Metalaxyl is an effective approach to control Phytophthora palmivora infection in durian plantation. However, inappropriate metalaxyl usage may increase production cost, pathogen with fungicide resistance, and environmental toxicity. This study established and validated a simple and reproducible procedure to measure metalaxyl concentration in the durian leaf using HPLC. Linearity of the detection ranged from 1–100 µg/mL. The limits of detection (LOD) and quantification (LOQ) were 0.27 and 0.91 µg/mL, respectively. The extraction method gave recovery rates ranging from 88% to 103%. Durian seedlings were treated with 4 g/L metalaxyl either by foliar spray or soil drench. The highest metalaxyl accumulation in durian leaf was found between 6–24 h after treatment and persisted above its effective concentration at least 60 days after foliar application. The dissipation pattern fit to a first-order kinetics equation showed a half-life of 16.50 days. Soil drenching led to eight times higher metalaxyl concentrations in plants than foliar spraying and caused plant death within 15 days after application. These results suggest that foliar spraying of 4 g/L metalaxyl or soil drenching at a lower concentration every two months is sufficient in controlling P. palmivora infection in durian seedlings.
The study aimed to observe the flowering of macadamia grown under different locations in northern Thailand. It is hoped that the success of macadamia growing would be an opium substitute crop as well as a reforestation tree in northern Thailand. Although introduced cultivars have adapted well and are grown widely from sea level to the top of mountains, the yield is still low compared to those reported in other countries. The role of microclimate as a factor influencing annual growth cycle should be clearly understood to further develop appropriate cultural practices. Fifteen uniform mature macadamia trees were selected from three sites with two types of microclimate characteristics; mountain ridge and valley at commercial plantations of Doi Tung Development Project in Chiang Rai, northern Thailand. Floral biology, fruiting and vegetative flushing characters were observed from limb at 1.5-2 m above ground level. Air temperature and light intensity, as microclimate parameters were recorded during 2007-2008. Mostly racemes and fruits set on two-year-old shoots. The fruiting shoots of trees located at mountain ridge had significantly shorter length than at the valley site. Seasonal new vegetative shoots at three sites flushed on the same period. Racemes of trees at mountain ridge bloomed earlier in late November; however, it was one month later for trees at valley site. Interestingly, the flower phenology at the valley site showed better performances with a shorter bloom period and higher floret numbers resulting in higher fruiting rate. Daily light intensity, minimum and average temperature of two microclimate types or three altitudes showed similar pattern. Nevertheless, maximum temperature during flowering at the valley site was lower. Thus, the amount of daily temperature interval occurring at lower level might cause the differences in flowering and yield performances. In addition, the flowering and fruit setting of rain-fed and irrigated sites were observed on ten mature trees at the ridge. It was found that trees in rain-fed site had two periods of flowering; the first in-season bloom was in January after annual nut harvesting started and the second bloom, a so-called off-season, was found later in October. The off-season bloom of macadamia trees grown in northern Thailand reflected their adaptability to Thai environment. Thus, it might be a good potential that is of benefit to further develop off-season macadamia nut production.
Vegetative ground covers are commonly used in urban, tropical roadside gardens. Such landscaping ground covers usually encounter extreme water-deficits and high temperatures from vehicles and urban infrastructures. However, information about the plant species that are appropriate for low maintenance gardens is not available, especially in tropical areas. This study aimed to investigate potential indicators for evaluating plant tolerance to water-deficit situations. A non-irrigated rooftop model was used to test 25 commercial ground cover species in a greenhouse at Mahidol University, Nakhon Pathom Province, Thailand. Each of these 25 species was potted and subjected to one of two conditions: with or without irrigation for 7 days. Physiological responses relevant to plant endurance during water-deficits were monitored, including changes in leaf relative water content (RWC), percent stomatal opening, leaf surface temperature, leaf total chlorophyll content, leaf greenness, maximum quantum yield, and light quantum yield. Moreover, an additional indicator of landscape utility was evaluated, where each species was judged by trained panelists for their esthetic appeal. Diverse responses were observed based on the type of physiological parameter measured, plant species, and duration of drought conditions. Water withdrawal for three days was deemed an appropriate time to determine plant tolerance to water-deficit conditions, as signs of stress were clearly observed in three parameters, i.e., changes in leaf RWC, percent stomatal opening, and esthetic score. Lastly, cluster analysis revealed that seven plant species were appropriate for tropical, urban ground covers, as they had high endurance under water-deficit conditions, namely, Allium schoenoprasum,Liriope muscari, Aloe sp., Sedum x rubrotinctum, Alternanthera ficoidea, Pilea libanensis and Plectranthus scutellarioides.
การปลกขาวในพนทประสบปญ หาขาดธาตฟอสฟอรสซงพบไดบอยในประเทศไทยสงผลใหขาวมผลผลตตกตำ Phosphorus-starvation tolerance 1 (PSTOL1) เปนยนทสงผลตอความสามารถในการทนตอสภาวะขาดธาต ฟอสฟอรส ในขาวพนธดงเดมบางพนธ ขาวพนธทไดรบการพฒนาใหมและพนธการคาจานวนมากถกพบวาขาดยน PSTOL1 และการนากลบของยนนชวยเพมประสทธภาพในการใชธาตฟอสฟอรสในขาวพนธเหลานได ดงนน งานวจยน จงมจดมงหมายเพอตรวจสอบการมอยของยน PSTOL1 ในพนธขาวดงเดมของไทย จโนมกดเอนเอจากตนกลาขาวถก สกดดวยวธ CTAB (Cetyl Trimethyl Ammonium Bromide) และถกนาไปวเคราะหดวยวธ PCR (Polymerase Chain Reaction) โดยใชไพรเมอรทจาเพาะตอแอลลล ตามดวยการแยกชนดเอนเอดวยวธอเลคโทรโฟรซส ในอะกาโรสเจล (agarose gel electrophoresis) ผลของการศกษาแสดงใหเหนวา พนธขาวไทยบางพนธมยน PSTOL1 ปรากฏอย ขอมลพนฐานนอาจนำไปใชเพอชวยเลอกพนธทเหมาะสมตอการปลกในพนทประสบปญหาขาดธาตฟอสฟอรสและการ ปรบปรงพนธขาวเพอการคาดวยวธผสมขามในอนาคต
The aim of this investigation was to identity effective criteria for classification of salt tolerance and salt sensitivity in rice cultivars by using multivariate characters. Osmolarity in salt-stressed leaves decreased, and was positively related to low water potential (Ψw) (r 2=0.99 and r2=1), leading to chlorophyll a degradation (r2=0.65 and r2=0.77) in both salt-tolerant (HJ and Pok), and salt-sensitive cultivars (PT1 and IR29). Chla, Chlb, TC and Cx+c in salt-stressed seedlings decreased by 0, 8.88, 1.37 and 0% in the salt-tolerant lines, respectively, whereas the same pigments in the salt-sensitive lines were reduced by 41.06, 20.74, 35.96 and 41.40%, respectively. Multivariate parameters of pigment degradation and chlorophyll a fluorescence diminution were used to classify salt-tolerant (HJ and Pok) and salt-susceptible (PT1 and IR29) rice cultivars. In addition, salt-tolerant HJ, 21 and Pok (positive control), moderately salt-tolerant 26, 409 and 306, and salt-susceptible PT1, 31, 20, IR29 (negative control), 598, 18 and 2 were classified using the multivariate parameter indices. 1National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park, Paholyothin Rd, Klong 1, Klong Luang, Pathu mthani 12120, Thailand
