Evaluation of three cycles of full-sib reciprocal recurrent selection in two maize populations from the Northeast of Spain

Abstract

In Europe a heterotic pattern commonly used in maize breeding is "American Dent× European Flint". Maize breeding programs generally use only a small portion of the useful genetic variability present in the local open-pollinated varieties which, otherwise, have a poor performance that hampers their use. Two maize composites, EZS33 formed by open-pollinated flint varieties from dry or Mediterranean Spain, and EZS34 from USA dent populations, were developed in Zaragoza (Spain). Both were subjected to three cycles of full-sib reciprocal recurrent selection (RRS) for yield. The objective of our study was to evaluate after three cycles of selection the effect of RRS. The selection significantly increased yield in the population crosses (3.0% per cycle) and in the crosses of the populations with testers of different origin. The correlated responses for the population crosses in other agronomic traits like flowering and early vigor were in the desired direction, but plant height was reduced. We propose that stover yield or related traits could be included in selection programs as selection criteria to prevent their decline. The adapted population increased the frequency of favorable alleles for yield, but the inbreeding depression counteracted their effect on the mean. RRS had a positive effect on other traits. According to our data, RRS can be useful to develop improved populations from which it would be possible to develop lines with improved both specific and general combining ability with different heterotic groups. We conclude that the heterotic pattern "Mediterranean Spain x US Dent" is potentially very useful for maize breeding for adaptation to Mediterranean conditions and an interesting source of cultivars for low-input agriculture.

Changes in heterosis of maize (Zea mays L.) varietal cross hybrids after four cycles of reciprocal recurrent selection

“…The response in the varietal crosses for grain yield and other agronomic traits was greater than the response of the various selection cycles of the two composites, suggesting that dominance was the major type of gene action involved (Keeratinijakal and Lamkey 1993;Souza Jr and Pinto 2000). Inconsistent trends in grain yield observed in varietal crosses in the present study was consistent with the results reported in other studies (Romay et al 2011;Peña-Asin et al 2013). The linear response obtained for grain yield in our program was similar to the response obtained in other RRS programs (Coors 1999;Peña-Asin et al 2013).…”

“…Responses to selection in the various selection cycles of the two composites in the present study were inconsistent for most traits while others remained unchanged until C 4 , which agrees with the reports of Souza Jr (1999) and Romay et al (2011). Grain yield improved in TZL COMP4 at a rate of 0.9% per cycle, although the largest mean performance was reached during the third selection cycle, whereas, the improvement for grain yield was not consistent in TZL COMP3 resulting in a negative response, consistent with the negative, positive or lack of response observed in one or two populations improved through RRS in other breeding programs (Butruille et al 2004;Moreno-Perez et al 2004;Peña-Asin et al 2013;Reis et al 2013). A plausible explanation for negative response of TZL COMP3 could be because it was formed by crossing an orange maize variety from Thailand (Suwan 1-SR) with an adapted variety (TZB-SR) developed at IITA (Menkir et al 2015).…”

Genetic Advance in Grain Yield and Other Traits in Two Tropical Maize Composites Developed via Reciprocal Recurrent Selection

“…Kling, 1999;Rademacher et al, 1999;Souza and Pinto, 2000;Santos et al, 2005). However, the realized genetic gain in grain yield in our study was higher than the genetic gains reported in other studies varying from 2.1 to 3.0% (Paterniani and Vencovsky, 1978;Hallauer, 1984;Peña-Asin et al, 2013). The difference between our results and other RRS programs could be attributable to differences in the test environments, the genetic base of the populations studied, the number of progenies selected for recombination in each cycle, and selection intensity.…”

“…In addition, the improved population crosses could be used as elite openpollinated cultivars until conventional hybrids involving inbred lines are developed. Peña-Asin et al (2013) reported a 3.0% cycle −1 increase in grain yield after three cycles of full-sib RRS in two maize composites. Hallauer (1992) stated that genetic gain might not always be apparent from cycle to cycle and, in some instances, it could even be erratic among cycles.…”

“…Previous estimates of genetic gains in grain yield per cycle resulting from different RRS methods range from 3.0 to 7.3% in different maize populations (Souza and Pinto, 2000;Santos et al, 2005;Hallauer and Carena, 2012). Peña-Asin et al (2013) reported a 3.0% cycle −1 increase in grain yield after three cycles of full-sib RRS in two maize composites. Noor et al (2013) also reported that two cycles of half-sib RRS increased grain yield by 5.1% cycle −1 .…”