Criopreservação e crioterapia de ápices caulinares para erradicação do complexo viral associado a murcha (PMWAV) em variedades silvestres do gênero ANANAS

Abstract

Strategies for the conservation and eradication of pathogens have been proposed for several cultures that have as collections in vitro and in the field. The attack of pests and diseases has caused significant losses in germplasm of the genus Ananas. Thus, the development and optimization of creativity and cryotherapy protocols of cultivated and wild pineapple varieties are necessary for conservation of genetic resources. In the present study, pineapple plants of four botanical varieties belonging to the Pineapple Active Germplasm Bank (AGB Pineapple) and two hybrids from the genetic improvement program of the Embrapa Cassava and Fruits research unit (Embrapa Mandioca e Fruticultura). The main objective was to evaluate the conditions of the starting material (stem tips) after different cultivation intervals of the donor plant and their correlation with the regeneration rates, as well as to establish cryotherapy protocol for removal of the pineapple mealybug wilt-associated virus (PMWaV) complex. The suitability of the starting material was studied using cryopreservation of pineapple stem tips. Plants were cultivated in vitro for 30, 45 and 60 days before removal of the stem tips for cryopreservation. The regeneration rates of each treatment were calculated and histological sections were observed to evaluate the anatomy of the starting material. For the cryotherapy tests, indexation by RT-PCR was performed before and after freezing. The results indicated an interaction between cultivation time of the donor plant and the genotypes, with a significant influence on the regeneration percentages of the stem tips. The accessions A. comosus var. comosus (AGB-009) and A. comosus var. bracteatus (AGB-119) showed the highest regeneration rates, of 95% and 90%, respectively, for cultivation time of 30 days. The histological sections revealed the failure of some treatments after thawing. For AGB-009 and AGB-376 (A. comosus var. parguazensis), the cryotherapy was efficient in removing the viral complex. However, for AGB-119, the PMWaV-3 was eliminated in 83% of the plants. These results are promising for improvement of the cryopreservation method and for use of cryotherapy for routine removal of the pineapple mealybug wilt-associated virus complex from germplasm material.