PROGRESSO GENÉTICO E SELEÇÃO PRECOCE EM GENÓTIPOS DE PINHÃO-MANSO EM FASE JUVENIL

O pinhão manso (Jatropha curcas L.) é uma euforbiácea utilizada na produção de biodiesel. A espécie possui base genética estreita o que dificulta o processo de lançamento de cultivares. Caracterizar precocemente os genótipos constitui etapa importante no melhoramento da cultura. Objetivou-se com este estudo realizar uma seleção precoce em caracteres morfoagronômicos, predizer o progresso genético de tais caracteres e indicar genitores potenciais para obtenção de progênies. O delineamento experimental utilizado foi o de blocos casualizados com 26 tratamentos e três repetições. As variáveis morfoagronômicas foram analisadas via modelos mistos e o progresso genético obtido pela seleção direta, indireta e índices de seleção. A dissimilaridade genética foi determinada pela distância de Mahalanobis, com agrupamento hierárquico UPGMA e coeficiente de correlação cofenética adquirido de 1.000 permutações. As estimativas demonstraram variabilidade genética, com identificação de genótipos juvenis promissores. Os genótipos JCCE034, JCCE014 e JCCE103 apresentam melhores progressos genéticos e os genótipos JCCE036 e JCCE86 apresentam maiores divergências genéticas, formando clusters individuais. Os genótipos de pinhão-manso são promissores na seleção precoce e possuem satisfatórios ganhos com a seleção para os caracteres avaliados. Os genótipos apresentam boa capacidade para compor grupos de genitores em cruzamentos direcionados, constituindo populações-base no melhoramento de J. curcas. Palavras-chave: Jatropha curcas; diversidade genética; ganhos com a seleção; índices de seleção. Genetic progress and early selection of juvenile physic nut genotypes ABSTRACT: Physic nut (Jatropha curcas L.) is a euphorbia used in the production of biodiesel. The species has a narrow genetic base which the process of launching cultivars is difficult. Early characterization of the genotypes is an important step in crop breending. The aims of this study were to perform an early selection in morpho-agronomic traits, to predict the genetic progress of such traits and to indicate potential parents for progeny development. The experimental design used for the randomized blocks with 26 treatments and three replications. The morpho-agronomic traits were analyzed via mix models and the genetic progress added by direct, indirect selection and selection indexes. The genetic dissimilarity was provided by the Mahalanobis distance, with UPGMA hierarchical grouping and co-phenetic correlation coefficient acquired from 1,000 permutations. The indicators demonstrated genetic variability, with the identification of promising juvenile genotypes. The genotypes JCCE034, JCCE014 and JCCE103 show better genetic progress and the genotypes JCCE036 and JCCE86 show greater genetic divergences, forming individual clusters. J. curcas genotypes are promising in early selection and have satisfactory genetics gains for the traits. The genotypes have a good ability to compose groups of parents in targeted crosses, constituting base populations in the improvement of J. curcas. Keywords: Jatropha curcas; genetic diversity; selection gains; selection indexes.

Selecting Drought-Tolerance Markers: An Exploratory Analysis in Contrasting Soybeans

Identifying high-yield genotypes under low water availability is an important goal for soybean breeding. However, a major bottleneck lies in phenotyping, particularly in selecting cost-efficient markers associated with stress tolerance and yield stabilization. Here, we conducted in-depth phenotyping experiments using two soybean genotypes with contrasting drought tolerance, MUNASQA (tolerant) and TJ2049 (susceptible), aiming to identify and statistically validate stress tolerance and yield stabilization markers. Firstly, at the R5 critical reproductive stage, the molecular differences between the genotypes responses to mild water deficit were explored through massive analysis of cDNA ends (MACE)-transcriptomic and gene ontology. MUNASQA transcriptional profile, compared to TJ2049, revealed significant differences when responding to drought. Next, both genotypes were phenotyped under mild water deficit, imposed in vegetative (V3) and R5 stages, by evaluating 22 stress-response, growth and water-use markers, which were subsequently correlated between phenological stages and with yield. Several markers showed high consistency, independent of the phenological stage, demonstrating the effectiveness of the phenotyping methodology and its possible use for early selection. Finally, these markers were classified and selected according to their cost-feasibility, statistical weight and correlation with yield. Here, pubescence, stomatal density and canopy temperature depression emerged as promising markers for early selection of drought-tolerant soybeans.

Random Regression Model for Genetic Evaluation and Early Selection in the Iranian Holstein Population

The objective of this study was to use a model to predict breeding values for sires and cows at an early stage of the first lactation of cows and progeny groups in the Iranian Holstein population to enable the early selection of sires. An additional objective was to estimate genetic and phenotypic parameters associated with this model. The accuracy of predicted breeding values was investigated using cross-validation based on sequential genetic evaluations emulating yearly evaluation runs. The data consisted of 2,166,925 test-day records from 456,712 cows calving between 1990 and 2015. (Co)-variance components and breeding values were estimated using a random regression test-day model and the average information (AI) restricted maximum likelihood method (REML). Legendre polynomial functions of order three were chosen to fit the additive genetic and permanent environmental effects, and a homogeneous residual variance was assumed throughout lactation. The lowest heritability of daily milk yield was estimated to be just under 0.14 in early lactation, and the highest heritability of daily milk yield was estimated to be 0.18 in mid-lactation. Cross-validation showed a highly positive correlation of predicted breeding values between consecutive yearly evaluations for both cows and sires. Correlation between predicted breeding values based only on records of early lactation (5–90 days) and records including late lactation (181–305 days) were 0.77–0.87 for cows and 0.81–0.94 for sires. These results show that we can select sires according to their daughters’ early lactation information before they finish the first lactation. This can be used to decrease generation interval and to increase genetic gain in the Iranian Holstein population.

Age-age correlations and prediction of early selection age for diameter growth in a 35-years old Pinus brutia Ten. Genetic experiment

Aim of study: Forest geneticists developed various methods to predict an early selection age for forest tree species in order to shorten the breeding cycles. This study aims to estimate age-age correlations among diameter growth of trees at different ages and predict early selection age for Pinus brutia Ten. Area of study: P. brutia populations in the study were sampled from the most productive distribution range of the species, which is an important forest tree in the eastern Mediterranean Basin. To understand genetic variation and determine early selection age for the species, a common garden experiment was established in two test sites near Antalya city, Turkey, in 1979. Material and methods: Wood increment cores at breast height were collected at age 30 years, and diameters (dbh) were measured for the ages 13, 15, 19, 21, 23, 25, and 27 years on the cores. Diameters at ground level (dgl) and dbh were also measured on live trees at age 35. Variance components, age-age correlations, heritability and selection efficiency were estimated for the diameters. Main results: Age-age genetic correlations for diameters were high (mostly > 0.90). Genetic correlations between dgl (at age 35) and dbh (at all measurement ages) ranged from 0.84 to 0.99. Regressions of genetic correlation on natural log of age ratio (LAR) of juvenile age to older age were significant (P < 0.0001). Selection efficiencies estimated by employing the prediction equation indicated that for rotation age 40, the optimum selection age would be between 3 to 5 years, and for rotation age 100 it would be between 5 to 9 years. Research highlights: The results of this study provide information that can be used to find early selection ages in P. brutia. On relatively poor test sites most trees may not attain enough height growth to have measurable dbh trait. In such cases, dgl and/or tree height traits (both of which are highly correlated with dbh traits of all ages) can be measured and used instead of dbh trait for evaluations.

Multi-Level Genetic Variation and Selection Strategy of Neolamarckia cadamba in Successive Years

Neolamarckia cadamba (Roxb.) Bosser is a tropical evergreen broadleaf tree species that could play an important role in meeting the increasing demand for wood products. However, multi-level genetic variation and selection efficiency for growth traits in N. cadamba is poorly characterized. We therefore investigated the efficiency of early selection in N. cadamba by monitoring the height (HT), diameter at breast height (DBH), and tree volume (V) in 39 half-sib families from 11 provenances at ages 2, 3, 4, 5, and 6 years in a progeny test. Age-related trends in growth rate, genetic parameters in multi-level, efficiency of early selection, and realized gain in multi-level for growth traits were analyzed. The result showed that genetic variation among families within provenances was higher than that among provenances. The estimated individual heritability values for the growth traits ranged from 0.05 to 0.26, indicating that the variation of growth traits in N. cadamba was subject to weak or intermediate genetic control. The age–age genetic correlations for growth traits were always positive and high (0.51–0.99), and the relationships between the genetic/phenotypic correlations and the logarithm of the age ratio (LAR) were described well by linear models (R2 > 0.85, except the fitting coefficient of genetic correlation and LAR for HT was 0.35). On the basis of an early selection efficiency analysis, we found that it is the best time to perform early selection for N. cadamba at age 5 before half-rotation, and the selection efficiencies were 157.28%, 151.56%, and 127.08% for V, DBH, and HT, respectively. Higher realized gain can be obtained by selecting superior trees from superior families. These results can be expected to provide theoretical guidance and materials for breeding programs in N. cadamba and can even be a reference for breeding strategies of other fast-growing tree species.

FEASIBILITY OF EARLY Pinus taeda L. SELECTION TO ASSESS GROWTH VARIABLES IN PROGENY TEST

Forest species breeding programs require a long period-of-time for plants to reach the proper age to enable selecting superior genotypes, which is a critical factor in selection processes. Thus, the aims of the current study are to estimate genetic parameters in juvenile and adult plants (6, 10 and 20 years) in order to investigate genetic correlations between variables at different ages and at certain ages; as well as to determine whether it is possible performing efficient early selection in juvenile plants. The test was implemented in 1997; it comprised 120 progenies and followed a randomized block design, with five repetitions - linear plots comprised 5 plants at 2.5 m x 2.5 m spacing. DBH (cm), H (m) and VOL (m³) of all tested subjects were measured at the age of 6, 10 and 20 years. Variance components, genetic parameters, as well as genetic correlations between variables and between ages were estimated in Selegen REML/BLUP® software. Genetic parameter estimates have shown superiority at 10 years, in comparison to that estimated at 6 and 20 years. Variable ‘DBH’ has shown high genetic correlation to height (H) and volume (VOL), whereas DBH x VOL have shown high genetic correlation (0.98) in 10-year-old plants. With respect to genetic correlation between ages, 10-year-old plants have shown moderate correlation to 6- and 20-year-old plants. Early selection is indicated for 10-year-old plants, in 20-year cycles, since plants at this age have shown higher selection efficiency to predict gains in comparison to adult plants.

Early selection for resistance to cacao witches’ broom in new parental combinations

ABSTRACT Progenies from 69 crosses between parents obtained by recurrent selection for resistance and yield were inoculated with Moniliophthora perniciosa basidiospores. The symptoms were evaluated and compared with those in the equally inoculated progenies of Catongo, SIC 23 and SCA 6. Forty-three of the new progenies did not differ statistically from SCA 6, while 10 new progenies were statistically better than this control. The female parents that can be highlighted are (P4B x SCA 6), (MA 16 x SCA 6), (CEPEC 86 x SCA 6), and the EET 75 clone. The best male parents were (CAB 214), (CAB 208) and (P4B x OC 67), which did not differ from each other. This study proved the existence of gene combinations between fathers and mothers, the occurrence of additive effects and the dominant inheritance of these factors, which should allow the selection of clones with higher resistance levels and durability.