Conservation Agriculture and Genotypes – Are There Interactions?.

Conservation agriculture (CA) is based on minimum tillage, crop residue retention, and crop rotation. By minimizing erosion risks and improving soil quality and water availability CA has the potential to improve sustainability of crop production.  Conservation agriculture imposes distinct growing conditions to crops. Most breeding programs operate under conventional tillage (CT) conditions and varieties specially adapted to CA do not exist. The question whether targeted breeding programs could improve yield in CA remains unanswered.

We conducted yield potential trials at CIMMYT’s experiment station near Ciudad Obregon in northwestern Mexico. Our objective was to test for genotype by agronomic system interaction (GxS) within bread (BW) and durum wheat (DW) varieties. Twenty-six varieties (created 1965-2007) were screened for yield and related traits in four agronomic systems. Those included CA and CT each with full (FI) and reduced irrigation (RI). 

Yield potential had increased over time. While BW yield was highly correlated to thousand kernel weight (TKW) DW yield showed no correlation to TKW but increased with number of grains per spike. Yield increase was observed in all tillage systems and irrigation regimes. Durum wheat yields were continuously higher in CA. Yield increase of DW was slightly higher under CA conditions. Bread wheat yield and yield increase were equal for both tillage regimes under FI. Under RI older BW varieties performed poorer in CA. However, yield progress was stronger under CA conditions. Bread wheat varieties released in the 1980s and later performed better under CA than CT. Interactions of GxS were significant for BW yield under FI and RI. Durum wheat varieties did not show significant GxS interaction. The results suggest that breeding progress can be higher under CA conditions, even though selections were done under CT. Further investigation and selection experiments need to be conducted to clarify benefits of selection under CA.