Field studies on genetic variation for frost injury in pigeonpeaK BSaxenaauthorR VKumarauthorYongGuauthorZhenghongLiauthorYongGuauthorPigeonpea (Cajanus cajan) cultivation in China is being revived primarily for soil conservation and fodder production. Experiments show that in certain areas freezing temperatures (<0°C) cause considerable damage to the foliage of the crop. Considering the potential of pigeonpea in China, this study was conducted to understand the nature and magnitude of damage caused by freezing temperatures and to assess the feasibility of identifying freezing tolerant genotypes. Three genotypes (ICPL 151, ICP 8863, ICP 11298) bred by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, India and one local landrace were evaluated. Four test sites were selected in different agroecological zones in Yunnan province in China. At each location, about 500 plants of each genotype were grown in June 1999 in an unreplicated block. The crop was grown with recommended cultural practices. In September/October, 30 competitive plants of each genotype were tagged randomly during the vegetative stage and in January 2000, these plants were scored for frost injury on five-point scale as: 0 = resistant, no visible symptom of damage; 1 = tolerant, up to 10% leaves killed; 2 = moderately tolerant, only terminal branches and tender leaves killed; 3 = moderately susceptible, upper-half of plant canopy killed; and 4 = susceptible, entire plant killed. In March 2000, when the temperatures for pigeonpea growth were conducive, 40 moderately susceptible (score 3) plants were tagged randomly in each block for visual assessment for their regeneration capability. Mean frost injury grade (ã) and average frost injury index (δ) were estimated for each genotype using the formulae given by Wang (1987): Σ (a × n) Σ (a × n) ã = ________ δ = _______ N amax × N where a = frost injury score; n = index in certain grade; and N = total number of plants.Pigeonpea2002International Crops Research Institute for the Semi-Arid Tropics Article