Genetic changes in durum wheat yield components and associated traits in Italian and Spanish varieties during the 20th century

Abstract

Twelve field experiments comparing 24 durum wheat varieties from three periods-old (<1945), intermediate and modern (1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)-were carried out in order to ascertain the advances made in durum wheat yield components and related traits in Italian and Spanish germplasm. Grain yield improvements were based on linear increases in the number of grains per m 2 and harvest index, while grain weight and biomass remained unchanged. Yield per plant increased at a rate of 0.36 and 0.44% y -1 and the number of grains per m 2 improved by 39% and 55% in Italian and Spanish varieties, respectively. The mean rate of increase in the number of grains per m 2 was 0.55% y -1 . Plants per m 2 , spikes per plant and grains per spike contributed 20%, 29% and 51%, respectively, to the increase in the number of grains per m 2 . The enhance of the number of grains per m 2 was due to the greater grain set in the modern varieties, since the number of spikelets per spike remained unchanged. Harvest index increased overall by 0.48% y -1 (0.40 and 0.53% y -1 in Italian and Spanish varieties, respectively). Plant height was the trait that suffered the most dramatic changes (it decreased at a rate of -0.81% y -1 , with little difference between the varieties of the two countries), as consequence of the presence of the Rht-B1 dwarfing gene. Harvest index and plant height, which were the traits that most contributed to discriminating between periods, remained unchanged from 1980 to 2000. The higher rates of improvement in Spain are discussed in the context of the contrasting strategies followed to improve durum wheat yield in the two countries.

Changes in durum wheat root and aerial biomass caused by the introduction of the Rht-B1b dwarfing allele and their effects on yield formation

“…PCR-based markers specific for the base pair responsible for the semi-dwarf phenotype were used to identify specifically wild-type (Rht-B1a) and mutant (Rht-B1b) allelic variants at the Rht-B1 locus following the methodology described by Ellis et al (2002), thus allowing classifying the cultivars into two groups: tall, carrying the RhtB1a allele, and semi-dwarf, with the Rht-B1b allele. This methodology confirmed the presence of the Rht-B1b allele in the genome of the Italian cultivar 'Adamello', which had previously been considered not to carry any dwarfing allele (Isidro et al 2011;Álvaro et al 2008a, 2008b, 2008cRoyo et al 2007), according to the results of the test for sensitivity to gibberellic acid (Gale and Gregory 1977). At anthesis (Zadoks stage 65, Zadoks et al 1974) plant height was measured from the soil to the top of the spike excluding the awns, and the entire plants, including the roots, were removed from the tubes (Fig.…”

“…In addition to the reduced height of the plant, the Rht-B1b allele has well-known pleiotropic effects on plant growth, and morphological and physiological characters (Gale and Youssefian 1985;Li et al 2011;Rebetzke et al 2012). It increases yield, mostly under favourable conditions, by altering the proportion of dry matter allocated to grain (De Vita et al 2007;Royo et al 2007Royo et al , 2008Álvaro et al 2008a). However, the effect of the Rht-B1b allele on the root system has been poorly explored (Waines and Ehdaie 2007).…”

“…The effect of breeding activities during the 20th century and the introduction of dwarfing alleles on yield, yield components, biomass production and allocation was previously studied by our team on a historical series of 24 Italian and Spanish durum wheat cultivars released in different periods and with different allelic compositions in the Rht-B1 gene (Royo et al 2007(Royo et al , 2008Álvaro et al 2008a, 2008b, 2008cSubira et al 2014). The same set of cultivars was used in the present study with the following aims: (i) to quantify the changes occurring in root biomass due to the introduction of the Rht-B1b dwarfing allele, (ii) to determine the relationship between the changes in root biomass and the changes in aerial biomass, and (iii) to study the relationship between biomass and yield formation in tall and semi-dwarf cultivars.…”

Genotype × tillage interaction in a recurrent selection program in wheat

“…1(B), Table 2). Similarly to Royo et al (2007) conclusions, increases in grain yield were due to changes in photosynthates partitioning within the plant. Guarda et al (2004) and Shearman et al (2005) results showed that number of grains per unit land area contributed to the genetic gain of grain yield.…”

Changes in stem and spike related traits resulting from breeding in Iranian wheat cultivars: associations with grain yield

“…Past genetic gains in wheat plants have been widely associated with increased harvest index and grain per m 2 and decreasing stem length (Royo et al 2007).…”