Page 1 of 7
European Journal of Applied Sciences – Vol. 10, No. 1
Publication Date: February 25, 2022
DOI:10.14738/aivp.101.11608. Osijo, T. A., Otusanya, M. O., Enikuomehin, O. A., Afolabi, C. G., & Olowokere, F. A. (2022). Rhizopus Rot Controlwith Calcium Nitrate
in Dioscorea Rotundata Var. Apepe. European Journal of Applied Sciences, 10(1). 192-198.
Services for Science and Education – United Kingdom
Rhizopus Rot Controlwith Calcium Nitrate in Dioscorea Rotundata
Var. Apepe
Osijo, T. A.
Department of Crop Protection
College of Plant Sc.& Crop Production (COLPLANT)
Federal University of Agriculture Abeokuta (FUNAAB), Ogun State, Nigeria
Otusanya, M. O.
Department of Crop Protection
College of Plant Sc.& Crop Production (COLPLANT)
Federal University of Agriculture Abeokuta (FUNAAB), Ogun State, Nigeria
Enikuomehin, O. A.
Department of Crop Protection
College of Plant Sc.& Crop Production (COLPLANT)
Federal University of Agriculture Abeokuta (FUNAAB), Ogun State, Nigeria
Afolabi, C. G.
Department of Crop Protection
College of Plant Sc.& Crop Production (COLPLANT)
Federal University of Agriculture Abeokuta (FUNAAB), Ogun State, Nigeria
Olowokere, F. A.
Department of Soil Science and Land Management
COLPLANT., Federal University of Agriculture
Abeokuta, Ogun State, Nigeria
ABSTRACT
This study investigated the response of Dioscorea rotundata variety Apepe to tuber
rot by Rhizopus stolonifer with Calcium nitrate foliar spray. The experiment was a
randomized complete block (RCBD) with three replications. In the pre-planting soil
analysis, Calcium, Magnesium and Potassium were 31.58cmol kg-1, 2.34cmol kg- 1and 0.52cmol kg-1 respectively in the soil of the experimental site, higher than the
criticals reported for the three elements for optimum production of yam in South
West Nigeria. However, Nitrogen and Phosphorus were 1.06% and 11.79ppm
respectively, below the criticals. Calcium nitrate at 0mgl-1, 750mgl-1, and 12000mgl- 1 was sprayed 16 weeks after planting (16WAP), and then four weekly until 28WAP.
Tubers inoculated at 32WAP with R. stolonifer for four weeks, had weight loss not
significantly different across the three treatments. It was 0.26% for the control,
1.23% for the 750mg l-1 treatment and 5.50% for the 12000mgl-1 treatment.
Infection in the 750 mgl-1 treatment was 2.26% significantly lower than the control
which was 6.66%. The 750mgl-1 treatment was lower than the control by 66%. But
infection in the 12000mgl-1 treatment was 60.29%, higher than the control and is
Page 2 of 7
193
Osijo, T. A., Otusanya, M. O., Enikuomehin, O. A., Afolabi, C. G., & Olowokere, F. A. (2022). Rhizopus Rot Controlwith Calcium Nitrate in Dioscorea
Rotundata Var. Apepe. European Journal of Applied Sciences, 10(1). 192-198.
URL: http://dx.doi.org/10.14738/aivp.101.11608
thus not suitable for the control of R. stolonifer tuber rot. However, 750mgl-1calcium
nitrate foliar spray is recommended for control of R. stolonifer tuber rot in variety
Apepe. Tuber yield at 32WAP was the equivalent of 35.80tonsha-1, 32.50tonsha-1
and 31.10tonsha-1 in the 0mg-1, 750mgl-1 and 12000mg-1treatments respectively.
Overall mean yield of 33.13tons ha-1is similar to the optimum of 34.20tons ha- 1reported for economic production of yam in South West Nigeria.
INTRODUCTION
Yam (Diosciorea.species) is a tuber crop belonging to the family of Dioscoreaceae with over 600
species, and white guinea yam (Dioscorea rotundata Poir.) is one of the six most important in
the tropics (Onwueme, 1978, Hahn et al., 1993). The tuber is an important source of
carbohydrate/calories in many developing nations, especially Africa (Maroya, 2014). Nigeria
accounts for over 75% of world production (FAO, 2014). Despite its importance in the country,
it has suffered many setbacks in production as a result of both abiotic and biotic factors. One of
the most important is disease, especially by fungi which attack yam both in the field and in
storage.
Rhizopus stolonifer Ehrenb. is reported to be the second highest occurring fungal rot pathogen
of yams in Nigeria (Dania et al., 2012). It causes soft rot, with the fungal mycelia invading the
cells, collapsing their walls, with a characteristic foul smell within a short period. Fungicides for
yam rot control are no longer encouraged because of their adverse effects on man, animals and
environment. Effort to store yams in cold or low temperature environment damaged yam tissue
and were too expensive to maintain (Adesuyi, 1973; Osunde, 2008). Biological agents have also
been used for control (Okigbo, 2004). Resistance of plants or plant products to disease is being
improved by nutrient fertilization. Calcium foliar sprays have been used to reduce Alternaria
rot and bitter rot pathogens in apple fruits (Biggs et al., 1993, Biggs, 1999). Calcium foliar sprays
have been used to increase calcium content of strawberry to reduce grey mould infection
(Cheour et al., 1990).Calcium fertilization has been reported to control damage caused by
storage pathogens on both potatoes and two improved yam lines (Ozygen et al., 2003, Otusanya
et al., 2016). The effect of calcium nitrate foliar spray in yam anthracnose control has also been
recently reported (Otusanya et al., 2017).This study was carried out to investigate the effect of
foliar-sprayed calcium nitrate on tuber rot by Rhizopus stolonifer in a popular white guinea yam
variety from South West Nigeria known as Apepe.
MATERIALS AND METHODS
Source of Planting Material
Tubers of Dioscorea rotundata var. Apepe were sourced from the Lafenwa yam market in
Abeokuta, Ogun State, Nigeria.
Soil Sampling and Analysis
Soil samples were collected from the experimental plot with a soil auger. Samples were air- dried, sieved and bulked according to standard methods (Page et al, 1982). Analysis of mineral
elements in the samples was also according to standard methods (Page et al., 1982).
Field Experiment
The field experiment was carried out at the Directorate of University Farms (DUFARMS),
Federal University of Agriculture, Abeokuta (FUNAAB), Ogun State, Nigeria. A randomized
Page 3 of 7
194
European Journal of Applied Sciences (EJAS) Vol. 10, Issue 1, February-2022
Services for Science and Education – United Kingdom
complete block design (RCBD) was used with three replications. Each replicate block had thirty
mounds. Mounds were 1metre (m) by 1m and 80cm high. Each mound was established with a
2m stake. Inter-row, intra-row and inter-replicate spacing were 0.5m, 0.5m and 1m
respectively. There was a field border of 1m around the plot.
Planting and Foliar Spray Application
Whole tubers without bruises were selected and cut into setts of 0.5kg size. Sett cut surfaces
were air-dried before planting, one per mound, at the onset of rains in 2016. At 16WAP, Calcium
Nitrate (analar grade) concentrations of 750mg1-1, 12000mg1-1 were prepared with distilled
de-ionized water and 0.01% Polysorbate 20 (Tween 20) as surfactant. Foliar spray rate of 0mgl- 1 (control), 750mg1-1, and 12000mg1-1 calcium nitrate was sprayed, randomized in each
replicate using a two-litre Presto Hand Sprayer, in the early morning hours (6.00am to 7.00am).
Spraying was repeated at 20WAP, 24WAP and 28WAP.
Field data collection
Assessment of number of tubers per plant and fresh tuber weight per plant were taken at
32WAP, to determine any difference in treatments before physiological maturity (36WAP),
when shoot above the mound would have senesced. Measurement of tuber weight was with a
top-loading field mettler balance (field scale).
Source of Pathogen
Pure isolates of Rhizopus stolonifer were obtained from infected tubers from a market (Omida
in Abeokuta) yam lot. Seven-day old pure cultures of the pathogen were prepared according to
standard methods (CMI, 1983) in petri-dishes for the inoculation experiment.
Inoculation of Tubers and Inoculation Experiment
The inoculation experiment was a completely randomized design (CRD) with 3 replicates.
Tubers without bruises were selected from each treatment per replicate and weighed using a
field scale. Cotton wool soaked in 80% methylated spirit was used to surface sterilize the middle
portion of the selected tubers. Then a 5mm diameter hole was bored into the surface-sterilized
portion (inoculation site), using a flame-sterilized and cooled cork borer. The yam core from
the hole was removed with the aid of a flame-sterilized and cooled pair of forceps. A four
millimetre (4mm) disc of R. stolonifer was transferred using a flame-sterilized (and cooled) cork
borer from the pure culture into the hole bored in the tuber. The yam tissue core was then
plugged back into the hole, and the inoculation site sealed with pure petroleum jelly. The
inoculated tubers were transferred in plastic trays into raised, ventilated, wooden, netted
structures designed for the experiment (Otusanya et al., 2016) in the College screen house. This
was for four weeks incubation period. After the incubation the inoculated tubers were weighed
again after the petroleum jelly had been cleared from the inoculation site of each tuber (with
spatula and cotton wool). Each tuber was cut through its inoculation site with a sharp stainless
steel knife and infected tissue within pared away with a scalpel, on to a pre-weighed aluminium
foil. Weight of infected tissue were recorded with an electronic balance. Percentage infection
and percentage weight loss were calculated using the corrected weight of infected tissue
(Otusanya, 1994).