Early Vigor of Advanced Breeding Lines and Modern Cotton Cultivars

Abstract

Stand establishment and early vigor are critical to the successful production of cotton (Gossypium hirsutum L.). Rapid early growth could provide significant advantages to young plants relative to diseases, insects, and weeds. The objectives of this research were to identify traits that contribute to differences in early growth, characterize genotypic variation in early vigor among modern cultivars and advanced breeding lines, and determine the effect of the seed production environment on early vigor. Early growth of 10 genotypes from private companies and 18 unreleased breeding lines was compared through measurements of leaf area and biomass under field conditions in 2 yr. A positive correlation of seed weight and rapid early growth was observed up to 32 d after planting (DAP). Cotyledon area was positively associated with shoot dry weight over the course of the first 52 DAP. Significant genotypic differences were observed for cotyledon and total leaf areas, and for cotyledon, first true leaf, total leaf, stem, and total shoot dry weights in both years within approximately the first 4 wk after planting. No correlation between lint yield and rapid early growth was found. For the first 17 (2009) and 32 (2008) DAP—but not after that—plants grown from seeds produced in distinct environments differed in early vigor. Overall, seeds from breeding lines produced more vigorous seedlings than did seeds of commercial genotypes. Although heritability of the examined traits has not been established, the broad range in values and significant genotypic variation suggest that breeding for enhanced early vigor should be possible without compromising yield.

Morphological Traits Underlying Differences in Early Vigor among Four Cotton Genotypes

“…Decreases in RGR with time are commonly observed and are generally explained by ontogenetic changes, higher allocation to low-efficiency tissues, and self-shading (Hunt, 1982(Hunt, , 2003Poorter and Pothmann, 1992;Romero and Marañón, 1994;Hunt and Cornelissen, 1997;Enquist et al, 1999;Shipley, 2000;West et al, 2001). 5) were expected and are consistent with previous observations for cotton by Liu et al (2015Liu et al ( , 2019. 5) were expected and are consistent with previous observations for cotton by Liu et al (2015Liu et al ( , 2019.…”

“…Therefore, three genotypes previously identified to differ in seedling vigor and one commercial cultivar were selected for detailed characterization of early growth in greenhouse and field conditions. Other studies have provided some information on photosynthesis (Cook and El-Zik, 1992), development of an early true leaf (Ortiz and Bourland, 1999), and biomass and leaf area production (Liu et al, 2015(Liu et al, , 2019 during early growth based on limited samplings, but these studies lack detailed growth analyses. Environmental conditions prevailing in field and greenhouse conditions differentially affected seedling growth, including cotyledon biomass, root weight ratio (RWR), net assimilation rate (NAR), and specific leaf area (SLA).…”

“…Growing environment and genotype effects were significant for many of the measured traits. So far, there is still no universal agreement on a definition of seedling vigor; however, shoot or total dry weight during early plant development has been used as criterion for seedling vigor in cotton (Liu et al, 2015(Liu et al, , 2019Snider and Oosterhuis, 2015;Snider et al, 2016) and other crops, including rice (Roy et al, 1996), wheat (Gan and Stobbe, 1996), and maize (Zea mays L.) (Fakorede and Ojo, 1981). Genotypic differences were found in one or both environments for cotyledon area, area of the first leaf, total leaf area, and leaf, stem, root, and total biomass.…”

“…To this end, based on shoot biomass characterization of 144 genotypes, three genotypes (Liu et al, 2019) and one commercial cultivar (Liu et al, 2015) were selected. To this end, based on shoot biomass characterization of 144 genotypes, three genotypes (Liu et al, 2019) and one commercial cultivar (Liu et al, 2015) were selected.…”

“…In addition, Liu et al (2019) also evaluated a subset of 40 of 144 germplasm lines and these advanced breeding lines and commercial cultivars (Liu et al, 2015) under field conditions. Based on results obtained from these experiments (Liu et al, 2015(Liu et al, , 2019, four genotypes differing in early vigor were selected for this study: PI529472 (low vigor [LV], average weight of acid-delinted seed = 63 mg seed −1 ), PI 528960 (medium vigor [MV], average weight of acid-delinted seed = 80 mg seed −1 ), PI 529480 (high vigor [HV], average weight acid-delinted seed = 94 mg seed −1 ), and commercial PHY 315RF (COM, medium-high vigor, average seed weight = 88 mg seed −1 ).…”