Peculiarities of the seed quality formation in switchgrass varieties of different maturity groups under the effect of weather conditions

Abstract

Purpose. The article presents research results on the influence of weather conditions on the seed quality formation in switchgrass (Panicum virgatum L.) of different maturity groups.
 Methods. Laboratory, measuring and weighing, mathematical and statistical.
 Results. Switchgrass is one of the promising perennial grasses for biofuel production. Its propagation is possible by seeds and rhizomes; however. the most favorable way is a reproduction by seeds. This crop has relatively small seed size with a high level of dormancy. At a high level of dormancy, seed germination can be only 5% and such seeds do not germinate at all in field conditions. The reasons that cause a state of biological dormancy are very diverse. For the purpose of a comprehensive assessment of the influence of average daily temperatures and the level of moisture for a certain growing season, the hydrothermal coefficient (HTC) was used. Thus, the vegetation season of 2018 was the most favorable for seed formation of both maturity groups. Vegetation seasons of 2019–2021 were less favorable, especially for late and very late ripening varieties, which affected the seed quality. The analysis of weather conditions based on HTC as a whole during the vegetation season does not sufficiently reveal the influence of weather conditions on the seed quality formation during individual stages of organogenesis. Therefore, weather conditions were analyzed according to the main interstage periods of plant growth and development, specifically in the seedlings – throwing of panicles and the seed formation and ripening interstage periods and the flowering stage. In the most favorable year 2018, the interstage period - seedlings – throwing of panicles was excessively moistened (HTC 1.8), which contributed to the intensive growth and development of plants. The flowering stage was characterized by optimal moisture (HTC 1.1), and the seed formation and ripening interstage period was dry (HTK 0.9).
 Conclusions. For the high-quality switchgrass seeds formation, the optimal conditions during the stages of growth and development of the crop are the following: in the interstage period seedlings – throwing of panicles excessive moisture that ensures intensive growth and development of plants; in the flowering stage close to optimal or optimal moisture; and the in the interstage period seed formation and ripening dry.