Deterioration of ovary plays a key role in heat stress-induced spikelet sterility in sorghum |
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Authors: | Anuj Chiluwal Raju Bheemanahalli Vinutha Kanaganahalli Dan Boyle Ramasamy Perumal Meghnath Pokharel Halilou Oumarou SV Krishna Jagadish |
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Institution: | 1. Department of Agronomy, Kansas State University, Manhattan, Kansas, USA;2. Division of Biology, Kansas State University, Manhattan, Kansas, USA;3. Agricultural Research Center, Kansas State University, Hays, Kansas, USA |
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Abstract: | In sorghum (Sorghum bicolor L.] Moench), the impact of heat stress during flowering on seed set is known, but mechanisms that lead to tolerance are not known. A diverse set of sorghum genotypes was tested under controlled environment and field conditions to ascertain the impact of heat stress on time-of-day of flowering, pollen viability, and ovarian tissue. A highly conserved early morning flowering was observed, wherein >90% of spikelets completed flowering within 30 min after dawn, both in inbreds and hybrids. A strong quantitative impact of heat stress was recorded before pollination (reduced pollen viability) and post pollination (reduced pollen tube growth and linear decline in fertility). Although viable pollen tube did reach the micropylar region, 100% spikelet sterility was recorded under 40/22°C (day/night temperatures), even in the tolerant genotype Macia. Heat stress induced significant damage to the ovarian tissue near the micropylar region, leading to highly condensed cytoplasmic contents and disintegrated nucleolus and nucleus in the susceptible genotype RTx430. Whereas, relatively less damages to ovarian cell organelles were observed in the tolerant genotype Macia under heat stress. Integrating higher tolerance in female reproductive organ will help in effective utilization of the early morning flowering mechanism to enhance sorghum productivity under current and future hotter climate. |
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Keywords: | heat stress in vitro pollen germination and tube growth ovarian cell organelle damage sorghum spikelet fertility time of day of flowering transmission electron microscopy |
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