Genetic Evaluation and Combined Selection for the Simultaneous Improvement of Growth and Wood Properties in Catalpa bungei Clones

Catalpa bungei is an important timber tree. Improvements in growth and wood quality are important goals of C. bungei breeding, and it is necessary to understand the genetic parameters of specific target traits and genetic correlation between growth traits and wood properties for tree breeding. In this study, the genetic parameters of height, diameter at breast height (DBH) and wood properties were estimated and genetic and phenotypic correlations between growth traits and wood properties were evaluated in C. bungei. Finally, different selection scenarios were used to evaluate and select optimal clones. The results showed that there were significant differences in growth and wood properties among clones. The wood hardness (0.66–0.79), basic density (0.89), air-dried density (0.89) and compression strength parallel to the grain of wood (CSP) (0.84) had high repeatability. The variance component proportions indicated that the variation in wood properties came mainly from different genotypes (clones) rather than from different individuals of the same clone. The DBH showed a significant negative genetic correlation with the hardness of radial section (HRS) (−643), basic density (−0.531) and air-dry density (−0.495). This unfavorable relationship makes it difficult to improve growth and wood quality simultaneously in C. bungei. We selected the optimal clones under different scenarios, and we obtained 7.75–9.06% genetic gains for growth in the scenario in which height and DBH were the target traits. Genetic gains of 7.43–14.94% were obtained for wood properties by selecting optimal clones in the scenario in which wood properties were the target traits. Approximately 5% and 4% genetic gains were obtained for growth and wood properties, respectively, for the combined selection. This study provides new insights into the genetic improvement of wood quality in C. bungei.

Red Hybrid Tilapia (Oreochromis spp.) Broodstock Development Programme in Malaysia: Status, Challenges and Prospects for Future Development

The red hybrid tilapia (Oreochromis spp.) and the black tilapia, including the genetically improved farmed tilapia (GIFT) (Oreochromis niloticus (Linnaeus, 1758)) collectively contributed to about 30.7 % of the total freshwater aquaculture production in Malaysia in 2018. The red hybrid tilapia is the most important, accounting for 94 % of total tilapia production. Among the major problems encountered in tilapia farming is the inconsistent supply of quality and adequate seeds, which could be solved through systematic breeding programmes. Among the major problems encountered in tilapia species farming is the inconsistent supply of quality and adequate seeds, which could be solved through systematic breeding programmes. This paper discusses the status of the red hybrid tilapia breeding programme in Malaysia, including issues and future perspectives. In brief, the first systematic breeding programme was initiated by the Fisheries Research Institute (FRI) in 2008. Selected founder stocks from Malaysia, Taiwan and Thailand were used to establish a base population for the programme. In this programme, the combined selection was practised which produced six generations of selection and successfully improved 12.5 % of harvest body weight per generation. The 6th generation was used as one of the founder stocks, apart from FRI Glami Lemi, Negeri Sembilan and Pahang populations to improve resistance to Streptococcus agalactiae. In 2017, the scope of the programme was expanded to include molecular tool in identifying markers for growth. Ten SNP markers associated with high growth performance traits were discovered. The provision of better breeding stocks for the aquaculture industry and the development of safe and productive operations are expected to result in more stable fish production and an improved income for farmers.

Selection for Papaya Resistance to Multiple Diseases in a Base Population of Recurrent Selection

Papaya has a narrow genetic base concerning disease resistance, with few genetically distinct cultivars for planting in the world. Losses in crop production caused by fungal and viral diseases, added to the absence of resistant cultivars available to producers, have reduced the competitiveness of crops. Therefore, this study aimed to estimate the direct and combined genetic gains in the base population of the recurrent papaya selection and to indicate promising individuals for resistance to phoma spot and black spot. The population used in this study originated from the crossing of dioecious, female individuals and holders of a gene pool for resistance to phoma spot and black spot. These were crossed with elite individuals with a gene pool for production traits and fruit quality. The experiment was carried out without an experimental design, containing one plant per plot. Three measurements were taken on 255 individuals for five traits of disease resistance, being: four associated with black spot (incidence and severity on the leaf and fruit) and one associated with phoma spot (severity on the leaf). With the observations obtained, the REML/BLUP procedure was performed to estimate the temporary and permanent environmental effects. Such values were used to know the genetic parameters of the population and to elaborate a combined selection index, as well as to compare the gains with the direct selection. The results indicate low repeatability for the traits and that the gains obtained from the use of the combined selection index better rank the genotypes in comparison to the gains obtained by direct selection.

Changes of genetic variances and heritability by effect of selection in a Mexican local variety of Squash

A local variety of squash (Cucurbita pepo L.), ‘Round Zuchinni’ type from Los Reyes Acatlixhuayan State of México, México, was simultaneously evaluated and selected. The objective was to study effect of selection on genetic variance and heritability. Additive genetic variance decreased in seven of nine traits studied: fruit height (79.93 %); fruit weight (65.72 %); fruit width (60.91 %); flesh thickness (57.66 %); flesh color (43.70 %); dry weight of seed (39.54 %); flesh flavor (16.60 %); except in width and seed length traits where it increased 63.40 % and 0.81 %, respectively. Only weight of seed had dominance genetic variance. The coefficient of additive genetic variance (CVA) fluctuated from 9.4 to 61.7 % in the first cycle, and from 9.4 to 51.8 % in the second cycle of selection-evaluation among traits. Heritability diminished in seven from nine characters. In general, the estimated genetic variances (additive and dominance) and heritability decreased as a result of combined selection of falf sib families.