Analysis of variance of primary data on plant growth analysis

Plant growth analysis presents difficulties related to statistical comparison of growth rates, and the analysis of variance of primary data could guide the interpretation of results. The objective of this work was to evaluate the analysis of variance of data from distinct harvests of an experiment, focusing especially on the homogeneity of variances and the choice of an adequate ANOVA model. Data from five experiments covering different crops and growth conditions were used. From the total number of variables, 19% were originally homoscedastic, 60% became homoscedastic after logarithmic transformation, and 21% remained heteroscedastic after transformation. Data transformation did not affect the F test in one experiment, whereas in the other experiments transformation modified the F test usually reducing the number of significant effects. Even when transformation has not altered the F test, mean comparisons led to divergent interpretations. The mixed ANOVA model, considering harvest as a random effect, reduced the number of significant effects of every factor which had the F test modified by this model. Examples illustrated that analysis of variance of primary variables provides a tool for identifying significant differences in growth rates. The analysis of variance imposes restrictions to experimental design thereby eliminating some advantages of the functional growth analysis.

Resistance of genetically modified potatoes to Potato virus Y under field conditions

The objective of this work was to evaluate the resistance of genetically modified clones of potato to Potato virus Y (PVY) under field conditions. Genetically modified plants were compared with nontransformed plants of the same cultivar. The plots were flanked with potato plants infected with both PVYº and PVY N strains (spread lines), in order to provide the experimental area with the source of virus, which was naturally spread by the native aphid population. The experiment was weekly monitored by visual inspections and by DAS-Elisa in the plants produced from the harvested tubers, in order to evaluate the resistance of transgenic plants throughout the plant growth cycle. By the end of the third year, no infection symptoms were observed in the 1P clone; clone 63P showed 1% of infection, in contrast to about 90% of nontransformed plants infected. The stable expression of resistance to PVY provided by the coat protein gene was obtained in genetically modified clones of potato plants cultivar Achat under field conditions, during three consecutive years.

Transgene inheritances and genetic similarities of near isogenic lines of genetically modified common beans

The objective of the present work was to determine the inheritance and stability of transgenes of a transgenic bean line expressing the genes rep-trap-ren from Bean golden mosaic virus and the bar gene. Crosses were done between the transgenic line and four commercial bean cultivars, followed by four backcrosses to the commercial cultivars. Progenies from each cross were evaluated for the presence of the transgenes by brushing the leaves with glufosinate ammonium and by polymerase chain reaction using specific oligonucleotides. Advanced generations were rub-inoculated with an isolate of Bean common mosaic necrosis virus (BCMNV). The transgenes were inherited consistently in a Mendelian pattern in the four crosses studied. The analyzed lines recovered close to 80% of the characteristics of the recurrent parent, as determined by the random amplified DNA markers used, besides maintaining important traits such as resistance to BCMNV. The presence of the transgene did not cause any detectable undesirable effect in the evaluated progenies.

Feeding strategies and energy to protein ratio on tambaqui performance and physiology

The objective of this work was to evaluate the effect of feed deprivation and refeeding with diets containing different energy to protein ratios (E/P) on the performance and physiology of juvenile tambaqui (Colossoma macropomum). A 4x2 factorial arrangement with three replicates was used, with four E/P ratios (11.5, 10.5, 9.5, and 8.5 kcal g-1 digestible energy per protein) and two feeding regimens (with and without deprivation), during 60 days. Fish from the food-deprived group were fasted for 14 days and refed from the fifteenth to the sixtieth day, whereas the remaining fish were fed for 60 days. At the end of the experimental period, weight of fish subjected to food deprivation was lower than that of those continuously fed; however, this condition did not influence the physiological parameters analyzed. Tambaqui fed 11.5 kcal g-1 achieved lower final weight than those fed with the other diets, in both regimens. Among the physiological parameters, only plasma protein presented significant increase in fish fed 8.5 kcal g-1, in both feeding regimens, probably due to the higher dietary protein concentration. These results indicate that fish show a partial compensatory growth, and that 10.5 kcal g-1 can be recommended for the diet of juvenile tambaqui.