Hindawi
International Journal of Agronomy
Volume 2019, Article ID 3926765, 8 pages
https://doi.org/10.1155/2019/3926765
Research Article
Evaluation of Yield, Reaction to Diseases, and Grain Physical
Attributes of Some Introduced Rice Hybrids in Ghana
Samuel Oppong Abebrese ,1 Alex Yeboah,1 Wilson Dogbe,1 Paul Kofi Ayirebi Dartey,2
Richard Akromah,3 Vernon Edward Gracen,4 Samuel Kwame Offei,4
and Eric Yirenkyi Danquah4
1CSIR-Savanna Agricultural Research Institute, P.O. Box TL 52, Tamale, Ghana
2CSIR-Crops Research Institute, P. O. Box 3785, Kumasi, Ghana
3Department of Crop and Soil Sciences, KNUST, Kumasi, Ghana
4West Africa Centre for Crop Improvement, University of Ghana, Legon, Ghana
Correspondence should be addressed to Samuel Oppong Abebrese; sam555oppa@yahoo.com
Received 25 October 2018; Revised 13 January 2019; Accepted 12 February 2019; Published 13 March 2019
Academic Editor: Maria Serrano
Copyright © 2019 Samuel Oppong Abebrese et al. )is is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in anymedium, provided the original work is
properly cited.
Hybrid rice technology is one of the promising, sustainable, and proven technologies for increasing rice production and
productivity with a yield advantage of 15–30% over modern inbred varieties. )e potential of hybrid rice has so far not been
exploited in Ghana.)is study was undertaken to evaluate the yield potential, reaction to diseases, and physical grain attributes of
some introduced hybrids. )e trials were laid out in a randomized complete block design (RCBD) with three replicates across
three locations. Data were taken on grain yield, yield components, reaction to diseases, and grain physical characteristics. Four
promising hybrids (SWARNA 2, ARGH 1501, ARGH 1502, and ARGH 1503) with a mean yield advantage of 15–20.8% over the
best inbred check “AgraRice” were identified. With few exceptions, the hybrids were broadly adapted and had adequate resistance
to blast and bacterial leaf blight. Most of the test hybrids had long slender grains which make them acceptable to the Ghanaian
market but lacked aroma.
1. Introduction improving the yield potential of rice is through the use of
hybrid varieties [5–8]. )e potential of hybrid rice has so far
Rice (Oryza sativa L.) is the second most important cereal in not been exploited in Ghana. Commercialization of hybrid
Ghana after maize [1]. Local production is around 40% of rice in Ghana has begun by interested private seed com-
national consumption resulting in the importation of about panies introducing and testing hybrids mostly from Asia.
680 000 tons of rice, which cost the country over 500 million Hybrid rice is a promising and sustainable technology
USD annually [2, 3]. With population growth, urbanization, for increasing rice production and productivity [9–11]. It has
and shifting consumer preferences, demand of rice is ex- been proven practically that hybrid varieties could out-yield
pected to keep increasing [4, 5]. Ghana is endowed with their inbred counterparts grown under similar conditions by
suitable land resources to be self-sufficient in rice production 15–20% [10, 12].)e superiority of hybrids over their inbred
[1]. Recent data show that rice production has been in- counterparts may be expressed in grain yield, vigor, panicle
creasing at 7.5% annually since 2009, but most of this in- size, number of spikelets, and number of productive tillers
crease (6%) comes from land area expansion, and only 1.5% [10–12]. Since hybrid rice seeds cannot be used for
comes from productivity improvements [3]. )ere is the replanting due to the resulting segregation in most of the
need to exploit all available technologies to increase local valuable agronomic traits, farmers are forced to buy fresh
production and productivity. One technology for genetically seeds for each season’s planting [12]. )is presents an
2 International Journal of Agronomy
opportunity for private seed companies and encourages by environmental interaction (GEI), GGE biplot graphically
private-sector involvement in seed production, research, and analyses the nature of the interactions [24, 29]. However, the
development [13]. Since the hybrid varieties yield 15–20% total variation of a phenotype could be partitioned into the
more than the pure line varieties, farmers prefer hybrid seeds genotype (G) effect, environment (E) effect, and genotype by
if the price is economically beneficial and seeds are reliably environment interaction (GEI) effect, and the GGE biplot
available [14]. Hybrid rice is extensively commercialized in model considers only G and GEI as relevant to cultivar
China where over 50% of the total land area for rice is evaluation and the two factors are considered simulta-
planted to hybrids [15, 16]. Other Asian countries like India, neously, removing the environment (E) effect [29]. )is is
Philippines, )ailand, Vietnam, Indonesia, and Bangladesh because the concept of crop performance and stability, as
have also commercialized hybrid rice [12]. It is also effec- considered by crop scientists when selecting superior ge-
tively utilized in Brazil and the USA [12]. In Africa, Egypt is notypes, is centered on G and GEI effects only [24, 25, 29].
the only country which has successfully developed a hybrid )e “mean versus stability” view of GGE biplot ranks entries
rice breeding program that produces local rice hybrids on a according to their performance and stability across envi-
commercial scale [13]. AfricaRice (Africa Rice Centre) ronments [29, 30].
initiated a hybrid breeding program in 2010 to develop )is study assessed the yield potential and stability of
superior hybrids for sub-Saharan African countries [13, 17]. some introduced rice hybrids across locations, their reaction
Successful adoption of hybrid rice by farmers depends to local biotic stresses, and physical grain quality attributes.
highly on the availability of superior hybrids which combine
higher yields with farmer preferred traits [12]. Rice blast
(caused by Pyricularia oryzae (anamorph) andMagnaporthe 2. Materials and Methods
oryzae (teleomorph)), bacterial leaf blight (BLB) (caused by 2.1. Plant Materials. A total of fourteen hybrids were as-
Xanthomonas oryzae), and rice yellow mottled virus sembled from interested private seed companies and
(RYMV) are the three most important rice diseases in Ghana agencies: Wienco Ghana, Advanta Seeds Company, and
[2, 18]. A yield loss of 3.5–77% has been reported for the rice IFDC-Agricultural Technology Transfer Project (IFDC-
blast disease [19]. RYMV disease, although sporadic, can ATTP) in 2014 and 2015. Eight of these hybrids were in-
cause complete yield loss to susceptible varieties [2]. Varietal troduced and evaluated in 2014, whilst the remaining six
resistance is the recommended management strategy for were introduced in 2015. )e performances of these hybrids
these three diseases. Released varieties are therefore required were benchmarked to the two local inbred checks Jasmine 85
to possess adequate levels of resistance to survive these and AgraRice (Table 1).
diseases. Rice grain quality is a major determinant of rice
varietal adoption in Ghana [2, 20].)e Ghanaian market has
high preference for intermediate amylose, long slender ar- 2.2. Experimental Locations. )e trials were conducted at
omatic rice grains, with these characters accounting for over Nyankpala (09°24′17.8″N, 000°57′57.0″W, 143m), Golinga
40% increase in price quotations [2, 21, 22]. Locally de- (09°21′06.0″N, 000°57′01.0″W, 139m), and Navrongo
veloped rice varieties are expected to possess these grain (10°36′4.89″N, 1°15′9.47″W, 195m) in 2014. )e 2015 loca-
quality attributes in order to be able to compete with the tions were Golinga, Navrongo, and Nobewam (06°37′23.8″N,
imported brands in the market. 001°07′03.8″W, 193m). )e Nyankpala and Golinga sites
Before the release of a variety, many genotypes are were within the Guinea Savanna agro-ecological zone, the
evaluated for performance capabilities relative to checks Navrongo site was within the Sudan Savanna zone, and
under various environmental conditions over several sea- Nobewam within the semideciduous rainforest. Golinga,
sons and years to enable prediction of future performance in Navrongo, and Nobewam were irrigated ecologies, whereas
farmers’ fields [23, 24]. Yield stability of the test varieties is Nyankpala site was rainfed lowland ecology. )ese locations
also important in such trials [24, 25]. )orough genotype by are considered as blast disease hot spots and were selected as
environmental interaction (G×E) and stability analyses in key screening sites from the previous study [19].
multienvironment trials (MET) help us to select varieties
that are adapted to specific environments and those with
broad adaptation across a set of environments [25, 26]. 2.3. Experimental Design and Trial Management. )e trials
Many statistical methods are available for assessing the were laid out in a randomized complete block design
stability of genotypes across environments [24–26]. Among (RCBD) with 3 replicates across locations in a plot size of
them, the genotype main effect plus genotype by environ- 10m2. Seeds were pregerminated, nursed, and transplanted
ment interaction (GGE) biplot is recognized as the most one seedling per hill after 21 days in a spacing of 20 cm
innovative methodology in biplot graphic analysis which is within and between rows. Seeds were directly sown and
applied in plant breeding [25, 27, 28]. GGE biplot produces a thinned to one seedling per hill at Nyankpala (the rainfed
graphical display of results that facilitates a better un- lowland ecology).)e recommended fertilizer rate of 90 : 60 :
derstanding of complex genotype by environment in- 60 kg NPK/ha was applied in two splits. Basal application of
teraction in multienvironment trials of breeding and 60 : 60 : 60 was applied a week after transplanting at the
agronomic experiments [26, 29]. It complements the results irrigated sites and two weeks after germination at Nyankpala
of the analysis of variance (ANOVA) in that, after the (the rainfed ecology). Top dressing with 30 kg nitrogen in the
ANOVA had shown significant mean squares for genotype form of urea was done at the booting stage. Weeds were
International Journal of Agronomy 3
Table 1: List of hybrids and inbred checks used for the study. Table 2: Descriptive key for recording leaf blast disease severity.
Variety/entry Status Source Year Score Description of symptomsevaluated 0 No lesions observed
INDAM 200-002 Hybrid IFDC-ATTP 2014 1 Small brown specks of pinhead size or long brownINDAM 100-002 Hybrid IFDC-ATTP 2014 specks without sporulating centre
INDAM 100-001 Hybrid IFDC-ATTP 2014 Small roundish to slightly elongated, necrotic grey
GR-2 Hybrid IFDC-ATTP 2014 2 spots, about 1-2mm in diameter with a distinct
GR-1 Hybrid IFDC-ATTP 2014 brown margin
GR-3 Hybrid IFDC-ATTP 2014 3 Lesion type is the same as in scale 2, but a significant
S71680676 Hybrid Wienco Ghana 2014 and number of lesions are on the upper leaves2015 4 Typical susceptible blast lesions, 3mm or longer,S72180002 Hybrid Wienco Ghana 2014 infecting less than 4% of the leaf area
PAC 832 Hybrid Advanta Seeds Co. 2015 5 Typical blast lesions infecting 4–10% of the leaf area
PAC 801 Hybrid Advanta Seeds Co. 2015 6 Typical blast lesions infecting 11–25% of the leaf area
SWARNA 2 Hybrid Advanta Seeds Co. 2015 7 Typical blast lesions infecting 26–50% of the leaf area
ARGH 1501 Hybrid Advanta Seeds Co. 2015 Typical blast lesions infecting 51–75% of the leaf area
ARGH 1502 Hybrid Advanta Seeds Co. 2015 8 and many leaves are dead
ARGH 1503 Hybrid Advanta Seeds Co. 2015 9 More than 75% leaf area affected
Jasmine 85 Inbred CSIR-SARI 2014 andcheck 2015
AgraRice Inbredcheck CSIR-SARI
2014 and
2015 Table 3: Descriptive key for recording BLB severity.
Scale % dead leaf area
controlled manually whenever necessary. Standard agro- 0 No incidence
nomic practices were followed as recommended. 1 1–5
3 6–12
5 13–25
2.4. Data Collection. Data were collected on grain yield per 7 26–50
plot, number of tillers per plant, number of panicles per 9 >50
plant, number of filled grains per panicle, days to 50%
flowering, plant height at maturity, thousand grain weight, 3. Results
presence of aroma (fragrance), disease score for leaf blast,
and bacterial leaf blight (BLB); grain length, grain width, and When comparing all locations per year, the effect of factors
grain shape (length/width ratio) all were based on In- was significant (P< 0.05) for six traits excluding grain yield
ternational Rice Research Institute’s Standard Evaluation in 2014. Significant difference was observed for all seven
System for rice (IRRI SES) [31]. Visual scores of leaf blast traits including grain yield in 2015 (Table 4). Genotype by
incidence and severity were recorded using the IRRI’s SES location interaction was significant for number of tillers,
scale of 0–9 based on percent diseased leaf area (Table 2). days to 50% flowering, days to maturity, and grain yield in
Visual scores of BLB incidence and severity were also 2014. In 2015, significant genotype by location interaction
recorded using IRRI SES scale of 0–9 based on percent dead was observed for plant height, days to 50% flowering, days
leaf area (Table 3). Based on the average disease score, ge- to maturity, thousand grain weight, and grain yield
notypes were categorized into resistant (0–3), moderately (Table 4).
resistant (4–6), and susceptible (7–9). To detect the presence )e mean yield (across locations) of hybrids ranged
of aroma, samples of decorticated rice grains were put into from 4.15 t/ha to 6.24 t/ha in 2014. )e highest yielding
an eppendorf tube. 2-Acetyl-1-pyrroline (AcPy), the main hybrid (INDAM 200-022) recorded a yield advantage of
component of aroma in rice, was vaporized by adding 10ml 12.43% over the best inbred check (AgraRice, 5.55 t/ha).
of 1.7% solution of potassium hydroxide (KOH) and capped )e yield of the hybrids was not statically different
for 10minutes. )e levels of expression of aroma were (P< 0.05) from the inbred checks in 2014 (Table 5). SWARNA
compared to those of Jasmine 85, a released aromatic variety 2 and PAC 832 yielded significantly higher (P< 0.05) than the
as control [31]. inbred checks in 2015 (Table 6).)emean yield of the hybrids
ranged from 7.91 t/ha to 9.57 t/ha in 2015.)e highest yielding
hybrid in 2015 (SWARNA 2) recorded amean yield advantage
2.5. Data Analysis. Analysis of variance (ANOVA) for grain of 20.8% over the best inbred check (AgraRice, 7.92 t/ha)
yield, yield components, and disease scores was carried (Table 6).
separately for each location using GenStat statistical package With the exception of INDAM 100-001 and ARGH 1503
(12th edition) [32]. Combined ANOVA across locations was which were taller, the test hybrids generally had similar
also conducted. Least significant difference (LSD 0.5) was heights as the inbred checks. )e test hybrids matured
used for mean comparisons and separation. Stability of hy- between 113 and 120 days. With the exception of S71680676,
brids and checks was assessed with GGE biplot analysis S72180002, and INDAM 200-022, all hybrids had a grain
performed in R statistical package (GGEBiplotGUI) as in [30]. length width ratio greater than three (L/W> 3.0) and were
4 International Journal of Agronomy
Table 4: Combined ANOVA mean squares for seven traits evaluated on hybrids and checks across locations in 2014 and 2015.
Source df aNT bPH c50% FL dDM ePP f1000Gwt gGyield
2014
Rep 2 8.82 155.56 27.23 6.74 4.75 7.12 11.95
Geno 9 42.82∗∗∗ 814.89∗∗ 186.49∗∗∗ 101.25∗∗∗ 36.80∗∗∗ 129.05∗∗∗ 3.19ns
Loc 2 47.170∗∗∗ 896.06∗∗ 4251.433∗∗∗ 34.411∗∗∗ 64.288∗∗∗ 37.979∗∗∗ 4.06ns
G∗ L 18 9.31∗∗∗ 35.89ns 23.17∗∗∗ 38.09∗∗∗ 6.20ns 4.47ns 3.88∗
Residual 58 3.91 36.59 7.89 2.76 4.22 5.48 1.92
Total 89
2015
Rep 2 8.41 57.26 1.83 0.42 0.42 0.35 0.66
Geno 8 23.55∗ 234.68∗∗∗ 126.22∗∗∗ 50.67∗∗∗ 23.65∗ 6.38∗∗∗ 3.34∗∗∗
Loc 2 341.82∗∗∗ 9813.27∗∗∗ 359.57∗∗∗ 1451.66∗∗∗ 20.62ns 67.60∗∗∗ 247.22∗∗∗
G∗ L 16 11.44ns 190.87∗∗∗ 15.22∗∗∗ 14.11∗∗ 7.38ns 6.38∗∗∗ 2.26∗∗∗
Residual 52 9.88 42.77 3.34 5.67 3.79 0.45 0.76
Total 80
∗,∗∗,∗∗∗Significant at P< 0.05, P< 0.01, and P< 0.001, respectively; df� degree of freedom, ns�not significant, anumber of tillers; bplant height; cdays to 50%
flowering; ddays to maturity; epanicles per plant; f1000 grain weight; ggrain yield.
Table 5: Yield (t/ha) of hybrids and checks across locations in 2014.
Variety Golinga Navrongo Nyankpala Mean across locations Yield advantage over AgraRice (%)
AgraRice 5.69 5.50 5.47 5.55
Jasmine 85 5.07 6.20 4.29 5.19 −6.5
GR-1 5.58 5.06 6.55 5.73 3.2
GR-2 5.60 5.63 4.43 5.22 −5.9
GR-3 5.61 6.76 5.98 6.12 10.2
INDAM 200-022 6.02 1.48∗ 6.45 6.24 12.4
INDAM 100-012 5.69 3.24 3.53 4.15 −25.2
INDAM 100-001 5.85 6.11 4.77 5.58 0.5
S71680676 6.48 5.66 5.55 5.90 6.2
S72180002 6.42 5.66 4.98 5.69 2.5
Mean 5.80 5.13 5.20
SD 0.41 1.59 0.98
LSD (0.05) ns ns ns
∗Destroyed by pest (excluded from mean calculation); ns�not significant; SD� standard deviation; LSD� least significant difference.
Table 6: Yield (t/ha) of hybrids and checks across locations in 2015.
Variety Golinga Nobewam Navrongo Mean across locations Yield advantage over AgraRice (%)
AgraRice 7.24 6.15 10.35 7.92
Jasmine 85 6.94 6.87 9.92 7.91 −0.2
ARGH 1501 8.03 6.28 13.18 9.16 15.7
ARGH 1502 8.05 6.08 13.24 9.12 15.2
ARGH 1503 7.44 6.35 13.65 9.15 15.5
PAC 801 7.27 6.70 11.04 8.33 5.2
PAC 832 8.76 6.28 12.72 9.25 16.8
S71680676 7.50 6.08 12.28 8.62 8.8
SWARNA 2 9.40 6.21 13.10 9.57 20.8
Mean 7.85 6.33 12.16
SD 0.81 0.26 1.38
LSD (0.05) 1.20 ns 1.89
ns�not significant; SD� standard deviation; LSD� least significant difference.
classified as slender. Blast and BLB incidence was confirmed detected in the inbred checks, none of the test hybrids was
by the presence of the disease symptoms on the inbred check found to be aromatic (Table 7).
(Jasmine 85) which is known to have some moderate re- )e first two axes (Axis 1 and Axis 2) obtained by
sistance. With the exception of GR-1, INDAM 200-022, and singular-value decomposition (SVD) of the centered data
ARGH 1501 which scored 5. 0, 5.0, and 4.5, respectively explained 95.63% of the total variation attributable to ge-
(moderately resistance), for bacterial leaf blight, the scores of notypes and genotype by environment interaction in 2014
the remaining hybrids to blast and bacterial leaf blight were (Figure 1). )at of 2015 was 98.2% (Figure 2). )e perpen-
similar to the inbred checks (resistance). Whilst aroma was dicular double-headed arrows indicated the mean genotype
International Journal of Agronomy 5
Table 7: Yield components, reaction to diseases, and grain quality attributes of hybrids and checks in 2014 and 2015.
Variety aNTP bPH (cm) cDM dNP eNFG f1000GT (g) gLB hBLB iGL (mm) jGW (mm) kL/W Aroma
2015
AgraRice 10.7 106.3 120 7.3 146.8 28.8 1.0 3.0 7.0 2.4 2.8 Present
Jasmine 85 13.6 99.8 116 9.5 125.3 27.8 1.0 3.0 7.1 2.3 3.1 Present
GR-1 10.1 92.2 113 7.3 64.0 28.2 1.0 5.0 7.1 2.3 3.1 Absent
GR-2 11.0 98.4 116 7.5 88.3 28.6 1.5 3.0 7.0 2.3 3.1 Absent
GR-3 9.0 105.5 114 6.4 148.0 31.9 1.0 3.0 7.6 2.8 2.6 Absent
S71680676 12.7 99.9 122 10.5 137.5 24.7 1.1 0.0 6.6 2.2 2.9 Absent
S72180002 10.9 104.1 115 7.7 146.3 26.2 1.0 3.0 7.2 2.1 3.4 Absent
INDAM 100-001 12.4 126.3 118 10.3 95.0 23.3 1.0 0.0 7.7 1.9 4.1 Absent
INDAM 100-012 11.3 109.1 120 9.7 116.0 24.7 1.3 1.0 8.0 1.8 4.2 Absent
INDAM 200-022 8.5 112.2 114 8.4 124.0 26.2 1.0 5.0 6.5 2.5 2.6 Absent
Mean 11.0 105.4 116.8 8.5 119.1 27.0 1.1 2.6 7.2 2.3 3.2 —
SD 1.6 9.3 3.0 1.4 28.5 2.5 0.2 1.8 0.5 0.3 0.6 —
LSD (0.05) 2.4 8.8 3 3.0 45.7 2.1 0.1 1.1 0.3 0.2 0.4 —
2015
AgraRice 11.2 122.8 120 9.2 123.7 26.5 1.0 0.5 7.0 2.3 3.0 Present
Jasmine 85 13.3 114.2 118 11.2 209.7 23.5 3.0 2.0 7.1 2.2 3.2 Present
ARGH 1501 18.4 107.5 115 16.2 238.7 22.5 2.0 4.5 6.5 2.0 3.3 Absent
ARGH 1502 15.2 121.7 120 12.3 236.0 22.5 1.5 0.0 7.1 2.1 3.4 Absent
ARGH 1503 18.0 132.2 116 12.9 305.0 20.5 1.5 3.0 6.2 2.2 2.9 Absent
PAC 801 15.7 122.2 116 14.0 118.1 19.0 1.5 2.0 7.2 2.1 3.4 Absent
PAC 832 15.6 120.9 120 11.5 198.7 26.5 1.0 0.8 7.2 2.3 3.2 Absent
S71680676 14.3 120.9 118 10.7 266.7 23.5 0.8 0.8 6.7 2.3 2.9 Absent
SWARNA 2 16.0 124.5 120 12.0 230.7 23.0 0.5 0.3 6.7 2.2 3.0 Absent
Mean 15.3 120.8 118.1 12.2 214.1 23.1 1.4 1.5 6.9 2.2 3.1 —
SD 2.2 6.8 2.0 2.0 61.3 2.4 0.7 1.5 0.6 0.1 0.2 —
LSD (0.05) 3.2 7.5 2.7 2.2 99.6 1.8 1.1 1.0 0.2 0.1 0.1 —
aAverage number of tiller per plant; baverage plant height; cdays to maturity; daverage number of panicles per plant; enumber of filled grains per panicle
(average); faverage thousand grain weight; gmean leaf blast score, IRRI SES (0–9); hmean bacterial leaf blight score, IRRI SES (0–9); igrain length (mm); jgrain
width (mm); kgrain length width ratio; SD� standard deviation; LSD� least significant difference.
score of the experiments. Performances of genotypes were hybrid in 2014 (INDAM 200-022) had a mean yield of
ranked in the direction indicated by the single-headed arrow 6.56 t/ha representing 12% yield advantage over AgraRice
(average tester coordinate) in the ascending order of themean (the best available inbred; 5.91 t/ha) across locations. )e
genotype. )us, GR-3 (G4) and SWARNA 2 (G9) were the 12% yield advantage was considered low compared to the
highest yielding hybrids in 2014 and 2015, respectively anticipated yield advantage of 20–30% and motivated the
(Figures 1 and 2). Stability of genotypes was ranked on the introduction of new set of hybrids in 2015. Four hybrids
basis of their projection from the average tester coordinate (ARGH 1501, ARGH 1503, PAC 801, and SWARNA 2)
(axis) on the average environment main effect.)e greater the with mean yield advantage range of 15–20.8% over
length of the projection of a genotype, the more unstable that AgraRice were identified in 2015. )is yield advantage is
genotype is.)us, GR-3 (G4) and S71680676 (G9) were stable within the range of what has been reported in Asia and
genotypes with yield above the mean in 2014, and those of some parts of Africa [12, 13]. Based on yield superiority,
2015 were ARGH 1501 (G2) and ARGH 1502 (G3) (Figures 1 these hybrids could serve as startups whiles exploiting the
and 2, respectively). SWARNA 2 (G7), PAC 832 (G9), and possibility of identifying higher yielding ones through
ARGH 1503 (G4) were the less stable genotypes with yield introduction and testing of more hybrids or developing
above the mean in 2015 (Figure 2). locally superior ones.
Heterosis is exhibited in grain yield, yield components,
4. Discussion and a range of agronomic, physiological, and biochemical
traits in plants [10]. Increased yield of rice hybrids has been
Hybrid rice varieties exploit the phenomenon of heterosis attributed to heterosis of the panicle number, spikelet
to break the yield ceiling of their inbred counterparts to number, and thousand grain weight to a lesser extent [12].
increase productivity per unit area [10, 11]. Although )e highest yielding hybrid (SWARNA 2) yielded signifi-
hybrid rice seed costs more than inbreds and cannot be cantly higher than AgraRice (7.89 t/ha) with a yield ad-
used for replanting, farmers prefer hybrids if the yield vantage of 20.8% in 2015. With respect to yield components,
advantage over the best available inbred is high [12]. the number of panicles per plant and number of filled grains
Generally, a yield advantage of 15–20% has been reported per panicle of SWARNA 2 were significantly higher than
for hybrid varieties over their inbred counterparts evalu- that of AgraRice. Although the thousand grain weight of
ated in similar conditions [12, 13]. )e highest yielding SWARNA 2 was lesser than AgraRice, its yield superiority
6 International Journal of Agronomy
2
2
G6
1 1 G4
G3G8 E3
G7
0 G10 G8 GG23
E1 GG19 E2 0 GE62
G5 G5G4 G1–1 G2
G7
–1
–2 G9
E1
–3 E3 –2
–2 –1 0 1 2 3 4 5 –1 0 1 2 3 4
Axis 1 69.82% Axis 1 85.24%
G1 = AgraRice G8 = Jasmine 85 G1 = AgraRice G7 = PAC 832
G2 = GR-1 G9 = S71680676 G2 = ARGH 1501 G8 = S71680676
G3 = GR-2 G10 = S72180002 G3 = ARGH 1502 G9 = SWARNA 2
G4 = GR-3 E1 = Golinga G4 = ARGH 1503 E1 = Golinga
G5 = INDAM 200-022 E2 = Navrongo G5 = Jasmine 85 E2 = Nobewam
G6 = INDAM 100-012 E3 = Nyankpala G6 = PAC 801 E3 = Navrongo
G7 = INDAM 100-001
Figure 2: Mean versus stability of grain yield for hybrids and
Figure 1: Mean versus stability of grain yield for hybrids and checks in 2015.
checks in 2014.
could be recommended for any of the defined locations as
might be accounted for by the number of panicles per plant these possess stability characteristics. Although SWARNA 2,
and number of filled grains per panicle. PAC 832, and ARGH 1503 had yields above the mean, they
Hybrids are generally reported to respond better to were less stable. )ese cultivars could be recommended for
higher dose of nitrogen [12, 33, 34]. )e local recommended specific locations. Stability across environments is an im-
fertilizer rate of 90 : 60 : 60 kg NPK/ha was used for the portant index of genotype performance, adaptation, and
evaluations. Since the realizable field heterosis will be a adoption by farmers since rice farmers in Ghana normally
major determinant for hybrid rice adoption by farmers, have fragmented lands and seasonal regimes. )e stability of
studying the response of these hybrids at higher doses of the hybrids, however, has limited interpretation since they
nitrogen (120 kg and 150 kg) is recommended. )e hybrids were tested in a limited number of environments. Significant
had a medium number of days to maturity like the checks G× L interaction for some agronomic traits such as plant
making them fit for cultivation in the tested ecologies. With height and days to flowering might be due to weather,
the exception of INDAM 100-001 and INDAM 100-012 particularly, temperature difference, at the test locations.
which were taller than the checks and are likely to be sus- Such slight differences are often encountered for those traits
ceptible to lodging, the test hybrids had similar heights as the even in the wet and dry seasons of same location. )ousand
checks which improve their chances of farmer adoption. (1000) grain weight is one of the known stable characters of
)e significant genotype by location (G× L) interaction rice varieties. Significant G× L interaction for this trait could
for grain yield indicates that there is fluctuation in the ranks also be due to differences in soil moisture content at the
of the hybrids and checks across the test locations. )us, one locations, especially, during the grain filling stage.
hybrid selected as the best in one location based on grain Susceptibility to pest and diseases is one of the main
yield might not be the best hybrid in another location. )is drawbacks of hybrid rice adoption [12]. Earlier study by El-
necessitated a thorough stability analysis to identify hybrids namaky and Demont [13] has indicated that hybrids from
with broad adaptation across the locations and those Asia are susceptible to African pest and diseases.)e hybrids
adapted to specific locations. )e test locations are really generally did not encounter difficulty with two (blast and
different and represent the Guinea Savanna, Sudan Savanna, BLB) of the three important rice diseases (blast, BLB, and
and the semideciduous rainforest agroecologies. Yields in RYMV). With the exception of a few hybrids which were
the irrigated ecology are also known to be higher than the particularly susceptible to blast and BLB at some locations,
rainfed lowland ecology. Breeders normally develop culti- the hybrids had appreciable levels of resistance to the two
vars that can adapt to a wide range of environments [24, 26]. biotic stresses. Although the hybrids were graded based on
Our mean versus stability GGE biplot results revealed average disease score across locations, some differential
promising hybrids that were stable across locations. For scores of same hybrid at different locations was observed.
example, GR-3, S71680676, ARGH 1501, and ARGH 1502 )is suggested differences in disease pressure at the test
Axis 2 25.81%
Axis 2 12.96%
International Journal of Agronomy 7
locations. )us, testing reaction of genotypes to diseases Conflicts of Interest
should not rely only on natural field infestation but be
supported with artificial (screen house) screening where a )ere are no conflicts of interest between authors and
quantified disease pressure could be inoculated. Level of partners who supported this work.
resistance to RYMV could not be ascertained since there was
no outbreak of the disease during the evaluation period. Acknowledgments
Artificial screening of promising hybrids to RYMV is rec-
ommended before the final release as varieties. Although Many thanks are due to the Alliance for a Green Revolution
insect pest is often not a major problem for farmers [1], one in Africa (AGRA) for funding part of this research through
of the test hybrids (INDAM 200-022) was totally destroyed the West Africa Centre for Crop Improvement (WACCI),
by an unidentified pest at Navrongo in 2014. )e damage University of Ghana. Many thanks are also due to Wienco
which basically involved defoliation of the plant and, in Ghana, Advanta Seeds Company, and the Agricultural
severe conditions, devouring the entire shoot was typical of Technology Transfer Project (ATTP) for providing the hy-
grasshopper and related insects damage. )is draws the brid seeds and additional funding.
attention of a possible specific preference of particular hy-
brid variety by local insects. References
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