U nderstanding and quantifying photoperiod × temperature interactions often directly aff ects soybean [Glycine max (L.) Merr.] breeders and producers when selecting varieties, determining dates of planting, predicting dates of fl owering and maturity, and predicting fi nal yields (Zhang et al., 2001). Eff ect of the photoperiod response on area of adaptation is more pronounced in the soybean than in any other major crop. As soybean is classifi ed as a short-day plant, sensitivity to photoperiod is a hindering factor in increasing its adaptation range. When soybeans are cultivated under short-day conditions, in out-of-season plantings or in low latitude, those plants with the classic response to photoperiod fl ower early and result in short plants and low grain yields (Carpentieri-Pípolo et al., 2000). The length of the growing season for photoperiodic sensitive crops such as soybean is defi ned by complex interactions between temperature and photoperiod (Raper and Kramer, 1987). ABSTRACTMaturity classifi cation is an important concept to provide the best allocation of resources for soybean [Glycine max (L.) Merr.] research and commercialization. A similar maturity group system used in North America is being used for some seed companies in Brazil and needs research to improve its use. This study evaluated the maturity stability of 48 midwestern and 40 southern Brazilian commercial cultivars ranging from North American maturity groups VI to VIII at 15 locations. Relative maturity groups were attributed to all cultivars. All trials were planted in the fi rst half of November. The effect of location was very important in infl uencing the number of days to maturity, number of days to fl owering and reproductive growth period (RGP). The genotype × environment interaction, although statistically signifi cant, was much lower than the individual effects of environment and genotype for all traits and regions. Genotype × latitude and genotype × altitude, considering also years of evaluation, were generally low or nonsignifi cant. A recommended list was developed of the most stable genotypes and, consequently, of the most suitable check genotypes for each maturity group classifi cation in the southern and midwestern regions. Results indicate that the use in Brazil of a maturity group system similar to that used in North America to classify soybean genotypes is an effi cient method for describing relative maturity on a broad environmental basis.

Damping‐off of soybean is a common problem in some fields in southern Brazil. Frequently, Phytophthora sojae has been pointed out as the main causal agent. However, questions were raised as to whether other oomycetes could also be present. Hence, the objectives of this study were to isolate, identify, and determine the pathogenicity and aggressiveness of oomycetes isolated from soybean seedlings. Thirty‐three isolates were obtained from 13 fields. Isolates were identified based on morphology and molecular methods. Nine species were recovered: Pythium conidiophorum (n = 14, 42.4%), Globisporangium rostratifingens (n = 7, 21.2%), G. irregulare (n = 2, 6.1%), G. spinosum (n = 1, 3.0%), G. ultimum var. sporangiiferum (n = 2, 6.1%), Pythium acanthicum (n = 2, 6.1%), P. deliense (n = 1, 3.0%), P. inflatum (n = 1, 3.0%), and P. torulosum (n = 3, 9.1%). Pathogenicity and aggressiveness were determined with two soybean cultivars (DM57i52 and NEO530) in a seed rot assay and a root rot assay. All isolates were pathogenic to soybean with variable levels of aggressiveness in both assays. The range of seed disease severity index varied from 7.5 to 100 for DM57i52 and from 23.1 to 100 for NEO530. The mean root disease severity index of the soybean cultivars ranged from 29.4 to 92.8. This is the first official report of G. irregulare, G. rostratifingens, G. spinosum, G. ultimum var. sporangiiferum, P. acanthicum, P. conidiophorum, P. deliense, P. inflatum, and P. torulosum causing damping‐off of soybean in the state of Rio Grande do Sul in southern Brazil.

Soybean [Glycine max (L.) Merril] is one of the main crops produced worldwide, and on‐farm yields have increased considerably in the last decades in Brazil. We evaluated the genetic gain for agronomic, phenological, and end‐use quality traits in 29 cultivars in the South Region, and in 38 cultivars in the Midwest Region in Brazil, released from 1966 to 2011. Field trials were conducted in Macroregions 1, 2, and 4, in 2016–2017, 2017–2018, and 2018–2019 crop seasons. The best linear unbiased predictors (BLUP) of the cultivars were obtained for each trait using a linear model. The BLUPs were regressed with the year of release using linear and quadratic regression models. The rates of genetic gain for seed yield ranged from 11.98 to 15.31 kg ha–1 yr–1 (0.33 to 0.42% yr–1) in the South Region, and from 13.58 to 21.84 kg ha–1 yr–1 (0.47 to 0.77% yr–1) in the Midwest Region. New cultivars presented taller plants and more seed oil content, oil and protein yield, and lower seed weight, days to flowering, days to maturity, and seed protein content than old cultivars in the South Region, although with differences between the Macroregions. In the Midwest Region, new cultivars showed higher seed oil content, oil and protein yield, and lower bottom pod height and seed protein content than old cultivars. Our results showed that breeding programs have been efficient to improve soybean yield and other traits across the years, without yield plateaus in sight.

Brazil is the largest soybean producer in the world (USDA, 2022). The area cultivated with soybean in the country is divided into macroregions due to the differences in environmental conditions (Kaster & Farias, 2012), which require cultivars adapted to each macroregion.Damping-off of soybean is a common problem reported by several growers in Macroregion 1 (Costamilan et al., 2013;Molin et al., 2021a), which includes the southern region of Brazil (Kaster & Farias, 2012). Symptoms of the disease include seed decay and root rot (Broders et al., 2007;Rojas et al., 2017), which can compromise seed germination, seedling emergence and initial establishment of