Premature degeneration of tapetum cells causes monogenically controlled environmentally stable male sterility in psyllium.

Psyllium (Plantago ovata Forsk.) is an important medicinal species cultivated throughout the semi‐arid areas in India. The seed coat, commercially known as psyllium husk, is used as a laxative for treating irritation of gastro‐intestinal tract and relieving constipation. There is an urgent need to enhance its productivity to make the crop more profitable. Artificial crossing is difficult in the species because of its small‐sized sessile florets that are compactly arranged on a soft inflorescence axis. Male sterility has been reported in the species; however, no conclusive studies have been conducted to reveal the inheritance, mode of action, and cytogenetic basis of male sterility. Hence, the purpose of this study was to determine (a) the histological and cytogenetic bases of anther development and microsporogenesis in male‐sterile and fertile plant types and (b) the genetic basis of male sterility. The study revealed that male sterility in psyllium was not attributable to meiotic abnormality or to tetrad abnormalities, but it was attributable to premature degradation of the tapetum layer, which subsequently causes the microspore degeneration, resulting in nonproduction of pollen grains. Male sterility was controlled by a single recessive gene, which was found to be stable across years and hence can easily be bred into any psyllium genotypes of breeders' choice. Newly developed male‐sterility‐maintainer line can be used to generate new sets of male‐sterile lines for hybrid seed production or harnessing hybrid vigor in the field. Core Ideas: Male sterility mechanism and genetics has been revealed in psyllium.In psyllium, meiosis and tetrad formation are normal in both sterile and fertile lines.Male sterility is due to the premature degradation of tapetum layer in the anther sac.Male sterility is controlled by a single recessive gene and stable across years/generations.Newly developed male sterile maintainer line can be used in hybrid vigor/ molecular genetics. [ABSTRACT FROM AUTHOR]