Correlation Of Grain Yield Research Articles

Performance of different bread wheat varieties for yield and yield attributes under diallel combinations

Abstract The present research work was conducted during winter 2013–14 and 2014–15 at Agricultural Research Station, Chitral-Pakistan. Objectives of the present research was to determine the mean performance and correlations of parents, direct and reciprocal crosses in bread wheat varieties for different yield components under 6X6 diallel combinations. Days to heading of parents exhibited highly significant differences for plant height, grains per spike, grain weight per spike, 100-grain weight and grain yield while significant for days to heading and days to maturity and non significant for biological yield. Both direct and reciprocal crosses showed highly significant differences for all the studied traits. Correlations of grain yield with 100-grain weight of parents was significant and positive while grains per spike and grain yield with plant height of direct crosses was significant and positive and grain yield with biological yield of reciprocal crosses was highly significant and positive. Maximum days to heading of parent (Dirk), direct cross (NR-218 X Dirk), reciprocal cross (Pirsabaq-2013 X Dirk) and difference were 171 days, 170 days and 172 days, and 6 days, respectively. Parent (Dirk), direct (NR-218 X Dirk) cross, reciprocal cross (Dirk X pirsabaq-2013) and difference were 190 days, 184 days, 189 days and 7 days, respectively. Maximum 138.97 cm, 115.00 cm and 129.17 cm plant height was recorded by parent (Dirk), direct cross (NR-218 X Dirk) and reciprocal cross (Pirsabaq-2013 X Dirk) while the maximum difference was 25.1 cm. Parent (N-46), direct cross (NR-218 X N-46), reciprocal cross (N-46 X Dirk) and difference for grains per spike was 61 grains, 66 grains, 71 grains and 22 grains and was maximum. Recorded maximum grain weight per spike of parent (Fakhr e Sarhad), direct cross (Dirk X Pirsabaq-2013), reciprocal cross (Fakhr e Sarhad X Pirsabaq-2013) and difference were 3.33 g, 4 g, 5 g and 3 g, respectively. Parent (Dirk), direct cross (Dirk X N-46), reciprocal cross (Fakhr e Sarhad X Pirsabaq-2013) and difference for 100-grain weight was 9 g, 6 g, 7 g and 2 g and was maximum. Maximum biological yield for parents (NR-218), direct cross (NR-218 X Dirk), reciprocal cross (Fakhr e Sarhad X Dirk) and difference were 1.1001 kg/Plot, 0.6853 kg/Plot, 1.15 kg/Plot and 0.8147 kg/Plot, respectively. The recorded maximum grain yields for parent (Suliman-96), direct cross (Dirk X N-46), reciprocal cross (Dirk X NR-218) were 1.0175 kg/Plot, 0.575 kg/Plot, 1.405 kg/Plot and 0.895 kg/Plot, respectively.

Genetic Variability, Correlation and Path Coefficient Analysis of Morphological Traits in some Extinct Local Aman Rice (Oryza sativa L)

Thirty five local aman rice varieties were evaluated for their variability with regards to yield and yield components. Estimates of heritability and genetic advance in per cent of mean were also obtained for the above traits. In addition, studies on character associations and path coefficients were also undertaken. The highest σ2g was found for number of root hair (103415.40) and the lowest magnitude of σ2g was observed in number of primary branches per panicle (1.97). The highest σ2p was found for number of root hair (109410.31) and the lowest magnitude of σ2p was observed in number of primary branches per panicle (2.61). High GCV and PCV for number of effective tiller, root weight, number of root hair and grain yield per hill (g) indicated that selection of these traits would be effective. Correlation of Grain yield per hill was found to be highly significant and positive for number of root hair, days to flowering and plant height at both genotypic and phenotypic level and negatively significant for number of secondary branches per panicle at both level. Significant positive correlation of grain yield per hill with number of root hair, days to flowering and plant height implied that selection for these characters would lead to simultaneous improvement of grain yield in rice. Further, yield was observed to be positively associated with panicle bearing tillers and number of filled grains per panicle and these characters were noticed to exert high direct effects on grain yield per plant. High indirect effects of most of the traits were noticed mostly through panicle bearing tillers per hill indicating importance of the trait as selection criteria in crop yield improvement programs.

Assessment of Diversity in Commercial Hybrids of Pearl Millet in India

Availability of diverse cultivars is essential in order to meet necessity of regional adaptation to various climatic conditions and to fulfil the farmers’ need of differential preference of various phenotypic traits in pearl millet. The present study attempted to quantify the degree of diversity in commercial hybrids of pearl millet and to understand the relationship among various phenotypic and quality traits. A total of 122 commercial hybrids were evaluated at three diverse locations. Results showed large variation for flowering time (42-58 days), tillering (1.1-4.4 panicles/plant), individual grain size (7.6-17.3 mg), plant height (185-268 cm), panicle length (20-33 cm) and grain yield (35-72 q/ha). Clustering of hybrids resulted in 7 distinct clusters, which highlighted the successful efforts of national programme of pearl millet improvement toward genetic diversification of hybrids. These results are discussed as to how this reported diversity has helped in extending the hybrid technology in some of the most difficult and diverse production ecologies. Phenology, tillering and height had significant influence on yields of hybrids. Taller hybrids provided higher yield. Hybrids with lesser duration and shorter height produced more tillers and tillering decreased with the increase in panicle length. The correlation of grain yield with Fe and Zn concentration in grains was not significant suggesting that both these micronutrients can be improved without significantly compromising on grain yield.

Elevated temperature and carbon dioxide concentration effects on wheat productivity in Madhya Pradesh: a simulation study

The Agricultural Production System Simulator (APSIM) Wheat model was used to test the sensitivity of wheat cropping system for the Bhopal region in Madhya Pradesh to changes in temperature (0 to 5°C from the base mean temperature) and atmospheric carbon dioxide concentration (0 to 550 ppm from the base of 350 ppm). The wheat cultivar Sujata was used for this simulation study. It was found that there was a negative relationship between grain yield and temperature while there were positive correlations of grain yield with atmospheric CO2 concentration for the region under study. However, the rate of decrease in grain yield was more for higher temperatures rise in contrast to lower temperatures, and the rate of increase in grain and biomass yield was more for higher CO2 concentration compared with the lower levels. On an average, there was 8% decrease in wheat grain and biomass yield per 1 °C increase in temperature. On the contrary, wheat grain yield increased by 33% and biomass yield by 35% with the elevation in CO2 concentration from 350 to 850 ppm. Increasing the temperature by1 oC and CO2 concentration to 500 ppm, the yield decline in wheat was lower than individual effect of increased temperature. This study showed that environmental factors have significant effects on wheat grain and biomass yield with changes in atmospheric CO2 and temperature. These findings provided a sound basis for preliminary coping and prioritizing adaptation options for the future climate change scenarios.

English

Correlation coefficients and stability of grain yield were determined using 6 extra-early quality protein maize (QPM) parental inbred lines and their F1 (15) single crosses evaluated in selected ecological zones of Ghana. The objectives were; to estimate the genetic correlation between grain yield and other agronomic traits and to determine the stability of the single cross hybrids across four locations. Randomized Complete Block Design (RCBD) with three replications was used for each location. Estimates of correlation coefficients and stability analysis of grain yield was done using Genstat 9.2 and additive main effects and multiplicative interaction (AMMI) statistical model (MATMODEL 2.0). Results from phenotypic correlation of grain yield showed highly positive correlation with thousand grain weight (TGW) and number of kernels per row (NKR) across all locations suggesting that selection efficiency could be improved through indirect selection. AMMI analysis revealed non-significant genotype by environment interaction (GEI) for grain yield whilst genotypic and environmental main effects were highly significant. However, the contribution of the environment was higher which suggests that anyone of the locations used in this study can be used for subsequent evaluations in order to manage the limited resources available for the testing program.   Key words: Correlation, stability, grain yield.

Toward a Selection of Broadly Adapted Germplasm for Yield Stability of Hybrid Rye under Normal and Managed Drought Stress Conditions

ABSTRACTClimate change will have an influence on crop production and lead to a focus on stable and high‐yielding varieties in breeding programs. Winter rye (Secale cereale L.) is an important crop in Central and Eastern Europe, especially in marginal environments where varying weather conditions have a strong impact on grain yield. Because these environments are the first to suffer from abiotic stress, yield stability is an important breeding goal for rye. The objectives were to evaluate phenotypic diversity for genotype by irrigation interaction (GII) and the potential of hybrid rye to combine high yield potential with superior yield stability. Two intrapool and one interpool population with each of 218 to 220 testcross progenies were grown in a total of 16 to 18 environments (location by year combinations). In six of these environments, managed drought stress trials (rainfed vs. irrigated) were conducted. We observed a wide range of grain yield, from 4.9 to 11.5 Mg ha−1. In the managed drought stress experiments yield reduction in the rainfed regime ranged from 2 to 41% with an average of 18%. Only in a few environments did significant GII occur, although in most environments yield reduction was significant. Genotypic correlations of grain yield between irrigated and rainfed regimes were generally high (0.8–1.0). The coefficient of linear regression (bi) was not significantly different from 1 among progenies. Mean square deviation from linear regression (S2di), however, varied significantly (P < 0.01). To ensure broad adaptability of germplasm, managed drought stress environments should be included in test environments, but they need no special selection procedures. In conclusion, modern rye breeding material already combines high yield potential and stability.

Introduction of New Landrace Varieties Adapted to Drought Stress

Screening and introducing landrace varieties (as useful cultigens) is important for cultivation under abiotic stresses in temperate regions with low precipitations. To evaluate the response of wheat (Triticum aestivum L.) landraces to post-heading drought stress, two types of cultigens including commercial cultivars and landrace varieties were cultivated under drought stress and fully irrigated conditions in 2010/11 and 2011/12. Drought stress reduced grain yield by 22 and 19% compare to fully irrigated conditions in the first and second year respectively. Regression models indicated that genotypes with higher grain yield under fully irrigated had higher grain yield under drought conditions. Thousandgrain weight and harvest index strongly affected by drought stress although plant height and heading date were less affected. Under drought condition, the highest grain yield (5.8-8.1 ton ha -1 ) was found in the landrace varieties KC4557, KC4633, KC4542, KC4862, KC3891 and KC4551 in both years. Grain yield of Shiraz and Cross-Boolani were 4.7 and 5.5 ton ha respectively. Significant correlations of grain yield in fully irrigated (Yp) and drought (Ys) conditions with the indices of mean productivity (MP) and stress tolerance index (STI) support the idea that these indices are able to discriminate genotypic differences under drought conditions. Heading was Original Research Article Heidari et al.; IJPSS, 5(4): 201-211, 2015; Article no.IJPSS.2015.074 202 not significantly correlated with grain yield. Therefore, selection for earliness does not affect grain yield under drought stress. Analysis of principal components indicated that the landrace varieties numbers KC4557 and KC4551 in 2010/11 and KC4633, KC4537, KC4862 and KC3891 in 2011/12 had higher grain yield under drought conditions. Results showed that landrace varieties had better performance than commercial cultivars under drought and KC4557, KC4633, KC4542, KC4862, KC3891 and KC4551 were more tolerant to drought conditions.

Genotype × environment interaction and stability of grain yield and selected quality traits in winter wheat in Central Asia

Abstract: High grain yield and improved quality determine the commercial success of winter wheat (Triticum aestivum L.) varieties in Central Asia. This study was conducted to determine the effect of environment on grain yield, 1000-kernel weight (TKW), test weight (TWT), protein, and gluten content, and to identify superior wheat genotypes for yield and quality. Thirty winter wheat genotypes were evaluated in 3 years (2010-2012) over multiple locations. A genotype and genotype A— environment interaction biplot analysis was used to determine the superior genotypes. There were significant effects of environment and genotype A— environment interaction on yield and quality traits. The 30 wheat genotypes showed variations for grain yield (3.7-5.6 t ha-1), TKW (33.6-42.4 g), TWT (753-797 g/L), protein (13.3%-14.8%), and gluten (27.2%-29.5%) content. There was a significant positive correlation between grain yield and TKW in three out of seven environments. There was no correlation of grain yield with TWT, protein, and gluten content with one exception. There were different sets of five most superior genotypes for individual traits. However, certain genotypes were superior based on grain yield and quality traits. Gozgon, Elomon, ID800994.W/Vee//Lagos-12, Jaikhun, and Kroshka were the five most superior genotypes for four quality traits. Elomon, Gozgon, Jaikhun, ID800994.W/Vee//Lagos-12, and Kiriya were the five most superior genotypes based on grain yield, TKW, TWT, protein, and gluten content. This study demonstrates success in wheat breeding for combined high yield and improved quality in winter wheat. This study provides information on the combined stability of high yield and improved quality of the internationally important winter wheat genotypes. Therefore, the results of this study could be valuable for national and international winter wheat breeding programs to develop new varieties with high stable grain yield and quality.

Daya Gabung Inbred Jagung Pulut untuk Pembentukan Varietas Hibrida

Plant breeder utilizes performance of the experimental hybrid to study the effect of inbred parents on the hybrid development. Combining ability analyses using diallel mating indicates the potential heterosis effect on their hybrid combinations, which could be used in the breeding programs. Griffing’s model II was used to measure the responses of F1 hybrids relative to the parents and the overall F1 performances. The experiment consisted of 8 waxy corn inbred parents each was crossed in half-diallel combinations, resulting of 36 entries, including the inbred parents. The entries were set in a randomized complete block design with two replications, 2 rows (5 m) for each plot. Research was conducted in Gowa District of South Sulawesi from April to July 2012. The objectives of the research were to obtain the phenotypic correlation, General Combining Ability (GCA), Spesific Combining ability (SCA) and the heterosis effect of the parents. Results showed there were significant effects of genotypes on all traits, except for the number of kernels per ear row. The highest phenotypic correlation for grain yield was with the ear diameter (r = 0.86). The GCA effect among genotypes for grain yield was not significant, but for the 1,000 seed weight, ear length, and ear diameter, each was significant. The highest GCA was obtained by P8, of 38,375 for 1,000 seed weight. The SCA was significant for yield and yield components, except for the row number per ear and kernel per ear row. The highest SCA was indicated by P1xP5, and the hybrid yielded 2.29 t/ha, with the mid parents heterosis of 71%. But, the highest grain yield of the hybrid was obtained by P4 x P8 of 2.32 t/ha with 51% heterosis. Based on the yield and SCA value, two spesifik hybrid combinations (P1 x P5; P4 x P8) were considered a good potential for waxy corn hybrid development

Character Association and Parent Progeny Regression Studies for Yield and its Related Traits in Segregating Generations of TGMS Rice (Oryza sativa L.)

The aims of this study were to determine the response to selection for high grain yield and yield related components, to estimate the heritability of these traits, to compute the correlation of grain yield with yield components and to estimate the genetic potential transferred from one generation to other by using different segregating generations of rice (Oryza sativa L.). Various segregating populations (F2, F3 and F4) of the cross, TS 29 / CO(R) 49 were evaluated for yield and its related traits. The results indicated that correlation studies in F3 generation had positive association of single plant yield with fertility percentage, number of productive tillers per plant, panicle length, panicle exertion percentage, stigma exertion percentage and spikelet fertility percentage. Study on parent-progeny regression revealed positive significant regression and correlation coefficient estimates observed in F3-F4 generation for days to 50 per cent flowering, number of productive tillers per plant, panicle length, panicle exertion percentage and stigma exertion percentage which indicated that F3 are good indicators of F4 performance for all these traits. Narrow sense heritability increased with advancement of generation from F2 to F4 indicating the additivity of gene effects for number of productive tillers per plant, panicle length and panicle exertion percentage. It indicated the chances of selecting high yielding genotypes at early generations based on these characters are valuable.

CORRELATION AND HEAT SUSCEPTIBILITY INDEX ANALYSIS FOR TERMINAL HEAT TOLERANCE IN BREAD WHEAT

Six generations namely, P1, P2, F2, F3, BC1s and BC2s (2006-07) and P1, P2, F3, F4, BC1ss and BC2ss (2007-08) developed from four parental genotypes viz. DBW 14 (heat tolerant), NP 846 (heat and drought tolerant), WH 147 and Raj 4014 (heat susceptible for late sown). All the six generations from four crosses were evaluated during Rabi 2006-07 and Rabi 2007-08 in a compact family block design with three replications on two sowing dates. Heat susceptibility index values revealed reduction in grain yield in both the years for all the generations of the four crosses. Significant estimates of correlation of grain yield with days to heading, days to anthesis and days to maturity were recorded in late sown condition during first year. While under timely sown condition spike length has high estimate correlation with grain yield in first year itself. Significant estimated were recorded for tillers per plant in both the environments in second year. Lowest yield loss was reported in backcross populations of Cross I in both years and among segregating populations of Cross IV observed to be least affected and therefore suggested to be forwarded to further generations and further selection of heat tolerant genotypes.

Genetic Diversity and Correlation for Grain Yield and Quality Traits in Local Maize (Zea mays L.)

The aim of the study was to estimate the genetic diversity and correlation analysis among yield and quality traits in 20 local maize populations. The study of variation included the quantity of grain yield, and quality traits such as protein, oil and starch content in grain. Results showed that there were significant differences among the populations. The mean grain yield of all populations was 79.33 g plant -1 and the highest in ‘GBK-7’ (105.13 g plant -1 ). Protein and oil contents ranged between 11.02 to 13.02% and 2.56 to 5.57%, respectively and starch content varied from 68.58 to 70.92%. First two canonical discriminant functions were significant ( p<0.01) and the relevance of the first two discriminant functions justifying 95.80% variability among populations. There were also big differences regarding phenotypic correlations. Study suggests that the quality traits are phenotypically and genotypically highly variable and therefore very useful for breeding program.

Genetic Variation for Grain Yield and Yield Related Traits in Tef [&amp;lt;i&amp;gt;Eragrostis tef&amp;lt;/i&amp;gt; (Zucc.)Trotter] under Moisture Stress and Non-Stress Environments

Tef [Eragrostis tef (Zucc.)Trotter] is an ancient and major cereal crop in Ethiopia. Increasing tef grain yield partly requires developing cultivars that are adapted to drought stress environment. An experiment was carried out using 18 tef genotypes grown during September to December, 2010, under two water supply environments (stress during grain filling period, and non-stress) to identify genetic variation, heritability and correlations of grain yield and yield related traits. Broad-sense heritability values under respective stress and non-stress environments were grain yield (g/m2) 0.80 and 0.89, total biomass (g/m2) 0.89 and 0.73, harvest index 0.69 and 0.79, panicle weight (g/plant) 0.93 and 0.92, and seed weight (g/plant) 0.96 and 0.86. The correlations of grain yield under respective stress and non-stress environments were total biomass rp = 0.64, rg = 0.70, and rp = 0.48, rg = 0.56, harvest index rp = 0.70, rg = 0.64, and rp = 0.87, rg = 0.90, panicle weight rp = 0.98, rg = 1.00, and rp = 0.96, rg = 1.00, and seed weight/plant rp = 0.98, rg = 1.00, and rp = 0.90, rg = 1.00. The present experiment showed that either grain yield per se, or seed weight/plant could be used to improve grain yield under stress and non-stress environments.

Introgression of a major gene for high grain protein content in some Indian bread wheat cultivars

In bread wheat, high grain protein content (GPC) determines nutritional value, processing properties and quality of the end-product. In view of this, marker-assisted selection (MAS) was performed for introgression of a major gene for high GPC ( Gpc-B1) into 10 wheat genotypes. As a result, 124 BC 3F 5/F 6 progenies with Gpc-B1 were developed and evaluated in multi-location field trials. Significant interaction of Gpc-B1 with the recipient parent genotypes and the environment was noticed. However, a total of seven MAS-derived progenies with significantly higher GPC (14.83–17.85%) than their recipient parental genotypes and having no yield penalty were obtained. In these selected progenies, no significant negative correlation of grain yield with GPC (%) or protein yield was observed suggesting that GPC could be improved without yield penalty. This study thus suggested that MAS in combination with phenotypic selection is a useful strategy for development of wheat genotypes with high GPC associated with no loss in yield.

Estimation of Variability and correlation analysis for quantitative traits in chickpea (Cicer arietinum L.)

A study was carried out in the fields of Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad, Pakistan during 2010-2011. Twenty elite genotypes including three standard varieties of chickpea were evaluated for means and components of variability, heritability (h2bs), genetic advance and interrelationships for various parameters. Correlation studies showed that Genotypic and phenotypic correlations of grain yield per plant with number of secondary branches per plant, biomass per plant, number of pods per plant and number of grains per plant was positive and highly significant. Genotypic correlation of grain yield per plant with plant height was positive and significant. Genotypic and phenotypic correlations of grain yield per plant with number of days taken to maturity were negative and highly significant.

Evaluation of yield potential and stress adaptive trait in wheat genotypes under post anthesis drought stress conditions.

Twenty winter wheat genotypes were evaluated under both post-anthesis drought stress and normal conditions in Ardabil Agricultural Research Station in two successive growing seasons 2005 - 2007 using randomized complete block design with three replications. The results showed that there were significant differences between genotypes in stem reserve under both normal and post anthesis drought stress conditions. Post-anthesis drought stress did not affect kernel numbers per spike. The rate of dry matter accumulation by kernels considerably decreased by water deficit. Dry weight of vegetative organs decreased in grain filling period under stress and normal conditions, contrasting anthesis stage. But, the rate of translocated dry matter was much higher in genotypes nos. 14, 15, 16, 18, 19 and 20 under drought stress condition. 1000 GW and weight of kernels per spike were more severely reduced by water deficit. The positive correlation of grain yield with grain weight per spike, 1000 GW, remobilization of dry matter, harvest index and stress tolerance index (STI) and significant negative correlation of grain yield with drought susceptibility index (SSI) revealed that selection must be exercised for high harvest index, grain weight per spike, 1000 GW, remobilization of dry matter and STI in stress condition. The negative correlation of ‘STI’ with ‘SSI’ indicated the efficiency of ‘STI’ as a selection criterion for identifying the drought tolerant with high yield potential in winter wheat genotypes. Key words: Winter wheat, drought stress, dry matter, remobilization.

Grain yield and quality of maize hybrids in different FAO maturity groups

An improvement in the quality of maize grain by increasing the level of components responsible for its biological value is possibleby using genetic means. However, a change in the genotype, together with improving the nutrient properties of the grain, also has someadverse consequences connected with a fall in yield and in resistance to diseases.Field experiments were conducted during three years (2003, 2004and 2005) to evaluate environmental effects on grain yield andquality responses of maize hybrids. Twenty one hybrids of various maturity groups (FAO 150-400) were planted to achieve an optimum(60-70 000 plants per hectare) plant populations and grown under the medium-N (80 kg N ha-1) fertilization. Environmental conditionssignificantly affected maize hybrid responses for grain yield, starch, oil and protein contents, and consequently, starch, oil and proteinyields per hectare. Hybrids of flint type, which have a short vegetation period, had high protein and oil content but the yield averageswere low due to the slower rate of starch incorporation. Hybrids of the dent type have a longer growing season and more intensecarbohydrate accumulation, but low protein and oil contents. In wet years there was a higher rate of starch accumulation, while dryyears are favorable for protein and oil accumulation. Positive correlation existed between starch content and grain yield and 1000-weight as well as between oil content and volumetric weight among tested hybrids. Negatively correlation existed between grain oil andstarch content as well as between oil content and grain yield and 1000-weight. Thus, end-users that require high quality maize may needto provide incentives to growers to off set the negative correlation of grain yield with oil and protein content.

Durum wheat (Triticum durum Desf.) in rotation with faba bean (Vicia faba var. minor L.): long-term simulation case study

The aim of this work was to apply the CropSyst simulation model to evaluate the effect of faba bean cultivation as a break crop in the continuous durum wheat cropping system in southern Italy. The model was previously calibrated and validated for durum wheat and faba bean on data derived from experiments carried out in southern Italy (for different years and treatments), comparing observed and simulated crop growth, yield, soil water, and nitrogen output variables. The validation showed good agreement between simulated and observed values for cumulative above-ground biomass, green area index, and soil water content for both crops and grain yield for durum wheat; a negative correlation for grain yield in faba bean was observed due to a reduction in harvest index in the well-watered crop, which the model does not simulate well. Subsequently, a long-term analysis was carried out to study the effects on durum wheat of introducing a legume crop in rotation with the cereal in 2 and 3-year sequences. A long-term simulation, based on 53 years of daily measured weather data, showed that faba bean, due to a lower level of transpirated water (on average 247 mm for durum wheat and 197 mm for faba bean), allowed for greater soil water availability at durum wheat sowing for the cereal when in rotation with a legume crop (on average, +84 mm/m for durum wheat following the faba bean), with positive effects for nitrogen uptake, above-ground biomass, and grain yield of wheat. The yield increase of wheat when following a faba bean crop was on average +12%, but this effect was amplified in drier years (up to 135%). In conclusion, the case study offered the potential to confirm the positive results previously obtained in long/medium-term field experiments on the introduction of faba bean in rotation with durum wheat, as well as reduction in the chemical application of nitrogen.

Rotation effects of grain legumes and fallow on maize yield, microbial biomass and chemical properties of an Alfisol in the Nigerian savanna

Understanding changes in soil chemical and biological properties is important in explaining the mechanism involved in the yield increases of cereals following legumes in rotation. Field trials were conducted between 2003 and 2005 to compare the effect of six 2-year rotations involving two genotypes each of cowpea (IT 96D-724 and SAMPEA-7) and soybean (TGx 1448-2E and SAMSOY-2), a natural bush fallow and maize on soil microbial and chemical properties and yield of subsequent maize. Changes in soil pH, total nitrogen (N tot), organic carbon (C org), water soluble carbon (WSC), microbial biomass carbon (C mic) and nitrogen (N mic) were measured under different cropping systems. Cropping sequence has no significant ( P > 0.05) effect on soil pH and C org, while WSC increased significantly when maize followed IT 96D-724 (100%), SAMPEA-7 (95%), TGx 1448-2E (79%) and SAMSOY-2 (106%) compared with continuous maize. On average, legume rotation caused 23% increase in N tot relative to continuous maize. The C mic and N mic values were significantly affected by cropping sequence. The highest values were found in legume–maize rotation and the lowest values were found in fallow–maize and continuous maize. On average, C mic made up to 4.8% of C org and N mic accounted for 4.4% of N tot under different cropping systems. Maize grain yield increased significantly following legumes and had strong positive correlation with C mic and N mic suggesting that they are associated with yield increases due to other rotation effects. Negative correlation of grain yield with C mic:N mic and C org:N tot indicate that high C:N ratios contribute to nitrogen immobilization in the soil and are detrimental to crop productivity. The results showed that integration of grain legumes will reverse this process and ensure maintenance of soil quality and maize crop yield, which on average, increased by 68% and 49% following soybean and cowpea, respectively compared to continuous maize.

Quantitative genetic studies on breeding maize for adaptation to organic farming

Organic farming has gained in importance in Germany during recent years. Therefore an increasing demand exists for varieties with specific adaptation to this farming system. In the present study we therefore conducted comparative field experiments with modern maize breeding materials under organic versus conventional farming conditions (ORG and CON, respectively) to estimate quantitative genetic parameters needed for developing optimal breeding strategies and to investigate the perspectives of selection for specific adaptation to ORG. Starting from two broad samples of elite germplasm, consisting of 178 flint and dent lines, respectively, fractions of 11 flint and 11 dent lines were selected based on their testcross performance under ORG. A corresponding set of lines was selected under CON. Testcross performance was evaluated in three regions of Germany and selection of superior lines was practiced across two stages in 2004 and 2005, respectively. The specifically selected lines were crossed in a factorial manner for production of experimental inter-pool single-cross hybrids which were field-tested under ORG and CON in two regions in 2006. Average grain yields were about 16% lower under ORG than under CON. Variance components and entry-mean heritability coefficients under ORG largely resembled those obtained under CON. Phenotypic correlations between ORG and CON were moderate for grain yield and strong for grain dry matter content. No consistent estimates were obtained for the corresponding genotypic correlation for grain yield. At the first stage of testcross selection no evidence of specific adaptation to ORG or CON was observed whereas the factorial crosses tested in 2006 displayed distinct, yet non-significant, advantages when evaluated under the respective target farming system. A small top fraction of hybrids showed outstanding performance under both ORG and CON. The chances of detecting such broadly adapted genotypes are increased if ORG test sites are included in the regular testing system.