Genetic improvement of bread wheat yield and associated traits in Spain during the 20th century

Abstract

SUMMARYA collection of 26 wheat genotypes widely grown in Spain during the 20th century was evaluated in eight contrasting environments in order to quantify breeding achievements in yield and associated traits. From 1930 to 2000, yield increased at a rate of 35·1 kg/ha/yr or 0·88%/yr, but estimations of relative genetic gain (RGG) were environment-dependent. RGG estimated for yield were positively associated with the average minimum daily temperatures from sowing to heading in the testing environments (R2 = 0·81; P < 0·01). The number of grains/spike and the number of spikes/m2 increased at a rate of 0·60%/yr and 0·30%/yr, respectively, while grain weight remained unchanged. The present study detected two main episodes of yield improvement during the century. The first one coincided with the introduction, during the 1950s, of the first improved cultivars derived from intra-specific crosses, which increased the yield of landraces by 30% due to an increase of c. 58% in the number of grains/spike, accompanied by a 16% reduction in grain weight. These initial cultivars (termed ‘old-bred’ in a previous study by Sanchez-Garcia et al. 2012) exhibited a higher harvest index (HI), increased from 0·25 to 0·40, but maintained the same aboveground biomass at maturity as the landraces (despite reducing both plant height and the number of tillers/plant) due to increases in the proportion of tillers bearing spikes. The second yield gain occurred after the introduction, in the early 1970s, of semi-dwarf germplasm from CIMMYT (International Maize and Wheat Improvement Centre) and some French cultivars. This new germplasm further reduced plant height, improved HI up to 0·45 and increased the number of tillers/plant while maintaining their rate of fertility, thus resulting in a yield gain of c. 37%. The cultivars released during the last decade of the century did not contribute to significant yield improvements.

Genotype × tillage interaction in a recurrent selection program in wheat

“…Our results under conventional tillage ( Fig. 1(C)) are coincident with those of other authors (Green et al 2012;Lopes et al 2012;Matus et al 2012;Xiao et al 2012;Sanchez-García et al 2013), where a significant genetic progress was achieved during the…”

The agrarian metabolism as a tool for assessing agrarian sustainability, and its application to Spanish agriculture (1960-2008)

“…First, industrialized farming uses herbicides and/or intensive tillage to prevent the growth of phytomass that farmers are not interested in appropriating. Second, modern varieties, mainly cereals, have been selected to increase the harvest index (Sanchez-Garcia et al 2013). Finally, the role of biomass in the maintenance of soil fertility was replaced, to a certain extent, by mineral fertilizers and pesticides, whose most extreme manifestation was the increase in crop residue burning.…”

Wheat: A Crop in the Bottom of the Mediterranean Diet Pyramid

“…Using Norin 10, a Japanese variety, and the cross Norin/Brevor as a parental, Borlaug obtained 'semi-dwarf wheats' that yielded far beter than the taller wheats grown in most parts of the world at that time. The incorporation of the dwaring genes designated as Rht-B1b (formerly Rht1) and Rht-D1b (formerly Rht2) resulted in an increased earliness, a reduction in plant height and lodging without signiicant decreases in total plant dry weight and a larger allocation of resources in grains, thus improving the harvest index [41][42][43][44]. In addition, the incorporation of photoperiod insensitivity in the wheats developed in Mexico, as consequence of the shutle breeding between contrasting environments, allowed them to be adapted to a wide range of environments all around the world, showing good adaptation to a number of environmental conditions.…”

“…Advances in yield during the twentieth century in Mediterranean countries due to variety improvement have been widely reported in the literature for bread wheat [43][44][45] and durum wheat ( [42,46] and references therein). The role played by the variety is generally ascertained by growing historical series of cultivars in a common environment.…”