Search

New technologies have been developed over the last few years aiming to support breeding pipeline optimization for long‐term genetic gains. However, the implementation of these new tools and their impact on any breeding program's budget are not well studied. Here, we compare multiple breeding pipeline strategies accounting for genomic selection and high‐throughput phenotyping (HTP) by means of hybrid gain and cost‐effectiveness. We simulated a hybrid crop breeding program through coalescent theory. We compared two strategies for parental updates and four breeding pipelines: conventional breeding pipeline; conventional breeding pipeline with HTP; conventional breeding pipeline with genomic selection; conventional breeding pipeline with genomic selection and HTP. All analyses were implemented under three different levels of genotype‐by‐environment interaction (G×E) and two trait heritabilities (0.3 and 0.7). Overall, the results show that scenarios with early parental selection perform better than the others. In addition, the implementation of HTP delivered the highest hybrid gain in the long‐term, whereas the implementation of genomic selection seems to be more cost‐effective. We suggest, considering breeding programs with complex trait inheritance and accounting for higher levels of G×E, investing in breeding pipelines accounting for genomic selection as a strategy to create and maintain long‐term hybrid gain. Moreover, considering an unconstrained budget, the investment in both, genomic selection and HTP, represents the best strategy. Hence, these results provide strategies that may aid breeders in optimizing self‐pollination breeding programs. Core Ideas: Early parental selection has the potential to increase long‐term genetic performance.High‐throughput phenotyping (HTP) can aid breeding program improvement.Breeding pipelines focusing on complex traits should consider the implementation of genomic selection and HTP. [ABSTRACT FROM AUTHOR]

The genetic diversity of a comprehensive germplasm collection involving 192 Jatropha curcas L. accessions collected throughout Brazil, spanning a wide latitudinal range from the states of Maranhao (1[degrees]49' S, 44[degrees]52' W) to Rio Grande do Sul (29[degrees]33' S, 55[degrees]07' W), was studied with 96 random amplified polymorphic DNA (RAPD) primers and six selected microsatellite markers. Only 23 of the 381 replicated RAPD markers and one microsatellite were polymorphic. Surprisingly, all accessions were homozygous at all but one microsatellite, in contrast with the outcrossing mating system reported for the species, suggesting that J. curcas not only supports selfing but possibly breeds by geitonogamy. Similarity based clustering revealed only 43 unique multilocus profiles in the 192 accessions. The probabilities of accessions with indistinguishable multilocus profiles being true duplicates varied between 83 and 99%. No relationship between clustering of accessions and geographic origin was observed, suggesting that J. curcas has experienced a widespread dispersion across regions by seeds and possibly vegetative propagules. The narrow genetic base and extent of potentially duplicated accessions likely reflects a recent common ancestry, drift, and intensive selection of the currently cultivated materials since the time of introduction. This result highlights an urgent need for the introduction of new and diverse accessions to this germplasm collection if Brazil is to drive and sustain successful breeding programs. doi: 10.2135/cropsci2010.02.0112

Kiwifruit (Actinidia spp.) is native to southern China, but was first cultivated in New Zealand and then spread worldwide. Emerging diseases such as ceratocystis wilt have attracted the attention of kiwifruit growers due to the great losses observed in southern Brazil. Effective control can be achieved by screening for resistance, but the genetic variability of the pathogen must be considered. Thus, this study aimed to assess the genetic diversity and variation in aggressiveness of Ceratocystis isolates from kiwifruit in southern Brazil and then evaluate the resistance of kiwifruit cultivars with the most aggressive isolates. A collection of 46 isolates were obtained from southern Brazil and 14 simple‐sequence repeat (SSR) markers was successfully used for genotyping. Out of 14 markers, 13 were polymorphic and identified 26 genotypes. Fourteen distinct genotypes were tested on a susceptible cultivar to select the most aggressive ones. Finally, inoculation with an equal mixture of five of the most aggressive isolates was used to evaluate the resistance of seven kiwifruit cultivars: Red Arguta, Green Arguta, Allison, Chieftain, Hayward, Monty, and Tomury. Cultivars varied in levels of susceptibility, with disease severity ranging from 40% to 100%. Considering the length of stem lesions, Chieftain showed the lowest level of severity at 40%, while no wilt symptoms were observed at 45 days after inoculation. In addition to the seven cultivars, a half‐sibling progeny with 618 plants of the rootstock cv. Bruno was also assessed, but only seven individuals were resistant. These seven plants can be cloned and used as resistant rootstocks in commercial orchards. [ABSTRACT FROM AUTHOR]

Biotic and abiotic stresses have been making it difficult to maintain the rates of genetic gains in forest tree breeding. Planting a mixture of genotypes or clonal composites can be an alternative to increase the security of forest plantations. The formation of clonal composites is complex due to inter-genotypic competition and indirect genotypic effects that can affect the efficiency of genetic selection. This study aims to understand how indirect genotypic effects can impact the response to selection and how the stand composition can be used to explore these effects and enhance forest yield. We used two clonal trials of eucalyptus hybrids implanted in a randomized complete block design with 24 replications, containing a single tree per plot evaluated for mean annual increment at 3 and 6 years. We focused on partitioning the genotypic variation into direct and indirect genotypic effects based on competition intensity factors. We identified aggressive, homeostatic, and sensitive clones based on the magnitude of indirect genotypic effects. Considering indirect genotypic effects, for mean annual increment, the total heritability decreased from 0.25 to 0.10 for 3 years and from 0.30 to 0.14 for 6 years, respectively. We proposed a workflow that uses the direct and indirect genotypic effects to predict the mean values for clonal composite combinations and to select the one with the highest yield. Our methodology considered spatial variation and interplot competition that can affect the total heritable estimates and response to selection in forest trials. The clones were classified as aggressive, homeostatic, and sensitive, according to their deviation from the indirect genotypic effects means. Our methodology enabled the extraction of useful information and predict many clonal composites' performance, which can be used in recommending genotypes to be planted in mixtures. • The heritabilities are overestimated by not considering indirect genotypic effects. • The trade-off between direct and indirect genotypic effects must be considered. • A method for predicting high-performance clonal composites was proposed. • Total genotypic values were used to identify high-performance clonal composites. [ABSTRACT FROM AUTHOR]