Combining ability of extra‐early biofortified maize inbreds under Striga infestation and low soil nitrogen

Open Access Article; Published online: 06 May 2020Striga hermonthica (Del.) Benth parasitism, low soil N, and nutritional deficiencies of normal‐endosperm maize (Zea mays L.) threaten maize yield and exacerbate nutritional problems in sub‐Sahara Africa (SSA). This study was conducted (a) to evaluate genetic variation among extra‐early maturing maize hybrids with provitamin A and quality protein characteristics, (b) to investigate gene action governing the inheritance of Striga resistance, grain yield, low N tolerance, and other measured traits under low‐N, high‐N, and Striga‐infested environments, and (c) to identify hybrids with high yield and stability across environments. One hundred and fifty hybrids developed using North Carolina Design II were evaluated with six checks under low‐N, high‐N, and Striga‐infested environments in Nigeria. Mean squares for hybrids were highly significant (P < .01) for grain yield and other traits across environments. Only general combining ability (GCA) for female and/or male mean squares were significant for measured traits under low N. In addition to significant GCA effects for most traits, specific combining ability was significant (P < .05) for Striga emergence count under Striga infestation, and ear height and ears per plant under high N, indicating that additive and nonadditive genetic effects controlled the inheritance of few traits under Striga and high N, whereas additive genetic effect governed the inheritance of the traits under low N. Hybrids TZEEIORQ 55 × TZEEIORQ 26, TZEEIORQ 49 × TZEEIORQ 75, and TZEEIORQ 52 × TZEEIORQ 43 were high yielding and stable across environments and have potential for improving nutrition and maize yields in SSA

Optimizing sample size for molecular characterization of open-pollinated maize (Zea mays L.) varieties using simple sequence repeat markers

Molecular-based characterization of open-pollinated varieties (OPVs) in maize is useful to define their unique profiles. A total of 58 SSR markers selected from a panel of 70 were used for genotyping three samples of 30, 50 and 100 plant bulks for each of 32 OPVs. The SSR markers detected a total of 253 alleles in the 32 maize OPVs across the three bulk samples. The number of alleles per marker varied from 2 to 7, with an overall mean of 4.36. The genetic distance among the OPVs varied from 0.17 to 0.93 with an average of 0.70 ± 0.007 for bulk samples of 30 plants, 0.20 to 0.91 with an overall mean of 0.70 ± 0.007 for bulk samples of 50 plants and from 0.30 to 0.95 with an average of 0.75 ± 0.006 for bulk samples of 100 plants. Cluster analysis separated the 32 maize OPVs into two major groups, which were further separated into two sub-groups for each type of bulk sample. The groupings of the OPVs into two major groups and their corresponding sub-groups was consistent with known breeding history (common parentage) and common target traits during development of the OPVs irrespective of the sample size used. However, in the bulk samples of 50 and 100 plants, some sub-groups were composed of OPVs with mixed maturity classes and diverse genetic backgrounds. Of the three independent bulk samples, the smallest sample size of 30 plants was found to be optimal for characterizing heterogeneous and heterozygous maize populations and OPVs owing to its cost-effectiveness and relative ease of sample processing

FIELD PERFORMANCE OF Shrunken-2 MAIZE HYBRIDS AND ITS RELATIONSHIP WITH GENETIC DISTANCE OF THEIR INBRED PARENTS

Maize ( Zea mays L.) is an important crop in West and Central Africa, where flint and dent types are the widely cultivated and used as food, feed and raw materials in industries. Sweet maize, the generic term used for maize types with elevated levels of sugar in their kernels, is increasingly popular in Nigeria and other countries of West Africa. This study evaluated the field performance of some super-sweet shrunken-2 (sh-2 ) maize hybrids and determined its relationship with SSR-based genetic distance of their inbred parents. A total of 21 shrunken-2 maize hybrids and seven shrunken-2 maize hybrid checks were evaluated. Analysis of variance was carried out on data collected and correlation analysis between the genetic distance of parental lines and agronomic traits of their hybrids. There were significant differences (P &lt; 0.01) among the hybrids for all agronomic traits studied. Field emergence ranged from 28.2 to 97.4%; while fresh cob weight and husk cover (1-9) ranged from 0.05 to 0.17 and 2.7 to 6.7 g plant-1, respectively. Among the hybrids, UI1 x UI75 was the most promising, combining high emergence with high fresh cob yield, good husk cover, resistance to endemic foliar diseases, good plant aspect and moderate ear aspect. Genetic distance between parental inbred lines was not useful for predicting hybrid performance among the sets of shrunken-2 inbred lines considered. The parental lines, however, have potential for use in shrunken-2 maize breeding programmes.Le ma\uefs (Zea Mays L.) est une culture importante en Afrique de l\u2019Ouest et du Centre, o\uf9 les types de silex et dent\ue9 sont largement cultiv\ue9s et utilis\ue9s comme aliments, aliments pour animaux et mati\ue8res premi\ue8res dans les industries. Le ma\uefs doux, le terme g\ue9n\ue9rique utilis\ue9 pour les types de ma\uefs avec des niveaux \ue9lev\ue9s de sucre dans leurs grains, est de plus en plus populaire au Nigeria et dans d\u2019autres pays d\u2019Afrique de l\u2019Ouest. Cette \ue9tude a \ue9valu\ue9 la performance au champ de certains hybrides de ma\uefs super-doux shrunken-2 (sh-2) et a d\ue9termin\ue9 sa relation avec la distance g\ue9n\ue9tique bas\ue9e sur le SSR de leurs parents consanguins. Au total, 21 hybrides de ma\uefs shrunken-2 et sept t\ue9moins hybrides de ma\uefs shrunken-2 ont \ue9t\ue9 \ue9valu\ue9s. Une analyse de variance a \ue9t\ue9 effectu\ue9e sur les donn\ue9es recueillies et une analyse de corr\ue9lation entre la distance g\ue9n\ue9tique des lign\ue9es parentales et les caract\ue8res agronomiques de leurs hybrides. Il y avait des diff\ue9rences significatives (P &lt; 0,01) entre les hybrides pour tous les caract\ue8res agronomiques \ue9tudi\ue9s. L\u2019\ue9mergence au champ variait de 28,2 \ue0 97,4 %; tandis que le poids de l\u2019\ue9pi frais et la couverture de l\u2019enveloppe (1-9) variaient de 0,05 \ue0 0,17 et de 2,7 \ue0 6,7 g plante-1, respectivement. Parmi les hybrides, UI1 x UI75 \ue9tait le plus prometteur, combinant une \ue9mergence \ue9lev\ue9e avec un rendement \ue9lev\ue9 en \ue9pis frais, une bonne couverture de brou, une r\ue9sistance aux maladies foliaires end\ue9miques, un bon aspect de la plante et un aspect mod\ue9r\ue9 de l\u2019\ue9pi. La distance g\ue9n\ue9tique entre les lign\ue9es consanguines parentales n\u2019\ue9tait pas utile pour pr\ue9dire les performances hybrides parmi les ensembles de lign\ue9es consanguines shrunken-2 consid\ue9r\ue9es. Les lign\ue9es parentales, cependant, ont un potentiel d\u2019utilisation dans les programmes de s\ue9lection de ma\uefs Shrunken-2

Shoot and plantlet regeneration from meristems of Dioscorea rotundata poir and Dioscorea alata L.

Open Access JournalIn vitro culture media capable of regenerating moderate to high shoots and/or plantlets from meristems of two yam species – Dioscorea rotundata and Dioscorea alata within comparable duration of 10 weeks as commonly obtained in other monocots and root and tuber crops were investigated. The study comprised 125 phytohormone combinations investigated in three factorial experiments each consisting of an auxin (NAA) and a cytokinin (BAP or kinetin), or two cytokinins only. The frequency of direct plantlet regeneration, though significantly (P < 0.05) higher for D. alata than for D. rotundata, was low and ranged from 0 to 10% at 3 weeks after culture (WAC) and 0 to 35% at 8 WAC. At 8 WAC, shoot regeneration of 42-75% was obtained in D. rotundata in MS medium supplemented with 0.1 M NAA + 0.20 M BAP, and shoot + plantlet regeneration of 60-82% obtained in media containing 0.05 M + 0.20 M BAP or 0.46 M BAP + 0.50 M kinetin in D. alata. Both shoot induction and plantlet regeneration were species-dependent. Induced shoots were successfully rooted in MS medium within 3 to 4 weeks, bringing time taken for plantlet regeneration to 11 to 12 weeks. Regenerants were morphologically similar to the mother plants. Results of the present study will facilitate regeneration of plantlets via meristem in D. rotundata and D. alata

Combining ability and performance of extra-early maturing yellow maize inbreds in hybrid combinations under drought and rain-fed conditions

Article purchased; Published online: 06 Nov 2017Maize (Zea mays L.) is a major staple food and cash crop in sub-Saharan Africa (SSA). However, its production and productivity are severely constrained by drought. A total of 120 single-cross hybrids and an open-pollinated control variety were evaluated for 2 years at two locations under managed drought and rain-fed conditions in Nigeria. The objective of the present study was to assess their performance, classify them into distinct heterotic groups and identify promising hybrids for commercialization in the West and Central Africa sub-region. General combining ability and specific combining ability mean squares were highly significant for grain yield and other traits under the research environments. However, there was a preponderance of additive gene action over non-additive. Only six out of 39 inbreds were classified into distinct heterotic groups by the testers. The highest-yielding drought-tolerant hybrid, TZEEI 102 × TZEEI 95, out-yielded the open-pollinated control variety by 43·70%. The average yield reduction under drought was 54·90% of the yield under rain-fed conditions. The hybrids TZEEI 81 × TZEE1 79, TZEEI 100 × TZEEI 63 and TZEEI 64 × TZEEI 79 were the highest-yielding and most stable across environments. These outstanding drought-tolerant hybrids, which are also resistant to Striga, have the potential to contribute to food security and increased incomes in SSA and should be tested extensively on-farm and commercialized

Validation of diagnostic markers for streak virus disease resistance in maize

Open Access Journal; Published online: 05 Feb 2021Maize streak virus (MSV) is responsible for streak disease of maize and poses a serious threat to maize production in sub-Saharan Africa. Polygenic resistance to MSV has become an essential requirement in modern maize cultivars to mitigate yield losses. Many single nucleotide polymorphism (SNP) markers linked to putative MSV resistance loci have been identified for use in forward breeding. This study aimed to validate, using the high-throughput kompetitive allele specific PCR (KASP) assay, the diagnostic ability of the three SNP markers linked to the loci for the Msv1 resistance trait in 151 early generations inbred lines with diverse genetic backgrounds, together with nine MSV-resistant elite lines and a susceptible check (cv. Pool-16). The phenotypic responses were determined by MSV inoculation using viruliferous leafhoppers (Cicadulina triangular) under screenhouse conditions. Based on an established MSV disease rating system, the maize lines were categorized into resistant, moderately resistant, susceptible, and highly susceptible. The three SNPs associated with MSV resistance were detected in 133 lines, which were categorized as resistant (54), moderately resistant (76), and susceptible (1). The 18 early generation lines without these SNPs were classified as moderately resistant (10), susceptible (5), and highly susceptible (3). This study confirms the strong association of SNPs with MSV resistance and their usefulness for forward breeding in maize while emphasizing the need to identify additional markers to screen lines for MSV resistance without any ambiguity

Inheritance of pod length and other yield components in two cowpea and yard-long bean crosses

Open Access Article; Published online: 2 Apr 2021This study determined the gene effects involved in the inheritance of pod length and other yield-related traits and relationships among traits in crosses between two cowpea lines (TVu 2280 and TVu 2027) and a yard-long bean (TVu 6642) line with long pods. Plants of six generations (P1, P2, F1, F2, BC1P1, and BC1P2) derived from TVu 2280 × TVu 6642 and TVu 2027 × TVu 6642 were evaluated under field conditions. Data collected on 14 yield components of each cross were used for generation mean analysis. Gene effects and their magnitudes varied with the crosses; digenic epistatic gene effects were detected for 10 traits in TVu 2280 × TVu 6642 and 11 traits in TVu 2280 × TVu 6642. Only additive gene effect was significant for pod length in TVu 2280 × TVu 6642 while additive, dominant, and two of the three digenic epistatic gene effects were significant in TVu 2027 × TVu 6642. Models that incorporated only significant additive, dominant, and digenic epistasis were adequate for all 14 traits in TVu 2280 × TVu 6642 and eight of the 12 traits in TVu 2027 × TVu 6642 for which model-fitting was possible. Across segregating generation of the two crosses, pod length (PodLNT) was significantly (p < 0.001) correlated with three major yield components viz. pod weight (0.84, 0.77), number of seeds per pod (0.41, 0.30) and seed weight per pod (0.61, 0.29). Significant correlation of PodLNT with seed yield per plant was moderate and significant (p < 0.01–0.001) in the BC1P1 of the two crosses (0.31 and 0.41). An improvement in cowpea seed yield is feasible through selection for long pods in segregating generations involving crosses with yard-long bean

Characterization of host tolerance to Striga hermonthica

One of the most promising control options against the parasitic weed Striga hermonthica is the use of crop varieties that combine resistance with high levels of tolerance. The aim of this study was to clarify the relation between Striga infestation level, Striga infection level and relative yield loss of sorghum and to use this insight for exploring the options for a proper screening procedure for tolerance. In three pot experiments, conducted in Mali (2003) and The Netherlands (2003, 2004), four sorghum genotypes were exposed to a range of Striga infestation levels, ranging from 0.0625 to 16 seeds cm−3. Observations included regular Striga emergence counts and sorghum grain yield at maturity. There were significant genotype, infestation and genotype × infestation effects on sorghum yield. The relation between infestation level and infection level was density dependent. Furthermore, the relation between Striga infection level and relative yield loss was non-linear, though for the most resistant genotype Framida only the linear part of the relation was obtained, as even at high infestation levels only moderate infection levels were achieved. The results suggest that for resistant genotypes, tolerance can best be quantified as a reduced relative yield loss per aboveground Striga plant, whereas for less resistant genotypes the maximum relative yield loss can best be used. Whether both expressions of tolerance are interrelated could not be resolved. Complications of screening for tolerance under field conditions are discussed

Applications and Action Mechanisms of Probiotic-Based Multi-Components

editorial reviewedProbiotic-based multi-component preparations refer to a mixture of bioactive agents, containing probiotics or postbiotics as main functional ingredients, and prebiotics, protectants, stabilizers, encapsulating agents, and other compounds as additional constituents.One Health approaches to support agroecological transformation of peri-urban farming1. No poverty2. Zero hunger3. Good health and well-being10. Reduced inequalities11. Sustainable cities and communities12. Responsible consumption and production13. Climate action17. Partnerships for the goal

Responses of tolerant and susceptible maize varieties to timimg and rate of nitrogen under Striga hermonthica infestation

urple witchweed [Striga hermonthica (Del.) Benth.], here called just striga, parasitizes cereal crops in the savanna zone of sub-Saharan Africa. The objectives of this study were to investigate the expressions of a tolerant and a susceptible cultivar of maize (Zea mays L.) to striga as affected by timing (0, 2, 4, and 6 wk after maize planting) and rates (60 and 120 kg N ha−1) of N application under striga infestation. The experiment was designed as a split-split plot with four replications. Timing of N application and N rates significantly affected striga emergence, host-plant damage scores, agronomic traits, and grain yield. Nitrogen rate x application time interaction was highly significant for striga emergence. Time of N application was more important than N rate in suppressing striga emergence and host-plant damage. Nitrogen application at 2 wk after planting and 120 kg N ha−1 gave the best result in terms of maize performance and reduction of striga emergence. Host-plant damage symptoms were more useful in differentiating response of host genotypes to striga than striga emergence values. The tolerant cultivar (hybrid 8322-13) produced 188% higher grain yield than the susceptible cultivar (hybrid 8338-1) across all treatments. Grain yield of the tolerant cultivar at 60 kg N ha−1 was 88% higher than that of the susceptible cultivar at 120 kg N ha−1. The tolerant cultivar produced an average 157% more ears at 60 kg N ha−1 and 51% more ears at 120 kg N ha−1 than the susceptible cultivar. Among all the factors studied, the most important component for striga management was genetic tolerance, the ability of a host plant to withstand the parasite