Abstract
The silvopastoral system is a viable technological alternative to extensive cattle grazing, however, for it to be successful, forage grass genotypes adapted to reduced light need to be identified. The objective of this study was to select progenies of Panicum maximum tolerant to low light conditions for use in breeding programs and to study the genetic control and performance of some traits associated with shade tolerance. Six full-sib progenies were evaluated in full sun, 50% and 70% of light reduction in pots and subjected to cuttings. Progeny genotypic values (GV) increased with light reduction in relation to plant height (H) and specific leaf area (SLA). The traits total dry mass accumulation (DM) and leaf dry mass accumulation (LDM) had GV higher in 50% shade and intermediate in 70% shade. The GV of tiller number (TIL) and root dry mass accumulation (RDM) decreased with light reduction. The highest positive correlations were obtained for the traits H and RDM with SLA and DM; the highest negative correlations were between TIL and SLA and RDM, and H and LDM. The progenies showed higher tolerance to 50% light reduction and, among them, two stood out and will be used in breeding programs. It was also found that it is not necessary to evaluate some traits under all light conditions. All traits had high broad sense heritability and high genotypic correlation between progenies in all light intensities. There is genetic difference among the progenies regarding the response to different light intensities, which will allow selection for shade tolerance
Highlights
The use of Panicum maximum cultivars for pasture establishment in conventional production systems has grown in Brazil, and there is an increased demand of genotypes for silvopastoral areas
coefficient of genotypic determination (CGD) explains the amount of the phenotypic variability that was due to genotype variation, i.e., it is equivalent to the broad sense heritability of the trait
Tiller is a genetic trait, but may be greatly influenced by the environment (Langer, 1972), and our results indicate that the progenies have genetic variability for light reduction, facilitating the selection of individuals with better agronomic and qualitative forage characteristics for silvipastoral systems
Summary
The use of Panicum maximum cultivars for pasture establishment in conventional production systems has grown in Brazil, and there is an increased demand of genotypes for silvopastoral areas. The development of new cultivars of this species for silvopastoral systems is possible, since these plants have satisfactory tolerance to light reduction (Wong & Wilson, 1980; Eriksen & Witney, 1981; Andrade et al, 2004). Panicum maximum has a high genetic variability in its center of origin and Brazil has a large germplasm bank (Embrapa Beef Cattle), allowing the improvement of the species. Forage biomass accumulation results from genetic and environmental factors, which enable the selection of genotypes better fit for specific environments through quantitative morphological and physiological characteristics
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