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The best yielding and most stable cultivars are identified by growing cultivars in different environments.

If these environments are planting dates and row spacing, these identifications are very important, to manage the cycle of cultivars to obtain best grain yield and harvest index (correlated positively) avoiding hydric stress and high air temperatures on filling grain period.



OBJECTIVE

To estimate stability of grain yield and harvest index of 6 resistant to glifosato herbicide cultivars of Maturity Groups III and IV sown in 14 environments, with the method of Relative Yield (Yau and Hamblin, 1994).



METHODS

• GY: was determined in the two central furrows in each plot.
  
  
• HI: was determined as a quotient between seed weight and plant weight belonging to 1 linear meter of row in 5 out 14 assays.
  
  Relative Yield method (RY)
  
  
• GY and HI of each cultivar in each environment were expressed relative to the average for the environment in which it were determined RGY and RHI), assigning a value of 100 to the latter.
  
  
• Standard deviations of RGY and RHI of each cultivar across environments were used as a measure of stability.
  
  
• The smallest standard deviations mean stable cultivars.
  
  
• Values higher than 100 mean cultivars with specific adaptability to a particular environment

RESULTS

RGY, RHI and standard deviations for all cultivars are shown in Table I and II.



Table 1: RGY and mean standard deviations (sd)

Table 2: RHI and mean standard deviations

• DM 3800 and DM 3000 showed the lowest values of sd and the highest values of RGY and RHI, in early and late plantings, with different spacing rows, in the two years.
  
  
• Positive correlation among GY and HI was again confirmed.
  
  
• DM4400 showed the highest values of RGY and sd (specific adaptability to environments of high GY).
  
  
• DM4800 showed specific adaptability in environments of low HI, and low sd.

MATERIALS

Environments, grain yield and harvest index averages.

Cultivars

All cultivars are belonging to Don Mario enterprise from Argentina:
DM 3000 (1), DM 3600 (2), DM 3800 (3), DM 4050 (4), DM 4400 (5), and DM 4800 (6).



Experimental design

• Split plot design was used in 1999, 4 replications, 4 rows each plot
  
  
• Randomized complete block was used in 2000, 4 replications, 4 rows each plot
  

Traits

• Grain yield (GY)
  
  
• Harvest index (HI)

CONCLUSION

It was possible to select cultivars with high values of GY and HI and with low sd in different environments of the south of Buenos Aires province, in Argentina.



REFERENCES

Yau, S.K.; Hambin, J. 1994. Relative yield as a measure of entry performance in variable environments. Crop Sc. 34: 831-837.

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