Maize research at Institute for Agricultural Research, Samaru, Nigeria resulted in sustained growth in yields in the last two decades. Maize is grown throughout the country with guinea savanna as the most important ma...Maize research at Institute for Agricultural Research, Samaru, Nigeria resulted in sustained growth in yields in the last two decades. Maize is grown throughout the country with guinea savanna as the most important maize growing zone. In the last five years, four new open pollinating varieties developed in collaboration with the International Institute of Tropical Agriculture （IITA, Ibadan） had been released for production. Hybrid varieties are also marketed by seed companies. The research was focused on variety improvement, improved management practices, integrated pests and disease control, soil fertility management, on-farm testing of improved production packages and socio-economics of production as well as adoption studies. The recently released quality protein maize has improved the nutritional status of vulnerable groups. Drought tolerant maize for Africa research project has contributed to sustainable maize production, poverty reduction and food security in the continent.展开更多
Maize is one of the most important cereal crops in Sub-Saharan Africa and an important source of energy for humans. However, the difference in the dedifferentiation frequency of immature embryos among various genotype...Maize is one of the most important cereal crops in Sub-Saharan Africa and an important source of energy for humans. However, the difference in the dedifferentiation frequency of immature embryos among various genotypes indicates that callus induction and genetic transformation is dependent on the genotype. This phenomenon is an impediment in the fundamental process of improving tropical maize germplasm especially through genetic engineering. Here, five tropical maize （Zea mays L.） genotypes, CML 216, CML 144, A 04, E 04 and TL 21, were evaluated for callus induction on MS medium supplemented with the growth regulator dicamba. Embryogenic and non embryogenic callus induction was independent ofgenotype when young immature embryos, 12 days after pollination （DAP） were used for tissue culture in combination with dicamba. The optimal concentration of dicamba for induction ofembryogenic callus in all the genotypes was 3 mg/L, which was also the concentration at which non embryogenic callus formation was lowest. The frequency of embryogenic callus induction ranged from 35% to 79% among the five genotypes and somatic embryos regenerated R0 shoots that produced normal R1 progenies. This regeneration method is expected to facilitate the development of a more efficient genotype independent Agrobacterium- mediated transformation system for tropical inbred lines.展开更多
Although there are many earthquake relics preserved in the southeast segment of the Ganzi-Yushu Fault in the central Tibetan Plateau,the recurrence regularity of paleoearthquakes is not yet clear.This work studies pal...Although there are many earthquake relics preserved in the southeast segment of the Ganzi-Yushu Fault in the central Tibetan Plateau,the recurrence regularity of paleoearthquakes is not yet clear.This work studies paleoearthquakes on this fault segment since the Holocene through geomorphic investigation and trench excavation.The results show that sinistral dislocation of the T3/T2 terrace boundary is up to 80 m at the Cuoa Township.A 1.5 m-high fault scarp extends 3 km near the Renguo Township.A number of paleoearthquakes are exposed in trenches at two places,respectively.In combination with historical records,our work has identified 5 or 6 paleoearthquakes on this fault segment since last 5600 years.The occurrence times and recurrence intervals of these paleoearthquakes are estimated by 14C dating on strata in the trenches.Our analysis shows that these paleoearthquakes do not exhibit evident periodicity,but instead show a clustering characteristic.From 5600 a to present,seismicity of the southeastern segment of the Ganzi-Yushu Fault has two active periods and one quiet period,and the present-day time is just in the second active epoch.The recurrence intervals of each active epoch are different:1000-1300 a in the first one,534 a in the second one.展开更多
文摘Maize research at Institute for Agricultural Research, Samaru, Nigeria resulted in sustained growth in yields in the last two decades. Maize is grown throughout the country with guinea savanna as the most important maize growing zone. In the last five years, four new open pollinating varieties developed in collaboration with the International Institute of Tropical Agriculture （IITA, Ibadan） had been released for production. Hybrid varieties are also marketed by seed companies. The research was focused on variety improvement, improved management practices, integrated pests and disease control, soil fertility management, on-farm testing of improved production packages and socio-economics of production as well as adoption studies. The recently released quality protein maize has improved the nutritional status of vulnerable groups. Drought tolerant maize for Africa research project has contributed to sustainable maize production, poverty reduction and food security in the continent.
文摘Maize is one of the most important cereal crops in Sub-Saharan Africa and an important source of energy for humans. However, the difference in the dedifferentiation frequency of immature embryos among various genotypes indicates that callus induction and genetic transformation is dependent on the genotype. This phenomenon is an impediment in the fundamental process of improving tropical maize germplasm especially through genetic engineering. Here, five tropical maize （Zea mays L.） genotypes, CML 216, CML 144, A 04, E 04 and TL 21, were evaluated for callus induction on MS medium supplemented with the growth regulator dicamba. Embryogenic and non embryogenic callus induction was independent ofgenotype when young immature embryos, 12 days after pollination （DAP） were used for tissue culture in combination with dicamba. The optimal concentration of dicamba for induction ofembryogenic callus in all the genotypes was 3 mg/L, which was also the concentration at which non embryogenic callus formation was lowest. The frequency of embryogenic callus induction ranged from 35% to 79% among the five genotypes and somatic embryos regenerated R0 shoots that produced normal R1 progenies. This regeneration method is expected to facilitate the development of a more efficient genotype independent Agrobacterium- mediated transformation system for tropical inbred lines.
基金supported by the Yushu Earthquake Science Investigation of China Earthquake Administration
文摘Although there are many earthquake relics preserved in the southeast segment of the Ganzi-Yushu Fault in the central Tibetan Plateau,the recurrence regularity of paleoearthquakes is not yet clear.This work studies paleoearthquakes on this fault segment since the Holocene through geomorphic investigation and trench excavation.The results show that sinistral dislocation of the T3/T2 terrace boundary is up to 80 m at the Cuoa Township.A 1.5 m-high fault scarp extends 3 km near the Renguo Township.A number of paleoearthquakes are exposed in trenches at two places,respectively.In combination with historical records,our work has identified 5 or 6 paleoearthquakes on this fault segment since last 5600 years.The occurrence times and recurrence intervals of these paleoearthquakes are estimated by 14C dating on strata in the trenches.Our analysis shows that these paleoearthquakes do not exhibit evident periodicity,but instead show a clustering characteristic.From 5600 a to present,seismicity of the southeastern segment of the Ganzi-Yushu Fault has two active periods and one quiet period,and the present-day time is just in the second active epoch.The recurrence intervals of each active epoch are different:1000-1300 a in the first one,534 a in the second one.
