SEXUAL AND ASEXUAL REPRODUCTION IN BLACKBERRY (Rubus spp.) AND ITS RELATIONSHIP WITH CHROMOSOME STABILITY

Abstract

Blackberry (Rubus spp.) reproduces sexually and asexually, the form of propagation can modify the chromosomal stability in its genome, which is undesirable for the maintenance of germplasm, use of commercial varieties and breeding. Therefore, the objective of this study was to determine the number and length of chromosomes in wild and cultivated genotypes of blackberry reproduced sexually and asexually in order to analyze whether the form of propagation is related to chromosomal stability. The research was carried out under greenhouse conditions and at the Cytogenetics Laboratory of Colegio de Postgraduados, Campus Montecillo, Mexico. The varieties used were Kiowa, Apache, Cheyenne, Shawnee, Ebano, Choctaw and two populations from Teziutlán, Puebla and Jalacingo, Veracruz, Mexico. Propagation was carried out by seed and aerial layering of apical meristem. Cold pretreatment (4 °C) and the squash technique were used for chromosomal analysis. Chromosomes were counted and length data were obtained, which were subjected to analysis of variance under a completely randomized experimental design, followed by a Tukey test (P ≤ 0.05). Variability was found in chromosome number and ploidy level: Kiowa 4x = 28 and 3x = 21, Shawnee 4x = 28, Cheyenne 4x = 28, Apache 4x = 28, Ebano 4x = 28, Choctaw 4x = 28, Teziutlán 2x = 14 and Jalacingo 3x = 21. The variation in chromosome length was highly significant for varieties or populations, statistical differences were evident among those varieties reproduced asexually; in contrast, there were no differences between varieties or populations reproduced sexually. Reproduction by seed was associated with chromosome stability in number and length; asexual propagation on the other hand, was related to chromosomal instability.