VOLUME 16 NUMBER 1 (January to June 2023)

Imeldalyn G. Pacada* and Fredi Jan A. Francia

Plant Breeding and Biotechnology Division,
      Philippine Rice Research Institute,
      Central Experiment Station, Maligaya, Science City of Muñoz,
      Nueva Ecija, 3119 Philippines

Research around the world has established the good performance of the varietal mixture (VarMix) approach in mitigating the ill effects of biotic stresses on various crops. Thus, the efficiency of this approach against abiotic stresses is also being studied. In the Philippines, the evaluation of VarMix is limited especially in large rice areas that experience water scarcity and unpredictable occurrence of pests and diseases. In this study, yield performances of 12 VarMix combinations and their corresponding single varieties were evaluated in 12 environments nationwide that suffer from water scarcity. VarMix ADCEF yielded highest at 7.7t/ha. Analysis of mixing effects showed that 10 of the 12 combinations gained positive MErelml mean ranging from 0.25 to 17.37%. This shows that their mean yield was higher by 0.25% to 17.37% than the yield mean of their single component varieties in different environments. VarMix ABCE achieved the highest MErel_ml value of 175.86% in Carmen, Bohol with a 17.37% mean. ABCE also had positive MErel_ml (1.44% to 19.76%) in Agusan del Norte; Aurora; Nabonton, Ligao, City Albay; Batac City, Ilocos Norte; Iloilo; Nueva Ecija; PhilRice Batac, and PhilRice Bicol. Further, ABCE had the highest positive MEmax_ml value of 100.79% (found in Bohol), indicating that its yield was 100.79% higher than the maximum yield of its corresponding variety. Batac City and Iloilo likewise had positive MEmax_ml of 1.40% and 0.90%. VarMix combinations BDE, AFE, ABCEF, and ABCDEF reached higher D(x)_ml with the same mean values of 0.7 across the 12 locations. The highest D(x)_ml of 1.9 was found in BDE and BCD. Based on the static measure of all genotype stability, BDE and single variety NSIC Rc 298 attained small S²i values of 2.0, where the lower the value of variability the more stable they were. In the analysis on responsiveness to environmental productivity, ADCEF was the most responsive and the largest stability (bi) value of 1.2 followed by ACDE, ABC and AFE with 1.1; bi >1 means they have higher responses to a given environment. VarMix combinations that showed yield increase through the mixing effects analysis in actual field conditions will facilitate the selection of elite VarMix for future deployment in areas with similar environment. Results from this study highlighted the potential of VarMix as a stop-gap approach for increasing yield in rice production areas with limited source of water and unpredictable occurrences of pests and diseases.