Novel Chloroplast Microsatellite (cpSSR) Markers for Genetic Diversity Assessment of Cultivated and Wild Hevea Rubber

Understanding the genetic diversity and population structure of Hevea is of great importance for managing its conservation and for utilization of rubber genetic resources. In this study, we investigated the genetic diversity and population structure of eight populations of Hevea rubber genotypes from Malaysia (MY), India (IN), Sri Lanka (LK), Indonesia (ID), France (FR), Thailand (TH), Brazil (BR), and China (CN), in addition to individual primary clones, using 10 nuclear and 11 polymorphic novel chloroplast microsatellite markers (nSSRs and cpSSRs, respectively). The BR population exhibited the greatest genetic diversity (H _e ) for both nSSR (0.841) and haploid genetic diversity (cpSSR; 0.207) markers. Bayesian analysis was applied to infer genetic structure based on nSSR data using STRUCTURE software, and a neighbor-joining tree was used to construct an unrooted phylogram based on Nei’s genetic distance that clustered these Hevea genotypes into three groups. Six polymorphic cpSSR markers produced 13 alleles and eight chlorotypes. Seven chlorotypes, A, B, C, D, E, F, and H were detected among Brazilian populations from Acre (AC), Rondônia (RO), and Mato Grosso (MT) locations. The G and H chlorotypes were found in Asiatic genotypes or Wickham clones and only one genotype, 15 AC-F-7 38-62 from AC location. These results provide valuable data for in situ or ex situ conservation and utilization of germplasm collections for breeding programs.

     

Molecular and phenotypic characterization of potential plant growth-promoting <Emphasis Type="Italic">Pseudomonas</Emphasis> from rice and maize rhizospheres

In this study, Pseudomonas species were isolated from the rhizospheres of two plant hosts: rice (Oryza sativa cultivar Pathum Thani 1) and maize (Zea mays cultivar DK888). The genotypic diversity of isolates was determined on basis of amplified rDNA restriction analysis (ARDRA). This analysis showed that both plant varieties selected for two distinct populations of Pseudomonas. The actual biocontrol and plant promotion abilities of these strains was confirmed by bioassays on fungal (Verticillum sp., Rhizoctonia solani and Fusarium sp.) and bacterial (Ralstonia solanacearum and Bacillus subtilis) plant pathogens, as well as indole-3-acetic acid (IAA) production and carbon source utilization. There was a significant difference between isolates from rice and maize rhizosphere in terms of biological control against R.  solanacearum and B.  subtilis. Interestingly, none of the pseudomonads isolated from maize rhizosphere showed antagonistic activity against R.  solanacearum. This study indicated that the percentage of pseudomonad isolates obtained from rice rhizosphere which showed the ability to produce fluorescent pigments was almost threefold higher than pseudomonad isolates obtained from maize rhizosphere. Furthermore, the biocontrol assay results indicated that pseudomonad isolated from rice showed a higher ability to control bacterial and fungal root pathogens than pseudomonad isolates obtained from maize. This work clearly identified a number of isolates with potential for use as plant growth-promoting and biocontrol agents on rice and maize.     

Isolation of 55 microsatellite markers for Jatropha curcas and its closely related species

Jatropha curcas L. (physic nut) is native to Central America and now naturalized widely in many tropical and subtropical areas. Microsatellite markers were isolated and characterized. Eleven out of 55 markers showed polymorphisms, and the allelic variation was investigated using 26 accessions of J. curcas collected from several provinces in Thailand. Each marker showed 2 to 5 alleles and the average polymorphic information content (PIC) was 0.49. Thirty four markers (62 %) were also successfully amplified in J. integerrima, J. gossypifolia and J. podagrica.     

Effect of Salicylic Acid Formulations on Induced Plant Defense against Cassava Anthracnose Disease

This study was to investigate defense mechanisms on cassava induced by salicylic acid formulation (SA) against anthracnose disease. Our results indicated that the SA could reduce anthracnose severity in cassava plants up to 33.3% under the greenhouse condition. The β-1,3-glucanase and chitinase enzyme activities were significantly increased at 24 hours after inoculation (HAI) and decrease at 48 HAI after Colletotrichum gloeosporioides challenge inoculation, respectively, for cassava treated with SA formulation. Synchrotron radiation–based Fourier-transform infrared microspectroscopy spectra revealed changes of the C=H stretching vibration (3,000–2,800 cm⁻¹), pectin (1,740–1,700 cm⁻¹), amide I protein (1,700–1,600 cm⁻¹), amide II protein (1,600–1,500 cm⁻¹), lignin (1,515 cm⁻¹) as well as mainly C–O–C of polysaccharides (1,300–1,100 cm⁻¹) in the leaf epidermal and mesophyll tissues treated with SA formulations, compared to those treated with fungicide carbendazim and distilled water after the challenged inoculation with C. gloeosporioides. The results indicate that biochemical changes in cassava leaf treated with SA played an important role in the enhancement of structural and chemical defense mechanisms leading to reduced anthracnose severity.     

Isolation and characterization of purple acid phosphatase gene during seedling development in mungbean

Purple acid phosphatases (PAPs), which are normally found in plant tissues, can hydrolyze a broad spectrum of phosphate esters. In this study, a mungbean [Vigna radiata (L.) Wilczek cv. KPS1] acid phosphatase gene (VrPAP1) was isolated from seedling cotyledons. The full-length of VrPAP1 cDNA contained an open reading frame of 1 644 bp encoding 547 amino acid residues with a predicted molecular mass of 62.07 kDa. Sequence analysis showed that VrPAP1 is purple acid phosphatase. RNA blot analyses indicated that the VrPAP1 accumulated during the first hour in cotyledons of germinating seeds and reached a maximum expression after 24 h and then decreased. The VrPAP1 mRNA was observed in cotyledons, hypocotyls and leaves but not in radicles or dry seeds. DNA blot analysis indicated that VrPAP1 is a single copy gene in the mungbean genome.     

Differentiation of phytoplasmas associated with sugarcane and gramineous weed white leaf disease and sugarcane grassy shoot disease by RFLP and sequencing

 Restriction fragment length polymorphism (RFLP) and sequencing were used to elucidate the genetic relationship between phytoplasmas that cause white lead disease and grassy shoot disease in sugarcane and white leaf disease in gramineous weeds found in the cane-growing areas (Crowfoot grass, Bermuda grass and Brachiaria grass). A 1.35-kb DNA fragment encoding for the 16s rRNA was amplified by PCR using universal primers and analysed by digestion with nine restriction endonucleases. A DNA fragment containing the 3′ end of the 16s rRNA and the spacer region between the 16s rRNA and the tRNA(Ile) was amplified by PCR and sequenced. Analysis of the RFLP patterns and of the sequence showed that grassy shoot and white leaf diseases in sugarcane are caused by two different phytoplasmas. Sequence analysis of phytoplasma DNA obtained from three species of weeds showing symptoms of white leaf disease failed to detect any organism that is identical to those infecting the sugarcane. Moreover the phytoplasma species that infect the three types of gramineous weeds, although closely related, are nevertheless different Received: 15 April 1997 / Accepted: 18 April 1997     

Salicylic acid-induced accumulation of biochemical components associated with resistance against Xanthomonas oryzae pv. oryzae in rice

Seed treatment and foliar sprays of salicylic acid (SA) provided protection in rice against bacterial leaf blight (BLB) caused by bacterial Xanthomonas oryzae pv. oryzae (Xoo). Treatment of rice with exogenous SA reduced disease severity by more than 38%. Superoxide anion production and hypersensitive response increased approximately 28% and 110% at 6 and 48?h after Xoo inoculation, respectively, for plants treated with SA. Moreover, the Xoo in treated rice plants grew more slowly, resulting in a population that was half of that observed in the control. Fourier transform infrared spectroscopy analysis revealed that the higher ratios of 1233/1517, 1467/1517, and 1735/1517?cm^?1 observed in treated rice suggested alteration of monomer composition of lignin and pectin in the rice cell wall. Exogenous SA-treated rice had more amide I β-sheet structure and lipids as shown by the peaks at 1629, 2851, and 1735?cm^?1. These biochemical changes of rice treated with SA and inoculated with Xoo were related to primed resistance of the rice plants to BLB disease.