Performance and genetic assessment of rubber tree clones in Southern Thailand

Thailand is the world leader in the production of latex extracted from the rubber tree (Hevea brasiliensis). However, the most cultivated clone RRIM 600, is highly susceptible to diseases, and there is economic incentive to develop new rubber tree clones. Four rubber tree clones (T2, SK1, NK1 and SK3) that have high latex yield potential from plantations in Southern Thailand were selected for this study. Yield performance, latex biochemical parameters and anatomical characteristics of bark were monitored for two years, using RRIM 600 clones in the same fields as paired controls. The average yields of the clones SK1, NK1 and SK3 were 129.3, 74.2 and 53.9 g per tree per tapping, respectively, surpassing the paired RRIM 600 controls (94.3, 49.9 and 43.9 g per tree per tapping in matching order). There was a difference in girth increment of SK1, SK3 and T2 clones when compared with RRIM 600, whereas the clones SK1 and T2 had higher renewed bark thickness than the paired RRIM 600. The anatomical measurements showed that the diameter of the latex vessels and density of latex vessels mm−2 were the highest in clone NK1, which also had the best latex biochemical parameters. This indicates NK1 is superior, and supports its use in Hevea breeding programs to improve latex yield. Our genetic characterization and assessment of the four clones selected used Random Amplified Polymorphic DNA (RAPD) and Simple Sequence Repeats (SSR). Seventeen recommended rubber clones were included as references. The clones SK3 and SK1 were closely related to RRIM 600 with similarity coefficients of 0.891 and 0.809, while NK1 and T2 were closely related to RRIT 250 (0.836) and RRIC 110 (0.864), respectively

Genetic variation and phylogenetic relationships in oil palm (Elaeis guineensis Jacq.) based on RAPD analysis

The genetic variability and phylogenetic relationships in oil palm (Elaeis guineensis Jacq.) were studied using RAPD (Random Amplified Polymorphic DNA). Leaf samples of 151 plants were collected from different areas in southern Thailand. DNA from the leaf samples was isolated using CTAB buffer and screened by decamer oligonucleotide primers. Among the total of 160 primers screened, 7 primers (OPB-08, OPR-11, OPT-06, OPT-19, OPAB-01, OPAB-09 and OPAB-14) were chosen to analyse for genetic variation in 151 individuals representing 52 dura, 60 tenera and 39 pisifera. Two hundred and nine amplified fragments were obtained from 7 primers with an average of 29.85 RAPD markers per primer. A dendrogram showing genetic similarities among oil palm was constructed based on polymorphic bands using UPGMA (Unweighted Pair-Group Method Using Arithmetic Average). Cluster analysis was performed using the SPSS program, which revealed four major clusters: 1) dura, tenera and pisifera from Paorong Oil Palm Company, Oil Palm Research Center, dura and tenera from private plantation in Krabi, and dura from Thepa Research Station;2) dura and tenera from Thai Boonthong Company, pisifera and tenera from Thepa Research Station, dura, tenera and pisifera from Klong Hoi Khong Research Station; 3) and 4) dura and tenera from Univanit Company, respectively. In general, a similarity index showed relatively high levels of 0.6 or greater

Screening of antagonistic bacteria against the green mold disease (Trichoderma harzianum Rifai) of Grey Oyster Mushroom (Pleurotus pulmonarius (Fr.) Quel.)

A total of 174 strains of bacteria antagonistic against the green mold (Trichoderma harzianum), isolated from cultivating bags and fruiting bodies of the mushrooms, were screened for effects on mushroom mycelia and ability to control the green mold disease. Twenty-eight of them promoted the primodia formation of the Pleurotus pulmonarius mycelia on agar plates. Twenty-two isolates were selected and further tested in a mushroom house. Cell suspension of each isolate was prepared and sprayed onto the spawn surface of P. pulmonarius. Fifteen isolates shortened the times required from watering to 2nd and 3rd flushing and increased yield of the basidiocarps by 1.1-34.3% over 30 days. Six isolates of bacteria which showed an inhibitory effect against T. harzianum, enhanced primordia formation and increased yield of P. pulmonarius were selected and used for control testing in a cultivation house. The suspension of each isolate was sprayed onto the spawn surface immediately after exposure to the air in the mushroom house, followed by spore suspension of T. harzianum two days later. The number of infected bags was counted at 30 days after inoculation and the cumulative yield was compared after 60 days. The results showed that bacteria isolate B012-022 was highly effective in suppressing the green mold disease.Only 6.7% of the cultivating bags were found to be infected by T. harzianum when bacteria isolate B012-022 was applied. Cumulative yield obtained from 900 g of 94% sawdust + 5% rice bran + 1% Ca(OH)2 was 300.0 g/bag after 60 days, 71.1% higher than the bags infected by the green mold and without bacterial spraying. Identification of the six bacterial isolates showed all to be Bacillus spp

Characterization of the phenylalanine ammonia lyase gene from the rubber tree (Hevea brasiliensis Müll. Arg.) and differential response during Rigidoporus microporus infection

Phenylalanine ammonia lyase (PAL) is a specific branch point enzyme of primary and secondary metabolism. It plays a key role in plant development and defense mechanisms. Phenylalanine ammonia lyase from Hevea brasiliensis (HbPAL) presented a complete open reading frame (ORF) of 2,145 bp with 721 encoded amino acids. The sequence alignment indicated that the amino acid sequence of HbPAL shared a high identity with PAL genes found in other plants. Phylogenetic tree analysis indicated that HbPAL was more closely related to PALs in Manihot esculenta and Jatropha curcas than to those from other plants. Transcription pattern analysis indicated that HbPAL was constitutively expressed in all tissues examined, most highly in young leaves. The HbPAL gene was evaluated by quantitative real-time PCR (qRT-PCR) after infection with Rigidoporus microporus at 0, 12, 24, 48, 72 and 96 hours post inoculation. The expression patterns of the PAL gene differed among the three rubber clones used in the study. The transcription level of the white root rot disease tolerant clone, PB5/51 increased sharply during the latter stages of infection, while it was relatively subdued in the white root rot disease susceptible clones, RRIM600 and BPM24. These results suggest that the HbPAL gene may play a role in the molecular defense response of H. brasiliensis to pathogen attack and could be used as a selection criterion for disease tolerance

Standard sampling method of Longkong leaf for evaluation of plant nutrient status

Leaf analysis is a tool for effective fertilizer recommendations in fruit trees. To achieve this goal, suitable leaf sampling method is a very important step. This study aimed to investigate leaf age, leaflet from different compound leaf positions and number of trees to be sampled as a representative sample for plant nutrient status of Longkong (Aglaia dookkoo Griff.) tree. The middle pair of leaflets from the 1st, 2nd, 3rd, and 4th compound leaves from growing twigs at the lower canopy of Longkong trees were separately sampled and the following nutrients were determined: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg). The effect of soil fertility management and leaf age collected from twigs flushed at flowering and post harvest stages on nutrient concentration was investigated. Results showed that concentrations of plant nutrients in leaflets collected from different compound leaf positions were not significantly different. The leaf nutrient concentration depended on soil fertility management, higher fertilizer input resulting in higher leaf nutrient concentration. As leaf age increased, concentrations of N, P and K tended to decrease. In contrast, concentrations of Ca and Mg increased with leaf age. However, concentrations of most nutrients showed minimum variation with leaf aged 3-6 months. It is, thus, suggested that the middle pair leaflet of the 2nd compound leaf position aged 3-6 months of the lower twig should be sampled at post harvest stage from 25-35 trees to be used as a composite sample for plant nutrient analysis