Genetic variability, heritability and genetic advance studies in topcross and three-way cross maize (Zea mays L) hybrids

Understanding the genetic variability, heritability and genetic advance of traits in any plant population is an important pre-requisite for selection program. This study was designed to assess the magnitude of genetic variability, heritability and genetic advance of traits in top-cross and three-way cross maize (Zea mays L) hybrids evaluated at three locations in South-Western Nigeria. The trial consisted of ten genotypes each of top-cross and three-way cross hybrids arranged in randomized complete block design with three replications. Data on grain yield and other desirable traits across the three locations were used to estimate the genetic variability parameters, heritability and genetic advance (GA). Highly significant (P ≤ 0.01) differences were detected within each hybrid class for all the traits. Traits evaluated in this study exhibited different levels of variability, heritability and genetic advance between the two hybrid classes. Low to moderate phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) were recorded. Also, low to very high heritability and low to high GA values were recorded for all the traits measured in the top-cross hybrids, whereas the three-way cross hybrids exhibited low to moderately high heritability estimates and low to moderate GA values. Grain yield and field weight showed moderate GCV, moderately high heritability and high GA values in top-cross hybrids. These characters exhibited moderate GCV but low heritability and GA values in three-way hybrids. More characters in top-cross hybrids revealed sufficient amount of variability than in three-way cross hybrids, thus offer scope for genetic improvement through selection

Genetic analysis of mode of inheritance of seed yield and its components in tropical soybean genotypes

The decision related to efficient breeding methods depends largely on the understanding of the type of gene action controlling the expression of the characters to be selected. The objective of this study was to estimate the gene action controlling yield and components in soybean (Glycine max L. Merrill). The study involved six basic soybean generations (P1, P2, F1, F2, BC1 and BC2) of two crosses, i.e. cross I (TGx1987-62F × TGx1830-20E) and cross II (TGx1987-10F × TGx1740-2F), at the Research farm of the International Institute for Tropical Agriculture, IITA, Ibadan. Data were subjected to generation mean analysis to determine gene actions and interactions, using Hayman model. The results obtained from the individual scaling test A, B, C indicated that the simple additive-dominance model was inadequate to reveal the inheritance of the gene governing most traits. Non-allelic gene interaction was crucial in the inheritance of most studied traits. The Hayman six-parameter genetic model demonstrated that the signs of [h] and [l] were contrasting for most of the traits; suggesting duplicate epistasis. In fact, the effect of dominance was important and significant in the genetic control of most of the traits studied. Therefore, improvement of soybean seed yield and its related characters need intensive selection and should be delayed until later generations. &nbsp

PRELIMINARY EVALUATION OF GRAIN AMARANTH (Amaranthus spp.) ACCESSIONS FOR DROUGHT TOLERANCE BY MULTIVARIATE TECHNIQUE

Ciljevi ovog pokusa bili su usporediti različite pokazatelje tolerantnosti na sušu za predviđanje tolerantnosti na sušu i procijeniti trideset potomaka zrnatog amaranta (Amaranthus spp.) na tolerantnost na sušu primjenom nekoliko pokazatelja tolerantnosti na sušu. Sjeme trideset (30) potomaka zrnatog amaranta sakupljeno u Nacionalnom poljoprivrednom istraživačkom institutu (NIHORT) u Ibadanu selekcionirano je 2011. godine u Selekcijskom centru NIHORT-a. Sjeme je uzgajano u rasadniku tri tjedna i zatim presađeno u polietilenske vreće. Uveden je vodeni stres 4, 6 i 8 tjedana nakon presađivanja (WAT), a kontrola je provedena u 100% terenskim uvjetima. Pokus je bio potpuno randomiziran plan (CRD) postavljen u faktorijalnom rasporedu 4 x 30 u tri ponavljanja. Upotrijebljeni su agronomski podaci i pokazatelji tolerantnosti na sušu za procjenu performance zrna amaranta. Obavljena je analiza varijance (ANOVA) da se ustanovi značajan učinak (P0,05) je smanjio visinu biljke, te broj listova i grančica amaranta. Amarant je u terenskim uvjetima dao značajno (P<0,05) veći prinos sjemena od amaranta pod stresom od 8 WAT-a (54 odnosno 25 gbiljaka-1) Prinos sjemena bio je u znatnoj pozitivnoj korelaciji s duljinom korijena (r=0,86++), suhom težinom izdanka (r=0,79**), STI (r=0,96**, GMP (re=0,97** i HM(r=0,95**), ali ne sa SSI. Analiza klastera je pokazala da su potomci imali tendenciju kategorizacije u tri skupine na razini 96% sličnosti, potomci AMES 5647, PI576464, PI576483 i PI576483 imali su najviši STI, GMP, MP, HM i prema tome su smatrani najpoželjnijim klasterom u oba uvjeta. U zaključku, ovaj je rad pokazao da se selekcija na tolerantnost na sušu može temeljiti na STI, GMP, MP i HM na osnovi njihove značajne pozitivne korelacije s prinosom zrna.The objectives of this experiment were to compare different drought tolerance indices for drought tolerance prediction and evaluate thirty accessions of grain amaranth (Amaranthus spp.) for drought tolerance using several drought tolerance indices. Seeds of thirty (30) accessions of grain amaranth collected from National Horticultural Research Institute (NIHORT), Ibadan were screened in 2011 at the screen house of NIHORT. Seeds were raised in nursery for three weeks and later transplanted into polyethylene bags. Water stress was imposed at 4, 6 and 8 weeks after transplanting (WAT) and the control was maintained at 100 % field capacity. The trial was a completely randomized design (CRD) laid out in a 4 × 30 factorial arrangement replicated three times. Agronomic data and drought tolerance indices were used to assess the performance of grain amaranth. Analysis of variance (ANOVA) was performed to establish significant effect (P ≤ 0.05; F-test) of the treatments on the parameters taken, significant means were separated using standard error of the difference of means in post ANOVA t-tests. Result of the experiment showed that grain amaranth stressed at 4 and 6 WAT died before reaching maturity, water stress significantly (P < 0.05) reduced plant height, number of leaves and branches of grain amaranth. Grain amaranth at field capacity produced significantly (P < 0.05) higher seed yield than those stressed at 8WAT (54 and 25 gplant-1 respectively). Seed yield had significant positive correlation with root length (r = 0.86**), shoot dry weight (r = 0.79**), STI (r = 0.96**), GMP (r = 0.97**) and HM (r = 0.95**) but not with SSI. Cluster analysis indicated that the accessions tended to be categorized into three groups at 96 % similarity level, accession AMES5647, PI576464, PI576454 and PI576483 had the highest STI, GMP, MP, HM and was thus considered to be the most desirable cluster for both conditions. In conclusion, this study showed that selection for drought tolerance could be based on STI, GMP, MP, HM based on their significant positive correlation with grain yield

Correlation and path coefficient analysis of top-cross and three-way cross hybrid maize populations

Open Access JournalGrain yield is a complex quantitative trait that depends on a number of other traits for selection. This study was carried out to reveal the pattern of association with and contribution of traits to grain yield in two maize populations evaluated in three agro-ecological zones of South-Western Nigeria during the 2014 cropping season. The experiment consisted of 10 top-cross and 10 three-way cross maize hybrids, laid out in a randomised complete block design with three replications. Genotypic and phenotypic correlation coefficients and path co-efficient analyses were performed for each hybrid population across the three locations. Results showed significant (p≤0.05) differences between the two hybrid populations for all the traits mentioned except days to 50% anthesis, ear diameter and 100-grain weight. Field weight in both hybrid populations, number of kernel rows per cob, ear diameter and ear height in top-cross hybrids, as well as ear length and 100-grain weight in the three-way cross hybrids were directly correlated with grain yield. The link between direct and indirect effects on grain yield depends on hybrid population, although some traits showed similar direct effects in both hybrid populations. These traits can be used as the main criteria for grain yield improvement in the respective hybrid populations

Combining ability of extra-early maturing provitamin A maize (Zea mays L.) inbred lines and performance of derived hybrids under Striga hermonthica infestation and low soil nitrogen

Open Access JournalLow soil nitrogen (low-N), Striga hermonthica infestation and vitamin A deficiency in normal endosperm maize are major challenges confronting maize production and nutrition of the people of sub-Saharan Africa (SSA). Development of pro-vitamin A (PVA) maize hybrids with combined resistance/tolerance to the two stress factors is crucial in mitigating the food insecurity and nutrition challenges resulting from low-N deficiency and Striga infestation. One hundred and fifty hybrids plus six hybrid checks were evaluated under low-N, Striga-infested and optimal conditions in Nigeria for two years. The study examined the combining ability of the PVA inbreds in contrasting environments, classified them into heterotic groups, examined the inter-relationships of grain yield and other agronomic traits of the inbreds in hybrid combinations and assessed the performance and stability of the PVA hybrids across environments. Additive gene action conditioned the inheritance of grain yield under Striga infestation and optimal conditions while non-additive gene action played the major role in the inheritance of grain yield under low-N. Hybrids TZEEIOR 217 × TZEEIOR 197 and TZEEIOR 245 × TZEEIOR 195 were the top-yielding under Striga and low-N conditions, respectively. Inbred lines were classified into three heterotic groups. Inbreds TZEEIOR 195 and TZEEIOR 221 were identified as testers while TZEEIOR 197 × TZEEIOR 82, TZEEIOR 132 × TZEEIOR 195 and TZEEIOR 205 × TZEEIOR 221 were identified as single-cross testers. Ear aspect had direct contribution to grain yield, justifying its inclusion in the multiple trait base index used for selection of Striga resistant and low-N tolerant maize genotypes in SSA. Hybrids TZEEIOR 195 × TZEEIOR 149, TZEEIOR 195 × TZEEIOR 150, TZEEIOR 245 × TZEEIOR 195, TZEEIOR 30 × TZEEIOR 150 and TZEEIOR 245 × TZEEIOR 30 were high-yielding and stable across test environments. These hybrids should be tested extensively in on-farm trials and commercialized to contribute to food security in SSA

RELATIVE DISCRIMINATING POWERS OF GGE AND AMMI MODELS IN THE SELECTION OF TROPICAL SOYBEAN GENOTYPES

Selection of crops is preceded by multi-locational testing in plant breeding; however, it becomes difficult for breeders to determine which genotypes should be selected in the presence of genotype by environment (GEI). Six genotypes of soybean ( Glycine max (L.) Merr.) were evaluated at ten locations in Nigeria for grain yield and stability. The analysis of variance revealed significant (P 640.05) GEI effect. Mean grain yield of the soybean genotypes ranged from 1148 kg ha-1 for genotype M351 to 1584 kg ha-1 for TGx 1448-2E. Ilorin in the southern guinea savanna of Nigeria was the most variable with high interaction principal component axes (IPCA); while Bauch in the northern guinea savanna was identified as more stable location in evaluating the soybean genotype. Mega-environments and the best yielding soybean genotypes in each mega-environment were revealed by the GGE biplot analysis. Furthermore, TGx 1448-2E and TGx 1440-1E, were established as the most promising, and stable genotypes across the test locations. Stability model of GGE biplot was superior, effective and informative in mega-environment analysis compared to AMMI analysis.La s\ue9lection des cultures est pr\ue9c\ue9d\ue9e de tests multilocaux en am\ue9lioration des plantes; cependant, il appara\ueet difficile pour les am\ue9liorateurs de d\ue9terminer quels types de g\ue9notypes s\ue9lectionner en pr\ue9sence du g\ue9notype x environnement (GEI). Six g\ue9notypes du Soja ( Glycine max (L.) Merr.) \ue9taient \ue9valu\ue9s dans dix milieux au Nigeria pour le rendement en grains et la stabilit\ue9. L\u2019analyse de la variance a r\ue9v\ue9l\ue9 un effet significatif (P 64 0.05) du GEI. Le rendement moyen en grains des g\ue9notypes du soja variait de 1148 kg ha-1 pour le g\ue9notype M351 \ue0 1584 kg ha-1 pour TGx 1448-2E. Ilorin au sud de la savanne guin\ue9enne au Nigeria \ue9tait le plus variable avec une interaction \ue9lev\ue9e des axes de la composante principale (IPCA); pendant que Bauch dans le nord de la savanne guinn\ue9enne \ue9tait identifi\ue9 comme milieu le plus stable dans l\u2019\ue9valuation du g\ue9notype du soja. Les Mega-environments et le meilleur g\ue9notype du soja du point de vue rendement dans chaque mega-environment \ue9taient r\ue9v\ue9l\ue9s par l\u2019analyse du biplot. En plus, TGx 1448-2E et TGx 1440-1E, \ue9taient jug\ue9s les plus promettants et g\ue9notypes stables \ue0 travers le test de milieu. Le mod\ue8le de stabilit\ue9 du biplot GGE \ue9tait sup\ue9rieur, effective et informative dans l\u2019analyse m\ue9ga-environmentale en comparaison avec l\u2019analyse du AMMI

Correlations and Path-Coefficient Analysis of Component of Seeds Yield in Soybeans

Twenty-four genotypes of soybeans ( Glycine max (L.) Merr) were grown in a randomized complete block experiment. Genotype and phenotypic correlation coefficients were calculated for 12 characters. Phenotypic correlation coefficients were generally lower than genotypic coefficients. While no character was phenotypically correlated with seed yield, days to maturity, nodulation, number of flowers per plant, height at harvest, shattering and 300-seed weight were genotypically correlated with seed yield. The genotypic correlation coefficients with seed yield of selected eight characters were partitioned into direct and indirect causes. Nodulation and number of flowers per plant had the largest positive direct effects on seed yield with largest indirect effect through height at flowering and reduction in nodulation, respectively. The study indicated that since no one character was absolutely important for seed yield, selection should be based on simultaneous consideration of various characters

Genetics of seed yield and related traits in biparental crosses of okra, Abelmoschus esculentus (L.) Moench

Gene action and interaction are very important in formulating the appropriate breeding technique to produce new varieties in okra. The objective of the study was to investigate gene action controlling yield and 12 related traits in okra. Sixteen bi-parental progenies of okra were evaluated in October, 2013 and May, 2014 at the Federal University of Agriculture, Abeokuta (Lat 7°29 N, Long 3°30 E), Nigeria. Seeds were sown in single-row plots laid out in randomized complete block design with three replicates. Mean squares were obtained for the thirteen characters according to North Carolina Design II. Heritable variances were partitioned into additive and dominance components. General (GCA) and specific combining abilities (SCA) of both parental and progenies respectively were estimated with a view to identifying high combiners among genotypes. Results suggested both additive and dominant gene effects for most characters with dominant gene effects for number of leaves per plant and weight of 100 seeds. The study concluded that both additive and dominant gene actions controlled the expression of characters in okra. NHGB/09/009A and FUNAAB-11-8 are high combiners for number of days to 50% flowering and number of pods/plant and they are recommended as high-yielding, early-maturing okra variety. FUNAAB-11-4 x LD 88 and UI4-30 x FUNAAB-11-8 can be further improved to develop high-yielding hybrid okra varieties due to their high SCA. Number of days to 50% flowering, plant height, number of branches per plant, pod weight and number of ridges per pod will respond to selection because of the preponderance of additive gene action