Importance of Canopy Attributes in Determining Dry Matter Accumulation of Pigeonpea under Contrasting Moisture Regimes

Abstract

Variability in the yield of extra-short-duration (ESD) pigeonpea [Cajanus cajan (L.) Huth.] genotypes in drought environments is related to variation in crop growth rate (CGR) and total dry matter (TDM) production. Our investigation was aimed at assessing the importance of canopy attributes in determining the growth of ESD pigeonpea under contrasting moisture regimes. Using two automated rain-out shelters (ROS), six genotypes were grown under well watered conditions or with water deficit imposed from flowering until maturity. Water deficit significantly decreased the cumulative intercepted photosynthetically active radiation (CIR). The relationship between biomass accumulation and CIR was linear and water deficit affected the slope of the relationship (i.e., radiation use efficiency, RUE) (b = 1.92 g MJ−1 for well watered vs. 1.43 g MJ−1 for water deficit). Genotypes differed in RUE under well watered (1.70 to 2.19 g MJ−1) and moisture deficit (1.30 to 1.66 g MJ−1) conditions. Genotypic variation in canopy attributes was significant. Leaf area duration (LAD) significantly correlated with CGR only under well watered conditions. Cumulative intercepted radiation and RUE accounted for nearly 99% of the genotypic variation in CGR under both moisture regimes, of which RUE alone contributed nearly 90%. Variation among genotypes in CIR alone did not explain the differences in dry matter accumulation under either moisture regime. Only RUE explained more than 90% of the genotypic variation in CGR and 70% in TDM under both moisture regimes. The results indicated that RUE is critical in determining pigeonpea productivity under well watered and moisture-deficit regimes.