Four Seasons of Learning and Engaging Smallholder Farmers - icrisat

Evaluation for phosphorus-use efficiency
Greenhouse potted soil (a mixture of subsoil and acid-washed sand) experiment was conducted to
evaluate variation in phosphorus use and response efficiency. Nodulation generally varied among
genotypes and so was the response to phosphorus application. Nodulation was highest in dual purpose
lines such as IT98K-166-44 but response to phosphorus application was higher in IT89KD-288
than IT98K-166-44. There were highly significant (P≤0.001) genotype, phosphorus and genotype
phosphorus effects on the utilization of P for shoot development. The genotype IT89KD-288 was the
most efficient and IT99K-7-21-2-2 was the least under low phosphorus conditions. Among the early
maturing lines, IT03K-351-1 formed the largest nodular tissue under low phosphorus conditions and
depended least on higher soil available phosphorus for nodule formation and development. In the
other genotypes however, nodulation was relatively low under low phosphorus conditions but the
increase in nodule mass development in response to the high soil available phosphorus ranged from
83 to 515%. Genotypic differences in phosphorus utilization under both low and high phosphorus
conditions were not extensive (P ≤ 0.05) even though IT00K-1263 appeared to have performed better
under low phosphorus conditions than most genotypes within the early maturity group.
S qg of germplasm lines for drought tolerance
Over 1,200 cowpea accessions among the germplasm maintained at IITA were randomly selected
and screened for drought tolerance in the field. The screening was carried out during the dry season.
Drought stress was imposed by withdrawing irrigation at five weeks after sowing while none stressed
plots were irrigated until plants matured. Data were collected on number of days to flower, extent of
wilting, and number of days to maturity as well as mean seed weight and seed weight per plant (see
Figures 2 and 3). Most plants flowered and matured earlier when drought stressed. Drought stressed
plants also produced lower grain yield per plant. Many of the germplasm lines remained green even at
seven weeks of no irrigation. However, a few of these plants did not set flowers and therefore produced
no seeds but remained green and stunted.
About 190 accessions with enhanced drought tolerance have been identified from this screening
activity. These selected lines were further evaluated in pots placed in the screen house. Drought was
imposed on the potted plants from three weeks after sowing and those that survived for more than four
weeks thereafter were regarded as being most drought tolerant. Some of these lines were selected and
used in making crosses among them and between them and some farmer-preferred varieties.
Frequency
1000
900
800
700
600
500
400
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100
0
Non stressed
Stressed
36.9-45.8 45.9-54.8 54.9-63.8 63.9-72.8 72.9-81.8
No of days
Figure 5-6: Number of days to flowering
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Engaging Smallholder Farmers | Tropical Legumes II Project