Effects of Inorganic Fertilizers and Brassica Species Leaf Extract and Green Manure in Controlling Enset Bacterial Wilt in Gurage and Silte Zones, Ethiopia
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Date
2020-06-06
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Addis Ababa University
Abstract
Enset (Ensete ventricosum) is one of the most important multipurpose crops grown in
Ethiopia that is a staple food for approximately 20 million people in the country. The
production and sustainability of enset agriculture is, however, threatened mainly by
bacterial wilt of enset, which is caused by Xanthomonas campestris pv. musacearum
(Xcm). This study was conducted in Gurage and Silte zones of Ethiopia with the objective
of exploring the effects of inorganic fertilizers and Brassica species leaf extract and green
manure in controlling enset bacterial wilt. The study began with an assessment of the
prevalence and incidence of Xcm in relation to altitude i.e. low, mid and high altitudes.
The assessments were done by random sampling of 60 farms. Qualitative analysis of leaf
extracts was carried out using standard methods. The role of different levels of NPK
fertilizers to control Xcm in tolerant (Yeshrakinkye) and susceptible (Ameratye) enset
clones were evaluated under field condition. Again, the effects of selected Brassica species
as a green manure and Brassica carinata seed extract residue on growth, physiology of
enset clones and their effect on the incidence and severity of Xcm were evaluated under
field condition. Field experiments were laid in Randomized Complete Block Design with
three replications. Standard procedures were used to collect data for all studies. The data
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were analyzed using descriptive and inferential statistics in SPSS and Microsoft Excel
software. The result showed that mid altitude had the highest disease prevalence (DP) in
2014 (55%) and 2015 (43.8%), the highest disese incidence (DI) in 2014 (12.2%) and in
2015 (8.2%) compared to low and high altitude sites. This indicated that there were
altitudinal based variations on enset bacterial wilt DP and DI in the study areas.
The extracts of Brassica oleracea var capitata and Brassica oleracea var acepala created
the widest bacterial growth inhibition zone at (400 and 200 mg/mL) compared to other
concentrations. This suggests that Brassica oleracea var capitata and Brassica oleracea
var acepala controls the growth and development of Xcm. Qualitative phytochemical
screening results revealed that the chemical constituents of extracts vary between Brassica
species. The highest total phenolic content was recorded from Brassica carinata seed
extracts residue, Brassica oleracea var capitata (Cabbage) and Brassica oleracea var
acepala (Tekur Gomen).
The result of field experiment showed that inorganic fertilizers treatments with N1/2P1/2K1/2,
NPK and N3/2P3/2K3/2 significantly (p<0.05) decreased DI and disease severity (DS) and
increased all growth parameters of both enset clones including plant height, pseudostem
girth, green leaf number, leaf length, leaf width, leaf area and leaf area index at different
measuring periods compared to positive controls. Application of N1/2P1/2K1/2, NPK and
N3/2P3/2K3/2 decreased the DI of tolerant enset clones by 6.8%, 7.7% and 13.8%,
respectively compared to the positive control. In the same way, the DI of susceptible enset
clones was decreased by 22.2%, 27.8%, and 33.1 %, respectively. Similarly, DS of tolerant
enset clone was decreased with application of N1/2P1/2K1/2, NPK and N3/2P3/2K3/2 by 12.4%,
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17.3% and 35.2%, respectively as compared to positive control whereas that of susceptible
enset clones was decreased by 10.1%, 15.7%, and 17.9 %, respectively. Similarly, the
lowest AUDPC value (623) was recorded on tolerant clones treated with N3/2P3/2K3/2
fertilizers while the highest AUDPC value (1455) was recorded in a susceptible clone
compared with positive control.
Application of Brassica species as green manures such as Brassica oleracea var capitata
(G1) and Brassica oleracea var acepala (G2) and Brassica carinata seed extract residue
(G3) did not bring significant difference at (P >0.05) all growth parameters compared to
positive controls. Similarly, compared to the positive control application of these Brassica
plants as green manure and Brassica carinata seed extract residue didn’t bring significant
difference (P < 0.05) on all physiological parameters except for assimilation rate and on
functional parameters of photosynthetic apparatus (chlorophyll content). However,
compared to the positive control, G1, G2 and G3 decreased the DI of tolerant enset clones
by 19.4%, 23.3% and 23.1%, respectively. In the same way, application of G1, G2 and G3
treatments decreased the DI of susceptible enset clones by 6.7 %, 12.3 %, and 4.6%,
respectively. DS of tolerant enset clone with G1, G2 and G3 decreased by 5.3 %, 7.8% and
11.4%, respectively as compared to positive control. Similarly, application of G1, G2 and
G3 treatments decreased the DS of susceptible enset clones by 11.4 %, 8.6 %, and 10 %,
respectively. The lowest AUDPC value (976.5) was recorded on tolerant enset clone
treated with G3 while the highest AUDPC value (1828.9) was recorded in susceptible clone.
In general, the results of the present study showed use of recommended levels of NPK and
N3/2P3/2K3/2 amount improved the growth performance of enset and reduce the effect of
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bacterial wilt on enset clones. Moreover, use of Brassica oleracea var capitata and
Brassica oleracea var acepala as green manure and Brassica carinata seed extract residue
were effective to control enset bacterial wilt. From these results, it can be recommended
that combined NPK fertilizer and brassica plants green manuring is crucial to control
bacterial wilt of enset.
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Keywords
Brassica Species, Disease Incidence, Disease Severity, Ensete Ventricosum, Inorganic Fertilizers, Phytochemicals, Seed Extract Residue, Xanthomonas Campestris Pv, Musacearum