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African Crop Science Journal
African Crop Science Society
ISSN: 1021-9730 EISSN: 2072-6589
Vol. 8, Num. 1, 2000, pp. 77-83
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African Crop Science Journal, Vol
African Crop Science Journal, Vol. 8. No. 1, pp. 77-83, 2000
PEARL MILLET GRAIN SIZE AND HARDNESS IN
RELATION TO RESISTANCE TO SITOPHILUS ORYZEA (L.) (COLEOPTERA:
CURCULIONIDAE)
K. Leuschner, E. S. Monyo1, E. Chinhema, E. Tembo and
D. Martin
Genetic Resources and Enhancement Program (GREP), International
Crops Research Institute for the Semi-Arid Tropics (ICRISAT)
1(corresponding author): SADC/ICRISAT, P O Box 776, Bulawayo,
Zimbabwe
(Received 1 September, 1998; accepted 12 November, 1999)
Code Number: CS00007
ABSTRACT
Fifty-seven varieties of pearl millet (Pennisetum glaucum (L.) R. Br.) were
evaluated for resistance to the rice weevil Sitophilus oryzea (L.) by using artificial
infestation. Kernels of each cultivar were separated into three grain sizes; small, medium and
large, to remove the effect of grain size from that of variety. Grain hardness was measured
using the sodium nitrate specific gravity floaters test. In general, larger and softer grains
supported more weevils. However, there seems to be a good spread of variability for weevil
progeny production within the large grain fraction, suggesting the possibility of selecting for
resistance among large grains. Most of the soft grain types had floury endosperm, but no
relationship was found between grain size and endosperm type. This suggests that floury
and/or vitreous endosperm is not influenced by size, and that it may be possible to develop
varieties with a combination of large grain, vitreous endosperm, and weevil resistance.
Irrespective of grain size, SDMV 90016, Nandi Code 24, TSPM 91018, and SDMV 89001
were resistant compared to the farmers local variety.
Key Words: Grain size and hardness, Pennisetum glaucum, rice weevil
RÉSUMÉ
Cinquante-sept variétés de mil, (Pennisetum glaucum (L.)
R. Br.) ont été évaluées pour leur résistance contre le
charançon du riz Sitophilus oryzea (L.) à travers une infestation
artificielle. Les graines de chaque cultivar ont été séparées en
trois groupes en fonction de leurs grosseurs - petites, moyennes et grosses - pour
différencier leffet de la grosseur de celle de la variété. La
dureté des graines a été mesurée en utilisant le test de grains
flottants de la gravité spécifique du nitrate de sodium. En
général, les graines les plus grosses et les plus tendres supportaient mieux les
charançons. Mais, il semblait y avoir une large gamme de variabilité pour la
production de descendances de charançons dans la fraction des grosses graines, ce qui
suggère la possibilité de sélectionner pour la résistance parmi
les grosses graines. La plupart des types de graines tendres avaient une endosperme
farineuse, mais il navait pas été trouvé de relations entre la taille de
la graine et le type dendosperme. Ceci suggère que lendosperme farineuse et/ou
vitreuse nest pas influencée par la taille et quil serait possible de
développer des variétés ayant une combinaison de grosses graines,
dendosperme vitreuse et de résistance aux charançons. Pour toutes les
tailles de graines, SDMV 90016, Nandi Code 24, TSPM 91018 et SDMV 89001 se sont
montrées résistantes par rapport à la variété locale
paysanne.
Mots Clés: taille et dureté de la graine, Pennisetum
glaucum, charançon du riz
INTRODUCTION
Pearl millet (Pennisetum glaucum (L.) R. Br.) is a major food crop in the
semi-arid areas of Africa. The crop is grown on 3.6 m ha in the Southern and Eastern Africa
Region (UNFAO, 1995), mainly in Sudan, Namibia, Tanzania, Zimbabwe, and Eritrea.
After harvest, pearl millet grain is stored in traditional granaries, usually without
insecticides application for protection against storage pests. The major storage pests are the
angoumois grain moth Sitotroga cerealella (Oliver) and the rice weevil Sitophilus
oryzae (L.) (Hill, 1987). No data on storage losses are available specifically for pearl
millet. Only recently did farmers in Namibia complain about poor storability of Okashana-1,
a newly released pearl millet cultivar with large grain (ICRISAT, 1995).
Kernel hardness and size are reported to be the main grain characteristics contributing to
grain weevil resistance in sorghum and small grains like pearl millet (Doggett, 1957; Davey,
1965; Seifelnasr and Mills, 1985; McFarlane et al., 1995). Grain size in particular
affects resistance to Sitophilus spp. Most information on these two resistance traits is
related to research on sorghum. However, Seifelnasr and Mills (1985) found a high
correlation (r=-0.648*) between kernel size and S. oryzea infestation in pearl millet;
smaller kernels were attacked more often. Unlike S. cerealella, which can feed on
several grains during the larval stage, each oryzea larva feeds and develops within a
single grain (Russel, 1961). This may explain the relationship with grain size. Farmers
perhaps did not complain about weevil damage because grains of traditional pearl millet
landraces often have hard endosperm and are generally too small to sustain the development
of weevil larva.
The pearl millet breeding research programme of ICRISAT (International Crops
Research Institute for the Semi-Arid Tropics) in Southern and Eastern Africa focuses on
developing large-grained cultivars that mature early (85-100 days), produce high yields, and
have resistance to storage insect pests. The objective of the study reported here was to screen
breeding lines developed by ICRISAT for resistance to S. oryzea and to assess the
relationship between grain size, hardness, and number of weevil progeny produced.
MATERIALS AND METHODS
Adult rice weevils were obtained from a laboratory culture maintained at the
ICRISAT station in Matopos, Zimbabwe. The culture originated from poorly stored pearl
millet harvested in 1994. Insects were reared for one generation at 27°C and 70% relative
humidity (RH) on kernels of a susceptible sorghum cultivar "Red Swazi".
Kernels of 57 pearl millet varieties were evaluated for resistance to the rice weevil. Of
these varieties, 26 are at the on-farm testing stage and 31 in advanced regional cooperative
trials with national programmes. The screening was part of an effort to ensure that no highly
susceptible varieties were released for cultivation. None of these varieties had previously
been screened for kernel resistance to S. oryzea; most of them were developed for
large grain size, a trait highly preferred by farmers in the region. Grain from each line was
separated into 3 size classes, 1.40-1.99 mm, 2.00-2.35 mm and >2.36 mm using
Endecott sieves of appropriate sizes (Endecotts Ltd.). Twenty grams of grain from each line
and grain-size class (replicated 3 times) were placed in plastic jars (5 cm diameter x 5 cm
tall) and infested with 30 unsexed 10-day-old weevil adults. Weevils were allowed to lay
eggs for 7 days and then removed. No susceptible or resistant controls were used because
none had been identified previously. The average grain moisture content for all lines was
13.5 ± 1%. Infested grain was maintained at 27°C and 70% RH. Weevil progeny (emerging
adults) produced were counted beginning 27 days after infestation and continuing at 2-days
intervals for 20 days.
Grain hardness was determined using the floater test developed by Hallgren and Murthy
(1983) for sorghum. For each variety, 100 kernels of each size class (replicated 3 times) were
placed in a solution of sodium nitrate with a specific gravity of 1.315 g mL-1.
The percentage of kernels that floated to the surface was used as a measure of grain hardness
("floaters" have lower density and softer endosperm). Hardness was also
determined visually by bisecting 10 kernels from each sample and recording the proportion
of soft floury endosperm in each kernel. For each trial, data were recorded on number of
weevil progeny, % floaters, and proportion of floury endosperm. The data were subjected to
analysis of variance and any effects that were more than three times the standard error of the
mean declared significant. The relationship between grain size classes and each of these
three parameters was also statistically analysed.
RESULTS
Significant differences in the number of emerging weevils were found among the
pearl millet varieties (Tables 1 and 2). No controls were used in these trials. Therefore, the
resistance/susceptibility of a variety (or size class within a variety) was judged by comparison
with the corresponding values for the farmers local and the trial mean. This resulted in a
somewhat arbitrary classification of varietal resistance, but was the only possible method
given the lack of data on weevil resistance in pearl millet.
TABLE 1. Mean numbers of grain weevil progenies
produced, percent floaters and proportion floury endosperm, in kernels of pearl millet
varieties under cooperative regional advanced variety trial in relation to three different grain
sizes
Entry no. |
Cultivar name |
1.40 - 1.99 mm |
2.00 - 2.35 mm |
>2.36 mm |
Weevil progeny |
Floaters (%) |
Floury endosperm |
Entry no. |
Weevil progeny |
Floaters (%) |
Floury endosperm |
Entry no. |
Weevil progeny |
Floaters (%) |
Floury endosperm |
5 |
SDMV 93003 |
170 |
46 |
0.27 |
18 |
221 |
58 |
0.44 |
9 |
283 |
54 |
0.37 |
16 |
SDMV 89002 |
153 |
36 |
0.34 |
5 |
188 |
46 |
0.29 |
26 |
257 |
52 |
0.48 |
13 |
ICMP 90104 |
142 |
52 |
0.54 |
20 |
184 |
51 |
0.47 |
19 |
240 |
55 |
0.41 |
27 |
SDMV 89005 |
141 |
24 |
0.27 |
13 |
178 |
43 |
0.59 |
16 |
237 |
44 |
0.36 |
26 |
SDMV 92026 |
135 |
38 |
0.45 |
9 |
177 |
47 |
0.33 |
20 |
229 |
68 |
0.51 |
30 |
ICMV 84425 |
132 |
37 |
0.58 |
8 |
175 |
54 |
0.37 |
17 |
218 |
67 |
0.40 |
19 |
SDMV 91003 |
124 |
51 |
0.40 |
2 |
171 |
43 |
0.32 |
12 |
213 |
37 |
0.32 |
20 |
SDMV 91121 |
116 |
51 |
0.40 |
14 |
170 |
30 |
0.36 |
2 |
208 |
48 |
0.34 |
29 |
ICMV-F 86415 |
115 |
33 |
0.41 |
15 |
168 |
35 |
0.37 |
18 |
204 |
68 |
0.47 |
14 |
Farmers Local |
110 |
24 |
0.38 |
16 |
165 |
40 |
0.34 |
23 |
194 |
45 |
0.34 |
15 |
RLBIC 912 |
108 |
35 |
0.35 |
11 |
163 |
49 |
0.33 |
31 |
193 |
68 |
0.35 |
2 |
SDMV 89008 |
103 |
42 |
0.30 |
22 |
161 |
24 |
0.31 |
8 |
189 |
60 |
0.46 |
21 |
SDMV 90004 |
99 |
24 |
0.32 |
25 |
157 |
42 |
0.41 |
21 |
184 |
38 |
0.37 |
22 |
SDMV 93023 |
98 |
24 |
0.29 |
10 |
157 |
33 |
0.24 |
11 |
184 |
53 |
0.36 |
3 |
SDMV 90031 |
95 |
31 |
0.37 |
24 |
156 |
42 |
0.40 |
15 |
181 |
48 |
0.38 |
11 |
SDMV 91018 |
85 |
48 |
0.32 |
4 |
148 |
47 |
0.24 |
24 |
181 |
44 |
0.41 |
9 |
SDMV 89007 |
83 |
40 |
0.31 |
30 |
147 |
38 |
0.59 |
14 |
178 |
52 |
0.38 |
12 |
PMV-2 |
83 |
24 |
0.29 |
6 |
146 |
53 |
0.26 |
10 |
175 |
53 |
0.30 |
7 |
SDMV 90027 |
78 |
42 |
0.35 |
19 |
141 |
51 |
0.40 |
27 |
173 |
42 |
0.30 |
4 |
SDMV 87001 |
70 |
32 |
0.30 |
26 |
141 |
36 |
0.46 |
29 |
172 |
50 |
0.40 |
6 |
SDMV 93002 |
62 |
51 |
0.26 |
29 |
141 |
42 |
0.43 |
13 |
171 |
56 |
0.64 |
23 |
SDMV 93021 |
45 |
23 |
0.29 |
7 |
140 |
45 |
0.39 |
25 |
165 |
50 |
0.36 |
1 |
SDMV 90016 |
44 |
44 |
0.49 |
31 |
139 |
48 |
0.34 |
28 |
165 |
67 |
0.40 |
10 |
SDMV 91004 |
40 |
31 |
0.22 |
28 |
133 |
52 |
0.39 |
7 |
160 |
55 |
0.38 |
18 |
SDMV 92040 |
* |
55 |
0.49 |
21 |
130 |
34 |
0.34 |
22 |
155 |
32 |
0.35 |
25 |
SDMV 93032 |
* |
42 |
0.48 |
17 |
130 |
45 |
0.33 |
3 |
153 |
53 |
0.38 |
24 |
SDMV 89001 |
* |
41 |
0.38 |
27 |
123 |
37 |
0.28 |
5 |
149 |
55 |
0.31 |
28 |
ICMV 87901 |
* |
62 |
0.36 |
23 |
122 |
29 |
0.33 |
30 |
141 |
38 |
0.59 |
17 |
SDMV 93005 |
* |
33 |
0.26 |
3 |
116 |
49 |
0.38 |
4 |
131 |
57 |
0.30 |
8 |
SDMV 91005 |
* |
53 |
0.37 |
1 |
102 |
43 |
0.51 |
6 |
123 |
53 |
0.30 |
31 |
ICMV 221 |
* |
48 |
0.33 |
12 |
* |
24 |
0.31 |
1 |
115 |
60 |
0.53 |
S.E.± Mean |
12.85 |
2.98 |
0.04 |
- |
17.24 |
2.62 |
0.05 |
- |
14.16 |
2.40 |
0.04 |
Mean |
101.29 |
39.26 |
0.36 |
- |
153.02 |
42.28 |
0.37 |
- |
184.54 |
52.29 |
0.39 |
CV% |
22.0 |
13.1 |
36.8 |
- |
19.5 |
10.7 |
40.5 |
- |
13.3 |
8.0 |
32.1 |
*Weevil progeny test not done
TABLE 2. Mean numbers of grain weevil progeny
produced, percent floaters and proportion flour endosperm, in kernels of pearl millet
varieties under on-farm trials in relation to three different grain sizes
Entry no. |
Cultivar name |
1.40 - 1.99 mm |
2.00 - 2.35 mm |
>2.36 mm |
Weevil progeny |
Floaters (%) |
Floury endosperm |
Entry no. |
Weevil progeny |
Floaters (%) |
Floury endosperm |
Entry no. |
Weevil progeny |
Floaters (%) |
Floury endosperm |
24 |
ICMH 356 |
185 |
66 |
0.54 |
16 |
334 |
77 |
0.65 |
16 |
350 |
86 |
0.76 |
20 |
SDMV 90031 |
158 |
45 |
0.53 |
19 |
280 |
40 |
0.41 |
19 |
291 |
43 |
0.56 |
19 |
NANDI CODE 21 |
148 |
39 |
0.40 |
11 |
242 |
42 |
0.60 |
11 |
262 |
51 |
0.63 |
9 |
SDMH 92018 |
136 |
38 |
0.59 |
22 |
220 |
81 |
0.58 |
15 |
248 |
70 |
0.73 |
15 |
SDMV 89002 |
132 |
52 |
0.53 |
15 |
204 |
53 |
0.62 |
22 |
247 |
92 |
0.54 |
17 |
SDMH 91015 |
130 |
76 |
0.65 |
1 |
204 |
46 |
0.56 |
24 |
245 |
93 |
0.61 |
11 |
ICMV-F 86415 |
124 |
43 |
0.49 |
26 |
203 |
20 |
0.49 |
4 |
243 |
88 |
0.76 |
8 |
SDMH 92025 |
111 |
94 |
0.76 |
8 |
201 |
97 |
0.55 |
13 |
242 |
44 |
0.56 |
6 |
SDMV 91018 |
109 |
40 |
0.65 |
24 |
198 |
76 |
0.57 |
23 |
240 |
24 |
0.43 |
21 |
SDMV 89008 |
106 |
66 |
0.50 |
21 |
197 |
66 |
0.46 |
8 |
240 |
96 |
0.62 |
12 |
SDMV 90016 |
103 |
37 |
0.57 |
10 |
175 |
43 |
0.55 |
10 |
239 |
69 |
0.58 |
1 |
HHB 67 |
101 |
45 |
0.44 |
9 |
175 |
50 |
0.61 |
26 |
239 |
24 |
0.57 |
2 |
SDMV 87001 |
98 |
23 |
0.53 |
17 |
170 |
77 |
0.65 |
18 |
228 |
30 |
0.61 |
23 |
Farmers local |
95 |
22 |
0.46 |
23 |
168 |
20 |
0.44 |
12 |
227 |
59 |
0.66 |
13 |
PMV-2 |
93 |
23 |
0.47 |
4 |
162 |
81 |
0.62 |
9 |
227 |
54 |
0.63 |
25 |
SDMV 89007 |
86 |
33 |
0.52 |
20 |
160 |
51 |
0.49 |
17 |
223 |
90 |
0.64 |
5 |
PMV-1 |
77 |
63 |
0.44 |
25 |
152 |
32 |
0.48 |
1 |
222 |
46 |
0.58 |
26 |
SDMV 89005 |
75 |
20 |
0.48 |
18 |
152 |
22 |
0.50 |
21 |
218 |
79 |
0.50 |
4 |
NANDI CODE 5 |
72 |
76 |
0.71 |
13 |
149 |
24 |
0.53 |
6 |
217 |
48 |
0.60 |
18 |
ICMV 88908 |
68 |
27 |
0.59 |
2 |
147 |
21 |
0.56 |
20 |
205 |
55 |
0.45 |
14 |
SDMV 89001 |
61 |
31 |
0.59 |
6 |
134 |
45 |
0.51 |
25 |
203 |
38 |
0.57 |
3 |
NANDI CODE 24 |
60 |
57 |
0.50 |
12 |
126 |
42 |
0.61 |
2 |
192 |
23 |
0.54 |
7 |
TSPM 91018 |
55 |
35 |
0.52 |
3 |
126 |
56 |
0.65 |
3 |
173 |
57 |
0.65 |
10 |
SDMV 90004 |
48 |
38 |
0.52 |
14 |
113 |
29 |
0.50 |
14 |
155 |
33 |
0.61 |
16 |
NANDI CODE 1 |
* |
70 |
0.70 |
5 |
111 |
64 |
0.59 |
5 |
140 |
65 |
0.46 |
22 |
NANDI CODE 3 |
* |
69 |
0.54 |
7 |
100 |
37 |
0.49 |
7 |
123 |
41 |
0.55 |
S.E.± Mean |
11.001 |
1.99 |
0.04 |
- |
11.27 |
1.96 |
0.04 |
- |
14.62 |
1.67 |
0.04 |
Mean |
101.35 |
47.27 |
0.55 |
- |
176.99 |
49.65 |
0.55 |
- |
224.59 |
57.64 |
0.59 |
CV% |
18.8 |
7.3 |
22.4 |
- |
11.0 |
6.9 |
23.9 |
- |
11.3 |
5.0 |
19.2 |
*Weevil progeny test not done
Tables 1 and 2 show the number of weevil progenies produced, percent floaters and
proportion floury endosperm in each size class in each of the 57 varieties tested. The 31
varieties in regional trials are shown in Table 1, and the 26 varieties under on-farm trials are
shown in Table 2. Within each variety, there were significant differences between size
classes for each of the three parameters. The trial means for the three size fractions (small,
medium and large) in the advanced regional trial was respectively 101.29, 153.02 and
184.54, whereas the farmers local had 110, 170 and 178 weevil progenies for the same
fractions. Similarly for the varieties under on-farm trials, the trial mean for the three size
fractions was 101.35, 176.99 and 224.59 whereas the farmers local had 95, 168 and 240
weevil progenies.
Among varieties in the advanced regional trial in the small grain size class
(1.40-1.99mm), 5 varieties had £
71.4 emerging weevil progenies, a number significantly fewer than the trial mean
and the farmers local. Two varieties in the medium grain size class and three in the large
grain size class were significantly superior to both the trial mean and the farmers local
(<118.3 and 135.5 emerging weevil progenies, respectively). Only one variety
SDMV 90016 showed weevil resistance across all three size classes (average across size
fractions weevil progenies was 87), whereas two varieties; SDMV 87001 and SDMV 93002
exhibited resistance in the small and large size fractions (average across size fractions weevil
progenies 100 and 92.5, respectively).
Among the varieties under on-farm trials in the small grain size class (1.40-1.99 mm), 5
varieties had significantly fewer emerging weevil progenies (£
68) than the trial mean. Six varieties in the medium grain size class and four varieties in the
large grain size class (£
143 for the medium and £
180.74 weevils for the large fraction) were significantly superior to the trial mean. Overall,
three varieties, namely, Nandi code 24, TSPM 91018 and SDMV 89001, showed weevil
resistance across all three size classes and were superior to both the trial mean and the
farmers local check.
Fewer total weevils emerged from the smallest sized grain fraction (1.40-1.99 mm) than
from the medium (2.00-2.35 mm) and large grain size fractions (³
2.36 mm) (Tables 1 and 2). Larger grains generally supported more weevils. This indicates
a relationship between kernel size and resistance/susceptibility with sufficient variability for
weevil progeny production among the large grain fraction as determined by the standard error
of the mean.
With regard to grain hardness as measured by the floater test, significant differences for
hardness were observed for all size fractions (Tables 1 and 2). This was also true in the case
of distribution of floury and non floury endosperm fractions. Larger numbers of weevil
progenies were distributed among genotypes that had a higher proportion of floaters (or soft
endosperm). In general hybrids tended to have a higher proportion of floaters than
open-pollinated varieties and also tended to support more weevil progenies. This is reflected
in the higher proportion of weevil progenies among the medium and large size fractions in
Table 2. There were no hybrids entered in the collaborative advanced trials (Table 1).
No relationship was found between grain size and endosperm type or grain size and
hardness (Table 3). Significant positive relationships were found between weevil progeny
number and grain size (r=0.743**), grain hardness (r=0.360**), and proportion of floury
endosperm (r=0.297**). It was also observed that both large and soft grains supported more
weevils, and grain hardness was influenced by endosperm type as shown by the positive
relationship (r=0.497**) between grain hardness (% floaters) and endosperm type (% floury
endosperm).
TABLE 3. Correlation matrix for weevil progeny, percent
floaters, proportion floury endosperm and grain size distribution in the pearl millet varieties
under study
Variables |
Grain size |
Weevil progeny |
Floaters |
Weevil progeny |
0.743** |
0.360** |
- |
Floaters |
0.193 |
- |
- |
Floury endosperm |
0.221 |
0.297** |
0.497** |
** Significant at <0.01 probability level
DISCUSSION
Storage pest problems in pearl millet in the region became more important with the
release of improved varieties with higher yields and larger grains (ICRISAT, 1995). The
increase in yields implied a larger harvest, and thus more time in storage than was earlier the
case with local landrace varieties. The larger grain size also provided a more favourable
environment for grain weevil larvae to feed and develop (Russel, 1961). The fact that some
varieties were resistant/susceptible across all three size fractions implies that scope exists for
improving grain size without necessarily increasing susceptibility to the grain weevil. Most
of the genotypes with a low percentage of floaters produced significantly fewer weevil
progeny. This implies that grain hardness is a possible component of resistance, as
previously suggested by Seifernasr and Mills (1995) for pearl millet and Doggett (1957) for
sorghum.
Most of the soft grain types had floury endosperm which in turn supported more weevils.
However, the fact that grain size was not related to endosperm type implies that one can
combine large kernels with vitreous endosperm. Vitreous endosperm, which is positively
associated with grain hardness, is a trait that can easily be selected for in a breeding
programme. We also noted that some varieties (SDMV 90016, Nandi Code 24, and PMV-1)
produced relatively few weevil progenies and could thus be classified as resistant, even
though they had a large percentage of floaters and a high proportion of floury endosperm.
This suggests that other mechanisms of resistance are also in operation.
Pearl millet is grown largely by resource poor farmers and almost the entire crop is
processed manually for food. Because small-seeded varieties take a long time to process into
food, farmers in the region prefer large-seeded varieties, and in fact demand that this trait be
incorporated into new improved varieties (Chintu et al., 1996; Ipinge et al.,
1996; Letayo et al., 1996). Soft endosperm grains are also similarly difficult to
process because of milling yield losses. The findings that grain size is not related to
endosperm type, and irrespective of grain size, some varieties are resistant to weevil
infestation, imply that it is possible to breed varieties with the combination of large grain
size, hard grains, and weevil resistance. The existence of a good spread of variability for
weevil progeny production among the large-grain fraction of the varieties further reinforces
this potential.
REFERENCES
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millet varieties in Malawi for farmer preferences, grain yield and food quality traits. In:
Drought-tolerant crops of southern Africa: Proceedings of the SADC/ICRISAT Regional
Sorghum and Pearl Millet Workshop, 25-29 July 1994, Gaborone, Botswana. Leuschner,
K. and Manthe, C. S. (Eds.), pp. 27-33. Patancheru 502 324, Andhra Pradesh, India:
International Crops Research Institute for the Semi-Arid Tropics.
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©2000, African Crop Science Society
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