Phenotypic and Genetic Parameters Estimated for Fresh Corn Under Different Nutrient Availability1

Abstract

The objective of this work was to estimate and compare phenotypic and genetic parameters after three cycles of intrapopulation recurrent selection for fresh corn grown under three nutrient availability conditions. Three experiments derived from the same population (MV-003) were conducted to assess the ability of progenies to absorb nutrients, one under adequate fertilization (control; MV-006), one under low nitrogen availability (N; MV-006N), and one under low phosphorus availability (P; MV-006P). The experiments were carried out in randomized blocks, with 64 half-sib progenies and three replications for each nutritional condition. Chlorophyll index, plant height, ear insertion, ear diameter, ear length, unhusked ear yield, and marketable husked ear were evaluated. The populations showed variability for the three nutrient availability conditions. The variability reduced after only three selection cycles; thus, evaluating a higher number of half-sib progenies, above 64, under low N and P availability is indicated. The rates used to identify the most efficient progenies in breeding programs should be close to the appropriate one, with a slow reduction after the selection cycles. The variability will be thus maintained, with a greater possibility of identifying more promising progenies. In addition, the frequency of favorable alleles increases more gradually and effectively. The N and P rate of 60 kg ha-1 is not indicated as a critical level for the initial phase of the program.

Experimental double hybrids of fresh corn grown under low and high phosphorus availability

“…Some experimental hybrids have more interesting characteristics to be marketed in trays, mainly shorter lengths; however, the larger ear diameters of the hybrids DH81 and DH82 resulted in higher grain weights (97.5-85.5 g, respectively), being more attractive to consumers. Ribeiro et al (2016) found that there is a low effect for these variables with the reduction of P doses between 75 and 150 kg ha -1 of P 2 O 5 , with increments of only 1.51 cm and 0.38 mm, respectively, what may also indicate a low number of alleles involved and a very small genotype by environment interaction, in this case, confirmed by the non-interaction of the diameter variable and low influence on the length under selection for low P availability, as stated by Resende et al (2021).…”

“…Therefore, the hybrids DH62, DH71, DH82 and DH102 presented a higher efficiency and responsiveness to P for unhusked and husked ear weight, based on the performance of the control (AG1051), and a higher chance of success in corn markets focused on growers with low to high technological levels (Table 4). Resende et al (2021) reported difficulties for generation of variability in hybrids under low nitrogen and P availability conditions, as breeding programs always prioritized cultivars for high P availability; thus, allelic combinations for low P availability conditions would be more difficult to be identified currently.…”

Five cycles of intrapopulation recurrent selection in half-sib progenies of fresh corn

“…The experiment was conducted at the Universidade Estadual de Goiás (UEG), in Ipameri, GO, Brazil, during the summer, after five selection cycles. The corn population used for the formation of progenies was from the MV-003 population, obtained through complex crossing between the imported hybrids CN19-50 and CN 23-50, which are sweet corn hybrids (susu), and the double experimental hybrid HD17 (SuSu) of the UEG plant breeding program (MELHORVE), which present more adequate characteristics to the national market and higher starch contents (SuSu), as shown by Resende et al (2021). The progenies were preselected and then subjected to five selection cycles, using intrapopulation recurrent selection of half-sib progenies.…”

“…Currently, there is only one corn cultivar focused on fresh consumption in the market, the BRS3046 (conventional), among the 98 corn cultivars available in the 2020-2021 crop season; four cultivars available for this niche were excluded and the number of cultivars in relation to previous crop season decreased approximately 45% (PEREIRA FILHO; BORGHI, 2021), which restricts this crop. Therefore, the development of improved populations, hybrids, and varieties with open pollination are essential to meet the demands of growers and consumers and, generate information and quality genotypes for fresh consumption (RESENDE et al, 2021). Therefore, the recurrent selection method is a viable option by selecting the best progenies over several cycles to obtain successive gains in each cycle without depleting the genetic variability of the population (HALLAUER; CARENA; MIRANDA FILHO, 2010).…”

“…Therefore, the recurrent selection method is a viable option by selecting the best progenies over several cycles to obtain successive gains in each cycle without depleting the genetic variability of the population (HALLAUER; CARENA; MIRANDA FILHO, 2010). Intrapopulation recurrent selection in corn half-sib progenies is among the strategies used for this purpose, due to its easy conduction, applicability, and high efficiency in obtaining genetic gains, as found for grain corn (SHEIKH et al, 2019), which includes works focused on resistance to corn weevil (Sitophilus zeamais) (LÓPEZ-CASTILLO et al, 2018), popcorn (GUIMARÃES et al, 2019, and fresh corn (RESENDE et al, 2021). In this context, the objective of this work was to evaluate the progress of five cycles of intrapopulation recurrent selection in half-sib progenies of fresh corn grown in the southwest region of Goiás.…”