Targeted free energy perturbation

A generalization of the free energy perturbation identity is derived, and a computational strategy based on this result is presented. A simple example illustrates the efficiency gains that can be achieved with this method.Comment: 8 pages + 1 color figur

Agronomic performance of striga resistant early-maturing maize varieties and inbred lines in the savannas of West and Central Africa

The potential maize (Zea mays L.) yield in the savannas of West and Central Africa (WCA) is constrained by Striga hermonthica (Del.) Benth. parasitism. Field trials at Ferkessedougou, Côte d'Ivoire; Abuja, Nigeria; and Mokwa, Nigeria, in 2002, and at Mokwa and Abuja in 2004, evaluated the performance of 11 early maturing maize varieties under artificial Striga infestation and Striga-free conditions. Another trial at Mokwa and Abuja in 2004 evaluated 100 early maturing inbred lines under Striga infestation and Striga-free conditions. The varieties differed significantly in grain yield under both conditions. Acr 94 TZE Comp 5-W, Acr TZE Comp 5-Y, and TZE-W Pop × 1368 STR C1 were identified as promising varieties, based on grain yield, Striga damage ratings, and Striga emergence counts. The most promising variety, Acr 94 TZE Comp. 5-W in terms of high grain yield, reduced Striga damage and low Striga emergence, outyielded the reference entry by 2% under Striga-free conditions and 45% under Striga infestation. Ward cluster analysis of the varieties and inbred lines produced four major clusters each, under both Striga-infested and Striga-free conditions. In each case, the varieties and inbred lines assigned to each cluster under Striga infestation differed from those in the Striga-free conditions. Several inbred lines with high grain yield, low Striga emergence and reduced Striga damage were identified as sources of Striga resistance for maize breeding programs in WCA

The pattern of grain yield response of normal and quality protein maize cultivars in stress and nonstress environments and nonstress environments

Maize (Zea mays L.) cultivars combining high grain yield with elevated levels of lysine, tryptophan, and desirable endosperm modification, could reduce food insecurity and malnutrition in West and Central Africa (WCA). Sixteen early- and nine extra-early-maturing quality protein maize (QPM) and normal cultivars were evaluated under Striga hermonthica (Del.) Benth infestation and Striga-free environments in Nigeria from 2006 to 2008 to identify stable and high yielding cultivars. The extra-early normal maize cultivars 2000 Syn EE-W STR and 99 TZEF-Y STR, were similar in yield to the QPM versions under both research conditions. While TZEE-Y Pop STR C4 was superior in grain yield to its QPM version only under Striga-free conditions, TZEE-W Pop STR C4 significantly out yielded the QPM version, under both test conditions and was superior in Striga resistance. In the early maturity group, TZE-W DT STR C4 out yielded the QPM version by 21% under Striga infestation and by 10% when Striga-free. In contrast, the QPM cultivar 98 Syn WEC STR QPM C0 out yielded the normal endosperm version by 31% when Striga-infested. GGE-biplot analysis demonstrated that two extra-early and three early maturing cultivars had outstanding performance in both research environments. TZEE-W Pop STR QPM C0 and EV DT-W 99 STR QPM C0 were high-yielding and stable when Striga-infested while TZE-Y Pop DT STR C4, TZE-W Pop DT STR C4, and TZE-Y Pop STR QPM C0 were superior when Striga-free. The QPM cultivars with grain yield performance and Striga resistance comparable or superior to those of their normal endosperm versions have been developed in our program

Evaluation of nicosulfuron for control of speargrass (Imperata cylindrica) in Nigeria

Nicosulfuron is a new alternative herbicide for post-emergence control of perennial weeds in maize. Field studies were conducted to evaluate the response of four maize cultivars (Low-N-Pool, TZB-SR, Oba Super-1 and Oba Super-2) and speargrass to different rates of nicosulfuron (35, 70, and 105 g a.i. ha − 1). Hand-weeded and unweeded plots were controls. All plots that received nicosulfuron had significantly lower speargrass shoot biomass than the unweeded control 3 weeks after treatment and at crop harvest. Maize biomass was highest in the weeded control in both years. In 2000, maize biomass in plots that received 35 g a.i. ha − 1 of nicosulfuron was similar to that in the unweeded control, and in both cases was higher than in all the other nicosulfuron treatments. In 2001, all rates of nicosulfuron produced significantly higher maize biomass than the unweeded control. Higher maize grain yield was obtained from 70 and 105 g a.i. ha − 1 than from 35 g a.i. ha − 1. All the cultivars responded similarly to nicosulfuron. A linear regression equation is given for grain yield and speargrass biomass. Our results suggest that nicosulfuron has the potential for effective speargrass control in Nigeria

Witchweed [Striga hermonthica (Del.) Benth] control using imazapyr seed coating in maize hybrids in the Nigerian savannah

Open Access Article; Published online: 06 Feb 2020Witchweed [Striga hermonthica (Del.) Benth] is a major parasitic weed of most cereal crops in Africa, including maize. Seed treatment with low doses of acetolactate synthase–inhibiting herbicides, such as imazapyr, was introduced in the 1990s to control witchweed. Field trials were conducted in four locations in Nigeria in 2007 and 2008, to assess the effect of coating seeds of several maize hybrids with imazapyr on witchweed control. The hybrids had genes for imidazolinone herbicide resistance (IR), as well as genetic tolerance to witchweed (ST). Treatments were 12 IR maize hybrids with ST and three checks without the IR gene (commercial, witchweed tolerant, and witchweed susceptible hybrids). Averaged across all locations, the coated IR hybrids with ST yielded more and supported fewer witchweed plants than the uncoated IR hybrids with ST. The IR hybrids with ST yielded 57%–60% more than the commercial and witchweed tolerant hybrid checks that were not coated. The witchweed susceptible hybrid check suffered a yield loss of 88% under infestation without seed coating. The IR hybrids with ST yielded 3564 kg ha−1 of grain when coated with imazapyr and 3266 kg ha−1 otherwise. The findings indicate that coating of IR/ST maize seeds with imazapyr improved tolerance to witchweed

Control of Imperata cylindrica (speargrass) with nicosulfuron and its effects on the growth, grain yield, and food components of maize

Imperata cylindrica (speargrass) is one of the most invasive weeds in the moist savannah zone of sub-saharan Africa. This study was conducted in 2001 and 2002 at Ijaye and Ilorin, Nigeria, to investigate the influence of four nicosulfuron doses (35, 70, 105, and 210 g a.i./ha) on the performance of maize, and its efficacy in the control of Imperata. The experiment was designed as a split-plot with three replications. Nicosulfuron was applied 2 weeks after planting maize. Hoe weeded and unweeded treatments were controls. In both years, 7 weeks after treatment, the unweeded control had lower maize leaf area index (LAI) (19% at Ijaye and 25% at Ilorin) than the weeded control. Maize LAI was highest in plots that received 35 g a.i./ha of nicosulfuron at Ijaye and the weeded control at Ilorin in both years. All plots that received nicosulfuron had significantly higher maize grain yield than the unweeded control at both locations in both years. Maize grain yield in the weeded control was similar to plots that received nicosulfuron at 35–210 g a.i./ha at Ijaye in 2002, 70–210 g a.i./ha at Ilorin in 2001, and 35 g a.i./ha at Ilorin in 2002. The protein content of maize in the weeded control and at 70 g a.i./ha was similar and higher than that at doses of 105 and 210 g a.i./ha while the carbohydrate content was not significantly different. The unweeded control had significantly higher weed LAI, shoot and rhizome biomass than all other treatments at both locations in both years . An increase in the nicosulfuron dose led to a decrease in weed LAI. Imperata rhizome biomass in the weeded control was similar to that in all nicosulfuron-treated plots. The findings of this study show that nicosulfuron is a suitable postemergence herbicide for speargrass control in maize in the moist savannah of Nigeria

Assessment of genetic diversity in extraearly Strigaresistant tropical inbred lines using multivariate analysis of agronomic data

An assessment of the genetic diversity among extra-early maturing maize inbred lines would be useful for identifying closely related lines, in determining the variation in genetic similarity among genotypes that show no variation for parentage and in planning crosses between genetically divergent parents. Genetic diversity in 65 extra-early maturing maize inbred lines was studied under Striga-infested and Striga-free conditions using the principal component analysis (PCA) and Ward's minimum variance cluster analysis. Based on the similarity of the quantitative characters, cluster analysis of the inbreds produced four major clusters under both Striga-infested and Striga-free conditions. However, the inbred lines assigned to each cluster under Striga infestation differed from those under Striga-free conditions. Based on the preliminary grouping of the inbreds, it may be predicted that the selection of specific combinations of inbred lines for the development of hybrids, or synthetics, or for introgression into breeding populations may best be done by selecting parents that combine high grain yield with reduced Striga damage symptoms and numbers of emerged Striga plants, as well as high numbers of ears per plant in each cluster. The most important variables for the classification of the inbreds under Striga infestation were grain yield, EPP, Striga emergence counts at 8 and 10 WAP and Striga damage syndrome rating at 10 WAP

S1 family selection in early maturing maize populations in Striga infested and Striga free environments

Striga and drought are major constraints to maize (Zea mays L.) production in the savannas of west and central Africa (WCA). A study was conducted in 2005 and 2006 in Nigeria to determine the level of resistance to Striga hermonthica for two early-maturing maize populations, one white and one yellow, and to assess the progress made in improving each for grain yield and level of resistance after four cycles of S1 recurrent selection. Percentage yield gain per cycle of the yellow population when Striga infested was 13% with r2 = 82% and 5% with r2 = 97% in a Striga-free environment. Corresponding values for the white population were 15% with r2 = 40% and 1% with r2 = 9% for the two Striga environments. For the two populations, therefore, realized gain in grain yield was higher under Striga-infested than Striga-free conditions. Yield gains in the advanced cycles of selection were accompanied by increased number of ears per plant in both populations. Striga damage at 10 wk after planting (WAP) and Striga emergence at 8 WAP decreased by about 5 and 4% cycle–1, respectively in the yellow population. For the white population, Striga damage decreased also by about 5 and 4% per cycle–1 at 8 and 10 WAP, respectively, while Striga emergence decreased by about 5% cycle–1 at 8 WAP. In conclusion, S1 recurrent selection was effective in improving grain yield and Striga resistance in the two early maize populations

Competition between Imperata cylindrica and maize in the forest savannah transition zone of Nigeria

Early viewoperate cylindricais a noxious weed that infests annual and perennial crops in most tropical regions. High crop densities may offer opportunities to reduce. Cylindricacompetition in small-scale farming systems. The competitive ability of maize relative toI. cylindricawas evaluated in an addition series experiment in the forest savannah transition zone in 2006and 2007 at Ibadan, Nigeria. Maize andI. Cylindrica were planted in eight monoculture densities (4, 8, 12,16, 20, 32, 48 and 64 plants m 2) and in a 1:1 mixture at eight total densities (2:2, 4:4, 6:6, 8:8, 10:10, 16:16,24:24 and 32:32 maize: I. cylindricaplants m 2)asinmonoculture. Non-linear regression models were used to relate crop and weed shoot biomass to their density and total grain yield to maize density. In maize, intraspecific competition was more than interspecific competition; inI. cylindrica, interspecific competitionwas higher than intraspecific. As expected, total grainyield was lower in the mixture than in maize monocul-ture at all total densities. Average maize grain yield inmaize monoculture differed from that in mixtures by0.77 t ha 1in 2006 and 0.57 t ha 1in 2007. Niche differentiation indices were1 in 2007,indicating that both species competed for similar resources in 2006, but not in 2007. The greater com-petitive ability of maize overI. cylindricamay be associated with rapid growth and canopy development observed in the field

Rimsulfuron for postemergence weed control in corn in humid tropical environments of Nigeria

Cogongrass and guineagrass are serious perennial weeds in small-scale farms in lowland subhumid zones of West Africa. Field studies were conducted in 2002 and 2003 at two sites in Ibadan, Nigeria [Ijaye and the International Institute of Tropical Agriculture (IITA)], to evaluate the effect of rimsulfuron on weed communities dominated by cogongrass and guineagrass in corn. At both sites, treatments were rimsulfuron dosages of 0 (nontreated control), 10, 20, 30, 40, 50, 60, 70, and 80 g ai/ha. Rimsulfuron did not cause any visible phytotoxicity on the corn at any dosage at either site. There was a rapid increase in weed control as the dosage of rimsulfuron increased from 0 to 20 g/ha. Weed control was not improved at rates higher than 20 g/ha. Rimsulfuron was very effective against sedges, Ipomoea involucrata, Bengal dayflower, gulf leafflower, old-world diamond-flower, and wild jute providing more than 80% control at dosages between 10 and 20 g/ha at Ijaye. Rimsulfuron was less effective for cogongrass, with a maximum of only 38% control observed. At IITA, the herbicide was very effective against guineagrass, Bengal dayflower, nodeweed, coat buttons, redfruit passionflower, and waterleaf; all of which were controlled more than 70% with any rate of rimsulfuron. Regression analysis showed that the dosage of rimsulfuron required to reduce shoot dry biomass by 70% was 5 g/ha for guineagrass and 35 g/ha for cogongrass at 3 wk after treatment (WAT). At crop maturity, the dosage of rimsulfuron required to reduce shoot dry biomass by 70% was 43 g/ha for guineagrass and 200 g/ha for cogongrass. The dry biomass of cogongrass and guineagrass was higher at crop harvest than at 2 WAT regardless of herbicide dosage. Corn grain yield was 1.8 times higher at IITA than at Ijaye. At both sites, corn grain yield increased with increased herbicide dosage. Maximum corn grain yields were obtained at a rimsulfuron dosage of 20 g/ha. Nomenclature: Rimsulfuron; coat buttons, Tridax procumbens L. TRQPR; cogongrass, Imperata cylindrica (L.) Beauv. IMPCY; old-world diamond-flower, Oldenlandia corymbosa L. OLDCO; guineagrass, Panicum maximum Jacq. PANMA; gulf leafflower, Phyllanthus amarus Schum. & Thonn. PYLAM; nodeweed, Synedrella nodiflora (L.) Gaertn SYDNO; redfruit passionflower, Passiflora foetida L. PAQFO; sedges, Cyperus, Mariscus, and Kyllinga spp; Bengal dayflower, Commelina benghalensis L. COMBE; waterleaf, Talinum triangulare (Jacq.) Willd TALTR; wild jute, Corchorus tridens L. CRGTR; corn, Zea mays L. ‘TZL Comp 4W’