Riqueza : a new soybean cultivar for the state of Minas Gerais

The release of cultivars has ensur ed higher yield associated with incr eased tolerance to climatic adversity . ‘UFUS Riqueza’ is resistant to natural dehiscence and to the diseases: bacterial pustule, downy mildew , frog ye leaf spot, br own stem r ot, stem canker and stem necrosis and can reach yields of 3475 kg ha -1, with grain contents of 18 % oil and 39 % protein.


INTRODUCTION
In the search for crop adaptation to the changing climate conditions, plant breeding has developed cultivars that respond better to today's challenges.
The direction of research underlying the release of a new cultivar is towards raising the yield levels of traditional production areas as well as to adapt cultivation to new areas.The indication of new cultivars with differentiated value-adding features has been a major tool to help farmers increase stability and yield.The high yield levels of soybean, with values above 3300 kg ha -1 in the major producing regions in the Midwest of the country, has substantiated competitiveness of Brazilian soybean on the international market (Hamawaki et al. 2007).
During the development of a cultivar, it is imperative that the target line be evaluated at different locations and years, due to the genotype -environment interaction, to express the entire genetic potential, minimizing the environmental effects as far as possible.In initial, intermediate and final trials it is possible to obtain important information preceding the release of a cultivar.
The propagation of soybean cultivars recommended for cultivation in each state is intended to inform technicians and businessmen of the productive sector about the annual advances in varietal technology of soybean (Embrapa 2008).
According to Priolli et al. (2004), several breeding programs have contributed to the development of highyielding cultivars adapted to different agro-climatic conditions of the country.These programs have favored the productive sector with the release of new cultivars, as in the case of common bean, e.g., cultivar IAC -Boreal, with increased tolerance to anthracnose, a major cause of crop losses, aside from higher yields (Chiorato et al. 2008).
The breeding program of the Federal University of Uberlandia (UFU) was initiated in 1995 with a Research Center on the Fazenda Capim Branco in Uberlândia, MG, divided into sub-centers at five other locations: Alto Taquari-MT, Chapadinha-MA, Luis Eduardo Magalhães-
UFUS Riqueza was developed by the UFU, Uberlândia-MG, Brazil, with a view to offer producers and companies an advantage over other cultivars on the market.The cultivar has a high yield potential, resistance to the major crop diseases, determinate growth habit, lodging resistance and a cycle of 129 days from emergence to harvest.

BREEDING METHODS
The cultivar UFUS Riqueza was derived from a biparental cross of cultivars (Cristalina RCH x IAC 100) in a greenhouse of the Fazenda Capim Branco -UFU, in Uberlândia-MG, in 1996.For the segregating generations, the SSD (Single Seed Descent) methodology was used, by which inferior and/or pest and disease-susceptible plants are eliminated over the generations.This cross was called 96UFU90 until selection and harvest of the progenies in the growing season 2000.
First field tests were carried out in the 1999 growing season, giving rise to progenies, where the best genotypes were selected and in the following year the best progenies.In the 2000/2001 growing season began the final tests, in which the line with best performance was selected and subsequently included in VCU trials according to MAPA standards, in 2002/03 and 2003/04, in three counties of Minas Gerais.Throughout the development it was found that the cultivar labeled line 96UFU90-86, then named UFU-502 and later UFUS Riqueza stood out from the other tested lines for disease resistance, yield and yield stability.Genetic seed production was initiated in 2007.

PERFORMANCE CHARACTERISTICS
The new cultivar was evaluated in accordance with the MAPA requirements in tests of Value for Cultivation and Use (VCU) and recommended for cultivation in the state of Minas Gerais, due to the superior performance over the controls 'UFV 19' and 'MD 339' in the growing seasons 2002/2003and 2003/2004, in the counties of Uberlândia, Araguari and Iraí de Minas in the state of Minas Gerais.
The grain contains 18 % oil and 39 % protein, serving as an alternative raw material for animal feed production or industrial use.Moreover, the yield potential reaches values above 3470 kg ha -1 , provided that all recommended cultural practices for the crop are applied.

CULTIVAR CHARACTERISTICS
The cultivar is characterized by: determinate growth habit, white flowers, light brown pubescence, light brown hilum, maturation of 129 days, average plant height of 80 cm and insertion height of the first pod at 12 cm, good resistance to lodging and to pod dehiscence (15 days after R8) and mean 100-seed weight of 16 g.

Table 1 .
Mean yield (MY) in kg ha -1 and relative yield (RY) of cultivar UFUS Riqueza and the controls, in the growing seasons 2002/2003 and 2003/2004, in three counties in the state of Minas Gerais