Efficient Selection Of Genotypes Research Articles

Wood and Pulping Properties Variation of Acacia crassicarpa A.Cunn. ex Benth. and Sampling Strategies for Accurate Phenotyping

Research Highlights: This study provides a comprehensive set of wood and pulping properties of Acacia crassicarpa A.Cunn. ex Benth. to assess variation and efficient sampling strategies for whole-tree level phenotyping. Background and Objectives: A. crassicarpa is an important tree species in Southeast Asia, with limited knowledge about its wood properties. The objective of this study was to characterize important wood properties and pulping performance of improved germplasm of the species. Furthermore, we investigated within-tree patterns of variation and evaluated the efficiency of phenotyping strategies. Materials and Methods: Second-generation progeny trials were studied, where forty 50-month-old trees were selected for destructive sampling and assessed for wood density, kraft pulp yield, α-cellulose, carbohydrate composition, and lignin content and composition (S/G ratio). We estimated the phenotypic correlations among traits determined within-tree longitudinal variation and its importance for whole-tree level phenotyping. Results: The mean whole-tree disc basic density was 481 kg/m3, and the screened kraft pulp yield was 53.8%. The reliabilities of each sampling position to predict whole-tree properties varied with different traits. For basic density, pulp yield, and glucose content, the ground-level sampling could reliably predict the whole-tree property. With near infrared reflectance spectroscopy predictions as an indirect measurement method for disc basic density, we verified reduced reliability values for breast height sampling but sufficiently correlated to allow accurate ranking and efficient selection of genotypes in a breeding program context. Conclusions: We demonstrated the quality of A. crassicarpa as a wood source for the pulping industry. The wood and pulping traits have high levels of phenotypic variation, and standing tree sampling strategies can be performed for both ranking and high-accuracy phenotyping purposes.

Morphological and Pomological Variability Analysis of Walnut (Juglans regia L.) Genetic Resources from the Middle and High Atlas of Morocco

The walnut (Juglans regia L.) is a traditional fruit crop in Morocco. This species is cultivated in mountain in different environments. However, little data is available on its genetic diversity and its adaptability. Morphological characters of leaf and fruit from 11 Moroccan accessions of walnut were used to assess phenotypic variation of this species. Significant differences were found between accessions for the most examined traits, indicating a high phenotypic diversity. Multivariate analyses lead to identify three groups of accessions. The first group composed by the accessions of both Middle and High Atlas Mountain with high weigh and percentage of kernel and low thickness of shell. The second group included the accessions for the High Atlas Mountain characterised by large leaf, high nut dimension and great nut size. The third group is composed by two accessions, one belongs to the Middle Atlas Mountain and the other originating from High Atlas Mountain, which are characterized by small leaf and nut. Then, the structuration of accessions in three groups was not correlated to the mountain range type. Moreover, this study showed a significant phenotypic heterogeneity between the eleven studied accessions which opens the way for the strategies for their conservation and the selection of efficient genotypes with the desired traits.

Artificial neural networks and linear discriminant analysis in early selection among sugarcane families

Abstract One of the major challenges in sugarcane breeding programs is an efficient selection of genotypes in the initial phase. The purpose of this study was to compare modelling by artificial neural networks (ANN) and linear discriminant analysis (LDA) as alternatives for the selection of promising sugarcane families based on the indirect traits number of sugarcane stalks (NS), stalk diameter (SD) and stalk height (SH). The analysis focused on two models, a full one with all predictors, and a reduced one, from which the variable SH was excluded. To compare and assess the applied methods, the apparent error rate (AER) and true positive rate (TPR) were used, derived from the confusion matrix. Modeling with ANN and LDA can be used successfully for selection among sugarcane families. The reduced model may be preferable, for having a low AER, high TPR and being easier to obtain in operational terms.

Ecophysiology as a tool for selecting more adapted and productive clones, in a clonal silvicultural frame of poplars

The genus Populus makes an excellent subject for any study due to its rapid growth and ease of vegetative propagation which facilitates the production of large amounts of clonal material for experimentation. Many ecophysiological studies confirm this fact and are aimed to determine the physiological basis of growth and adaptation to produce greater yield. Key growth traits in productivity are related to the capture of radiation and its conversion to biomass, such as leaf area, lifespan and light use efficiency. Stress factors influencing poplar productivity have been studied. The effects of water, salinity and ozone stresses on poplar physiology and the parameters for the selection of more tolerant clones are presented. Gains in productivity by clonal selection of desirable morphological and physiological characters, and their association to molecular markers, will allow a more efficient selection of genotypes.

Effect of Growing Rice on Nitrogen Mineralization in Flooded Soil

AbstractOnly a smally fraction of the total organic N in soils is mineralized to the plant‐available forms during a cropping season. The mineralization process and the availability of mineral N in soils are affected by various environmental factors and management practices, including the presence of growing plants. This study was conducted to determine the effect of rice (Oryza sativa L.) on mineral N availability in a flooded Maahas soil (Typic Tropaquept). Available N, extractable NH4‐ and NO3‐N in soil plus N accumulated in plants, referred to as mineral N availability, was significantly higher in planted than in unplanted soils. Increased N availability may result from reduced loss or enhanced supply of mineral N in the presence of growing plants. Average increase in mineral N supply in freshly flooded soil was 31% due to growing of rice through the first month (0–30 d) and 62% through the second month (30–60 d) of its life cycle. In soils under prolonged flooding, average increases in the mineral N supply due to 2 mo rice growing during the vegetative stage (10–70 d) were 14 to 47% depending on the initial mineral N status of the soils. The gain in mineral N achieved by growing rice plants was higher in soils with a low than a high initial mineral N content. Rice genotypes differed in their ability to increase mineral N availability in flooded soils, and the stronger influences were associated with higher dry‐matter yields of the plants (shoot plus root). Soil N availability to wetland rice, especially in soils with low mineral N supply, thus may be considerably enhanced by selection of efficient genotypes.