The performance of multiple imputations for different number of imputations

Multiple imputation method is a widely used method in missing data analysis. The method consists of a three-stage process including imputation, analyzing and pooling. The number of imputations to be selected in the imputation step in the first stage is important. Hence, this study aimed to examine the performance of multiple imputation method at different numbers of imputations. Monotone missing data pattern was created in the study by deleting approximately 24% of the observations from the continuous result variable with complete data. At the first stage of the multiple imputation method, monotone regression imputation at different numbers of imputations (m=3, 5, 10 and 50) was performed. In the second stage, parameter estimations and their standard errors were obtained by applying general linear model to each of the complete data sets obtained. In the final stage, the obtained results were pooled and the effect of the numbers of imputations on parameter estimations and their standard errors were evaluated on the basis of these results. In conclusion, efficiency of parameter estimations at the number of imputation m=50 was determined as about 99%. Hence, at the determined missing observation rate, increase was determined in efficiency and performance of the multiple imputation method as the number of imputations increased

Effect of Candidatus Phytoplasma pyri infection on fruit quality, total phenolic content and antioxidant capacity of ‘Deveci’ pear,

Pear decline is an important threat for Turkish pear production. In this study, we attempt to compare several pomological characteristics, total phenolic content and total antioxidant capacities in Candidatus Phytoplasma pyri infected and noninfected ‘Deveci’ pear from Bursa, Turkey. Based on pear decline symptoms, the fruit samples were taken in October 2008 on harvest maturity from four infected and non-infected trees. Presence of Candidatus P. pyri was later confirmed by nested PCR tests. The result indicated that infection significantly reduced fruit size, width, length; and increased pH, color values of a, b and hue. Abortive and healthy seed numbers and weights, soluble solids and acidity did not change significantly. Similarly, the infection did not affect the flesh color. To investigate a possible differential response on skin and flesh of fruits, total phenolic (TP) and total antioxidant capacity (TAC) analyses were conducted on skin and flesh tissues separately. The results indicated that, infected skin tissue had higher total phenolic and total antioxidant capacity for both methods analyzed (TEAC and FRAP). TP content of skin increased from 806 to 923 μg gallic acid equivalents (GAE)/g fresh weight (fw) while TP content of flesh increased from 195 to 249 μg GAE/g fw. TAC also found to be enhanced on infected fruits. On average, non-infected trees had 32.4 and 28.3 μmol TE/g fw for TEAC and FRAP, respectively. Infection increased these averages to 35.4 and 32.3 μmol TE/g fw tabulating 18 and 12% increase in flesh tissue. Similarly, the TEAC and FRAP averages increased from 4.0 to 5.8 and 3.3 to 4.9 μmol TE/g fw, respectively.Keywords: Abiotic stress, FRAP, pear decline, phytoplasma, TEA

Occurrence of Pospiviroid in potato, tomato and some ornamental plants in Turkey

In order to investigate the Pospiviroid in potato, tomato and some ornamental plants in Turkey, a survey study was carried out from 2006 to 2009. During this survey study, a total of 1766 samples (1047potato samples, 258 tomato leaves and 461 ornamental plants) were tested by reverse transcriptionpolymerase chain reaction (RT-PCR) and, the samples found to be positive in RT-PCR were also checked in return polyacrylamide gel electrophoresis (R-PAGE). Of these samples, potato tubers were collected from markets, leaf samples from potato fields (Erzurum), tomato samples from field (Tokat, Amasya, Balýkesir and Bursa) and greenhouses (Antalya and Mula), leaves and vines of ornamental plants from greenhouses (Yalova) and florists (Erzurum) and recreation areas (Ankara, zmir and Trabzon). In the result of RT-PCR test, PSTVd was detected in 6 out of 891 potato tubers and CSVd in 2out of 154 chrysanthemums. On the other side, tomato, citrus and most ornamental plants belonging to different families were found to be free from pospiviroid. This is the first report of CSVd in Turkey

Experimental transmission trials by Cacopsylla pyri, collected from Pear Decline infected orchards in Turkey

A study was carried out on the experimental transmission efficiency of the Pear Decline (PD) phytoplasma by Cacopsylla pyri (L.) C. pyri were collected from naturally infected orchards in Bursa province (Plots B1 and B2) and a non-infected orchard in the Hatay-Antakya province (Plot A) of Turkey. C. pyri adults captured from infected orchards were placed directly onto healthy periwinkle plants (Catharanthus roseus), whereas the C. pyri from plot A were allowed to feed first on infected pear for two weeks, then transferred to healthy periwinkle plants. Groups of five psyllids per plant were used for transmissison tests and the study was replicated three times. The presence of ‘Candidatus Phytoplasma pyri’ in psyllids and C. roseus plants was checked by nested PCR using P1/P7 and U3/U5 primer pairs. Although C. pyri have a limited host range they were able to survive up to 20 days on periwinkle plants. Insects collected from Bursa province survived 16-20 days whereas insects from Antakya survived 7-12 days on periwinkle plants. Symptoms consisted of yellowing or clearing of the veins in newly infected leaves, and shortening of the internodes of the main stem. The infected plants remained stunted and with small flowers. Results based on the RFLP analysis of infected plants exposed to psyllids from plot B1and B2 indicated that the experimental infection rate of periwinkle plants and psyllids was 33.3% and 16.6%, respectively. No infected periwinkle was found in plants exposed to psyllids from plot A, but the psyllids used for experimental transmission experiments were 33.3 % infected. Transmission trials under controlled conditions showed the capability of C. pyri to transmit PD from infected pears to healthy periwinkles and confirmed their potential as vectors of Ca. P. pyri in Turkey. Keywords: Candidatus Phytoplasma pyri, pear psyllid, transmission efficienc

Experimental transmission trials by Cacopsylla pyri, collected from pear decline infected orchards in Turkey

A study was carried out on the experimental transmission efficiency of the Pear Decline (PD) phytoplasma by Cacopsylla pyri (L.), collected from naturally infected orchards from Bursa and non-infected orchard from Hatay province of Turkey. C. pyri adults captured from infected orchards were directly transmitted to healthy periwinkle plants (Catharanthus roseus) whereas the second group firstly fed on infected pear for two weeks and then transferred to periwinkles. Groups of five psyllids per plant were used for transmissison tests and the study was replicated three times. The presence of ‘Candidatus Phytoplasma pyri’ in psyllids and C. roseus plants was analysed by nested PCR using P1/P7 and U3/U5 primer pairs.. Although C. pyri has limited host range, they were able to survive up to 20 days on periwinkles. Insects collected from Bursa province survived 16-20 days whereas second group from Hatay were survived 7-12 days on periwinkles. Symptoms consist of a yellowing or clearing of the veins in newly infected leaves and shortening of the internodes of the main stem. They also remain stunted and flowers were small. According to the RFLP analysis of Bursa samples, the experimental infection rate of periwinkle plants and psyllids was 33.3 % and 16.6 %, respectively. No infected periwinkle was found in second group but psyllids were 33.3 % infected. Transmission trials under controlled conditions showed the capability of C. pyri to transmit PD from infected pears to healthy periwinkles and confirmed as vector of Ca. P. pyri in Turkey.Keywords: Candidatus Phytoplasma pyri, pear psyllid, transmission efficienc

Danos de broca do tronco (Cratosomus sp) em tipos de gravioleiras (Annona muricata L.).

O objetivo deste trabalho e relatar algumas observações sobre a broca do tronco da gravioleira em área de cerrado do Amapá

Conservação de recursos fitogenéticos em quintais agroflorestais em Mazagão, Amapá.

O objetivo do trabalho foi estudar quintais agroflorestais quanto à conservação de recursos genéticos vegetais em Mazagão. Foi realizado o levantamento da composição botânica de quatro quintais, sendo três em área de terra firme e um em várzea. O número de famílias variou de 13 a 31, com intervalo de 26 a 63 espécies. As espécies frutíferas foram as mais frequentes em todos os quintais estudados e quando somadas às madeiráveis e medicinais totalizavam cerca de 90% de toda a composição botânica encontrada