CREA Journals (Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria)
Not a member yet
791 research outputs found
Sort by
Expected responses to selection for resistance to the pink stem borer (Sesamia calamistis Hampson) and the sugarcane borer (Eldana saccharina Walker) in two maize populations
Get PDFProgenies from two maize populations, one white-grained (DMR ESR-W) and the other yellow (DMR ESR-Y) were evaluated under artificial infestation with two borer species (Sesamia calamistis and Eldana saccharina) in two seasons to predict responses and correlated responses to selection for resistance to stem borers. Correlations between grain yield and most agronomic parameters were significant. There were negative correlations between grain yield and damage parameters in both maize populations. The highest genotypic correlation coefficient was observed between grain yield and stem tunneling (rg = -0.52) in DMR ESR-Y, and with stalk breakage (rg = -0.67) in DMR ESR-W. A Rank Summation Index (RSI) generated using plant aspect, grain yield, stem tunneling, leaf feed¬ing and tolerance had positive phenotypic correlations with damage parameters, but negative relationship with agronomic traits. All agronomic parameters including grain yield will increase with selection. Grain yield increase of about 210 kg/ha will be obtained per generation in DMR ESR-W using two seasons to complete a cycle, but a relatively low increase (73 kg ha-1) is expected in DMR ESR-Y. Response from single trait selection was better than from RSI in DMR ESR-Y, but reverse was the case in DMR ESR-W. Correlated responses to selection showed that direct selection for most of the traits would be better than indirect selection through any other trait. Appreciable progress is expected from selection for improvement of the maize populations for resistance to the two borer spe¬cies, although progress from selection may be slow
Variation in agronomic characters among high and low nitrogen S2 maize (Zea mays L) lines grown in high and low nitrogen environments
Get PDFPoor soil fertility, especially with low levels nitrogen (N), is a major constraint to productivity and the production of maize in Sub-Saharan Africa (SSA). This phenomenon has raised the need to combine the breeding goals of yield improvement for conditions with low levels of N and yield improvement for conditions with high input of N fertilizer. The objective of this study was to evaluate variation in agronomic characters, heritability, genotype x environment (GxE), and predicted gains from selection of high and low N S2 maize breeding lines in both high and low N envi¬ronments. Fertilizer was not applied in low N environments, while the high N environments were fertilized at the rate of 150 kg N, 75 kg P2O5 and 75 kg K2O per hectare. The high and low N S2 progenies were evaluated under high and low N environments respectively in the research farms of the Nigerian Institute for Oil Palm Research (NIFOR), near Benin City (Latitude 6o 33’ N and Longitude 5°33’E), Edo State and Delta State College of Agricul¬ture, Ozoro (latitude 6°13’E and longitude 5°33’N). Both locations are situated in the rainforest ecological zone of Nigeria with average rainfall of 2,500 mm. The experimental designs used for both high and low N environments were 10 x 10 and 8 x 8 lattices respectively. The mean squares for the two high N environments were significant for all agronomic traits evaluated. Moreover, the mean squares for the high N S2 progenies were significant for all the observed agronomic characters except ear height and leaf senescence. The high N progenies x environ¬ments interaction was significant in most of the observed agronomic characters except leaf area, ear height and leaf senescence. On the contrary, the mean squares for the two low N environments were significant for all the observed agronomic characters except leaf senescence. Significant mean squares were observed among low N S2 progenies in leaf area, ear height, leaf senescence and grain yield. However, there was no low N x environment interaction for all the observed agronomic characters. Grain yield of low N S2 progenies was only 5.46% of the yield obtained among high N S2 progenies. Nitrogen stress resulted in reduction of growth (height) and yield of low N S2 progenies by 52.3% and 94.5%, respectively. Low N environments resulted in lower broadsense heritability than high N in most of the observed agronomic characters except plant height, leaf senescence and ear height. Heritability estimates in low N and high N ranged from -9.8 to 53.9% and -7.8 to 59.5%, respectively. The results indicated that the magnitude of genetic variance, heritability, and gains from selection are dependent on the nature of the crop environment. In spite of lower heritability under low N stress conditions, selection under low N would be more efficient than selection under high N for targeting low N stress environment
Preliminary results on the preferences of Callosobruchus maculatus on Apulian germplasm of Cicer arietinum
Get PDFThe susceptibility of six genotypes of Cicer arietinum L. (Fabaceae) to Callosobruchus maculatus (Fabr.) (Coleoptera: Bruchidae) was evaluated through comparative laboratory bioassays. The egg-laying amount, pattern of adult emergence, median development time and pre-adult mortality were assessed under free-choice and no-choice bioassays on three local genotypes (Altamura, Grumo Appula White and Grumo Appula Black) and three commercial varieties (Barraco, Sultano and standard of large-scale retail trade as control). Trials were performed on a completely randomized experimental design under artificial conditions with the release of males and females (ratio 1:3), at the most 24-h old. Among the assayed genotypes, the local one provided with a black coat (Grumo Appula Black) was significantly (
Approaches to improve the determination of eligibility for plant variety protection: I evaluation of morphological characteristics
Get PDFThe demonstration of distinctness through comparisons of morphological characteristics is an essential require¬ment in order to obtain Plant Variety Protection (PVP) and registration. Desires for increased international harmoni¬zation and the increasing size of reference collections place increased emphasis on improving the efficiency of the process. Morphological characteristics are notoriously affected by environment and many may be correlated in their expression. We developed an approach using inbred lines of maize (Zea mays L.) to evaluate characteristics according to their performance for 9 parameters encompassing 3 categories of Variability, Power and Genotype by Environment interaction. These data provide a basis for selecting a reduced core set of characteristics with the goal of retaining discriminational ability while decreasing the time and resources required to obtain and to compare morphologies
Comparison between different fumagillin dosage and evaluation method in the apiary control of Nosemosis type C.
Get PDFFumagillin (dicyclohexylammonium) is an antibiotic with well-known microsporicidal activity widely used to control Nosema disease caused by Nosema apis in honeybees. Its use is permitted by law in Argentine and USA, but not in the EU countries, apart from specific cases under veterinary authorization. So far, the optimal dosage of this active ingredient in controlling Nosema ceranae has not been determined. The aim of the present work was to assess the efficiency of different fumagillin dosages on Apis mellifera colonies affected by different N. ceranae intensity. For this purpose, during April and May of 2007, in an apiary located near the Mar del Plata city (Buenos Aires Province, Argentine), forty eight A. mellifera colonies reared in Langhstroth hives, each containing 8 to 10 adult bee combs, were used in order to evaluate the effectiveness of different doses of fumagillin. The colonies were divided into those with mild or semi-severe disease intensity, based on the number of Nosema spores estimated in a sample of 60 returning bees (arb, spores abundance in returning bee). Then the colonies were randomly distributed forming 6 experimental groups (3 with mild intensity: one untreated left as control and the other two treated with 102 mg of fumagillin in two and three doses, respectively; 3 with semi-severe intensity: treated with 102 mg of fumagillin in two and three doses, and with 120 mg of fumagillin in four doses, respectively). Each dose was administered at intervals of 7 days. Before and during each administration, for a period of 35 days, the number of frames covered with adult bees was recorded in each hive and a sample of 100 workers per colony was collected from the hive entrance in order to determine the abundance (arb) and prevalence (prb) of spores. This alternative parameter (prb) was calculated by examining a sub-sample of 10 bees, crushing the propodeum of the bees in 0.5 ml distilled water, taking a drop of suspension and observing 20 fields under a optic microscope (450x) for spore absence (0) or presence (1); then the estimation of spores prevalence (prb) was recorded as percentage of spore presence in the 20 observed fields, and the average of two estimates were used. Moreover, spores from 5 randomly selected colonies were molecularly characterized to confirm the Nosema species. The sequencing results showed a 98% of homology with N. ceranae. The results obtained allow to establish that the efficiency of fumagillin in controlling Nosemosis type C caused by N. ceranae is affected by the intensity of the disease rather than from dosage or way of application. The best result was obtained when colonies were affected by a mild intensity and the drug was administered in two weekly doses of 51 mg per hive
In memory of Baccio Baccetti
Get PDFBaccio Baccetti, Editor-in-Chief of Redia since 2003, the centennial of publication of the journal, passed away on 18 December 2010. His death was a great loss for the entire Editorial Board of the journal and for the Italian scientific community
Recurrent selection methods to improve germplasm in maize
Get PDFRecurrent selection (RS) schemes were introduced to increase the frequency of favorable alleles for quantitatively inherited traits. The main goal of RS was to genetically improve germplasm resources for breeding programs. Data were summarized for 14 intra-population and eight inter-population maize (Zea mays L) RS programs conducted in 17 genetically broad-based populations. The intra-population programs included evaluation of half-sib and full-sib families, either S1 or S2 inbred progenies, and a combination of S1 and S2 inbred progenies. The inter- population reciprocal RS programs were restricted to either half-sib or full-sib family selection. Grain yield was the primary trait considered in selection, but selection indices that include grain moisture at harvest and resistance to root and stalk lodging also were considered in making the selections that were intermated to form the next cycle population. Approximately, 10 to 20 selections were intermated for each cycle. Estimates of the genetic variation among progenies tested ( ), interactions of progenies with environments ( ), and experimental error ( ) were obtained from the combined analyses of variance for each cycle of selection and then averaged across cycles for each selection program. From the estimates of the components of variance, estimates of heritability (h2) on a progeny mean basis , the genetic coefficient of variation among progenies tested relative to their mean, (GCV), selection differentials (D), predicted genetic gains ( ), and least significant differences (LSD) were calculated and averaged across cycles of selection. The average estimates of were largest for inbred progeny selection and smallest for half-sib family selection as expected. Averaged expected genetic gain across all intra-population selection programs was 3.17 q ha-1 yr-1 vs 2.32 q ha-1 yr-1 for inter-population reciprocal recurrent selection, or 2.64 q ha-1 yr-1 across all methods. On a per cycle and per year basis the differences among types of progeny were relatively small, ranging from (3.57 q ha-1 yr-1,1.78 q ha-1 cycle-1) for half-sib family selection to (9.62 q ha-1 yr-1, 3.21 q ha-1 yr-1) for S2 inbred progeny selection. Regression analyses of the square roots of with cycles of selection suggested that genetic variation was not reduced significantly with selection. Even though RS was used to determine the primary types of genetic effects that respond to selection and contribute the expression of heterosis and could ideally support basic association and genome selection studies, the principle goal of RS is to adapt and improve genetically broad-based germplasm sources for potential use in breeding programs. Few programs have integrated RS programs with development programs to isolate unique inbred lines that have potential either as parents of hybrids or use in elite line crosses to develop recycled lines. In the past 10 years North Dakota has released 18 (out of 28) derived from RS programs, six from the NDSU EarlyGEM program (also diverse), and four from elite x elite combinations. Based on the number of progenies evaluated (25,692) in the RS programs presented and the number of inbred lines (31) that met standards for a ‘B’ designation and release to other maize breeders, the frequency of released lines was 0.12% or 1.2 lines per 1000 tested. However, the value of each line is different. B73 is a successful example of integrating recurrent and pedigree selection programs in order to develop outstanding cultivars. These significant gains can be realized with long-term RS selection programs. National support for them is encouraged in order to develop the next generation of maize products
Recurrent selection methods to improve germplasm in maize
No full textRecurrent selection (RS) schemes were introduced to increase the frequency of favorable alleles for quantitatively inherited traits. The main goal of RS was to genetically improve germplasm resources for breeding programs. Data were summarized for 14 intra-population and eight inter-population maize (Zea mays L) RS programs conducted in 17 genetically broad-based populations. The intra-population programs included evaluation of half-sib and full-sib families, either S1 or S2 inbred progenies, and a combination of S1 and S2 inbred progenies. The inter- population reciprocal RS programs were restricted to either half-sib or full-sib family selection. Grain yield was the primary trait considered in selection, but selection indices that include grain moisture at harvest and resistance to root and stalk lodging also were considered in making the selections that were intermated to form the next cycle population. Approximately, 10 to 20 selections were intermated for each cycle. Estimates of the genetic variation among progenies tested ( ), interactions of progenies with environments ( ), and experimental error ( ) were obtained from the combined analyses of variance for each cycle of selection and then averaged across cycles for each selection program. From the estimates of the components of variance, estimates of heritability (h2) on a progeny mean basis , the genetic coefficient of variation among progenies tested relative to their mean, (GCV), selection differentials (D), predicted genetic gains ( ), and least significant differences (LSD) were calculated and averaged across cycles of selection. The average estimates of were largest for inbred progeny selection and smallest for half-sib family selection as expected. Averaged expected genetic gain across all intra-population selection programs was 3.17 q ha-1 yr-1 vs 2.32 q ha-1 yr-1 for inter-population reciprocal recurrent selection, or 2.64 q ha-1 yr-1 across all methods. On a per cycle and per year basis the differences among types of progeny were relatively small, ranging from (3.57 q ha-1 yr-1,1.78 q ha-1 cycle-1) for half-sib family selection to (9.62 q ha-1 yr-1, 3.21 q ha-1 yr-1) for S2 inbred progeny selection. Regression analyses of the square roots of with cycles of selection suggested that genetic variation was not reduced significantly with selection. Even though RS was used to determine the primary types of genetic effects that respond to selection and contribute the expression of heterosis and could ideally support basic association and genome selection studies, the principle goal of RS is to adapt and improve genetically broad-based germplasm sources for potential use in breeding programs. Few programs have integrated RS programs with development programs to isolate unique inbred lines that have potential either as parents of hybrids or use in elite line crosses to develop recycled lines. In the past 10 years North Dakota has released 18 (out of 28) derived from RS programs, six from the NDSU EarlyGEM program (also diverse), and four from elite x elite combinations. Based on the number of progenies evaluated (25,692) in the RS programs presented and the number of inbred lines (31) that met standards for a ‘B’ designation and release to other maize breeders, the frequency of released lines was 0.12% or 1.2 lines per 1000 tested. However, the value of each line is different. B73 is a successful example of integrating recurrent and pedigree selection programs in order to develop outstanding cultivars. These significant gains can be realized with long-term RS selection programs. National support for them is encouraged in order to develop the next generation of maize products
The homeologous Zea mays gigantea genes: characterization of expression and novel mutant alleles
No full textThe two homeologous Zea mays gigantea (gi) genes, gi1 and gi2, arose from the last genome duplication event in the maize lineage. Homologs of these genes in other species are required for correct circadian rhythms and proper regulation of growth and development. Here we characterized the expression of these two maize gi genes. Although gi1 and gi2 shared comparable 24-hour rhythmic expression profiles, gi1 levels were consistently higher than gi2. Furthermore, short day photoperiods repressed gi2 expression. The transcriptional unit for gi1 is established based on 5’-RACE analysis. Two independent mutant alleles for gi1 are described that are caused by transposons of the Mutator (Mu) class inserted into the 5’-end of the gene. The type of Mu element and position of the transposon in gi1 was different for each gi1 allele. Mutant plants had a marked reduction in gi1 expression and carried transcripts interrupted by the Mu element. Together, these results provide a deeper understanding of the gi genes in maize. In addition, the novel gi1 mutant alleles described here will be valuable tools to study gi1 function in maize, as well as the role of circadian clock regulation in maize metabolism, growth, and development
Relationship between seed harvesting method and seed physiological quality for a number of Pioneer maize hybrids
Get PDFThe seed germination and seed vigor of eight Pioneer Hi-Bred maize hybrids were evaluated immediately after harvesting and a year later. The aim was to determine whether the seed showed loss of germination and vigor when shelled mechanically. The seed was cleaned but not dressed, and then germinated according to the ISTA standard procedure in four seed analysis laboratories. In addition, the seed of two randomly chosen hybrids was divided into four fractions based on size and shape, and the germination of each fraction was examined separately. All the germination results were acceptable according to the ISTA (2010) standard (over 90%), but a higher germination percentage was observed after manual shelling than after mechanical shelling. The number of abnormal seedlings, however, was higher for mechanically shelled seeds than for those harvested as whole ears. When the seed of separate seed fractions was tested, the germination percentage was lowest for the medium-sized round fraction and highest for the large flat fraction. The seed vigor of three of the hybrids was highest when maize seeds were harvested shelled rather than on the ear. For all the hybrids the germination percentage was lower for both groups when analyzed a year after harvesting. Better germination results were obtained for all the hybrids after whole ear harvesting than in the shelled group, but the difference was not significant. In the vigor tests the results obtained for mechanically shelled seed were superior to those for whole ear harvesting for the same three hybrids, but again the difference was not significant. The experiments should be repeated over several years to determine whether mechanically shelling maize seed negatively affects seed germination and vigor