The 26-year-old Manyonga claimed the win with an 8.36m effort.
Manyonga has already set a new African record in the long jump this season with a leap of 8.65m.
Countryman Ruswahl Samaai took second with 8.29m, while Khotso Mokoena finished sixth with a best attempt of 7.98m.
On the track, 110m hurdler Antonio Alkana was disqualified for a false start, while LJ van Zyl finished last in the 400m hurdles.
Meanwhile, Canadian sprinter Andre de Grasse breezed to victory in the 100m, with a strong wind powering him to a blistering 9.69 seconds.
The 22-year-old De Grasse, seen as the sprinting heir to Usain Bolt when the great Jamaican calls it quits at the London world championships in August, would have been celebrating a personal best had the wind of +4.8m/s not exceeded the permitted limit of +2.0m/s.
It was a third successive Diamond League win for De Grasse, whose personal best remains the 9.91 he ran to win bronze at last year’s Rio Olympics.
“It’s great to sprint in such conditions, you cannot dream of any better,” said the Canadian. “Before I came here, I was told that it might be a bit cold, but when I warmed up, I realised that I could set a good time.
“I am very happy to have won despite the wind. I feel that I’m improving year after year. But these are only preparations for the big show of the worlds.
“That’s the fastest I’ve ever run, it’s going to be a shock to the body. Tomorrow’s going to hurt a little bit, but I’m just looking forward to the next race and see what I can do legally.”
Elsewhere, Timothy Cheruiyot of
His compatriot and triple world champion Asbel Kiprop was fourth in 3:33.17, with
In the women’s events,
African News Agency (ANA), AFP