong and rambutan, and they were y = -2.68+0.21x, r2 = 0.77** and y = -1.11+0.18x, r2 = 0.77**, respectively. The data recorded by SPAD were also linearly related in a positive manner to nitrogen status in longkong (y = 1.27+0.20x, r2 = 0.82**) and rambutan (y = 1.17+0.02x, r2 = 0.79**). The results show that using the SPAD-502 meter is convenient and fast for the evaluation of total chlorophyll and nitrogen status in leaves of longkong and rambutan

Evaluation of nitrogen status and total chlorophyll in longkong (Aglaia dookkoo Griff.) leaves under water stress using a chlorophyll meter

A chlorophyll meter (SPAD-502) was used to assess nitrogen status and total chlorophyll in longkong leaves, leaves from twelve of 10-year-old trees grown in the experimental plot at Prince of Songkla University, Songkhla province. The relationship between SPAD-502 meter reading and nitrogen status and total chlorophyll content analyzed in the laboratory was evaluated during 8 months (May-December 2003). It was found that the trend of the relationships in each month was similar. There was no significant differenceamong regression linears of all months. The data of 8 months showed that SPAD-reading and nitrogen content, and SPAD-reading and total chlorophyll content were related in a positive manner. They were Y = 0.19X+10.10, r = 0.76** (n = 240), and Y = 0.43X-7.89, r = 0.79** (n = 400), respectively. The SPAD-502 was then used to assess total nitrogen and total chlorophyll content during imposed water stress. Fifteen 4-yearold plants were grown in pots (each pot containing 50 kg soil volume). The experiment was arranged in acompletely randomized design with 3 treatments: (1) daily watering (2) once watering on day 7 (3) no watering with 5 replications during 14 days of the experimental period. Measurements showed a continuous decrease of SPAD-reading in the treatment of no watering. On day 14, a significant difference of SPAD- reading values between the treatment of daily watering and no watering was found. Then, the values of nitrogen content and total chlorophyll were assessed by using the linear regression equations. From the result, it is suggested that the measurement by chlorophyll meter is a rapid technique for the evaluation of total chlorophyll and nitrogen status in longkong leaves during water stress

Fruit splitting occurrence of Shogun mandarin (Citrus reticulata Blanco cv. Shogun) in southern Thailand and alleviation by calcium and boron sprays

Fruit splitting is a serious problem of Shogun mandarin in southern Thailand. To alleviate this impact, the applications of calcium and boron by spraying were investigated. An experiment was established in a farmer orchard (at Amphur Sadao, Songkhla province) where four-year plants were grown at 6 m x 6 m spacing. The experiment was arranged as a completely randomized design, and 16 trees were used. There were 4 treatments (1. control or water spray, 2. 1% CaCl2 spray or C treatment, 3. 0.8% boric acid spray or B treatment and 4. 1% CaCl2+ 0.8% boric acid spray or C+B treatment) with 4 replicates. The application was started at 4 months after fruit-setting, the sprays were done at 1 month intervals. It was found that the occurrence of fruit-splitting started at 3 months after fruit-setting, and there were 4 causes of fruit-splitting: 1. scab (28.33%), 2. sun scald (11.11%), 3. sun burn (7.78%) and 4. no primary peel damage (52.78%). Various patterns of fruit splitting were found: vertical, horizontal, oblique and informal shape. The treatments of calcium and boron sprays did not affect on fruit growth or fruit size compared with the control, but they significantly enhanced fruit firmness, total soluble solid (TSS) and total acidity (TA). The treatments of C, B, and C + B can reduce the percentages of fruit splitting to 5.56, 8.89 and 6.67%, respectively, and they were significantly different from that of the control (52.22%). It is suggested that calcium and boron sprays can alleviate fruit splitting in Shogun mandarin, and fruit quality is also enhanced

The effects of root pruning and limb strangulation on physiological responses and flower bud development of longkong (Aglaia dookkoo Griff.)

Flowering induction by physical methods of root pruning and limb strangulation to alleviate the incidence of biennial fruit-bearing in longkong were investigated. The experiment was conducted at the Department of Plant Science, Faculty of Natural Resources, Prince of Songkla University, Hat Yai, Songkhla Province, from December, 2001 to November, 2002. In the root-pruning trial, twelve 6-year-old longkong trees were used. Each tree was grown in 1 m3 soil volume. The experiment was arranged in a completely randomized design having 4 treatments in 3 replications. The treatments were: (1) control, (2) cutting 1 side 30 cm from the stem at 30 cm depth, (3) cutting 1 side 20 cm from the stem at 30 cm depth, and (4) cutting 2 sides 30 cm from the stem at 30 cm depth. In the limb strangulation experiment, six 6-year-old longkong trees were used. Again, each tree was grown in 1 m3 soil volume and the experiment was arranged in a com- pletely randomized design. The treatments were: (1) control, (2) limb strangulation 2 months before bloom, and (3) limb strangulation 1 month before bloom. All treatments were done on one plant with 6 replications (one plant per replicate). The root- pruning methods decreased diurnal water use and a physiological response as compared with the control. All three root-pruning treatments induced flowering; however, only the trees cut on 1 side, 30 cm from the stem at 30 cm depth, stimulated flower-bud elongation. Similarly, the limb strangulation treatments resulted in decreased water use and physiological response as compared with the control. Both limb strangulation methods induced flowering, but strangulation at 1 month before bloom was more effective in the flower-bud development

Growth and fruit development of mangosteen (Garcinia mangostana L.) in related with plant nutrients during phenological development

The imbalance or deficiency of essential nutrients in soils and plant may cause poor fruit quality of mangosteen fruit; translucent flesh disorder (TFD) and internal gumming fruits. Therefore, an investigation of nutrient changes in soils and plant (root, branch, leaf and fruit) of mangosteen (Garcinia mangostana L.) during phenological development is a useful guideline for fertilizer management. This research aimed to investigate the pattern of plant nutrients accumulation and nutrient requirement during phenological development of the mangosteen trees. Soil sampling was taken at 4 depths; 0-15, 15-30, 30-50 and 50-100 cm, from soil surface around the middle of the tree canopy and analyzed for some important chemical and physical properties. Roots, branches, leaves and fruits from mangosteen trees at 4 periods of growth; preflowering, flowering, fruit development (from bloom to 7th week) and harvesting were sampled, and analyzed related to the changes of soil nutrients. The results indicated that the soil texture varied from sandy clay loam to clay loam (Ruso soil series (Ro); Typic Pelehumults). In addition, the natural soils in mangosteen orchards was strong acid to very strong acid (pH 4.62-4.93, soil:water = 1:5). Mangosteen trees might take high amounts of nutrients from the surface soils (0-15 cm) as follows: N, K, Mg and S for growth in the preflowering period; N, K, S and B in the flowering period; K, Ca and Mg in the 1st half of fruit development period (bloom to 7th week of fruit development) and P in the 2nd half of fruit development period (7th week of fruit development to harvest) compared to other growth periods. The results also showed that in the root, branch and leaf, mangosteen trees required higher amounts of Ca for growth in the preflowering period; K, Mg and S in the flowering period; N in the 1st half of fruit development period and K, Mg and B in the 2nd half of fruit development period compared to other growth periods. In the fruit, N, K, Ca and B contents in the peel of normal fruit were higher than those of TFD fruit, whereas K, Ca, S and B contents in the flesh of normal fruit were higher than those of TFD fruit

The effects of paclobutrazol application on physiological responses, flowering and fruit qualities of longkong (Aglaia dookkoo Griff.)

Ways of alleviating the incidence of alternate bearing in longkong by flowering induction using a chemical method (paclobutrazol ) were investigated at an experimental plot of the Department of Plant Science, Faculty of Natural Resources, Prince of Songkla University, Hat Yai campus, Songkhla Province between December, 2001 and November, 2002. Twelve 10-year-old longkong trees grown in the experimental plot were used. The experiment was arranged as a completely randomized design in 4 treatments with 3 replications. The treatments were 1) control, 2) 1 g pt-1 of paclobutrazol application 3) 2 g pt 1 of paclobutrazol application and 4) 4 g pt-1 of paclobutrazol application. It was found that all paclobutrazol applications decreased plant water use, physiological responses (leaf water potential, stomatal conductance and chlorophyll fluorescences) and leaf nitrogen content, compared with the control. Paclobutrazol application increased flowering, fruit setting and fruit qualities. Paclobutrazol application of 4 g pt-1 gave a higher number of floral buds/plant than the other treatments. Paclobutrazol application of 1 g pt-1 gave higher fruit/cluster and fruit weight/cluster than the other treatments. Paclobutrazol application significantly increased total soluble solids, but there was no effect on titratable acidity. It was also noted that the paclobutrazol application increased peel thickness

Studies on the mechanism of transmission of pollen‐associated tobacco streak ilarvirus virus by Thrips tabaci

Mixed instars of Thrips tabaci were allowed to feed on test seedlings of cucumber, the thrips were removed and wounds caused by thrips feeding dusted with tobacco streak virus (TSV) carried in tomato pollen. Transmission of TSV occurred in three out of the four experiments conducted. When Chenopodium amaranticolor test seedlings were dusted with infective tomato pollen, and thrips introduced for varying periods before being killed with insecticide, TSV transmission occurred after exposure to thrips for 1 h, 5 h, 1 day or 2 days, but not 5 min. Pollen‐washing experiments indicated that TSV was carried both internally and externally in pollen of tomato and several weed hosts. T. tabaci was able to transmit TSV from pollen of Nicotiana clevelandii and Nicandra physalodes, and TSV from tomato pollen was transmitted to several weed species. It is concluded that T. tabaci transmits TSV associated with tomato pollen by a mechanical mechanism whereby virus carried externally, or released from inside the pollen, infects feeding wounds