Morphological traits, growth and yield performance, and Papaya ringspot virus strain papaya reaction in Vasconcellea cauliflora in Pune, India

Vasconcellea cauliflora is one of the few Vasconcellea species that have shown resistance against Papaya ringspot virus strain papaya (PRSV-P), a major limiting factor in papaya (Carica papaya L.) cultivation. It has a potential role in breeding PRSV-P resistance in papaya. It is neither cultivated nor found in the wild in India where only a few plantations are maintained for research purposes. Therefore, very little information is available about morphological traits related to growth and yield in India as well as its reaction against Indian isolates of PRSV-P. A V. cauliflora plantation maintained at Indian Agricultural Research Institute, Regional Station, Pune India since 2010 provided valuable information on morphological traits under Pune climate and reaction against Indian isolate of PRSV-P. Plants attained a height of 1.04 m and stem diameter of 9.49 cm in one season. Average fruit yield was 4.3 kg plant(-1) in the first year, which rose to 8.4 kg plant(-1) in the third year. Yellowish white, waxy female flowers were 3.9 cm long. Berry type fruits were long, round or intermediate in shape with smooth skin texture. The average fruit length and width was 6.76 and 3.68 cm, respectively. Ridges on fruits were deep in long fruits and intermediate in round ones. V. cauliflora seedlings showed resistance against a Pune isolate of PRSV-P when infected by challenge inoculation. There were no symptoms of PRSV-P infections even with exposure to severe disease pressure under field conditions for more than three years. Pollen from grafted plants (V. cauliflora on C. papaya) showed slightly different characteristics when compared with V. cauliflora. There is a renewed interest in V. cauliflora as the resistant parent in a PRSV-P resistant breeding programme, especially after overcoming the crossing barrier with C. papaya at some institutes in India.