Giovani Benin

The objective of this work was to identify the resistance behavior of soybean (Glycine max) F1 populations with pyramided Rps genes, when subjected to inoculation with pathotypes of Phytophthora sojae. In 2020 and 2021, hybridizations were performed considering the presence of Rps genes from different loci in the parents. To characterize the F1 generation, pathotypes PS2.4, PS14.4, PS34.1, PS36.1, and CMES1608 were inoculated into the lateral branches of adult plants. The reaction to the pathotypes was evaluated in a greenhouse experiment, through the percentage of infected, dead, and healthy lateral branches. The study allowed identifying the virulent reaction of parents and their inoculated progenies. Progenies from virulent combinations of the same pathotype did not present new resistances. Resistance is increased by the complementarity of different Rps genes from the genotypes used to obtain the F1 progenies. Soybean F1 populations with pyramided Rps genes are an efficient genetic tool to help control Phytophthora sojae.

Molecular markers are powerful tools for detecting genetic variation at the DNA level, offering a direct, reliable, and efficient approach for the characterization, conservation, management, and utilization of plant germplasm. Among these, Inter-Retrotransposon Amplified Polymorphism (IRAP) markers target the genomic regions between retrotransposon insertions, revealing polymorphisms based on insertion patterns. This study aimed to develop and validate new IRAP markers for the genetic characterization of common bean (Phaseolus vulgaris) genotypes. Twelve IRAP primers were designed based on LTR retrotransposon sequences identified in the P. vulgaris genome database and tested in a panel of 22 genotypes, including 11 landraces, 10 commercial cultivars, and one F₂ individual derived from a cross between cultivars IPR Andorinha and BRS Estilo. Genomic DNA was extracted from young leaves using a modified CTAB protocol, and PCR amplifications were performed using the newly designed primers. The average polymorphism rate among the markers was 90.67%, and the mean genetic similarity among the genotypes was 0.557. The polymorphic information content (PIC) values ranged from 0.086 (Pv_IRAP_8) to 0.500 (Pv_IRAP_10), with the most informative primers being Pv_IRAP_4, Pv_IRAP_6, Pv_IRAP_7, Pv_IRAP_9, and Pv_IRAP_10. High genetic similarity was observed between some landraces and commercial cultivars, suggesting redundancy within the germplasm collection and highlighting the importance of molecular tools in optimizing genetic resource management in common bean breeding programs.

The objective of this work was to select Artemisia annua genotypes based on the agronomic characteristics of half-sib families. The experiment consisted of 24 treatments, of which 23 with half-sib families of A. annua germplasm and one control with Artemis cultivar, in a randomized block design. Data analysis used the restricted maximum likelihood/best linear unbiased predictor methodology and the correlation among agronomic traits. The half-sibs of A. annua present high phenotypic variability in agronomic traits. The classification of the ten half-sibs with the greatest results based on the estimated mean of the best linear unbiased predictor for dry mass of the leaves as follows: 1005_2-1; 2713_3-2; 2612_4-1; 1315_2-2; 1107_3-1; 213_4-3; 2612_3-1; 213_1-1; 2612_4-2; and 2417_4-2. The variation of genotypes within half-sib families in leaf dry mass, diameter of the middle portion of the canopy, and the total number of branches enables the selection of specific plant architectures. The agronomic traits branch and leaf dry mass, diameter of the middle portion of the canopy, and total branches show higher heritability in A. annua and are suitable for field selection.

In this study, the aim of this study was to identify the source of resistance using KASP markers developed for Rpp1 – Rpp5 and screening for resistance in field trials in F₂ populations. Ten F₂ soybean (Glycine max (L.) Merrill) populations derived from crosses between rust-susceptible (55I57RSF IPRO, 63I64RSF IPRO) and rust-resistant sources (PI 200492, PI 594538A, PI 587880A, PI 594723, PI 230970, PI 506764, PI 459025A and PI 200487) were evaluated. All F2 plants were individually evaluated in field conditions for ASR phenotypic reactions and classified according to sporulation level. KASP markers were developed according to assays associated with Rpp genes available at SoyBase. Based on a slight difference in map position and different phenotypic disease reactions of PI 200492, we suggest that PI 594723 carries a resistance gene Rpp1-b. The Rpp1-b gene from PI 594723 was mapped on Chr 18 in a 12.4 cM region. The PIs carrying Rpp1-b (PI 594723, PI 587880A, and 594538A) showed strong resistance to ASR compared to the lines carrying Rpp1 (PI 200492). A total of 26 KASP markers were significantly associated (P < 0.01) with ASR resistance. Among those, M1, M5, and M6 (Rpp1), M13 and M14 (Rpp2), M16, M17 and M20 (Rpp3), M25 and M26 (Rpp4), and M27 and M28 (Rpp5) have the potential to be used in marker-assisted selection strategies.

Asian soybean rust (ASR) causes large reductions in soybean yield, affecting the entire grain market. With low fungicide efficiency, the use of resistant cultivars can be an economical, safe, efficient, and sustainable control alternative. However, the great variability and aggressiveness of ASR and the use of Rpp genes are limited. Thus, gene pyramiding is a promising strategy for the development of cultivars with high resistance to a greater number of isolates. Thus, the aim of this study was to evaluate sister lines with different pyramided Rpp gene for resistance to Phakopsora pachyrhizi and identify which combination of Rpp genes had higher levels of resistance under field conditions. All Rpp-pyramided lines showed higher levels of resistance, with significant reductions in sporulation levels (SL), number of uredinia per lesion (NoU), and frequency of lesions with uredinia (%LU), compared to the resistance sources PI200487 (Rpp5), PI200492 (Rpp1), PI230970 (Rpp2), PI459025A (Rpp4), PI506764 (Rpp3, 5), PI587880A (Rpp1-b), PI594538A (Rpp1-b), and PI594723 (Rpp1-b). Rpp-pyramided lines carrying Rpp1-b + Rpp1-b, Rpp2 + Rpp1-b, Rpp4 + Rpp1-b, and single gene Rpp1-b were classified as “highly resistant”. Furthermore, one sister line, 52117-57 (Rpp2 + Rpp1-b), showed immunity under field conditions. The Rpp-pyramided genes are an alternative for achieving high resistance levels against ASR.

The objective of this work was to evaluate the grain yield potential of modern soybean (Glycine max) cultivars subjected to high- and low-input management levels on different sowing dates, in the southwestern region of the state of Paraná, Brazil. The experiment was carried out in the 2017/2018 and 2018/2019 crop seasons in the municipality of Itapejara D’Oeste. Five soybean cultivars (BMX Zeus IPRO, BMX Ativa RR, BMX Lança IPRO, NS 5445 IPRO, and NA 5909 RG) were evaluated in four environments formed by the combination of input management levels (high and low) and sowing dates (first and second). The experimental design was a randomized complete block with three replicates. The evaluated traits were: grain yield potential (kg ha-1), in the R5 phenological stage; and grain yield (kg ha-1) and its components, in the R8 stage. Cultivar, sowing date, and input management are determinant for maximizing grain yield potential. In the first sowing date, in October, the BMX Zeus IPRO cultivar shows a better response to the high level management, with a higher yield potential in the R5 stage (19,682 kg ha-1) and a higher grain yield (8,248 kg ha-1), whereas NA 5909 RG shows the best results with the low input management.

Pyramiding Rpp genes is a promising strategy to achieve a more durable resistance against Asian soybean rust (ASR). The objective of this study was to develop Rpp‐pyramided populations and evaluate their resistance and yield in field conditions. Fifteen pyramided populations carrying different combinations of Rpp genes were developed, and the F₃ lines were evaluated to phenotypic resistance and yield performance. Our results suggest that the Rpp1‐b of different resistant sources (PI 587880A, PI 594723, PI 4538A) have higher resistance and yield performance compared with other Rpp genes. Rpp‐pyramided populations carrying two and three genes showed an increase in resistance compared with populations carrying a single Rpp gene. The best gene combinations were Rpp1‐b + Rpp5, showing neither uredinia formation nor sporulation (immunity + RB1 phenotype reaction) in more than 70% of the F₃ population. Rpp‐pyramided lines developed in this study have the potential to be used in backcross programs for improving ASR resistance.