CREA Journals (Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria)
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Characterization of a set of chromosome single-segment substitution lines derived from two sequenced elite maize inbred lines
Get PDFChromosome single-segment substitution lines (SSSLs) are powerful tools for detecting and precisely mapping quantitative trait loci (QTLs) and evaluating the action of genes as single Mendelian factors. In this study, 108 SSSLs, which included 46 uniquely substituted segments, were developed from an advanced backcross proce¬dure with the marker-assisted selection of 146 simple sequence repeat (SSR) markers using the elite maize inbred line Zheng58 as the recipient and Chang7-2 as the donor. Each SSSL contained a single substituted chromosome segment that was derived from donor strain Chang7-2 in the genetic background of the recipient Zheng58 strain. The 46 substituted segments were unevenly distributed on ten maize chromosomes, and the substituted segment length ranged from 2.7 centimorgan (cM) to 283.5 cM with an average of 66.0 cM. The total length of the 46 substi¬tution segments was 3,035.2 cM, which covered 2,142.6 cM (31.47%) of the entire maize genome. To evaluate the potential application of these SSSLs for QTL detection, 44 SSSLs were used for the phenotypic characterization of plant height in three field trials. Twenty-nine QTLs of plant height were identified, and the percentages of additive effects varied from -8.45% to 12.86%. The results demonstrated that these SSSLs possesses large genetic varia¬tions and are excellent tools for genetically dissecting complex traits over several environments
Overexpression of an Incw2 gene in endosperm improved yield-related traits in maize
Get PDFHigh yield is an eternal goal for crop breeding. Incw2 protein is the enzyme in the metabolic pathway that mobilizes photoassimilated sucrose into numerous reactions of the developing plant seeds, associated with grain yield. In the research, an Incw2 gene driven by 27 kD zein promoter was specifically over-expressed in the endosperm cells of maize inbred line 18-599R by Agrobacterium-mediated genetic transformation. PCR assay displayed that ten of the regenerated plants were integrated with the target gene. By semi-quantitative RT-PCR and invertase activity analysis, five of them showed significantly higher expression of Incw2 transcripts and enzyme activity compared to the wild type. Among them, line 1 stood out because it possessed the highest level of Incw2 mRNA and enzyme activity. The effects of Incw2 over-expression were reflected in the increased chlorophyll content, improved pho¬tosynthesis and delay of leaf senility. In addition, yield-related traits such as ear length, ear diameter, ear weight, grain weight per ear, and hundred-kernel weight appeared to be improved in three of the transformants compared with the wild type. The grain weight per plant of line1 was increased by nearly 10%. The results collectively indicate that it is potentially practical to enhance kernel yield of maize by overexpression of Incw2 in endosperm
The maze of Zea: I. Chloroplast SSRs and evolution
Get PDFThe evolution of Zea and, especially, the domestication of maize have undergone multifaceted assessment for many decades. New analyses have often demonstrated inconsistencies that prompted new thinking. Reexamination of chloroplast microsatellite data from a broad sampling of Zea reveals clear phenetic patterns, notably: 1) The various teosinte taxa are related to each other as expected; 2) Chloroplasts of the tested maize landraces form two very different groups; 3) Mexican annual teosintes are closely linked to only one maize group. These and other results are supported by a wide range of older studies. The latter two patterns deserve careful consideration because they contradict the model that a Mexican annual teosinte was domesticated, then evolved to all present maizes. They do not contradict the model that a small, domesticated maize was greatly changed by introgression, probably by a teosinte in section Luxuriantes of Zea. The introgression probably also led to great evolutionary acceleration, several important bottlenecks and the enormous diversity of modern maize. These chloroplast microsatellite relationships have various implications and deserve careful attention in designing future studies (see discussion)
Cyst nematodes of the genus Heterodera and Globodera in Sicily
Get PDFA survey was conducted in Sicily, from 2007 to 2009, to obtain insights on specific composition, frequency and geographical distribution of cyst nematodes associated to crops of agricultural economic importance. Soil and root samples were collected mainly from crops showing chlorosis, poor growth and reduced yield. Cysts and larvae were extracted and identified to species level by comparative examination of morphological and morphometric characters. Confirmation of the species identity was also made by molecular analysis for some species. Seven species of the genus Heterodera Schmidt, 1871 and two of the genus Globodera Skarbilovic, 1959 were found. They were H. avenae Wollenweber, 1924, H. bifenestra Cooper, 1955, H. carotae Jones, 1950, H. goettingiana Liebscher, 1892, H. hordecalis Andersson, 1974, H. latipons Franklin, 1969 and H. schachtii Schmidt, G. rostochiensis (Wollenweber, 1923) Behrens, 1975 and G. pallida (Stone, 1973) Behrens, 1975. All species dectected are known to occur in Europe and the Mediterranean basin, but H. avenae, H. hordecalis, and H. latipons had not been reported from Sicily and H. bifenestra is a new report for Italy
History of nematology in Italy
Get PDFNotwithstanding nematology is a rather new science, in Italy the first observations and publications on nematodes date back to several centuries ago and are from physicians and botanists. Among them are U. Aldrovandi (1522-1605), who was the first in the word to observe nematodes in insects, and F. Redi, who published in 1684 his observations about “living animals occurring in living animals”. However, the first observations on plant parasitic nematodes were made from the second half of 1800 to early 1900. They refer to Anguina tritici in wheat kernels (1867), Meloidogyne spp. (1875-1904) on several host plants, Ditylenchus dipsaci (1897) in oats. The sugar beet cyst nematode, Heterodera schachtii, was reported in 1931 and the citrus nematode, Tylenchulus semipenetrans, in 1940. The turning point in Italian plant nematology occurred during 1950-1970, when investigations and control trials started on Xiphinema index, the natural vector of the Grape fan leaf virus. In the same period, the Phytosanitary Service of Pescara addressed much of his efforts on plant parasitic nematodes and the Section of Nematology is established at the Experimental Institute of Agricultural Zoology, of the Ministry of Agriculture, in Florence. Moreover, in 1970, the Italian National Research Councils founded in Bari the Laboratory (later Institute) of Agricultural Nematology Applied to Plants. Later on, nematology attracted also the interest of several other Phytosanitary Services, Universities and firms producing nematicides. While nematology was growing up, research objectives evolved from mainly faunistic and chemical control to many more to encompass all aspects of agricultural nematology and that for number and quality made Italian nematology one of the leading nematology at world level
Inoculation experiments of Bursaphelenchus eremus Rühm (Goodey)(Nematoda Parasitaphelenchidae)on Quercus robur L.
Get PDFBursaphelenchus eremus Rühm (Goodey) occurs in declining oak forests of some European countries, althoughdata are lacking on the possibility of the nematode to colonize healthy trees. To evaluate the pathogenicity of thenematode, we carried out an inoculation test in Tuscany (central Italy) in 2007-2008: on May 2007, 32 Quercus robur L.plants (7 years old) were inoculated with an Italian isolate of B. eremus(IT37w) and 16 plants were maintained ascontrols. There were two inoculation sites on each plant: one immediately below the fresh top shoot and another 30 cmbelow the first site. All plants were kept outdoors under a zinc-coated cage covered with a cloth. After four months, 16inoculated plants and eight controls were randomly selected and each stem was cut into three parts, weighed, crushed ina grinder and subjected to Baermann funnel extraction. After 16 months, the remaining 18 inoculated and 6 controlplants were chosen and examined with the same procedure.Bursaphelenchus eremuswas obtained from the stems of all infected oak trees. The difference was in the numberof nematodes/g of fresh wood in the different plant portions both after four (F2,16=86.94) and 16 months (F2,18=400.71).The highest density was always recorded in the fresh top shoot tissue, while no nematode was obtained from the lowerstem portion. The RHS (relative host suitability) index value increased from 0.6 (4 months) to 2.1 (16 months) but itwas still too low to be accompanied by signs of wilting. Because of the resemblance between B. eremusand the PineWood Nematode, we suggest that further experimental studies are needed to evaluate the potential risk of thisnematode for different species of oaks common to the Mediterranean area, where the maximum summer temperaturesreach the optimal temperature range for B. eremusdevelopment
Aphids on almond and peach: preliminary results about biology in different areas of Tunisia
Get PDFFour aphid species are known to colonize peach and almond in Tunisia: Hyalopterus pruni species complex, Myzus persicae Sulzer, Brachycaudus amygdalinus Shouteden and Pterochloroides persicae Cholodkovsky. Eggs identification, date of lay and effect of orientation on egg laying were described. Brief information about biology, preferential host, distribution and growth rates are given for each species
Early growth of field-grown swiss flint maize landraces
Get PDFMild cold stress (chilling) limits early growth of maize (Zea mays L.) in central and northern Europe. Introgression of chilling tolerance from landraces has been proposed, because the genetic basis for chilling tolerance of European Flint x Dent hybrids is small. Therefore, the aim of this study was a detailed characterization of the chilling toler¬ance of Swiss maize landraces, hypothesizing a relatively good performance in marginal thermal environments. The environments were set up by different sowing dates in two years. A functional growth analysis of the shoot from the one-leaf to the six-leaf stage was conducted with eight Swiss landraces and a check hybrid (Magister). The mean air temperature calculated across the six environments was above 15°C. Under these conditions, none of the landraces grew consistently better than Magister. Some landrace-specific relative growth reactions were observed compared to Magister, apparently due to strong changes in the temperature course. However, based on this study direct use of Swiss maize landraces in breeding for the improvement of chilling tolerance is not recom¬mended. More detailed investigations of promising landraces are proposed
Inbreeding and yield of synthetic varieties derived from single and double cross hybrids
Get PDFMaize (Zea mays L) seed saving among producers in low-income and lesser in developed countries is often prac-ticed. In México, advanced generations of maize hybrids and even mixtures of single-cross (SCs) and double-cross hybrids (DCs) are grown. These populations are expected to perform similar to the synthetic varieties (SVs) . srenibmocd ooge ra, ylbamuserp, tahts dirbyhe htf on oitavirede htn id evlovnis enile htm orfd evirede bd luoct ahtThe derivation of SVs from hybrids seems attractive because would be easier because of the reduced number of potential parents. The frequencies of the genes of the SCs, however, may differ from those of the DCs, may affect the inbreeding coefficient, and thereby the genotypic mean. To address these and related issues, this study was conducted to derive formulae to calculate the inbreeding coefficient (IC) and to predict the genotypic mean (GM) of SVs derived from a mixture of s SCs and d DCs, each represented by m individuals. Formulae for its IC (FSynSC,DC) and GM (YSynSC,DC) were derived. For hybrid parents derived from fully inbred and unrelated lines, FSynSC,DC = [2ms+d(m+1)]/[4m(s+d)2] and, independently of the type of lines, YSynSC,DC = YPS/(s+d)+YPC(s+d−1)/(s+d), where YPS is the genotypic mean of the s + d populations that result from randomly mating the m individuals of each par-ent, and YPC is the mean of all crosses between the s + d parents. From eight lines, three sets of parents (each set involved all eight lines) were considered: 1) four SCs (4SC), 2) two SCs and one DC (2SC+DC), and 3) two DCs (2DC). The SV produced by 4SC shows the lowest IC, although for large m (m > 10) the IC of the SV produced by 2DC is about equal. The largest IC, and thereby the smallest GM, is associated to 2SC+DC because the coances-try between individuals and gene frequencies in SCs are twice those of DCs. What is more noticeable, however, is that 2DC produces the cheapest way of deriving and predicting a SV since only three entries are required (two parents and their cross) and with large m the IC is about the minimum
Genetic similarity of sweet corn inbred lines in correlation with Heterosis
Get PDFThe narrowness of sweet corn genetic base limited to the great extent its genetic improvement. This is associated to the fact that sweet corn does not have well defined heterotic groups such as those important in field corn breeding, and therefore application of marker assisted selection becomes a necessity. The objective of this study was to determine genetic similarity (GS) of six sweet corn inbred lines selected at Maize Research Institute Zemun Polje, based on SSR markers and to compare it with data of specific combining ability (SCA) and heterosis for fresh ear yield, obtained in a diallel study. SSR markers showed that all genotypes had specific genetic pattern. Estimates of GS varied from 0.422 (L4 - L2) up to 0.756 (L6 - L5). Cluster analysis and PCA showed clear groupings of inbreds into two subclusters, with inbred L3 less related to the others. Results of diallel analysis showed that data of heterosis and SCA were in concurrence with the data of GS based on SSR markers. Hybrid combinations with higher estimates of SCA and heterosis expressed less genetic similarity with each other (such in hybrids L2 x L1; L6 x L2; L3 x L2 and L5 x L2), while inbreds that were genetically most similar L5 and L6 expressed low heterosis and SCA in their hybrid combination. That was confirmed by rank correlation coefficients, whose estimates were negative and in most cases significant, indicating that more similar inbreds produced less expressed effects of heterosis and SCA