Diallel analysis of maize inbred lines for agronomic traits in nitrogen stress and optimal conditions

Increasing demand, soil cultivation pressure and adverse climate change effects necessitated maize production in nitrogen stress soils. This study examined the general combining ability (GCA) of 12 maize inbreds and specific combining ability of their crosses for agronomic traits under varied nitrogen conditions. GCA accounted for 53% of the variation for grain yield (GY) under stress and 40% under optimal condition. GCA contributed over 59% for days to anthesis (DTA) and days to silking (DTS), anthesis-silking-interval (ASI) and ear aspect (EASP) under both conditions. BD74-165 and BD74-161 had positive significant GCA for GY under stress with TZEI12 under optimal and BD74-222 under both conditions. TZEI13 and TZEI16 had positive significant GCA for DTA and ASI under stress, and TZEI12, TZEI11 and BD74-161 under optimal. Additive genes control DTA, DTS and PH; non-additive genes were responsible for ASI, PASP and EASP while both additive and non-additive genes governed inheritance of GY, EH and leaf-senescence (SEN) under stress. Inheritance of GY, ASI, PH, PASP and EASP were due to non-additive genes; DTA and DTS to additive genes while additive and non-additive genes control EH and SEN under opti­mal condition. Inbreds with significant GCA can be parents for GY improvement under respective conditions. Keywords: Combining ability; diallel; low nitrogen; maize lines; stress toleranc

Association studies between grain yield and agronomic traits of a MARS maize (Zea mays L.) population under drought and non-stress condition

Open Access JournalThe study aimed at examining the associations between yield and other traits under drought stress and non-stress conditions. A total of 150 MARS testcrosses were evaluated under both conditions at the International Institute of Tropical Agriculture substation for two years under during the dry season. Genotypic and phenotypic correlation, multiple stepwise regression and path co-efficient analyses were carried out to examine the relationship among the traits under both environments. Results showed anthesis-silking interval, days to silking, husk cover and plant aspect were significantly associated with yield under drought condition at both genotypic and phenotypic levels. Yield was positively correlated with plant and ear height but had a negative correlation with plant and ear aspect at both levels under well-watered condition. Regression analysis showed that ears per plant, plant aspect, ear aspect, days to silking, leaf death and plant height had a direct effect on yield, contributing a total of 71.1 % of observed variation under drought, while ears per plant, ear aspect, plant aspect, days to pollen shed, days to silking and plant height contributed about 31.42 % to yield under well-watered conditions. The study concluded that these traits be used as selection criteria as it will aid improvement of maize yield

Application of SSR Markers for Genetic Purity Analysis of Parental Inbred Lines and Some Commercial Hybrid Maize (Zea mays L.)

Aims: Morphological evaluation of seeds and growing plants used for certification for purity and variety distinctness in Nigeria is time consuming and expensive. This experiment set to evaluate the usefulness of SSR markers to determine genetic purity of commercial hybrids and their inbred lines. Place and Duration of Study: Bioscience unit, International Institute of Tropical Agriculture, Nigeria in December, 2011 Methodology: Seedlings of four F1 hybrids and four inbred lines were grown in the screen house of IITA for DNA extraction using Dellaporta method with some modifications. Six Simple Sequence Repeat (SSR) markers were used for Polymerase Chain Reaction (PCR) using Touch-Down PCR profile. The analysis is by fragment analysis as present (1) or absent (0) Mathematical equation to determine genetic purity of the genotypes was developed from the genetic distances matrix. Results: Simple descriptive analysis revealed that average genetic diversity and polymorphism information content (PIC) recorded by the markers was 0.592 and 0.512 respectively. Genetic purity level of inbred lines ranged between 91.3% and 98.7% while the hybrids ranged between 81.3% and 95%. Conclusion: SSR markers are powerful biotechnological tool capable of detecting genetic purity status of Nigerian maize hybrids therefore inclusion of DNA analysis of seeds using SSR markers to determine genetic purity of maize seed is recommended. However, further research work with larger number of seed samples per variety will be needed to validate reliability

Yield stability of yellow maize hybrids in the Savannas of west Africa

There is growing interest for yellow maize among farmers and the food and feed industries in West Africa. Testing of maize hybrids in multi-location trials is crucial for identifying adapted high-yielding candidates for quick release. This study was designed to evaluate yield stability of three-way cross yellow maize hybrids across 17 diverse environments in the savannas of West Africa. Highly significant differences (P < 0.001) were observed among hybrids across locations. The interaction between genotypes and environments was significant for grain yield and most other agronomic traits, with high repeatability (0.68) for grain yield across the test environments. The hybrid A1001-19 was found to be the highest yielding, with yield advantage of 10% over the commercial hybrid Oba Super 2. The genotype, genotype by environment biplot identified hybrid A1001-7 as the most stable hybrid with above-average grain yield, followed by A1001-10. However, A1001-19 was relatively stable and was the best hybrid in 12 of the 17 environments across Mali, Nigeria, and Sierra Leone. Kudu and Zaria 2013 were the most discriminating locations for the hybrids. The stable yield performance of A1001-7 and A1001-10, and to a larger extent A1001-19, would benefit farmers and seed producers with limited capacity to handle single-cross hybrids. Hybrid A1001-10 was released by partners, and hybrids A1001-7 and A1001-19 have been evaluated in national performance and on-farm trials for potential release. This would provide more food for resource-poor farmers and raw materials for food and feed industries and would result in increased household incomes of smallholder farmers in West Africa