Foliar application of systemic acquired resistance (SAR) inducers for controlling grape anthracnose caused by Sphaceloma ampelinum de Bary in Thailand

Chitosan and benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) are active-elicitors that induce protection in grapevine against several diseases. In this study, treatment of grapevine with chitosan and BTH provided protection to anthracnose, caused by Sphaceloma ampelinum. Chitosan and BTH treatment also increased chitinase, ß-1,3-glucanase and peroxidase activities levels in leaves over non-treated plants. Differential accumulation of these traits was more rapid and pronounced when chitosan and BTH treated plants were infected with S. ampelinum; this pattern indicating priming. The induced resistance by chitosan and BTH was also associated with increased production of salicylic acid (SA) in grapevine leaves, suggesting that SA-dependent signaling pathways are systemically triggered by these compounds. Apart from proteins with defense-related function, most of the proteins induced by chitosan and BTH were involved in defense mechanism, reflecting the strong direct positive effect that chitosan and BTH has on grapevine tolerance to anthracnose disease infection.Keywords: Anthracnose, grapevine, induce resistance, systemic acquired resistance (SAR) biochemical markers, Sphaceloma ampelinumAfrican Journal of Biotechnology Vol. 12(33), pp. 5148-515

Effects of Culture Media on Phytophthora palmivora Growth, α-elicitin Production and Toxicity to Dendrobium

Four culture media were evaluated for their ability to induce Phytophthora palmivora growth and produce culture filtrate (CF), and to determine a CF concentration and culture period effective for in vitro screening of black rot resistance in Dendrobium cv. ‘Earsakul’. Mycelial fresh weights of P. palmivora cultured in potato dextrose broth (PDB; the most commonly used medium for fungi), pea sucrose broth (PSB; a medium frequently used for Phytophthora spp.), and Murashige and Skoog broth (MSB; the most popular plant tissue culture medium) were found to be significantly higher than that in the newly developed modified oat meal broth (MOMB). When the total proteins of CFs were analysed with SDS-PAGE, a protein band of 10.5 kDa MW was found in CFs from all media with the highest level in PSB. LC-MS/MS analysis identified this protein as α-elicitin that had an identical amino acid sequence to the α-elicitin hibernalin of P. hibernalis and syringicin from P. syringae. The optimum conditions for in vitro selection of Dendrobium for black rot resistance using α-elicitin-containing CFs were also determined by evaluating the CF toxicity on Dendrobium protocorm-like bodies (PLBs) when cultured in all media supplemented with 0, 30, 50 and 100% CFs for seven, 14 and 21 d. The levels of PLB necrosis varied according to medium types, CF concentrations and culture periods. The maximum percentage of PLB necrosis (100%) was obtained in PSB supplemented with 50 and 100% CFs, and the severity of PLB necrosis was highest when treated with 100% CF for 14 and 21 d

Effects of peanut mottle virus infection upon nodulation of peanut (Arachis hypogaea L.).

The effects of peanut mottle virus (PMV) infection upon nodulation and nodule function of Early Prolific peanut, inoculated with either effective or ineffective cowpea Rhizobium grown under controlled conditions, were assessed at 4 different growth stages. Virus-infected plants showed differences in symptom expression, magnitude of yield reduction, and nodulation pattern, depending on whether they harbored the effective or ineffective rhizobial strain. In the virus-infected plants with effective Rhizobium, the commencing of nitrogenase (C(,2)H(,2)) activity was delayed and the activity measured per plant basis was reduced but the maximum nodular specific activity was not altered as compared with those of the healthy plants. There was no correlation between leghemoglobin content and nitrogenase (C(,2)H(,2)) specific activity of the nodules from PMV-infected plants but a positive correlation was observed in the healthy controls. The results from infectivity assays, electron microscopy and indirect immunofluorescence indicate the presence of infective PMV in the tissues of both effective and ineffective nodules. Histological and cytological abnormalities observed in the nodular tissues of PMV-infected plants are suggested as a cause of reduced nitrogen-fixation efficiency of the peanut

Evaluation of ten peanut genotypes for resistance to Peanut bud necrosis virus (PBNV)

Reactions of peanut genotypes to Peanut bud necrosis virus (PBNV) under sap-inoculation and natural field conditions may be different. Ten peanut genotypes (KK 60-3, KKU 72-1, KKU 72-2, Luhua 11, Tainan 9, JL 24, IC 10, IC 34, ICGV 86031 and ICGV 86388) were evaluated for their reactions to PBNV under field conditions in Thailand in 2001. The objectives of this study were (i) to determine breeding potential of the selected peanut genotypes in terms of PBNV disease resistance, and (ii) to explore the usefulness of disease incidence, disease score and area under disease progress curve (AUDPC) as the assessments of resistance for effectively discriminating susceptible and resistant genotypes of peanut. Significant differences were found between susceptible and resistant peanut genotypes as identified by disease incidence, disease score and AUDPC. Disease score and AUDPC tended to be equally effective and slightly better than disease incidence in identifying peanut genotypes resistant to PBNV. None of the resistance parameters could differentiate genotypes in the resistant group. IC 10, IC 34, ICGV 86031 and ICGV 86388 were identified as good sources of PBNV resistance. Among susceptible genotypes, KK 60-3 was more resistant than the others and could be used as a parent in peanut breeding programs

Combining ability analysis for traits related to N-fixation and agronomic traits in peanut 2 (Arachis hypogaea L.)

Symbiotic nitrogen fixation in peanut offers an alternative way to reduce chemical nitrogen fertiliz-ation. The objectives of this study were to estimate general combining ability (GCA) and specific combiningability (SCA) effects for traits related to N -fixation and agronomic traits and to identify the best parents2for use in peanut breeding programs aimed at improving nitrogen- ixing ability. Full diallel (F ) crosses of 2 peanut with reciprocals involving five parents were planted in a randomized complete block design with four replications. GCA mean squares were more important than SCA mean squares for plant dry weight, nodule dry weight, leaf color score, seed weight per plant, shelling percentage and harvest index. SCA mean squares were significant for pod weight per plant, seed weight per plant and 100 seed weight. SCA mean squares were more important than GCA mean squares for pod weight per plant, and equally important for seed weight per plant. Reciprocal mean squares were significantly important for 100 seed weight, shelling percentage and harvest index. KKU 72-1, (A3-1-1 (Bc 154) (PI 268770) and 42-G-105 (PI 269 109) were identified as good general combiners for traits related to N -fixation, plant dry weight, nodule dry weight and leaf color score, 2 whereas A3-1-1 (Bc 154) (PI 268 770) and KKU 72-1 were the best parents for 100 seed weight. A3-1-1 (Bc 154) (PI 268 770) was also the best general combiner for shelling percentage and harvest index

Heritability and phenotypic correlation of resistance to Peanut bud necrosis virus (PBNV) and agronomic traits in peanut

Peanut bud necrosis virus (PBNV) is a potential threat to peanut production in Thailand. Therefore, the improvement of peanut lines, which are resistant to PBNV and maintain acceptable agronomic traits, is important. The objective of this study was to estimate broad sense heritability and phenotypic correlation in 16 crosses of the F2 populations derived from cross of four resistant parents with four large-seeded peanut cultivars. A randomized complete block design with four replications was used. Peanut bud necrosis disease (PBND) incidence, PBND score and agronomic data were recorded. Estimates of heritability for PBND score on F2 individual plants were low at 60 days after sowing (DAS) and seemed to be improved at 70 DAS. Estimates of heritability for agronomic traits varied over crosses and traits and were generally low. However, high heritability estimates were observed for 100 seed weight in cross KKU 72-1 × IC 10 and for shelling percentage in crosses KKU 72-1 × IC 34 and Luhua 11 × ICGV 86388. High positive correlation coefficients were found among PBND score, PBND incidence and area under disease progress curve (AUDPC) but all PBNV resistance parameters had low correlation with all agronomic traits. High positive correlation coefficients were found among pod weight per plant, pod number per plant and seed weight per plant. Because of low heritability estimates for PBNV resistance and agronomic traits, selection among individual plants in the F2 generation will be ineffective. Selection should be carried out in advanced generations or on the progeny performance as family mean basis

Effects of Culture Media on Phytophthora palmivora Growth, α-elicitin Production and Toxicity to Dendrobium

Four culture media were evaluated for their ability to induce Phytophthora palmivora growth and produce culture filtrate (CF), and to determine a CF concentration and culture period effective for in vitro screening of black rot resistance in Dendrobium cv. ‘Earsakul’. Mycelial fresh weights of P. palmivora cultured in potato dextrose broth (PDB; the most commonly used medium for fungi), pea sucrose broth (PSB; a medium frequently used for Phytophthora spp.), and Murashige and Skoog broth (MSB; the most popular plant tissue culture medium) were found to be significantly higher than that in the newly developed modified oat meal broth (MOMB). When the total proteins of CFs were analysed with SDS-PAGE, a protein band of 10.5 kDa MW was found in CFs from all media with the highest level in PSB. LC-MS/MS analysis identified this protein as α-elicitin that had an identical amino acid sequence to the α-elicitin hibernalin of P. hibernalis and syringicin from P. syringae. The optimum conditions for in vitro selection of Dendrobium for black rot resistance using α-elicitin-containing CFs were also determined by evaluating the CF toxicity on Dendrobium protocorm-like bodies (PLBs) when cultured in all media supplemented with 0, 30, 50 and 100% CFs for seven, 14 and 21 d. The levels of PLB necrosis varied according to medium types, CF concentrations and culture periods. The maximum percentage of PLB necrosis (100%) was obtained in PSB supplemented with 50 and 100% CFs, and the severity of PLB necrosis was highest when treated with 100% CF for 14 and 21 d

Relationships between Nutrient Uptake and Nitrogen Fixation with Aflatoxin Contamination in Peanut under Terminal Drought

Terminal drought greatly enhanced Aspergillus flavus Link infection (AI) and aflatoxin contamination (AC) in peanut. Identification of new surrogate traits which have an association with AC may be effective to improve peanut varieties with reduced AI and AC. The objective of this work was to examine the relationships of nutrient uptake and N2-fixation (NF) with AC in peanut in a terminal drought condition. Five peanut varieties were tested in well-watered (WW) and terminal drought (TD) conditions (1/3 available water (AW) from R7 (7th reproductive growth stage; beginning of pod maturity stage)). Data were collected for nutrient uptake (nitrogen, phosphorus, potassium, calcium, magnesium), nodule dry weight (NDW), and NF. AI and AC were also examined. Nutrient uptake, NDW, and NF had negative and significant correlations with AI and AC in the TD condition. Negative and significant correlations of the drought tolerance index of nutrient uptake, NDW, and NF with AI and AC were also observed in the TD condition. The results showed that the ability to maintain nutrient uptake and NF in TD might be a mechanism of tolerance to AI and AC. Moreover, due to their negative impacts on AI and AC, nutrient uptake and NF could be used as selection traits for resistance to AI and AC in peanut in TD

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