Combining ability of maize inbred lines containing genes from Zea diploperennis for resistance to Striga hermonthica (Del.) Benth

Maize ( Zea mays ) is a staple food crop in sub-Saharan Africa, but its production is threatened by Striga hermonthica (Del.) Benth. Transfer of resistance genes from wild relatives may increase resistance to S. hermonthica in tropical maize. The objective of this study was to determine the combining ability of resistance to S. hermonthica among lines containing Zea diploperennis and tropical germplasm. Forty-five diallel crosses of 10 inbred lines were evaluated in an alpha-lattice design with and without artificial Striga infestation at two locations each in the Republic of Benin and Nigeria for 3 years. Results of analyses showed that only general combining ability (GCA) mean square was significant (P = 0.01) for number of emerged Striga plants (NESPP), while both GCA and specific combining ability (SCA) mean squares were significant for host damage score (HDS) and grain yield under Striga infestation. The ratio of GCA to SCA mean squares for the three traits varied from 3.5 to 57.5. Although GCA × environment interaction was significant for the three traits, two inbred lines containing Z. diploperennis (ZD 551) and tropical (TZL TC 87) germplasm had negative and significant GCA effects for NESPP and HDS and positive GCA effects for grain yield under Striga infestation in the two countries. Correlation between NESPP and HDS was strong and significant ( r  = 0.87, P = 0.01). Our results highlight the importance of harnessing useful genes from wild relatives to improve resistance to S. hermonthica in adapted maize germplasm.     

Association of Vertical Root-Pulling Resistance with Root Lodging and Grain Yield in Selected S1 Maize Lines Derived from a Tropical Low-Nitrogen Population

Root lodging and poor soil fertility are major constraints to maize production in the Guinea savannah of West Africa. Vertical root‐pulling resistance is an indicator of the rooting characteristics of maize cultivars and could be used to select cultivars which have higher resistance to root lodging, take up nitrogen efficiently and have high yield. Twenty maize breeding lines were evaluated in the southern Guinea savannah of Nigeria for vertical root‐pulling resistance, yield and root lodging in the 2000 and 2001 cropping seasons. There were significant differences amongst the breeding lines for all the characteristics measured. Vertical root‐pulling resistance correlated positively with grain yield (r = 0.71, P < 0.01). There was a moderate negative correlation between vertical root‐pulling resistance and root lodging (r = ?0.46, P < 0.05). This suggested that selecting for high root‐pulling resistance will improve grain yield and reduce root lodging. There was no significant association between root lodging and grain yield (r = ?0.14, P < 0.22). This was attributed to two factors; weak root systems and high cob weight, both of which caused significant lodging.     

Risk efficient juvenile haddock production systems: An ex‐ante recursive stochastic approach

Abstract

The risk efficient live feed system for juvenile haddock production is derived through recursive ex‐ante stochastic cost estimation. Four alternative feeding technologies are simulated to capture the economic costs associated with live feed and juvenile production and scale economies are investigated by simulating three production levels. Using Monte Carlo simulation techniques, multivariate stochastic cost functions are derived in a time‐dependent recursive production model. With the current technologies and price levels, land‐based juvenile haddock production is viable. The marginal impact, in terms of cost‐savings, to additional research on optimal feeding periods will be minimal. On the other hand, the high opportunity cost of capital used in aquaculture production, due to numerous perceived risk premia, may pose a more immediate constraint for capital formation and industry development.     

N-use efficiency of single, double and synthetic maize lines grown at four N levels in three ecological zones of West Africa

Efficiencies in uptake and use of N by maize cultivars have been widely studied, but little has been done on this subject in West Africa. Six single-cross hybrids, three double-cross hybrids and a synthetic line were grown at different N levels (0–210 kg N ha⁻¹) in three ecological zones of West Africa. The maize cultivars differed widely in grain yield and N-accumulation parameters. Most cultivars absorbed similar amounts of N ranging from 2.04 g plant⁻¹ to 2.60 g plant⁻¹, but produced different grain yields, with those that accumulated more N after silking tending to have higher grain yield. Grain yields in the forest zone were lower than those in two Savanna regions. Differences were also observed for N-uptake (total N-uptake per unit N supplied to the soil), N-utilization (grain produced per unit N absorbed from the soil) and N-use efficiency (NUE) (grain produced per unit N supplied to the soil). Cultivars varied in their response to change in available soil N. The hybrids were more efficient in N-use and its component traits than the synthetic cultivar. Hybrid 1368 × KU1414-SR yielded the most grain as well as exhibiting superior traits for N-uptake and N-use efficiency.     

Interactions Between Fusarium verticillioides, Aspergillus flavus, and Insect Infestation in Four Maize Genotypes in Lowland Africa

ABSTRACT An experiment was designed to compare cycles of selection of four maize genotypes for ear- and grain-quality characteristics, interactions with Aspergillus flavus and Fusarium verticillioides infection, and insect ear infestation in two seasons. Mean infection levels by A. flavus and F. verticillioides were significantly higher in inoculated rows than in the controls. The F. verticillioides-inoculated rows had significantly more coleopteran beetles and lepidopteran borers per ear than the controls and A. flavus-inoculated rows. Genotypes and cycles of selection within genotype were not different with respect to number of insects or percent fungal incidence in the ear, but they were different for husk extension, field weight, 100-grain weight, and grain density. Inoculation with either fungus resulted in significantly higher percentage of floaters (i.e., loss of grain density) and lower grain weight than the controls. Aflatoxin (B1 and B2) in A. flavus-inoculated rows averaged 327 ppb in the first season and 589 ppb in the second (dryer) season. Fumonisin levels in F. verticillioides-inoculated rows did not differ between seasons, with an average of 6.2 ppm across seasons. In the noninoculated control rows, fumonisin was significantly higher in the first (5.3 ppm) than in the second (3.1 ppm) season. For all genotypes, husk extension and yield parameters decreased in the fungal-inoculated treatments. General ear-rot scoring was significantly correlated with incidence of F. verticillioides in kernels and grain-weight loss but not with A. flavus in the grain.     

Prevention of allogeneic bone marrow graft rejection by H-2 transgene in donor mice

Rejection of bone marrow grafts in irradiated mice is mediated by natural killer (NK) cells and is controlled by genes linked to the major histocompatibility complex (MHC). It has, however, not been possible to identify the genes or their products. An MHC class I (Dd) transgene introduced in C57BL donors prevented the rejection of their bone marrow by NK cells in irradiated allogeneic and F1 hybrid mice expressing the Dd gene. Conversely, H-2Dd transgenic C57BL recipients acquired the ability to reject bone marrow from C57BL donors but not from H-2Dd transgenic C57BL donors. These results provide formal evidence that NK cells are part of a system capable of rejecting cells because they lack normal genes of the host type, in contrast to T cells, which recognize cells that contain abnormal or novel sequences of non-host type.     

Direct prediction of site-specific lime requirement of arable fields using the base neutralizing capacity and a multi-sensor platform for on-the-go soil mapping

Precision Agriculture - Liming agricultural fields is necessary for counteracting soil acidity and is one of the oldest operations in soil fertility management. However, the best management...