Indução de poliplóides em pimenteiras (Capsicum spp.)

Abstract

Peppers (Capsicum spp.) have great food, economic, cultural and ornamental importance worldwide. The present work investigated the potential phytotoxic effects of plant polyploidy inducing agents (trifluralin and oryzalin) on the emergence of four pepper genotypes (Capsicum spp.) and analyzed the induction of Capsicum annuum polyploids and the morphoanatomical differences produced in relation to the diploid controls subjected to different concentrations and exposure times. In the two chapters, two experiments were carried out with the adoption of a triple factorial scheme in a completely randomized design. The first factor studied were the genotypes, the second the concentrations of antimitotics (%) and the third the exposure times (hours). The only difference between the two experiments was the polyploidy-inducing agent used, oryzalin in the first and trifluralin in the second. In Chapter I, seedlings were obtained from treatments with the two antimitotic agents. Trifluralin and oryzalin showed a phytotoxic effect and caused a marked reduction in plant emergence for all genotypes compared to the control, however, trifluralin is more phytotoxic. Cultivar Floribela is more tolerant to the toxic effect of oryzalin when compared to the other genotypes, however, it was more sensitive to trifluralin in this comparison. The emergence speed was reduced as the agent concentration increased. Higher doses (0.4%) produce few seedlings, but these emerge in fewer days as a dispersion mechanism of oryzalin and trifluralin toxicity. In chapter II, there were significant interactions between the factors under study for seedling survival at the 1% probability level in both experiments. Two tetraploids and one triploid of C. annuum were formed with the use of oryzalin as inducing agent, however, there was no polyploidization from trifluralin in the experimental conditions tested. The polyploids presented a stomatal area (µm2), length and width of the stomata (µm) greater than the corresponding diploids, consequently, they presented a lower stomatal density. The increase in leaf thickness (µm) and the number of chromosomes per guard cell is a good indicator of polyploidization in C. annuum. Oryzalin is an effective polyploidy inducer from C. annuum seeds immersed in 0.1% solutions for 48 and 72 hours (h) for UFPB-001 and UFPB-004, respectively, and 0.2% for 48h in the Floribela cultivar.