13-paternity testing of selected abaca _musa textilis l. nee_ hybrids using morphometric markers

Oct. 2010, Volume 4, No.5 (Serial No.30) Journal of Agricultural Science and Technology, ISSN 1939-1250, USA

Paternity Testing of Selected Abaca (Musa textilis L. Nee) Hybrids Using Morphometric Markers

F. C. L. Zapico, C. H. M. Aguilar, J. M. Aujero and B. Y. Disca Science Department, College of Natural Sciences and Mathematics, Mindanao State University, Fatima, General Santos City 9500,

The Philippines

Received: April 21, 2010 / Accepted: July 6, 2010 / Published: October 15, 2010.

Abstract: Investigation into the paternity of four abaca (Musa textilis L. Nee) hybrids was done to ascertain the mode of transmission of selected morpho-agronomic traits and to detect possible heterosis. In situ morphological characterization was undertaken using twenty five qualitative and six quantitative characters. Results revealed that a great majority of the qualitative traits were shared by both parents and their hybrids. For the rest, the qualitative traits were inherited from one or the other parent though some variant phenotypes (i.e. chimerism) were also noted in the hybrids. Cases of heterosis were also observed and this could be exploited to increase fiber yield in the hybrids. Though inconclusive due to factors such as the heterogenous nature of abaca plants in the field and the susceptibility of morphological traits to environmental fluctuations, this study has provided baseline information on abaca hybridity that can be verified using more robust technologies as molecular markers. Key words: Abaca (Musa textilis L. Nee), paternity testing, morphological characterization, heterosis.

1. Introduction

Abaca (Musa textilis L. Nee) is a plant endemic to the Philippines where prevailing climatic conditions are suited for its cultivation. Known worldwide as Manila hemp, abaca resembles its more famous relative, the banana. In the early 1970s, the thriving abaca industry in the Philippines was brought to the brink of collapse primarily because of widespread virus infestation in abaca plantations. Until now, abaca farmers and even agricultural scientists have been unable to find viable solutions to eradicate three major diseases that perennially attack abaca farms: abaca mosaic, abaca bunchy top, and abaca bract mosaic [1, 2]. The strategy employed by scientists is breeding for abaca varieties with higher fiber yield and with resistance to viruses. In this study, four abaca hybrids developed by the Bureau of Plant Industry (BPI),

Corresponding author: F. C. L. Zapico, M.Sc., research fields: plant genetic resource conservation and management. E-mail: [email protected].

Philippines were subjected to morphological characterization. The objectives of this study were to investigate phenotypic diversity of selected abaca hybrids and parentals, determine the degree of association between them and recognize some favourable heterotic characters expressed by the hybrid plants. Morphometric analysis of quantitative characters is especially important since these are usually related to yield. As such, higher values for yield characters for the hybrid progeny (heterosis or hybrid vigor) can be exploited for certain yield-related characters [3-5].

2. Materials and Methods

2.1 The Study Site

This study was conducted on April 2009 at the abaca field genebank of the Fiber Industry Development Authority (FIDA XI) in Sitio Manambolan, Tugbok District, Davao City, Philippines. Found in the Southern Mindanao Region and with a latitude of 6°58′


102

Table 1 The morphological traits used in the characterization of the abaca hybrids and parentals.

Leaf habit Appearance of leaf upper surface Lamina attitude Pseudostem height

Pseudostem colour Colour of leaf lower surface Lamina tip shape Plant diameter

Pseudostem appearance Appearance of leaf lower surface Lamina tip bending Petiole length

Pseudostem blotching Wax on leaf sheaths Lamina base equality Petiole margin width

Sap colour Petiole canal leaf III Lamina base shape Leaf blade length Anthocyanin pigment at pseudostem base Petiole margin color Colour of leaf upper surface Leaf blade width

Petiole blotches colour Petiole margin corrugation Anthocyanin pigment at leaf midrib Lamina base handedness

Edge of petiole margin Blotches at the petiole base Anthocyanin pigment at leaf base

to 7°34′ North and a longitude of 125°14′ to 125°40′ East, Davao City enjoys good tropical weather with climatic elements that are distributed evenly. Temperature ranges from 15 ℃ to 34 ℃ all year round.

2.2 In Situ Morphological Characterization of Abaca Germplasm

Morphological characterization of abaca parental varieties and hybrids was done in situ. A total of six quantitative and twenty five qualitative morpho-agronomic descriptor states (Table 1). Collected data were used in the characterization of selected abaca varieties and their hybrid progenies. Collected data were based on 10 measurements where applicable. For characters involving color variations, these were evaluated using a standardized color chart [6]. The morphological parameters for evaluating the different abaca accessions were based on modified morpho-taxonomic descriptors for abaca [6, 7]. Qualitative data were obtained through visual inspection. As for quantitative data, these were collected using a steel tape or some such measuring tool. The collected quantitative data were then subjected to pairwise mean correlation using SPSS/PC+v. 16 to compare the degree of phenotypic association between hybrids and the abaca parentals.

3. Results and Discussion

3.1 Linlay (Linino×Laylay)

It was noted from very close examination that Linlay

exhibited a greater degree of pseudostem blotching than both parents. Of the twenty five qualitative traits evaluated, sixteen were common to both parents, implying their morphological similarity. Linlay also showed seven phenotypic features typical of the Laylay parent and a solitary feature (lamina tip shape) that was unique to Linino. This morphological proximity between Linlay and parent Laylay was borne out in the correlation analysis using six quantitative traits (shown in Table 2). Quantitative analysis also revealed five traits (pseudostem height, diameter, petiole length, petiole margin width and leaf blade length) with varying degrees of heterosis (Table 3). Heterosis on plant height and diameter is an indication of good breeding value of the parental lines [8]. It is considered of great significance for it connotes an increase in yield especially for the abaca fiber which is generated from the pseudostem.

3.2 Bontang (Bongolanon×Tanggongon)

Thirteen of the twenty five qualitative characters were shared by both parents and the hybrid. Bontang’s extensive pseudostem blotching, however, was manifested by neither parent (Table 4). The Bontang hybrid also exhibited two attributes of Bongolanon, (blunt lamina tip shape and straight with erect margins petiole canal leaf III), and seven qualitative features were inherited from the Tanggongon parent. These were leaf habit and lamina attitude, small blotches at petiole base, absence of anthocyanin pigment at the leaf base and auriculate shape of its lamina base (Fig. 1


103

Table 2 Quantitative pairwise mean comparison between the hybrids and parentals.

Hybrids Parentals Pairwise mean correlation Linlay Linino 0.989 Laylay 0.994 Bontang Bongolanon 0.992 Tanggonon 0.999 Inotang Inosa 0.999 Tanggonon 0.995 Maguino Maguindanaon 0.997 Inosa 0.382

Table 3 Mean values of the evaluated quantitative characters of Linino×Laylay and hybrid, Linlay (measurements in cm).

Parameters (Quantitative) Linino × Laylay LinlayPseudostem height 269.5 284 306.17Plant diameter 48.5 44.1 54.83Petiole length 41.88 45.3 52.17Petiole margin width 1.4 1.58 2.67Leaf blade length 157.75 176.56 224.5 Leaf blade width 47 43.67 46.67

Table 4 Selected qualitative and mean values of the evaluated quantitative characters of Bongolanon× Tanggonon and hybrid, Bontang (measurements in cm). Parameters (Qualitative) Bongolanon × Tanggonon Bontang

Pseudostem blotching Moderate Moderate Very extensive

Leaf blade length 171.17 263.6 246 Petiole margin width 1.58 2.5 2.42 Pseudostem height 269.25 339.4 319.5 Plant diameter 46 64 60 Leaf blade width 50.83 53.8 67.3 Petiole length 51.5 59.4 61.5

2a-c). In Table 2, the phenotypic similarity between Bontang and the Tanggonon parent was firmly established through pairwise mean analysis. Bontang also showed intermediate characteristics between those of the parents in terms of the pseudostem height, plant diameter, petiole margin width and leaf blade length. Slightly higher values were obtained for petiole length and leaf blade width in the hybrid than both parents (Table 4).

3.3 Inotang (Inosa×Tanggongon)

Table 2 shows a greater degree of similarity between Tanggongon and hybrid Inotang. Five traits were inherited exclusively from Tanggongon. In terms of the six quantitative traits tested, these appeared to be intermediate between those of the parents. Four qualitative traits were also seen to be distinctive to Inotang. These were petiole margin corrugation, lamina tip shape, margin petiole canal leaf III and chimeric pseudostem color (Fig. 1 3a-c). Occurrences of chimerism are commonly observed in flowers such as Brassica species [9] and in micropropagated plants as a manifestation of somaclonal variation. Furthermore, Abeyaratne and Lathiff [10] reported an incidence of chimerism in pseudostem color in field grown tissue-cultured Rathambala banana in Sri Lanka. Just like the Rathambala banana (AAA), the pseudostem of the Inotang hybrid showed a wide range of colors with different intensities. Reuveni et al. [11] theorized that chimerism is an innate feature of the initial explant and is not affected in vitro and by other factors in the field. This view was also supported by Swennen et al. [12] who revealed that much of the somaclonal variations observed in the field-grown materials are due to natural phenotypic variations enhanced by in vitro conditions. Abeyaratne and Lathiff [10] went further to say that this genetic phenomenon is not confined to micropropagated plants but can also be observed in nature.

3.4 Maguino (Maguindanaon×Inosa)

Four quantitative traits were intermediate between the hybrid Maguino and its parents. Pairwise mean comparison using quantitative traits (Table 2) revealed a very close association between hybrid Maguino and Maguindanaon (0.997) and a very distant association between Maguino and parent Inosa (0.382). This trend, however, was not consistent for qualitative characters which depicted seventeen characters which were common to Inosa and hybrid Maguino. One trait inherited by hybrid Maguino from Inosa is lamina tip


104

Fig. 1 Morphological comparisons of abaca parentals and hybrids.

bending (shown in Fig. 1 4a-c). Moreover, the hybrid showed six traits of Maguindanaon. Two unique traits were also seen in Maguino. These were absence of anthocyanin pigment at leaf base and its cuneate shape.

4. Conclusions

Morphological characterization had been success- fully used to ascertain hybridity in many crop species [4]. In this study, in situ morphological characterization was carried out to investigate the parentage of abaca intraspecific hybrids. This study has provided information, albeit inconclusive, on the paternity of the abaca hybrids. Notwithstanding the characters that have shown phenotypic variability, a remarkable degree of morphological similarity has been very evident between the hybrid progenies and the parental lines. This suggests low genetic variability and gradual loss of agronomic traits among abaca accessions in the field. On the other hand, one limitation of the study stems from the uncertainties associated with morphological characterization. The heterogenous nature of the abaca plants in the field and the susceptibility of morphological traits to environmental effects conspire to give a relatively

inaccurate estimate of phenotypic diversity in the abaca germplasm evaluated. Further studies using more robust marker technologies are therefore warranted to give an accurate assessment of variability in the abaca genotypes studied.

Research on the tolerance/resistance of these hybrids to viral infestation and environmental stresses is also necessary to evaluate their agricultural potentials [4]. This would also aid in the identification of hybrids suitable to field conditions in Mindanao island, the Philippines. Furthermore, a single case of chimerism was observed in Inotang (Inosa×Tanggongon) hybrid. Heterosis observed in the Linlay hybrids for pseudostem height and diameter can also be exploited for increased fiber yield in crop improvement efforts. Moreover, the information obtained through the morphological characterization of the abaca parental varieties and their hybrid progenies can also be used in the selection of suitable parentals for abaca breeding programs.

Acknowledgments

Heartfelt gratitude is extended to the Fiber Industry Development Authority Regions (FIDA) XI and XII

1 a-c Lamina Base of Laylay, Linino and hybrid, Linlay

2 a-c Lamina Base of Bongolanon, Tanggonon and hybrid, Bontang

3 a-c Pseudostem of Inosa, Tanggonon and hybrid, Inotang

4 a-c Lamina tip bending of Maguindanaon, Inosa and hybrid, Maguino


105

and their satellite offices for all the technical and logistical support extended to the researchers during the conduct of the study.

References [1] A. Raymundo, N. Bajet, A. Sumalde, B. Cipriano, R.

Borromeo, B. Garcia, Mapping the spread of abaca bunchy top and mosaic diseases in the Bicol and Eastern Visayas regions, Philippines, Phil. Agri. Sci. 84 (2001) 352-361.

[2] M. Sharman, C.F. Gambley, E.O. Oloteo, R.V.J. Abgona, J.E. Thomas, First record of natural infection of abaca (Musa textilis) with banana bract mosaic potyvirus in the Philippines, Australasian Plant Pathology 29 (2000) 69.

[3] J.H. Crouch, H.K. Crouch, A. Tenkouano, R. Ortiz, VNTR-based diversity analysis of 2x and 4x full-sib Musa hybrids, Electric Journal of Biotech 2 (1999) 99-108.

[4] J. Lima-Brito, A. Carvalho, A. Martin, S. Heslop-Harrison, H. Guedes-Pinto, Morphological, yield, cytological and molecular characterization of a bread wheat×tritordeum F1 hybrid, Journal of Genetics 85 (2006) 123-131.

[5] S. Muthulakshmi, T. Balamohan, W. Amuttha, R. Rani, K. Indira, P. Mareeswari, Inter specific hybridization in papaya (Carica papaya L.), Journal of Agriculture and Bio

-logical Sciences 3 (2007) 260-263. [6] IPGRI-INIBAP/CIRAD, Descriptors for Banana (Musa

spp.), 1996. [7] National Abaca Research Center, Undated, Gross

morphological characterization for abaca (Musa textilis), Descriptors for Abaca, Leyte State University, Baybay, Leyte, Philippines.

[8] H. Budak, Understanding of heterosis, KSU Journal Science and Engineering 5 (2002) 68-75.

[9] J. Liu, H. Wang, D. Yu, M. Li, Morphology and cytology of flower chimeras in hybrids of Brassica carinata×Brassica rapa, African Journal of Biotechnology 8 (2009) 801-806.

[10] W.M. Abeyaratne, M.A. Lathiff, In vitro propagation of Rathambala (Musa AAA) and the occurence of phenotypic variations in the pseudostem, Annals of the Sri Lanka Department of Agriculture 4 (2002) 191-197.

[11] O. Reuveni, S. Golubowicz, Y. Israeli, Factors influencing the occurrence of somaclonal variations in micro-propagated bananas, Acta Horticulture 336 (1993) 357-364.

[12] R. Swennen, D. Vuylsteke, R. Ortiz, Phenotypic diversity and patterns of variation in West and Central African plantains (Musa spp., aab group Musaceae), Economic Botany 3 (1995) 320-327.