Callum Matthews
BBC Sport journalist
Border-Gavaskar Trophy, first Test, day one, Perth
India 150: Kumar Reddy 41, Pant 37; Hazlewood 4-29, Marsh 2-12
Australia 67-7: Bumrah 4-17, Siraj 2-17
Australia trail by 83 runs
Australia collapsed to 67-7 as India rallied with the ball to seize the initiative - despite being dismissed for just 150 on an extraordinary opening day of the first Test in Perth.
After opting to bat first the tourists, who made a staggering six changes from their historic third Test defeat by New Zealand earlier in November, were reduced to 32-3 and 73-6.
Virat Kohli's struggles continued as he made just five, while Yashasvi Jaiswal and Devdutt Padikkal, both playing in Australia for the first time, were dismissed without scoring.
Rishabh Pant (37) and debutant Nitish Kumar Reddy (41) showed some form to counter-attack and drag India to 150, but they were bowled out within two sessions.
In reply, Jasprit Bumrah produced a breathtaking opening spell to leave Australia 19-3.
He removed debutant Nathan McSweeney lbw on review and had Usman Khawaja caught in the slips, before removing Steve Smith lbw first ball.
Travis Head and Mitchell Marsh both then fell cheaply, before Marnus Labuschagne, who batted resiliently for two off 52 balls, was trapped lbw by Mohammed Siraj.
Bumrah returned to remove Pat Cummins, as Australia reached 67-7 at stumps, and will resume 83 runs behind when play resumes at 02:20 GMT on Saturday.
The 17 wickets to fall is the most on the opening day of a Test in Australia since 1952.
Kohli fails again as India's top order blown away
There were questions over India's batting coming into the series, after being bowled out for 46, 156 and 121 in their 3-0 defeat by New Zealand.
Opener and captain Rohit Sharma is missing this game after the birth of his second child, while number three Shubman Gill was not considered for selection after injuring a thumb in India's intra-squad warm-up.
That led to KL Rahul opening and Padikkal, playing in his second Test, coming in at three.
With the pressure on Kohli to hold the innings and makeshift line-up together, he brought energy to the crease and looked proactive, but once again he failed.
It was beautiful bowling from Josh Hazlewood to set him up, going slightly shorter, and he found extra bounce to bring the outside edge.
It was Kohli's fifth single-figure score in his past 10 Test innings - where he averages just 21.2, compared to his career average of 47.6. His average innings has lasted just 29.4 balls, way down on the 80.3 across his career.
The rest of the India batting line-up was blown away by the accuracy of the Australia seamers.
There was barely a loose ball, and subtle changes of line often brought the edge, with nine of the wickets caught behind the stumps by Alex Carey or the cordon.
Rahul's dismissal, given out caught behind on review, was controversial, with the Indian convinced that the noise on the snickometer technology was bat hitting pad, rather than an outside edge.
Pant, who is the one Indian batter in form, offered resistance alongside Kumar Reddy - with both offered a life - but Australia's persistent nagging brought rewards.
Bumrah dazzles as questions remain for Australia
Australia came into the series with batting questions of their own.
After opting to move Steve Smith back to four in the absence of Cameron Green in the middle order, they had a four-way shootout for the vacant openers spot in a warm-up game against India A.
Nathan McSweeney won that contest, despite having never opened until that match, and the Queenslander was given a going over by the brilliant Bumrah.
He was hit on the thigh pad, looking to leave, first ball, before edging just short of the slip cordon. The reprieve was short-lived though as Bumrah had him lbw on review for 10.
As has become custom, Bumrah's line and length was exemplary throughout this new-ball spell, offering no width or freebies to the Australia batters.
That brought him the rewards of Khawaja and Smith, who Labuschagne tried to convince to review - but he simply shrugged his shoulders as if to say 'it's out'.
Bumrah was then ably backed up by Harshit Rana, who brilliantly bowled Travis Head, and Siraj.
Labuschagne threatened to blunt India, as he made his slowest start to a Test innings, but in the end his lack of scoring intent led to him being dismissed by Siraj, despite a review.
Carey showed positive intent for Australia, upper-cutting to the boundary, and whether he can stay around in the morning will likely play a key part in this Test.