Abstract
ABSTRACT: This study determined the effect of different defoliation frequencies in a long-cycle ryegrass cultivar on yield components and the physiological and sanitary quality of seeds. Four defoliation frequencies were applied (without, one, two, and three defoliations). The time between defoliations was 350 degree-days. At the first, second, and third defoliation time, the plants were 15 cm, 20 cm, and 35 cm, respectively, and were lowered to half their height. The yield components and plant structure were evaluated through the tillers, along with the physiological quality of the seeds, which was verified by germination tests, first germination count, accelerated aging, tetrazolium test, field emergence, and weight of a thousand seeds. For the sanitary quality analysis, the percentage (%) of fungi incidence in the seeds was verified. The second defoliation determined the seeds’ high physiological and sanitary quality due to the higher amount of primary and secondary tillers produced concerning the other treatments. However, there was no significant difference for the third defoliation since the aerial tillers issued the same quality of seeds originated from primary and secondary tillers. The average incidence of fungi such as Colletotrichum sp., Fusarium sp., Phoma sp., and Dreshslera spp. was lower in ryegrass plants subjected to three defoliations.
Highlights
The annual ryegrass Lolium multiflorum is a forage highly adapted to southern Brazil’s climate, providing high levels of forage and seed production (CUNHA et al, 2016; BOHN et al, 2020)
The soil in the experimental area is classified as Solodic Dystrophic Haplic Plano soil (SANTOS et al, 2018), which is submitted to conventional preparation, with liming and fertilization according to soil analysis
The following tests were applied according to BRASIL (2009): Germination conducted with four subsamples of 50 seeds, at 25 °C, in the presence of light and on blotting paper, moistened with a volume of distilled water 2.5 times the substrate weight
Summary
The annual ryegrass Lolium multiflorum is a forage highly adapted to southern Brazil’s climate, providing high levels of forage and seed production (CUNHA et al, 2016; BOHN et al, 2020). Defoliation management must prioritize the quality of the seed produced, as excessively defoliated plants tend to accumulate fewer reserves for seed formation (CASSOL et al, 2011). The time when this defoliation occurs will influence the arrangement of yield components since the quality is directly and positively correlated with the leaves’ dry matter production, cob length, and crude protein content (MÜLLER et al, 2012). In the ryegrass of the cultivar Comum, seed vigor reaches its maximum when the plants are subjected to two defoliations during the vegetative period (PASLAUSKI et al, 2014). The present study determined the effect of different defoliation frequencies in a longcycle ryegrass cultivar on the yield components and the physiological and sanitary quality of the seeds
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