Metodologias para seleção de genótipos de coentro visando melhoramento para resistência ao Meloidogyne incognita raça 1

Abstract

Due to the importance of identification and/or attainment of genotypes of coriander resistant to root-knot nematoid, this work aimed on proposing a methodology that could make viable such process and to evaluate the reactions of genotypes to the pathogen‟s attack. Four experiments were carried out in a greenhouse at the Federal Rural University of Pernambuco. In the first experiment, it was evaluated five cultivars of coriander – Verdão, Tabocas, Tapacurá, Palmeira e HTV Dom Luiz –, handled in three types of recipient – 400ml beaker, a tray of 128 cells and a 116ml tube – and three types of substrate – commercial substrate (CS), commercial substrate + coconut powder (CSP) and soil + sand + hummus (SSH) -, inoculated 15 days after seeding with 1,200 eggs per Meloidogyne incognita race 1 plant, conducted in a randomized block design (RBD) with three replications in a split-plot arrangement and experimental plot composed by 20 plants. 45 days after the inoculation, it was quantified the incidence of galls (IG), the number of galls in the root system (NGRS), the number of eggs (NE) and estimation of reproduction factor (RF) for each plant. The second work verified the behavior of five cultivars of coriander – Verdão, Tabocas, Tapacurá, Palmeira e HTV Dom Luiz – inoculated at the seeding with different concentrations of M. incognita race 1 eggs (0; 1,000, 2,000, 4,000, 8,000 and 16,000 eggs/plant), aiming to evaluate the percentage of emerging seedlings (PES), percentage of plants (PP) length of root (CSR), IG, NGRS, NE and RF 30 days after the inoculation, this experiment was conducted using a completely randomized design (CRD) with three replications and experimental plot composed by four plants. In the third experiment, we tried to verify the number of galls 30 days after the inoculation, the survival of the plant until the reproductive phase, the pollen viability and the fruit production in coriander plants from two cultivars – Verdão e HTV Dom Luiz – inoculated at the seeding with six different concentrations of M. incognita race 1 inoculum(0, 1,000, 2,000, 4,000, 8,000 and 16,000 eggs/cell); they were evaluated in RBD with four replications and an experimental plot composed by one plant. The fourth, and final, experiment verified the inoculation efficiency with 1,000 eggs/cell of M. incognita race 1 at the seeding and evaluation 30 days after the inoculation in the differentiation of 51 genotypes of coriander through the quantification of NGRS, NE, RF and estimated genetic parameters; RBD with four replications and experimental plot composed by eight plants. From the data attained we verified that the use of 128 cells tray with CS, experimental plot composed by eight plants and concentration of inoculum of 1,000 eggs/plant is the most indicated methodology since it allows a good development of the root system and to correctly classify the genotypes through the RF. The presence of the pathogen did not influence the pollen viability based on the results gathered from the Carmine Acetic and Alexander staining. Tetrazolium test and the in vitro pollen germination methods were not efficient in the identification of pollen viability. The inoculation of 1,000 – 4,000 eggs/plant, at the seeding, did not influence on the fruit production of the surviving plants of Verdão and HTV Dom Luiz cultivars, allowing the inoculation at the seeding, evaluation of NRRS 30 days after the inoculation and selection between and within the progenies with recombination of selected plants. According to the heritability, which varied of 75.91 (NGRS) – 96.72 (NE), on the CVg/CVa, of 2.71 for the reproduction factor and of 0.89 for the number of galls in the root system, and in the genetic correlations above 0.80 we indicate a selection based on NGRS in the initial cycles of the program of genetic improvement of coriander for the M. incognita race 1 resistance, that enables to perform a recombination of individuals selected in the same cycle, reducing the time to attain a new improved population and reinitiating a new cycle of recurrent selection of half-siblings progenies. Besides that, it was possible to determine that the inoculation at seeding and evaluation 30 days after was efficient in the differentiation of cultivars and progenies studied through the symptomatology caused by the pathogen‟s infection, allowing a selection of 12 superior progenies.