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European Journal of Applied Sciences – Vol. 9, No. 3

Publication Date: June 25, 2021

DOI:10.14738/aivp.93.10207.

Otusanya, M. O. (2021). Role of Nitrogen and Iron in Tuber Phenol Content for Resistance to Infection and Better Storability in

Bounty-Fertilized Dioscorea Rotundata Variety Oniyere. European Journal of Applied Sciences, 9(3). 127-132.

Services for Science and Education – United Kingdom

Role of Nitrogen and Iron in Tuber Phenol Content for Resistance

to Infection and Better Storability in Bounty-Fertilized Dioscorea

Rotundata Variety Oniyere

Otusanya, M. O.

Formerly of Dept. of Crop Protection

College of Plant Science and Crop Production

Fed. University of Agriculture, Abeokuta, Ogun State, Nigeria

ABSTRACT

The role of nitrogen and iron in promoting phenol with its antimicrobial properties

for disease resistance with implication of better storability of yam tubers is

indicated in Dioscorea rotundata variety Oniyere fertilized with an 8-mineral

component fertilizer namely Bounty, in this study. The experiment was arranged in

RCBD (Randomized Complete Block Design) with 3 treatments and 3 replicates. The

treatment was bounty fertilizer at the rate 0, 0.6 and 1.2 ml l-1 applied at 3MAP

(months after planting), Tubers were harvested at 6MAP and analyzed for

proximate, phenol and mineral content. Another set was incubated with

Botryodiplodia theobromae for 2 weeks and then analyzed for phenol and proximate

content. Tuber Ca was comparable across treatments, whereas N, S, and Fe were

higher in the 0.6 and 1.2 ml l-1 Bounty-fertilized treatments than the control. P was

higher only in the 0.6 ml l-1 treatment than the control, whereas K and Mg were

higher in the control than the 0.6 ml l-1 treatment and in the 1.2 ml l-1 treatments

respectively. Phenol was higher in the 1.2 ml -1 treatment than the control. Calcium

which is the second highest (7% w/w) component in Bounty fertilizer was a mean

of 14.15 mg/100gdm in Oniyere tubers, which is only 7.73% of phenol content with

a mean value of 183.3 mg/100gdm. Calcium also had no significant correlation with

phenol. Dry matter and moisture remained unchanged after the incubation,

whereas crude fibre and fat increased by 93.6% and 39.47% respectively. Ash

increased only in the 1.2 ml l-1 treatment by 22.54% and remained unchanged in the

control and 0.6 ml l-1 treatment. Phenol remained unchanged after the incubation

in the 0.6 ml l-1 and 0 ml l-1 treatments but decreased in the 1.2 ml l-1 treatment.

However carbohydrate and crude protein decreased across the 3 treatments by

2.16% and 51.33% respectively. Correlation of r = -0.5786 between Calcium and

moisture indicates Ca will not promote moisture. Positive implication of low

moisture for longer tuber storage has been reported. Nitrogen (N) the highest

component (15% w/w) of bounty, had significant correlation with phenol and Fe, r

= 0.7921 and 0.9840 respectively, thus will enhance production of both tuber

phenol and tuber Iron. Fe correlated significantly with S (r = 0.9751) and Fe and S

will each in turn promote phenol, r = 0.7629 and 0.7978 respectively. Iron content

in Bounty fertilizer is 2% w/w compared to Nitrogen which is 15% w/w, whereas

Sulphur is not present in Bounty fertilizer. A future trial should involve analysis of

total phenolic compounds (not only phenol), as well as proximate and mineral

content, in a longer and time-related incubation of about six to eight weeks, so as to

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European Journal of Applied Sciences (EJAS) Vol. 9, Issue 3, June-2021

Services for Science and Education – United Kingdom

determine all factors contributing to longer and better (quality) storage of variety

Oniyere tubers.

INTRODUCTION

Yam (Dioscorea species) tuber quality is important both for the consumer, retailer and exporter

in the country of production as well as the importer in any nation. Preservation of tuber quality

is important as this underground tuber is a staple in all regions where it is produced. High

storage losses, has placed emphasis also on inputs to be established by systematic research,

that would be feasible/ affordable by small holder farmers. Calcium carbonate fertilization

along with N.P.K. has been reported to reduce infection by Aspergillus niger and Botryodiplodia

theobramae in long-term storage in two improved varieties of Dioscorea rotundata and

Dioscorea alata (Otusanya et al., 2016). Even higher reduction in infection by Botryodiplodia

theobromae has also been reported by the 8-mineral component fertilizer Bounty, in two local

white guinea yam varieties namely D. rotundata variety Efuru and Oniyere (Otusanya, 2018 a,

2018 b). Factors which confer resistance were investigated in this study in Dioscorea rotundata

variety Oniyere fertilized with Bounty, an 8-mineral component fertilizer.

MATERIALS AND METHODS

Source of Tubers and Fertilization

Tubers of Dioscorea rotundata var. Oniyere were harvested from a Yam Project plot of the

Teaching and Research Farms of DUFARMS (Directorate of University Farms), Federal

University of Agriculture (FUNAAB), Abeokuta, Ogun State in South West Nigeria. The

Experimental plot had been laid out in RCBD with 3 replications and 3 treatments of Bounty

fertilizer at the rates 0, 0.6 and 1.2 ml l-1 applied at 3MAP (months after planting). Bounty

fertilizer contains 8-minerals in the following composition: Calcium 7% w/w, N 15% w/w, Iron

2% w/w, Zn 2% w/w, Cu 0.5% w/w and B 0.025% w/w, MgO 0.5% w/w, Mn 1% w/w.

Harvest at 6MAP, tuber processing and Analysis

Tubers were harvested at 6 MAP and washed with tap water. They were dried under a low- speed fan on Laboratory benches in the Crop Protection Laboratory, FUNAAB. Triplicate

samples per treatment were then cut into thin slices and dried further for 3 days. The dried

chips were milled to powder with a high-powered mill at the Central Workshop of the College

of Engineering, FUNAAB. The milled samples were then transferred to the Biotechnology

Centre FUNAAB and the Biological Tetfund Laboratory FUNAAB for tissue analysis. Analysis of

proximate content of dry matter, moisture, ash, crude fibre, crude protein, fat and carbohydrate

was according to routine methods of the A.O.A.C. (1990). Phenol content and minerals content

analysis of Calcium, Nitrogen Magnesium, Potassium, Phosphorus, Iron and Sulphur were

carried out according to routine methods of the A.O.A.C. (1990).

Incubation of Tubers with Botryodiplodia theobromae and phenol and proximate content

analysis

A second set of the harvested tubers were cleaned free of soil with a soft cloth, surface sterilized

with 80% methylated spirit and inoculated with a 7-day old pure culture of Botryodiplodia

theobramae according to the method of Otusanya and Jeger (1996), for a 2 week incubation

period. Phenol and Proximate content analysis was done after the incubation with triplicate

samples per treatment, using routine methods of the A.O.A.C (1990).