Abstract
Both the temperate-humid zone and the southern part of the Mediterranean climate region of Chile are characterized by high wheat productivity. Study objectives were to analyze the yield potential, yield progress, and genetic progress of the winter bread wheat (Triticum aestivum L.) cultivars and changes in agronomic and morphophysiological traits during the past 60 years. Thus, two field experiments: (a) yield potential and (b) yield genetic progress trials were conducted in high-yielding environments of central-southern Chile during the 2018/2019 and 2019/2020 seasons. In addition, yield progress was analyzed using yield historical data of a high-yielding environment from 1957 to 2017. Potential yield trials showed that, at the most favorable sites, grain yield reached ∼20.46 Mg ha–1. The prolonged growing and grain filling period, mild temperatures in December-January, ample water availability, and favorable soil conditions explain this high-potential yield. Yield progress analysis indicated that average grain yield increased from 2.70 Mg ha–1 in 1959 to 12.90 Mg ha–1 in 2017, with a 128.8 kg ha–1 per-year increase due to favorable soil and climatic conditions. For genetic progress trials, genetic gain in grain yield from 1965 to 2019 was 70.20 kg ha–1 (0.49%) per year, representing around 55% of the yield progress. Results revealed that the genetic gains in grain yield were related to increases in biomass partitioning toward reproductive organs, without significant increases in Shoot DW production. In addition, reducing trends in the NDVI, the fraction of intercepted PAR, the intercepted PAR (form emergence to heading), and the RGB-derived vegetation indices with the year of cultivar release were detected. These decreases could be due to the erectophile leaf habit, which enhanced photosynthetic activity, and thus grain yield increased. Also, senescence of bottom canopy leaves (starting from booting) could be involved by decreasing the ability of spectral and RGB-derived vegetation indices to capture the characteristics of green biomass after the booting stage. Contrary, a positive correlation was detected for intercepted PAR from heading to maturity, which could be due to a stay-green mechanism, supported by the trend of positive correlations of Chlorophyll content with the year of cultivar release.
Highlights
Since the green revolution, the yields of wheat and other cereals have increased considerably in many regions of the world, including Chile (Calderini and Slafer, 1998; Engler and del Pozo, 2013; del Pozo et al, 2014, 2019), as a result of genetic improvement and better agronomic practices
Wheat production is of great importance, being the dominant crop in terms of the planted area, 92% of them representing bread wheat (Triticum aestivum) with a production of 1.5 million tons (Oficina de Estudios y Políticas Agrarias [ODEPA], 2017, 2020)
The potential yield achieved by winter wheat cultivars in the temperate-humid zone of southern Chile was close to the 20.50 Mg ha−1 (Figure 2B) that some authors (Parry et al, 2011; Reynolds et al, 2011; Ray et al, 2012; Hawkesford et al, 2013) have proposed as a target for highyielding areas
Summary
The yields of wheat and other cereals have increased considerably in many regions of the world, including Chile (Calderini and Slafer, 1998; Engler and del Pozo, 2013; del Pozo et al, 2014, 2019), as a result of genetic improvement and better agronomic practices. Wheat production is of great importance, being the dominant crop in terms of the planted area (average 220.000 ha in the last 3 years), 92% of them representing bread wheat (Triticum aestivum) with a production of 1.5 million tons (Oficina de Estudios y Políticas Agrarias [ODEPA], 2017, 2020) It has the widest distribution of any crop in the country, covering diverse climatic regions from the semiarid Mediterranean-type climate (∼350 mm of rain) of the northern zone to the temperate-humid climate (∼2,000 mm rainfall) of the southern zone. The average national yield is 6.1 t ha−1, but the potential yield in many areas is much higher, in temperate-humid zones where wheat can attain very high yields (>15 t ha−1), probably due to genotype yield potentials and the remarkable soil and climatic conditions This unique genotype-by-environment interaction in southern Chile constitutes a unique combination for studying yield progress and the relative contribution of genetic improvement to increases in wheat yield potential
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