FACULTY OF AGRICULTURE

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Performance of tropical maize hybrids under conditions of low and optimum levels of nitrogen fertilizer application – grain yield, biomass production and nitrogen accumulation
(2013) Abe, A.; Adetimirin, V. O.; Menkir, A.; Moose, S. P.; Olaniyan, A. B.
Nitrogen (N) is the most limiting mineral nutrient in the soils of the major maize producing areas of West and Cen¬tral Africa. Low soil N and sub-optimal application of N fertilizers lead to N deficiency and poor grain yield (GY) in maize. Maize varieties with improved grain yield under low soil N and increased performance under optimal N availability could be beneficial to low input agriculture. This study evaluated the performance of a selection of ex¬perimental and commercial hybrids under suboptimal and optimal N fertilizer applications. Significant differences were observed among the hybrids, as well as significant interactions between hybrid and N level for GY and other measured attributes, with the severity of variation increasing as the level of N decreases. Mean GY reductions across the years was 76.5% at no-N and 35.4% at low-N. Depending on N treatment, GY varied from 0.48 to 4.42 Mg ha-1, grain N content from 0.17 to 1.26 g plant-1, total N content at harvest from 0.33 to 2.00 g plant-1, above ground biomass at silking from 30.6 to 91.2 g plant-1 and at maturity from 39.9 to 191.1 g plant-1. Number of kernels was the GY component most severely reduced by N stress and had significant (p ≤ 0.001) positive correlation with GY at all N levels. Six hybrids (4001/4008, KU1409/4008, KU1409/9613, 4008/1808, 4058/Fun 47-4, and 1824/9432) which showed consistent above average grain yields under no-N, low-N, high-N and across N levels were found and their use could further be investigated.
A somatic embryogenesis-based system for the production of fluted pumpkin (telfairia occidentalis hook F.) planting materials
(The Society for In Vitro Biology, 2015) Awosika, D. O.; Uchendu, E.; Balogun, M. O.; Adetimirin, V. O.
Fluted pumpkin (Telfairia occidentalis Hook. f.) is traditionally propagated by seeds, which have low viability after pod harvest, low percentage germination, and poor root development and often germinate during storage. The competition between use of seeds for consumption and propagation causes scarcity of propagules, necessitating development of more efficient propagation systems. Efficient protocols were developed for the induction of somatic embryos (SEs) and conversion into plantlets using cotyledons from mature zygotic embryos. This study evaluated the effects of 2,4- dichlorophenoxyacetic acid (2,4-D) and kinetin (25 combinations) on the induction of SEs, and of indole-3-acetic acid (IAA), 2,4-D, and kinetin (7 combinations) on conversion of SEs into plantlets. Significantly more SEs (381.7; p<0.01) were obtained on medium with 0.5 mg l−1 2,4-D and 0.1 mg l−1 kinetin than from the other 24 treatments after 4 wk of cotyledon culture. All SEs were obtained through an intermediary callus. For the production of SE-derived plantlets, treatments with 0.01 mg l−1 IAA and 0.02 mg l−1 kinetin resulted in significantly more shoots and roots than other treatments (p<0.001 for each) and gave 100% conversion of SEs to plantlets. The mean numbers of roots and shoots on this treatment were 3.7 and 1.3, respectively, and the mean shoot length was 2.2 cm. The plantlets had broad leaves and good vigor, similar to the parent cultivar. Nearly all plantlets (98–100%) survived acclimatization. The production of SEs from cotyledons and the high rate of conversion into quality plants will allow development of a mass production system for Telfairia planting material to meet the increasing demand for this crop.
A somatic embryogenesis-based system for the production of fluted pumpkin (telfairia occidentalis hook F.) planting materials
(The Society for In Vitro Biology, 2015) Awosika, D. O.; Uchendu, E.; Balogun, M. O.; Adetimirin, V. O.
Fluted pumpkin (Telfairia occidentalis Hook. f.) is traditionally propagated by seeds, which have low viability after pod harvest, low percentage germination, and poor root development and often germinate during storage. The competition between use of seeds for consumption and propagation causes scarcity of propagules, necessitating development of more efficient propagation systems. Efficient protocols were developed for the induction of somatic embryos (SEs) and conversion into plantlets using cotyledons from mature zygotic embryos. This study evaluated the effects of 2,4- dichlorophenoxyacetic acid (2,4-D) and kinetin (25 combinations) on the induction of SEs, and of indole-3-acetic acid (IAA), 2,4-D, and kinetin (7 combinations) on conversion of SEs into plantlets. Significantly more SEs (381.7; p<0.01) were obtained on medium with 0.5 mg l−1 2,4-D and 0.1 mg l−1 kinetin than from the other 24 treatments after 4 wk of cotyledon culture. All SEs were obtained through an intermediary callus. For the production of SE-derived plantlets, treatments with 0.01 mg l−1 IAA and 0.02 mg l−1 kinetin resulted in significantly more shoots and roots than other treatments (p<0.001 for each) and gave 100% conversion of SEs to plantlets. The mean numbers of roots and shoots on this treatment were 3.7 and 1.3, respectively, and the mean shoot length was 2.2 cm. The plantlets had broad leaves and good vigor, similar to the parent cultivar. Nearly all plantlets (98–100%) survived acclimatization. The production of SEs from cotyledons and the high rate of conversion into quality plants will allow development of a mass production system for Telfairia planting material to meet the increasing demand for this crop.

FACULTY OF AGRICULTURE

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