Soybean production in South and North America has recently been threatened by the widespread dissemination of soybean rust (SBR) caused by the fungus Phakopsora pachyrhizi. Currently, chemical spray containing fungicides is the only effective method to control the disease. This strategy increases production costs and exposes the environment to higher levels of fungicides. As a first step towards the development of SBR resistant cultivars, we studied the genetic basis of SBR resistance in five F2 populations derived from crossing the Brazilian-adapted susceptible cultivar CD 208 to each of five different plant introductions (PI 200487, PI 200526, PI 230970, PI 459025, PI 471904) carrying SBR-resistant genes (Rpp). Molecular mapping of SBR-resistance genes was performed in three of these PIs (PI 459025, PI 200526, PI 471904), and also in two other PIs (PI 200456 and 224270). The strategy mapped two genes present in PI 230970 and PI 459025, the original sources of Rpp2 and Rpp4, to linkage groups (LG) J and G, respectively. A new SBR resistance locus, rpp5 was mapped in the LG-N. Together, the genetic and molecular analysis suggested multiple alleles or closely linked genes that govern SBR resistance in soybean.

Genetic similarity among soybean genotypes was studied by applying the amplified fragment length polymorphism (AFLP) technique to 317 soybean cultivars released in Brazil from 1962 to 1998. Genetic similarity (GS) coefficients were estimated using the coefficient of Nei and Li (Nei and Li 1979), and the cultivars were clustered using the unweighted pair-group method with averages (UPGMA). The parentage coefficients of 100 cultivars released between 1984 and 1998 were calculated and correlated with the genetic similarity obtained by the markers. The genetic similarity coefficients varied from 0.17 to 0.97 (x = 0.61), with 56.8% of the coefficients being above 0.60 and only 9.7% equal to or less than 0.50. The similarity coefficients have remained constant during the last three decades. Dendrogram interpretation was hindered by the large number of cultivars used, but it was possible to detect groups of cultivars formed as expected from their genealogy. Another dendrogram, composed of 63 cultivars, allowed a better interpretation of the groups. Parentage coefficients among the 100 cultivars varied from zero to one (x = 0.21). However, no significant correlation (r = 0.12) was detected among the parentage coefficients and the AFLP genetic similarity. The results show the efficiency of AFLP markers in large scale studies of genetic similarity and are discussed in relation to soybean breeding in Brazil.

Soybean rust (SBR) caused by Phakopsora pachyrhizi Syd. is currently the most threatening fungal disease of soybean [Glycine max (L.) Merr.] in the Americas. Development of resistant or tolerant cultivars is a major goal in several soybean breeding programs. Four loci, all carrying dominant alleles that confer a resistant phenotype, have been described. We investigated the genetic basis of the resistance in PI 200456 and PI 224270 by crossing each of them with a susceptible cultivar (CD 208). Phenotypic segregation ratios for F2 plants and F2:3 lines showed that the resistance in each resistant parent was controlled by a single recessive gene. A test for allelism demonstrated that these genes are non‐allelic. This is the first report of recessive genes controlling SBR resistance in soybean and may represent a different type of resistance for breeding programs aimed at development of more durable resistance.

(12) , D Morresi (12) , M Garbarino (12) , G Alberti (13) , F Valdevit (13) , E Tomelleri (14) , M Torresani (14) , G Tonon (14) , M Marchi (15) , P Corona (15) , M Marchetti (16) Forest damage inventory after the "Vaia" storm in Italy On October 29, 2018, the Vaia storm hits the NorthEastern regions of Italy by wind gusts exceeding 200 km h-1. The forests in these regions have been seriously damaged. This contribution illustrates the methodology adopted in the emergency phase to estimate forest damages caused by Vaia storm, both in terms of damaged forest areas and growing stock volume of fallen trees. 494 Municipalities registered forest damages caused by Vaia, destroyed or intensely damaged forest stands amounted to about 42

Soybean rust (SBR) is the most threatening fungal disease in the major soybean [Glycine max (L.) Merr.] production areas around the world. In spite of the availability of chemical control with fungicides, the increase of production costs as well as operational difficulties associated with fungicide use for disease management has prompted the search for resistant genes in the soybean germplasm. Five genes (Rpp1, Rpp2, Rpp3, Rpp4, and Rpp5) have been reported as capable of conferring SBR resistance in soybean. Here we report the genetic segregation of the SBR resistance in two populations derived from crossing the SBR resistance source PI 594760B with the breeding lines TMG06_0012 (Population 1 [POP‐1]) and TMG06_0011 (Population 2 [POP‐2]). In both populations the resistance segregated as a single gene, but the resistance gene was dominant in POP‐1 and recessive in POP‐2. Molecular mapping of the phenotype placed it in the vicinity of the Rpp1 locus in both POP‐1 and POP‐2. When the breeding lines TMG06_0011 and TMG06_0012 where crossed with several other sources of resistance at the Rpp1, Rpp2, Rpp4, and Rpp5 loci or other putative loci, the inversion of gene action type observed with PI 594760B occurred only for the putative Rpp1 genotypes. We propose that a dominant susceptible allele, present in TMG06_0011, is causing the inversion of dominance observed in each of these crosses.

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Thirty isolates of Sclerotium rolfsii Sacc. from different hosts and regions of Brazil were studied in relation to morphology, mycelial compatibility, analysis of genomic DNA through random amplified polymorphic DNA (RAPD), variation within the nuclear rDNA [internal transcribed spacers (ITS)] and sequencing of ITS fragments. There was considerable variability among isolates in relation to the number, size and location of sclerotia on the medium surface. Thirteen mycelial compatibility groups (MCG) were identified among 23 isolates. Seven isolates were only self‐compatible. With the exception of group 3, where all the isolates came from soybean, there was no apparent correlation between group and isolate origin. On the basis of RAPD profiles, 11 haplotypes (A to K) were identified. There was an association between the RAPD groups and MCG. Haplotypes A, B, D, G, I and K belonged to MCG groups 1, 2, 3, 4, 5 and 6, respectively. All other RAPD haplotypes contained incompatible isolates. Polymerase chain reaction (PCR) amplification with primers 4R and 5F amplified two fragments containing ITS1, ITS2 and 5.8 S rDNA sequences, that were present in all isolates, with molecular sizes of 739 and 715 bp. Restriction analysis of PCR products showed that the two fragments had sequence divergency which is referred to as ‘ITS types’. Four arbitrarily chosen soybean isolates (2, 6, 7 and 23) and two non‐soybean isolates (11 and 22) were used to investigate the variation within the ITS sequence and its role in the phylogeny. The strict consensus of nine most‐parsimonious trees inferred from the data set which included six isolates of S. rolfsii, four of which have two different ‘ITS types’, showed three well‐supported groupings. The neighbour‐joining tree inferred from the data set also showed three major clades as did the parsimony tree. The major difference was that in the neighbour‐joining tree the ‘ITS type’ 11 was resolved and grouped in one clade. These results show that the ‘ITS types’ within isolates are almost always phylogenetically distinct. There was no clear correlation between ITS‐based phylogeny and isolate origin.

-Molecular markers have been used to predict the genetic variance of segregating soybean populations by measuring the genetic distance between parents. For this purpose we analyzed the genetic distance among six pairwise combinations of four soybean lines grown in Southern Brazil. The AFLP-based distances (AFD) were estimated with 21 primer-pair combinations. Additive genetic variance (D) was estimated in 100 advanced inbred lines for each cross for seven traits, including grain yield, for four sowing dates, and four years. Results showed a low but significant overall correlation (r=0.21*) between grain yield variance and AFD in the average of the four years and sowing dates. Considering the sowing dates the highest correlation was in October (r=0.41*). Significant correlations were also found for five out of the remaining traits evaluated. We found no significant correlations between D and parentage coefficient for all traits evaluated, except for 100 seed weight (r=0.32*).