The Sanskrit grammatical tradition, Vyākaraṇa, one of the six Vedangas, began in the late Vedic period and culminated in the Aṣṭādhyāyī of Pāṇini, which consists of 3990 sutras (ca. fifth century BCE). About a century after Pāṇini (around 400 BCE), Kātyāyana composed Vārtikas on the Pāṇini sũtras. Patanjali, who lived three centuries after Pāṇini, wrote the Mahābhāṣya, the "Great Commentary" on the Aṣṭādhyāyī and Vārtikas. Because of these three ancient Vyākaraṇins (grammarians), this grammar is called Trimuni Vyākarana. To understand the meaning of the sutras, Jayaditya and Vāmana wrote a commentary, the Kāsikā, in 600 CE. Pāṇinian grammar is based on 14 Shiva sutras (aphorisms), where the whole mātrika (alphabet) is abbreviated. This abbreviation is called the Pratyāhara.
Who composed Vartikas on the Panini sutras?
Kātyāyana