Open Pollinated Maize Varieties Research Articles

Agronomic Performance and Genotype × Environment Interaction of Herbicide‐Resistant Maize Varieties in Eastern Africa

ABSTRACTStriga hermonthica (Del.) Benth. and Striga asiatica (L.) Kuntze severely affect maize (Zea mays L.) production in sub‐Saharan Africa. A single Striga plant produces a large number of seeds that form a bank of viable but dormant seed in the soil until they get a chemical signal from suitable maize host roots. Imidazolinone‐resistant (IR) open‐pollinated maize varieties (OPVs) developed for Striga control were tested in diverse environments in four countries of eastern Africa in 2004. The objective of the study was to assess the agronomic performance of IR maize and genotype × environment interactions (GE) for grain yield (GY) and the number of emerged Striga plants across 17 environments under Striga‐infested and Striga‐free conditions. In the combined analysis of variance across Striga‐infested and Striga‐free locations, mean squares for genotypes and GE were significant for most measured traits. The best IR maize variety (STR‐VE‐216) outyielded the Striga‐tolerant and commercial genotypes by 113 and 89%, respectively, under Striga‐infested conditions. IR OPVs supported significantly fewer emerged Striga plants relative to the check varieties. Under Striga‐free conditions, IR OPVs showed GY advantage over commercial varieties. Under Striga‐infested conditions genotypic variance () was larger than genotype × location variance () for GY and number of emerged Striga plants at 12 wk after planting. The genetic correlations among locations under Striga‐infested conditions were high (0.990), suggesting little GE between most environments used. Cluster analysis of genotypes under Striga‐infested locations revealed two major groups that separated the IR OPVs from the check varieties. The outstanding performance of selected IR OPVs indicates that their use for Striga control would reduce the Striga seed bank while benefiting farmers with high GY.

Mycotoxins in maize grains grown in organic and conventional agriculture

Maize is traditionally used for bakery in several countries, and autochthonous varieties are increasingly demanded particularly for organic agriculture, but one of the dangers of cereal consumption is mycotoxin contamination. Mycotoxins are dangerous for health and might be present in any grain depending on genotypes and environments. In the present work we assess the natural levels of fumonisin and deoxynivalenol (DON) contaminations in nine diverse open-pollinated maize varieties grown in four different locations, under organic or conventional conditions, in two regions from the humid Spain during two years. Differences were significant among locations and among varieties for fumonisin contamination but not for DON content. Locations were the main environmental source of variation affecting fumonisins while DON was more affected by years. The Basque locations had more fumonisin than the Galician locations, but there were no differences between organic and conventional environments. Fumonisin contamination was more variable than DON among locations and among varieties. Fumonisin and DON were highly correlated on average but correlations were low for each particular environment. Mean fumonisin and DON were below the threshold allowed by the EU, but the white-kernel medium late variety Rebordanes(P)C2 had more than 4.00 mg/kg of fumonisin in one location, while the early yellow variety Sarreaus had the lowest contamination. We conclude warning producers of the danger of natural contamination with mycotoxins for some varieties in specific environments.

English

Smallholder farmer productivity in developing countries is limited by diverse biophysical, political and socio-economic factors. The objective of this study was to establish current agronomic practices of smallholder farmers in semi-arid Lower Gweru and Lupane areas of Zimbabwe and to identify possible research and extension interventions that may improve crop productivity of these farmers. Focus group discussions, interviews and desktop study were used to collect data. Horticultural production is the main livelihood in Lower Gweru, while field crop and livestock production are livelihoods in both areas.  Conventional tillage is the predominant tillage system. Important crops include maize (Zea mays L.), pearl millet (Pennisetum glaucum (L) R.Br.), sorghum (Sorghum bicolor L.) and groundnuts (Arachis hypogea L.).  Farmers grow both hybrid and open-pollinated maize varieties (OPVs) with more farmers in Lupane than in Lower Gweru, growing these OPVs. The number of farmers growing improved varieties of small-grain crops has increased, since mid 1990s. The method and frequency of weeding depends on tillage system used and availability of equipment as well as draft power. Adoption rates for technologies such as water conservation and use of adequate soil ameliorants as well as effective crop rotations are low due to limited resources. The study identified some research and extension interventions that may be employed to improve crop productivity in semi-arid areas of Central and Western Zimbabwe.   Key words: Smallholder farmers, agronomic practices, semi-arid areas, research and extension interventions.

Genetic relationships and structure among open-pollinated maize varieties adapted to eastern and southern Africa using microsatellite markers

Molecular characterization of open-pollinated maize varieties (OPVs) is fundamentally important in maize germplasm improvement. We investigated the extent of genetic differences, patterns of relationships, and population structure among 218 diverse OPVs widely used in southern and eastern Africa using the model-based population structure, analysis of molecular variance, cluster analysis, principal component analysis, and discriminant analysis. The OPVs were genotyped with 51 microsatellite markers and the fluorescent detection system of the Applied Biosystems 3730 Capillary Sequencer. The number of alleles detected in each OPV varied from 72 to 155, with an overall mean of 127.6. Genetic distance among the OPVs varied from 0.051 to 0.434, with a mean of 0.227. The different multivariate methods suggest the presence of 2–4 possible groups, primarily by maturity groups but also with overlapping variation between breeding programs, mega-environments, and specific agronomic traits. Nearly all OPVs in group 1 and group 2 belong to the intermediate-late and early maturity groups, respectively. Group 3 consisted of mainly intermediate maturing OPVs, while group 4 contained OPVs of different maturity groups. The OPVs widely used in eastern Africa either originated from the southern African maize breeding programs, or the majority of inbred lines used as parents by the two breeding programs in developing the OPVs might be genetically related. Some of the OPVs are much older than others, but they still did not show a clear pattern of genetic differentiation as compared with the recently developed ones, which is most likely due to recycling of the best parental lines in forming new OPVs.

Genotype × environment interactions and yield stability of stress-tolerant open-pollinated maize varieties in the Eastern Cape province, South Africa

Genotype × environment interactions are inherent in multilocational trials and complicate identification of superior genotypes. The aim of the study was to determine yield performance and stability of 13 maize genotypes in five locations of the Eastern Cape province, South Africa. The genotypes assessed were: ZM305, ZM423, ZM501, ZM525, ZM621, ZM627 and Obatanpa from the International Maize and Wheat Improvement Centre; BR993 and COMP4 from the International Institute of Tropical Agriculture; four local checks, AFRIC 1, Okavango, Nelson's Choice, and PAN 6479. Yield data were subjected to analysis of variance (ANOVA) and additive main effects and multiplicative interaction (AMMI) analysis. According to ANOVA, genotype × environment interaction was significant. PAN 6479 (5.21 t ha-1) and ZM525 (5.19 t ha-1) were the highest-yielding varieties, whereas Okavango (4.08 t ha-1) showed the lowest yield. Based on AMMI analysis, BR993 and Obatanpa were the least stable genotypes. PAN 6479 and ZM525 showed specific adaptations to high potential environments. Obatanpa was adapted to environments with low-yielding potential, since improvement of the environment did not improve its yield. ZM501 was the most stable genotype, and showed no significant yield difference to PAN 6479. ZM501 can therefore be assigned to several environments in the Eastern Cape.

English

Given that the majority of maize farmers in Kenya are small-scale, improvement in maize production must focus on increased production per unit area. While hybrid maize varieties outperform local open pollinated varieties under conventional farming practices, their relative performance has not been tested under small-scale intensive production practices. A study was conducted in 2013 in Kitale, western Kenya, to evaluate performance of ‘Namba Nane’; a local open pollinated maize variety, alongside a high yielding hybrid, ‘Hybrid 614D’ under a small-scale, intensive farming practice that utilizes deep tillage and compost/manure. Each variety was subjected to conventional and diagonal offset close spacing. The grain yield of the hybrid (12.8 tons ha-1) was not statistically different from that of ‘Namba Nane’ (10.2 tons ha-1), even though the number of rows per cob and number of ears per plant of the former were significantly greater than those of latter. However, yields of both varieties were about twice the published potential yield of improved hybrid maize (6 tons ha-1) grown with conventional practices. Seed kernels of ‘Namba Nane’ weighed 1.6 times more than those of ‘Hybrid 614D’. Diagonal off-set close spacing under this technology increased the maize grain yield of both varieties 1.3 times. The cost of producing ‘Namba Nane’ under the technology was significantly less than producing the hybrid and twice more profitable (gross margin). Growing ‘Namba Nane’ using small-scale, intensive farming practices may be a viable option for most small-scale, resource-challenged farmers to increase economic yields. Key words: Biointensive, double digging, hybrid, open pollinated, ‘Namba Nane’, small-scale intensive.

Evaluation of Evolution and Diversity of Maize Open-Pollinated Varieties Cultivated under Contrasted Environmental and Farmers’ Selection Pressures: A Phenotypical Approach

OPVs (open pollinated varieties) of cross pollinated crops are genetically heterogeneous and therefore likely to evolve over generations, under natural and human selection, which gives them a strong potential for organic and low input farming. OPVs of maize were cultivated and selected by different farmers in France and Italy for 2 generations. The third year, they were phenotypically evaluated for evolution, adaptation and level of diversity (estimated with Nei index) across evolution in a combined on farm and on station experimentation. The results showed that the varieties evolved and even adapted over 2 generations only (especially on maturity traits) but conserved their identity (no evolution of ear morphological traits). They all conserved their diversity, which demonstrated the pertinence of farmers’ selection (it is not a bottleneck). These results suggested that the genetically heterogeneous nature of OPVs is an asset for farmers because they can adapt these varieties to specific local conditions and production objectives. Therefore, farmer OPVs should receive more support through social and regulatory recognition, as well as further interest from research.

Comparative Growth and Grain Yield Response of Five Maize Varieties to Nitrogen Fertilizer Application

Field trials were conducted at the research field of Institute of Agricultural Research and Training, Moor plantation, Ibadan during 2010 and 2011 cropping season in order to evaluate the performances of five open pollinated maize varieties subjected to two fertility levels 0 and 100 kg Nha -1 fertilizer. The trials consisted of split-plots arranged in randomized complete block design of three replicates. The objective was to evaluate and compare the responses of five maize varieties to N fertilizer application. Data were obtained from plant height, ear height, leaf area, ear length, number of kernels per cob, weight of 100 kernels and grain yield. Data were analyzed using ANOVA and means separated by DMRT (P=0.05 and 0.01). The results obtained showed that N fertilizer significantly increased the growth and yield related parameters of all the traits except ear height and ear length while grain yield was higher in 2011. Varieties by nitrogen interactions differed significantly for the various parameters measured except for ear height and kernel/cob. In the fertilized plots ART SW5-OB had highest mean grain yield. Obatanpa and ARTSW6-OB had highest grain yield compared with other varieties in the fertilizer stressed plots while Ile1-OB had highest yield reduction under the two fertility environments. ARTSW5-OB had the highest nitrogen use efficiency while Obatanpa and ARTSW6-OB were least, but produces better grain yield under low nitrogen input. In conclusion, the result indicated a positive and varied response of maize varieties to nitrogen fertilizer application.

Interrelationship and path coefficient analysis of morpho-physiological traits among maize (<i>Zea mays</i> L.) diallelic crosses in the Southern Guinea Savanna of Nigeria

This study was done to determine the effect of the grain yield and its related characteristics on 10 open-pollinated maize varieties and their 45 F1 hybrids using correlation and path coefficient analysis. A two-year study was conducted on maize genotypes at the University of Ilorin Teaching and Research Farm Ilorin, Nigeria, during 2005 and 2006 growing seasons. Positive and significant phenotypic and genotypic correlations were found for days to 50% tasselling with plant and ear heigh t, and grain yield with plant height, number of grains ear-1 and ear weight. Positive and significant environmental correlation was also recorded for grain yield with plant and ear height, and ear weight. The path analysis revealed that, days to 50% silking, ear weight and number of grains ear-1 had the highest direct effect on grain yield, while number of grains ear-1 had the highest moderate indirect negative effects on grain yield. Days to flowering, plant and ear height, number of grains ear-1 and ear weight could be the important selection criteria in improving open pollinated maize varieties and hybrids for high grain yield.Key words: Phenotypic, genotypic correlation, open pollinated varieties, yield characters

Genetic Relationships Among Chinese Maize OPVs Based on SSR Markers

Bulk-SSR method was used to analyze the genetic diversity of 44 open-pollinated varieties collected from Henan, Shandong, Shanxi, and Jilin provinces and Guangxi Zhuang Autonomous Region, China using 70 pairs of SSR primers. The purposes of this study were to (1) compare the genetic diversity among 44 Chinese maize open-pollinated varieties; (2) estimate the minimum number of alleles for construction of a stable dendrogram; and (3) trace the genetic relationships among local germplasm from different regions of China. In total, these 70 SSR primers yielded 292 alleles in 176 samples (4×44) analyzed. The number of alleles per locus was 4.17 on average and ranged from 2 to 8. The highest number of alleles per open-pollinated variety (55.25) was detected in Shanxi germplasm, which indicated that open-pollinated varieties from Shanxi possessed the largest genetic diversity among those from the five locations. The correlation coefficients between different genetic similarity matrices suggested that 200 alleles were sufficient for analysis of the genetic diversity of these 44 open-pollinated varieties. The cluster analysis showed that 44 open-pollinated varieties collected from three growing regions in China were accurately classified into three groups that were highly consistent with their geographic origins, and there is no correlation between GS and geographic distance in this study.

Storage of open-pollinated maize variety seeds in active cattle kraal to suppress maize weevils and improve seed quality and seedling vigour

Open-pollinated maize (Zea mays) varieties remain popular in marginal communities since seeds can be selected and stored for the next season. However, maize weevil (Sitophilus zeamais) is an economic post-harvest pest of maize grains, which is difficult to manage. Various indigenous seed storage technologies had been in use within marginal communities, with little empirically-based support of their efficacy on weevils. The influence of storing maize seeds in active cattle kraal (ACK) for suppression of weevils and therefore protection of seeds was studied at three locations over two seasons. Water-tight plastic containers, each with 500 maize seeds infested with 20 maize weevils, with 10 replications, were stored in 30-cm-deep holes in ACK, with controls stored at farmer level. At 120 days after storage, relative to farmer controls, ACK reduced final S. zeamais numbers (73 to 95%) and damage of various seed sets (27 to 97%), but improved seed quality (101 to 3500%), seedling emergence (27 to 64%) and root/shoot ratio (19 to 50%). In conclusion, results of the study suggested that ACK storage has the potential for storing open-pollinated maize seeds throughout winter for farmers in marginal communities to allow for quality seeds that produce vigorous seedlings in the next growing season. Key words: Active cattle kraal, maize weevil, Sitophilus zeamais, seed quality, seedling vigour.

Evaluation of open pollinated varieties of maize for resistance to the maize weevil in a controlled temperature and humidity laboratory in Zimbabwe

Maize weevil (Sitophilus zeamais Motschulsky) is one of the major maize storage pests among smallholder farmers in eastern and southern Africa (ESA), thereby, reducing total on-farm maize harvests. Experiments were conducted in a controlled temperature and humidity (CTH) laboratory at CIMMYT-Zimbabwe to compare the resistance of new maize open pollinated varieties (OPVs) from regional trials undertaken in ESA to maize weevils. Twenty maize OPVs were shelled and cleaned before being placed in a deep freezer at −20 °C to kill any pests and eggs in the grain from the field. Fifty grams of grain from each OPV was measured after 3 weeks and placed in the CTH lab for conditioning. The samples were placed in 250-mL jars with brass-screened lids and then infested with 32 maize weevils aged between 10 and 14 days. Data were collected for kernel hardness prior to weevil infestation, as kernel hardness to confer resistance to weevils. The components of maize weevil resistance considered were: median development period, Dobie index of susceptibility, weevil emergence, weevil mortality, weevil fecundity, grain weight loss, kernel damage and germination. There were highly significant differences in maize kernel characteristics and median development period (P < 0.001) among the maize OPVs. There were significant differences in the number of damaged kernels, grain weight loss (P < 0.01), weevil mortality and germination (P < 0.05) among the maize OPVs. There were no significant differences found for weevil progeny emergence (F1), Dobie index of susceptibility and weevil fecundity, the last of which was positively and significantly correlated with kernel damage (P < 0.001). The DIS was positively and significantly correlated with weight loss and F1 (P < 0.001). The maize OPVs 07WEEVIL, Chitedze6, Strigoff126, Strigoff128 and ZM625 were found to be resistant; on the other hand, Strigoff140, Strigoff125, Strigoff133, VP05199 and VP074 varieties were highly susceptible.

Community based maize seed production in the hills and mountains of Nepal: A review

A review on the community based maize seed production and technology dissemination in Nepal was made in 2009 to know the seed production situation and technology dissemination approaches. Twenty three open pollinated maize varieties and one hybrid were released by the Nepal Agricultural Research Council (NARC) up to 2009. A number of stakeholders were involved on improved technologies dissemination, seed production and marketing. Approaches for technology dissemination include district seed self sufficiency program (DISSPRO) and community based seed production (CBSP) program. About 4500 ton of cereal seeds annually has been producing from these approaches. Approach include subsidies on source seeds, creation of revolving funds, group/co-operative formation, their mobilization for participatory varietal selection (PVS), demonstrations, training, informal research and development (IRD) kit distribution and exchange visits. In community level, activities such as community based seed production approaches, particiapatory technology development, verification and dissemination for sustainable seed production and marketing has been taken place. DOI: http://dx.doi.org/10.3126/ajn.v1i0.7550 Agronomy Journal of Nepal (Agron JN) Vol. 1: 2010 pp.107-112

Increase In Protein, Oil, Amylose and Amylopectin Contents of Two Populations of Maize (Zea Mays L.) After Two Cycles of Reciprocal Recurrent Selection

This research was conducted at the teaching and research farm of the Department of Crop Production and Landscape Management, Ebonyi State University, Abakaliki, from 2006 to 2012 cropping seasons to develop maize populations of increase protein, oil, amylose and amylopectin contents. Total of eight (8) maize varieties were used for the study and were grouped into two populations, A and B. Population A was coded A 1 , A 2 , A 3 and A 4 while population B was coded B 1 , B 2 , B 3 and B 4 . These two populations were genetically variable based on the time of maturity, percentage protein, oil, amylose and amylopectin. The mean protein content of the parents was 8.74% while their progenies after second cycle had percentage protein content of 13.27%, showing an increase of 4.53% with mid parent heterosis of 52%. The oil content of the open-pollinated maize varieties was pushed towards increasing order from 6.19% for population A and 4.19% for population B of the original populations to 5.61% and 5.62% for populations A and B respectively of the first cycle populations. These were further pushed up to 8.08% and 8.46% of the second cycle populations A and B respectively. The mean amylose content of the original population was 24.25% and the mean amylose content of the progenies after the first cycle was 22.02%. The second cycle synthetics had mean amylose content of 19.72%, showing a decrease of 4.53%. The mid parent heterosis was -9.2%. The mean amylopectin content of the original population was 75.75% and the mean amylopectin content of the selected high amylopectin was 82.13%, showing an increase of 6.38% over the mean amylopectin content of the original population. The breeding programme seems to be very effective in improving both the high, medium and low protein, oil, amylose and amylopectin contents of the original maize populations to all high protein, oil and amylopectin contents, except amylose, after the second cycle. In all, this method offers definite promise. Further progress in improving chemical constituents as well as other characters is theoretically possible in future cycles.

Heritability and Genetic Advance for Grain Yield and its Component Characters in Maize (&lt;i&gt;Zea &lt;/i&gt;&lt;i&gt;M&lt;/i&gt;&lt;i&gt;ays &lt;/i&gt;L.)

Knowledge of the magnitude of genetic variability, heritability and genetic gains in selection of desirable characters could assist the plant breeder in ascertaining criteria to be used for the breeding programmes. Ten open pollinated maize varieties were evaluated at the Teaching and Research farm, University of Ilorin, Nigeria, during 2005 and 2006 cropping seasons to estimate genetic variability, heritability and genetic advance of grain yield and its component characters. The effect of genotype and genotype by year interaction were significant for ear weight and grain y ield, while the effect of year was highly significant (P< 0.01) for all the characters. High magnitude of phenotypic and genotypic coefficient of variations as well as high heritability along with high genetic advance recorded for grain yield, number of grains ear -1 , ear weight, plant and ear heights provides evidence that these parameters were under the control of additive gene effects and effective select ion could be possible for improvement for these characters. Tze Co mp3 C2, Acr 94 Tze Co mp5, Tze Co mp 4-Dmr Srbc2 and Acr 90 Pool 16-Dt were identified as outstanding genotypes for maize grain yield and should be tested at mu ltilocation for their y ield performance.

On-farm evaluation of introduced maize varieties and their yield determining factors in East Timor

Maize is the major food crop of East Timor. It is grown under subsistence farming and its yields are low (1.0–1.7tha−1), with production insufficient to meet national needs. The “Seeds of Life” project, operating since 2001, has introduced open-pollinated maize varieties from other countries via the International Maize and Wheat Improvement Center (CIMMYT) and evaluated them for their suitability in local farming systems. Firstly, introductions were screened for yield potential and farmer-acceptable traits in replicated trials on research stations. Then, best selections were provided to farmers for evaluation against their local varieties under their own cultivation practices. More than 1000 on-farm trials were conducted across all of the agro-ecological zones of East Timor from the 2005/06 to the 2008/09 season. Mean annual yield advantage of the test varieties Suwan 5 and Sele over “local” varieties ranged from 36 to 54% and considerable initial adoption and diffusion to non-participating households was recorded. The large number of trials conducted over a wide range of agro-ecological and management conditions provided the opportunity to use analysis of variance to test the significance of factors contributing to yield. Major yield determinants were variety, agro-ecological zone, soil pH, plant density at harvest, frequency of project staff visits and wealth status of farmer. This combination of varietal testing with agronomic assessment has provided a basis for refinement of recommended cultivation practices for maize in East Timor. The project has demonstrated the feasibility of raising national maize production so as to approach national consumption needs. However, major constraints to realizing this potential are production of quality seed of improved varieties and its widespread distribution and effective extension of improved cultivation and grain storage practices.

Himalayan maize — potential pollen source for maize mediated system of chromosome elimination approach in DH breeding of bread wheat

To identify an efficient pollen source for maize mediated system of chromosome elimination, wheat genotypes (10 F1s) were pollinated with eight diverse Himalayan maize genotypes. Among these, two were composite varieties Early Composite (Check) and Bajaura Makka (L 201) and rest six were locally grown traditional open pollinated maize varieties collected from diverse regions of North-west Himalaya. The data were recorded for three haploid induction parameters viz. pseudo seed formation, embryo formation and regeneration. In most of the crosses, haploid embryos were produced, asserting the potential of wheat × maize system as a genotype non-specific system as compared to androgenesis and bulbosum technique, where the genotype specificity limits the development of haploid plants. Frequencies of all the three haploid induction parameters in different crosses of wheat × maize clearly indicated that both wheat and maize genotypes were behaving differently for different crosses. The line × tester analysis also ...

Grain yield and biomass response of a maize/dry bean intercrop to maize density and dry bean variety

An experiment was conducted under dryland conditions at the University of Limpopo experimental farm at Syferkuil in Capricorn district in 2007/2008 and 2008/2009 growing seasons to determine the effect of maize density and dry bean variety on maize/bean intercrop performance. The trial was at 2×2×2 factorial consisting of eight treatments: two maize densities (24 700 and 37 000 plants/ha), two dry bean varieties (small white haricot and red speckled sugar bean) and two cropping systems (sole cropping and intercropping). Open pollinated maize variety ZM 523 (ex CIMMYT) was used in the trial. The results showed that maize density of 24 700 plants/ha yielded lower maize grain than the recommended 37 000 plants/ha and maize grain yields in sole cropping were significantly higher than in intercropping in both growing seasons. Intercropping of maize with red speckled sugar bean resulted in lower grain yield than intercropping of maize with small white haricot in both seasons. Increasing maize density to 37 000 plants/ha reduced number of branches per plant and grain yield of dry bean in both seasons. Sole cropping produced the highest dry bean grain yield component values. Intercropping maize and beans was advantageous at the different bean variety x maize density combinations with all, except one, achieving Land equivalent ratio (LER) values greater than 1. Intercropping of maize plant density of 37 000 plants/ha with red speckled sugar bean gave the highest total LER value in 2007/8 season but less than 1 in 2008/9 season. Intercropping was more advantageous than sole cropping in this study. The highest monetary values were achieved by the bean sole crops and their intercrops with 24 700 plants/ha maize. In this study maize densities of 37 000 plants/ha and 24 700 plants/ha were found to be suitable for sole maize and maize/bean intercropping, respectively. Key words: Maize/bean, intercropping, smallholder, maize density, bean variety.

In vitro regeneration of selected commercial Tanzanian open pollinated maize varieties

Four Tanzanian open pollinated maize varieties namely; Kito, Situka M-1, Staha and TMV-1 were regenerated in vitro using immature zygotic embryos as ex-plants. Callus induction was achieved using Murashige and Skoog (MS) basal medium supplemented with 1, 1.5, 2 or 2.5 mg/l of 2, 4-D. Callus induction was significantly affected by the genotype of the varieties. Among the varieties tested, Kito, Situka M-1 and Staha had significantly higher callus induction frequency of 84.4, 92.7 and 88.7%, respectively compared to TMV-1 (43.3%). Embryogenic callus induction percentage was significantly influenced by the genotype, 2, 4-D concentrations and their interaction effect implying differential response of the genotypes to 2, 4-D concentrations. Among the genotypes tested, Kito gave significantly (p<0.05) the highest embryogenic callus frequency of 69.5%. Great variations were observed among the genotypes with regard to regeneration frequencies. Staha was comparatively the most regenerable variety with RF of 32.6% than even Kito which had the highest callus induction and embryogenic callus formation. MS medium amended with 1 mg/l 2, 4-D was observed to be the optimum formulation for the induction of embryogenic calli for genotypes tested in this study. Using this regeneration system Situka M-1, Staha and TMV-1 can now be improved against various production constraints through genetic engineering. Key words : 2, 4-dichlorophexyacetic acid, embryogenic callus, immature zygotic embryos, regeneration frequency, somatic embryos, Tanzanian open pollinated maize.

Correlation and path coefficient analysis of yield and agronomic characters among open pollinated maize varieties and their F1 hybrids in a diallel cross.

A two-year study was conducted on maize (Zea mays L.) at the University of Ilorin Teaching and Research Farm Ilorin, Nigeria, during 2005 and 2006 growing seasons. The objective was to investigate correlation between grain yield and other agronomic parameters using 10 open-pollinated maize varieties and their 45 F1 hybrids in a half diallel. Positive and significant phenotypic and genotypic correlations were found for days to 50% tasselling with plant and ear height, and grain yield with plant height, number of grains ear-1 and ear weight. Positive and significant environmental correlation was also recorded for grain yield with plant and ear height, and ear weight. The path analysis revealed that, days to 50% silking, ear weight and number of grains ear-1 had the highest direct effect on grain yield, while number of grains ear-1 had the highest moderate indirect negative effects on grain yield. Days to flowering, plant and ear height, number of grains ear-1 and ear weight could be the important selection criteria in improving open pollinated maize varieties and hybrids for high grain yield.