CREA Journals (Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria)
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Genetic evaluation of tropical popcorn inbred lines using BLUP
Get PDFThe objectives were to identify superior inbred lines and single-crosses, predict untested hybrids and analyze the importance of pedigree information and the prediction efficiency. We analyzed 24 experiments in the incomplete block design, including 20 tests of hybrids and 4 tests of inbred lines. The expansion volume (EV) and grain yield were measured in each plot. The analyses were made using ASReml software. Analyses of the general combining ability (GCA) effects and the additive genetic values of the inbred lines, and the genotypic values of the hybrids in relation to EV showed that no inbred line selection strategy resulted in a set of clearly superior or inferior inbred lines and hybrids. Including pedigree information resulted in an increase in the variance of the GCA effects in relation to EV and a reduction in relation to yield. For both traits, there was an increase in the variance of the specific combining ability effects. The cross-validation study showed that the prediction of the genotypic value of a hybrid based only on the GCA effects is not efficient in the presence of dominance. With dominance, the efficiency of the hybrid prediction depends on the degree of relationship among the inbred lines
Characterization of maize germplasm: comparison of morphological datasets compiled using different approaches to data recording
Get PDFDifferent methods are used to report morphological data to evaluate the eligibility criterion of distinctness for Plant Variety Protection (PVP). We compared morphological data for 152 maize (Zea mays L.) inbred lines generated according to both US (metric data) and EU data (summarized by reference to “note” scores from check inbreds). While modal notes were very similar for US and EU data, on average only 42.8% of the characteristics had identi¬cal scores. Associations among inbreds on the basis of comparisons of single or multiple characteristics were very similar regardless of data type. We conclude that maize morphological data collected according to either of these protocols cannot meaningfully be combined into a single dataset. However, each data type, provided an equivalent mechanism to test for distinctness. These results cause us to more fundamentally question the degree of reliance that should be placed upon morphological data for PVP and other applications, including for the man¬agement of accessions conserved in gene-banks
Variability for resistance to the pink stem borer (Sesamia calamistis Hampson) and the sugarcane borer (Eldana saccharina Walker) in two tropical maize populations
Get PDFA set of 100 S1 plants were selected from a white and yellow maize population to generate both full-sib and half-sib progenies using North Carolina Design II (NCD II) mating scheme. The 250 progenies generated in each population were evaluated under artificial infestation with two borer species (Sesamia calamistis and Eldana saccharina) at two locations in two seasons to determine levels of genetic variability for improvement purposes. There were wide ranges for most of the traits studied in both maize populations. Plant height and grain yield were significantly reduced with mean grain yield loss being between 25 and 30%. In the white population, additive variance was larger than dominance variance for grain yield, days to 50% silking, stalk breakage and ear per plant, but for the yellow counterpart, additive variance was larger for plant height, ear per plant, leaf feeding and cob damage. None of the gene actions was important for dead heart. Narrow-sense heritability was low to moderate for the resistance parameters. It ranged from 1.45% for leaf feeding to 40.6% for stalk breakage in the white population, and from 3.80% for leaf feeding to 40.1% for cob damage in the yellow population. Heritability for grain yield was 37.6% in the white population but much lower (10.5%) in the yellow population. Although, heritability was low to moderate for the traits studied, the wide ranges and moderate additive variances obtained suggest that substantial genetic variability exist in the two maize populations for reasonable improvement to be made. Breeding scheme that capitalizes on both additive and dominance gene action would be effective for improving the populations for stem borer resistance and grain yield
Selection of extra-early maize inbreds under low N and drought at flowering and grain-filling for hybrid production
Get PDFExtra-early maize (Zea mays L) tolerant to low-N and drought could stabilize yields in sub-Saharan Africa. Studies were conducted under drought and low-N conditions in Nigeria for three years to determine the potential of 90 extra-early inbreds for hybrid production and evaluate the performance of 36 hybrids derived from the inbreds under drought at flowering and grain-filling periods and well-watered conditions. Results showed significant ge¬notypic mean squares for grain yield and most other traits of the inbreds under drought and/or low-N conditions. TZEEI6, TZEEI4, TZEEI36, and TZEEI38 were identified as ideal inbreds under drought. Under low-N, TZEEI19, TZEEI96 and TZEEI45 were top ranking with TZEEI19 as the ideal inbred. TZEEI19, TZEEI29, TZEEI56, TZEEI38, and TZEEI79 were tolerant to both stresses. Eighteen of the 36 hybrids produced above-average yields across environments with four hybrids identified as very stable. TZEEI29 x TZEEI21 was the closest to the ideal geno¬type because it combines large mean performance with high yield stability. Hybrid yield under drought had large positive correlation with grain yield under well-watered environments. Selection for inbred traits such as days to silking and anthesis-silking interval under drought predicted fairly accurately hybrid yield under well-watered envi¬ronments. It was concluded that extra-early inbreds and hybrids are not only drought escaping but also possess drought and low-N tolerant genes
Phenotypic and genetic variation of Jatropha curcas L populations from different countries
Get PDFJatropha populations from Malaysia, India, Indonesia, and the Philippines were evaluated on inland soils at Uni¬versity Agriculture Park, Universiti Putra Malaysia with the main objectives are to select superior plants with high seed and oil yields production for commercial planting and to study inter-populations variation in morphological, seed and oil yields characteristics. Analysis of variance shows that all traits had significant variation among popu¬lations. Phenotypic correlations between seed yield per plant was positively and highly significantly correlated with days to flowering, number of inflorescences, number of fruits per plant, number of seeds per plant, seed yield per hectare, seed oil yield per plant, and seed oil yield per hectare. Seed yield per plant was highly significant negatively correlated with seed oil content. Cluster analysis based on standardized agro-morphological data, divided the Jatropha populations into three clusters through non-hierarchical clustering. Cluster I, II, III consisted of one, two and three populations respectively. Highly significant genotypic differences were obtained among the Jatropha populations for various traits measured. The relative large variations were observed for all traits except number of tertiary branches in first year of harvesting. The variation was large enough to suggest that six Jatropha populations could present appropriate genotypes to be used in intensive breeding programs
Agronomic response of drought-tolerant and Striga-resistant maize cultivars to nitrogen fertilization in the Nigerian Guinea savannahs
Get PDFIn additon to drought and Striga hermonthica parasitism, nitrogen deficiency is a major constraint to maize pro¬duction in the Guinea savannahs of Nigeria. The use of mineral fertilizers is limited because of unavailability and high costs. The use of maize cultivars that perform well under sub-optimal N conditons is therefore desirable. Breeders at IITA have selected maize cultivars that combine tolerance to drought and Striga hermonthica parasit¬ism. This study evaluated six of these cultivars under a range of N application rates and compared these with a widely grown variety, TZB-SR. The study was conducted in Zaria and Samaru Kataf in Kaduna State of Nigeria. Results showed N application significantly reduced days to flowering and increased yield and yield components. Cultivars selected for combined tolerance to drought and Striga recorded lower number of days to flowering under N stress and higher dry matter, higher grain yield, higher number of grains m-2 and higher 500-seed weight at all N rates. This confirms earlier reports that maize cultivars selected for tolerance to drought will perform well under N-limited conditions. Grain yield was significantly associated with dry matter, number of grains m-2 and 500-seed weight at all N levels suggesting that these agronomic traits are significant determinants of maize yield at all N rates. Two cultivars (DT STR SYN-W/IWD C3 SYN and IWD C3 SYN/DT-SYN-1-W) were particularly outstanding at all added N levels probably due to long term improvement for drought tolerance. These two cultivars can be recommended for large-scale demonstration and release to the farmers in the West African savannas
Nematode-wild plant interactions and their implication in nematode management
Get PDFMany species of plant parasitic nematodes are known to have hundreds of host plant species, both cultivated and wild. In the absence of host crop plants, wild plants often are good alternative hosts for the nematodes of which they not only ensure survival but also soil population densities larger than the tolerance levels for different host crop plants. This is known to occur for a few cyst nematodes, such as the sugar beet cyst nematode, Heterodera schachtii, in the presence of several crucifers and chenopodiaceous wild plants, and for many other nematodes known to have rather large host ranges. These include the bulb and stem nematode, Ditylenchus dipsaci, the root-knot nematodes, Meloidogyne spp., and the lesion nematodes, Pratylenchus spp., which have as host plants many wild plants infesting crops during a period of the year suitable for the nematodes. The control of infesting weeds not only improves the growth of the cultivated host plants because of absence of competitors, but also prevents increase of soil nematode densities in their absence and, therefore, may serve as an effective and useful control option of nematodes, especially suggested for inclusion in integrated pest management programmes based on control methods alternative to synthetic nematicides
Observations on the biology of a predatory nematode belonging to Diplogasteridae
Get PDFThe use of predatory nematodes as biological control agents of phytoparasitic nematodes has been re-evaluated only recently. To be effective, predatory nematodes should be easy to grow, cheap, and available on a commercial scale. In addition, they must show a reproductive rate sufficient to sustain a high population density and a significant longevity and stability for storage. The predators are not phytopathogenic nematodes, and among the positive outcomes of their introduction are remarkable their environment compatibility and safety for other non-target organisms, as well as the ability to search for prey. These features are present in Diplogasteridae. Their adaptability enables them to withstand changing climatic conditions, as well as the temporal variability between predator and prey. It should also be emphasized the ability to disperse, persist and reproduce in the absence of prey, the spectrum of action, all factors ideal for the management of phytoparasitic species. Adverse factor is cannibalism, due the lack of preys, that can reduce their biological control potential. We herein present preliminary data on occurrence, reproduction and intestine bacterial flora of the predatory nematode, Koerneria sudhausi
Interactions between nematodes and fungi: a concise review
Get PDFA short review of the complex interactions is reported between nematodes and fungi, which are not always clear because of the rhizosphere complexity and inadequate techniques of investigation
