Abstract
Trinexapac-ethyl (henceforth referred to as trinexapac) is a growth regulator that can mitigate some undesirable vegetative growth in Poaceae plants, reducing lodging and optimizing the distribution of photoassimilates to reproductive organs. The objective of this research was to evaluate the morphophysiological and productive responses of rye cultivars and trinexapac doses applied at different phenological stages of plants. Two field experiments were performed in two different seasons. In the 2015 growing season, 8 doses of trinexapac were evaluated: 0, 75, 85, 100, 115, 130, 150, 200 g ha-1 of active ingredient (a.i.), applied at the plant growth stage with the 4th node visible on the main stem (GS34). In the 2018 growing season, two cultivars (IPR 89 and BRS Serrano) and five doses of trinexapac were evaluated: 0, 50, 100, 150 and 200 g a.i. ha-1, applied at the plant growth stage with the 6th node visible on the main stem (GS36). The morphophysiological, productive and qualitative characteristics of grains were evaluated. In the 2015 season, trinexapac applied to shoot plants at GS34 only have low response in decreased plant lodging from around 20% to 10%. However, in the 2018 season, the application of trinexapac on plants at GS36, resulted in lower plant height, associated with reduced lodging and better quality of rye grains. Cultivar IPR 89 showed higher values for yield components and grain quality in comparison to cultivar BRS Serrano. Reduced lodging is dependent on speed of resumption of plant height growth, and the magnitude of response to trinexapac is also stage-cultivar-dose-dependent; in rye, the best response to trinexapac was found at GS 36 in comparison to GS 34, and for IPR 89 in comparison to BRS Serrano cultivar, respectively, with a dose range from 100 to 150 g ai ha-1. In conclusion, trinexapac (around 150 g a.i. ha-1), when applied to plants at GS36, reduces plant height, reduces the lodging index and enables the harvest of high-quality grains.
Highlights
IntroductionRye (Secale cereale) crops stand out for their adaptability to low temperatures (e.g., their physiological growth starts at 0 oC) and diverse environmental and edaphic conditions (Jung & Seo, 2019)
Rye (Secale cereale) crops stand out for their adaptability to low temperatures and diverse environmental and edaphic conditions (Jung & Seo, 2019)
The doses of trinexapac applied at growth stage GS34 only promote significant variances (P < 0.05) on lodging index and thousand-grain weight (TGW), but on plant height, hectoliter weight, sieve index of grains and grain yield no alterations were observed (P > 0.05) in the 2015 growing season in the cultivar BRS Serrano, as shown in the probabilities (Figure 2; P > 0.05)
Summary
Rye (Secale cereale) crops stand out for their adaptability to low temperatures (e.g., their physiological growth starts at 0 oC) and diverse environmental and edaphic conditions (Jung & Seo, 2019). In Brazil, rye is mostly cultivated in the states of Paraná and Rio Grande do Sul; most often, it is grown in acidic and degraded soils, at altitudes above 600 m (CONAB, 2020). Excess nitrogen fertilization and lower dry matter accumulation, resulting from excessive rainfall and winds, favor the occurrence of lodging during cultivation (Wu et al, 2019). These conditions are common in areas above 600 m of altitude in the south of Brazil. Rye plants grown in Brazil are taller, which may predispose susceptibility to lodging. Lodging significantly affects photosynthetic ability, carbohydrate transport, and water movement in plants
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