Productive potential of cassava plants (Manihot esculenta Crantz) propagated by leaf buds

Anais da Academia Brasileira de Ciências (2018) 90(2): 1733-1747 (Annals of the Brazilian Academy of Sciences) Printed version ISSN 0001-3765 / Online version ISSN 1678-2690 http://dx.doi.org/10.1590/0001-3765201820170867 www.scielo.br/aabc | www.fb.com/aabcjournal Productive potential of cassava plants (Manihot esculenta Crantz) propagated by leaf buds REIZALUAMAR J. NEVES1, RAFAEL P. DINIZ1,2 and EDER J. DE OLIVEIRA2 1 Centro de Ciências Agrárias, Ambientais e Biológicas, Universidade Federal do Recôncavo da Bahia, Rua Rui Barbosa, 710, 44380-000 Cruz das Almas, BA, Brazil 2 Embrapa Mandioca e Fruticultura, Rua da Embrapa, s/n, Caixa Postal 007, 44380-000 Cruz das Almas, BA, Brazil Manuscript received on October 26, 2017; accepted for publication on November 22, 2017 ABSTRACT New techniques of rapid multiplication of cassava (Manihot esculenta Crantz) have been developed, requiring technical support for large-scale use. This work main to evaluate the agronomic performance of plantlets obtained by leaf buds technique against stem cuttings in the field conditions. The work was conducted using the randomized block design in a factorial scheme with 3 varieties (BRS Kiriris, 98150-06, 9624-09) × 4 origins of the plantlets (conventional – stem cuttings of 20 cm length, leaf buds of the upper, middle and inferior stem part) × 2 agrochemicals (control and treated). There was a remarkable decrease in some agronomic traits that ranged from 23% (number of branches) to 62% (shoot weight) when using leaf buds plantlets. The treatment of plantlets with agrochemicals promoted significant increases in all traits, ranging from 26% (number of roots per plant) to 46% (shoot weight). The plantlets originating from leaf buds of the upper and middle parts were able to generate stem-like plants similar to stem-derived ones. Despite its lower agronomic performance under field conditions, multiplication by leaf buds may generate five times the number of propagules in comparison with the conventional multiplication, and therefore it could be a viable alternative for rapid cassava multiplication. Key words: propagation, vigor, field conditions, root production. INTRODUCTION Wide agroecological adaptability makes cassava the third most important source of energy in the tropics (Hasibuan and Nazir 2017). However, some bottlenecks such as a low plant material multiplication rate still remain as a challenge for cassava growers and producers (Ceballos et al. 2015). The conventional method of cassava planting via asexual propagation, coupled with the long Correspondence to: Eder Jorge de Oliveira E-mail: cycle of the crop, has hampered the development and implementation of crop breeding programs (Bredeson et al. 2016); this is because it takes about five to six years between the parents’ hybridization and the initial cycles of evaluation and selection to complete one breeding cycle (Boonchanawiwat et al. 2011, Okogbenin et al. 2012). For growers, the biggest challenge is to produce enough propagating material to replace obsolete varieties with new improved varieties. The FAO report (2013) points out that, in order to obtain gains in the cassava production system, it is necessary to An Acad Bras Cienc (2018) 90 (2) 1734 REIZALUAMAR J. NEVES, RAFAEL P. DINIZ and EDER J. DE OLIVEIRA reduce the restrictions related to planting material multiplication and distribution of, aiming at the sustainable intensification of crop production. In this sense, some propagation techniques have been used to overcome these problems. The cassava in vitro micropropagation technique allows the production of a larger number of plants, mainly disease-free in less space, than conventional methods of stem production (Aladele and Kuta 2008). However, some of the limiting factors of this technique are the need for laboratorial infrastructure, skilled and trained labor and above all the higher cost of plant production than conventional propagation systems (Ogero et al. 2010). In contrast, some alternative techniques of rapid multiplication were developed in order to increase the rate of cassava propagation at a lower cost, germinating two or three buds and then cutting shoots. These are subsequently submitted to rooting in water (Rodrigues et al. 2008). However, it is hard work and requires intensive labor for plantlet generation. Remison et al. (2015) pointed out that one way of increasing the availability of large-scale planting material in cassava crops would be to reduce the nodal units of the stake, i.e., by reducing the length of the cassava cuttings. The cassava stems are formed by nodal units composed of axillary buds, which are responsible for the development of new shoots (Ceballos and De La Cruz 2002). The stems’ leaves produce the carbohydrates necessary to maintain the nodal units and influence root growth (Cock 2012). Therefore, the use of the leaf bud cutting technique for cassava propagation becomes feasible, since it allows the multiplication of the planting material from a single leaf and a nodal unit from four or five months of planting (Burgos et al. 2009). Despite its potential as a new technique for rapid multiplication in cassava, no studies were found in the literature that demonstrated the agronomic performance of the plantlets produced from the leaf bud cutting technique. Conversely, An Acad Bras Cienc (2018) 90 (2) performance of plantlets from micropropagated plant cuttings was superior in number of storage roots and root weight per plant to the conventional stem cuttings cultivated in the field (Acedo and Labana 2008). In other species, such as Olea europaea L., the vegetative and productive performance of micropropagated plants against grafted and ungrafted plants indicated that in vitro propagation may be a powerful and rapid tool in this species, although there are important phenological differences (lower weight and fruit production) attributed to genetic modifications induced by in vitro propagation (Bati et al. 2006). Regarding conventional cassava propagation under field conditions, Remison et al. (2015) pointed out that sprouting rate and vegetative growth are related to the number of buds in the cuttings, considering their relationship with root and shoot development, although the size of the propagation material did not affect the productivity, dry matter content, root weight and root size. However, knowledge about the performance of cassava plantlets propagated by leaf bud cuttings under field conditions is still scarce, compared to several studies of the effect of different cutting sizes in yield components. Studies on vegetative propagation by leaf buds have mostly been related only up to the rooting stage and have shed little light on plant growth and development under field conditions. The objective of this work was to evaluate the performance in field conditions of the cassava plantlets obtained by the leaf bud cutting technique, considering agronomic traits of productivity (...truncated)