Influence of long-term nutrient deficiency on pollen and anther morphological traits in rye

Understanding how environmental factors shape male reproductive traits is crucial for plant breeding and evolutionary biology. Here, we investigated the impact of soil nutrient availability on male reproductive traits in the wind-pollinated grass Secale cereale, leveraging the long-term 'Eternal Rye' monoculture field trial established in 1878. We analysed 552 rye individuals of a population variety and 736 rye individuals of a diverse rye panel grown under nutrient-deficient and nutrient-enriched conditions. Our results show that nutrient deficiency, compared with nutrient enrichment, significantly reduced anther length and pollen number per anther, whereas pollen size and viability remained stable or increased in the population variety. Under nutrient-rich conditions, we observed a trade-off between pollen size and number, which was absent under nutrient-deficient conditions, suggesting shifts in resource allocation strategies. Importantly, this phenotypic plasticity corresponded to changes in the underlying genetic architecture, with distinct quantitative trait loci (QTLs) detected under nutrient-deficient versus nutrient-enriched environments. These findings highlight the substantial influence of environmental plasticity on male reproductive traits and their genetic control in rye.