Photoperiod Responses of Extra‐Short‐Duration Pigeonpea Lines Developed at Different Latitudes

Abstract

There is interest in growing pigeonpea [Cajanus cajan (L.) Millsp.], a tropical grain legume crop, in temperate regions. A few extra-short-duration lines were developed in Minnesota (∼45° N), USA, to improve the crop's adaptation to temperate regions. We investigated whether photoperiod responses of the Minnesota lines (MN #) differed with lines (ICPL #) bred in the tropics. Five ICPL lines and three MN lines were grown under artificially extended daylength (ED) simulating 45° N and normal daylength (ND) at Patancheru, India, (17° N) during the 1995 and 1996 rainy seasons. Six ICPL and two MN lines were also tested at Suwon (37° N), Korea, in 1998. At Patancheru, the line × photoperiod interactions were highly significant for grain yield, total dry matter (TDM), harvest index (HI), days to flowering (DF), and maturity (DM). Under ND, yield was significantly more for ICPL lines and correlated with TDM (r = 0.892 and 0.902, n = 8), DF, and DM, but not with HI. Under ED, yield was more for MN lines and correlated positively with HI and negatively with DF and DM (in 1996), but not with TDM. The additive main effects and multiplicative interaction (AMMI) analysis suggested a distinct interaction pattern for MN lines. Yield was correlated negatively with DF and DM in Korea also where a MN line gave the highest yield. The results suggest that there has been a selection for a high HI potential and early flowering in MN lines for better adaptation to longer days and a high TDM production potential in ICPL lines to shorter days.