André Ricardo Gomes Bezerra

Agronomical Aspects of the Development of Cultivars

Soybean breeding has been carried out with the objective of increasing the frequency of favorable genes of the traits object of the program. Undoubtedly, the increase in grain yield has been the main objective of breeding programs. Other traits aiming to improve crop management or the use of the grain for industrial purposes are also targeted by breeders. Early cultivars, erect plant architecture, incorporation of biotic and abiotic stress resistance via transgenic and physical, and chemical seed quality are some examples of traits of interest in many breeding programs. The soybean develop grown in a wide variety of environments, so its ideotype should be considered dynamic and varied according to each environment and cultivation condition. Under such circumstances, breeders should address different cropping regions, cropping systems, climatic adversities, biotic stresses, and the technological level of farmers, for example.

Economic Importance and Evolution of Breeding

Originating in northeast China, soybean (Glycine max (L.) Merrill) in the last decades has become the main oilseed in the world due mainly to being a great source of vegetable oil and protein. This crop currently occupies an area more than 118 million hectares worldwide. Due to the projections for the increase of the world population and the high purchasing power of this, the demand for the soybean grain will not decrease in the next years. In Brazil, soybean found adequate conditions for its development in the South. From this region, since the 1970s, soybean has been expanding in the Brazilian savannah, called Cerrado, a process known as the “tropicalization of soybean”. The genetic breeding of the species was one of the main factors responsible for the success of its expansion in Brazil. The evolution of soybean genetic breeding in Brazil can be divided into two phases. The first extends the introduction of the crop until the mid-1980s, marked by the participation of the public sector in the development of varieties, seed supply and technology transfer. This period was mainly marked by the adaptation of the soybean to the conditions of the Cerrado and regions of low latitudes. In the 1990s, a new phase for the soybean breeding in Brazil was started, which was marked by the participation of large groups of international capital. This period has been seeking, in addition to the development of adapted and productive varieties, new materials of greater market value from the development of transgenic events.

Registration and Protection of Cultivars

In Brazil, 1657 soybean cultivars are registered in the Ministry of Agriculture, Livestock and Food Supply (MAPA) in 2017. Every year a large number of new cultivars are submitted to registration and protection. Thus, from the moment that this new cultivar is obtained, the registration allows the production and commercialization of the seeds in the country. This process ensures the genetic identity and the varietal quality of the cultivars. In addition, the protection of cultivars guarantees the intellectual rights to the breeders and enables public and private research companies to benefit, as it guarantees the continuity of breeding programs, with the partial or total use of these materials. For the registration of a particular cultivar in the National Register of Cultivars (RNC), it must first be submitted to tests to determine the Value of Cultivation and Use (VCU), that is, the intrinsic value of the combination of the agronomic traits of the cultivar with its properties of use in agricultural, industrial, and commercial activities and for unprocessed product consumption. In order to be able to be protected, the cultivar must undergo field tests in which it must have distinctiveness (differences of any other coexistent at the date of the application for protection), uniformity (uniformity among plants within the same generation), and stability (maintenance of traits in successive generations). Thirty seven descriptors are used for the DUS test, 30 of which were compulsory and seven additional. Thus, knowledge of the plant morphology is essential to accurately describe the traits of the cultivar and always ensure the launch of new varieties, which are more productive with desirable traits.

Avaliação bioeconômica de estratégias de suplementação de novilhos zebuínos mantidos em pastagens diferidas de capim-marandu no período seco

The objective of this work was to evaluate different supplementation strategies on supplement intake, behavior, and performance of beef steers grazing stockpiled palisade grass (Urochloa brizantha cv. Marandu) pastures. There was used a completely randomized design trial to test five supplementation strategies: commercial mineral (SM), mineral plus25% of urea (SP), and three multimixtures (45.5% TDN) with 10% (MM10), 15% (MM 15), or 20% (MM20) of urea. Twenty zebuine steers weighting 300±24.9 kg of initial body weight, being four animals per treatment, were raised on five paddocks of 3.4 hectares under weekly rotation, from July to October of 2010. Data were submitted to ANOVA, using Tukey′s test to compare average values (P≤0.05); however, economic analysis determined the best strategy. Supplementation did not affect the grazing or rumination/resting time (P>0.05). The intake of supplements was affected (P<0.05) by supplementation strategy, being 106, 196, 852, 666, and 400 g/day for SM, SP, MM10, MM15, and MM20, respectively. SM resulted in losing weight (-137 g/animal/day). Using SP practically maintained the cattle weight. However, if gains are desired, multimixtures should be used (P<0.05). In those cases, daily weight gain reached 324 g/animal (MM10). Based on economic analysis, the best strategy was MM20, followed by MM10.