|DELA CRUZ, A.|
Submitted to: Journal of Horticultural Science and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2005
Publication Date: 8/20/2005
Citation: Fitch, M.M., Leong, T., Akashi, L., Yeh, A., White, S., Dela Cruz, A., Santo, L., Ferreira, S., Moore, P.H. 2005. Growth and yield of clonally propagated and seedling-derived papayas. i. growth. ii yield.. Journal of Horticultural Science and Biotechnology. 40(5): 1283-1290.
Interpretive Summary: Papaya seedlings segregate as females or hermaphrodites but only the hermaphrodite is grown commercially. Seedlings are multiple-planted and thinned to a single hermaphrodite, a practice that is wasteful of seed, labor, and resources. Researchers at ARS, HARC, and the University of Hawaii compared growth and yield of traditionally planted seedlings with hermaphrodite plants propagated by two clonal propagation methods, rooted cuttings and micropropagation. Clonally propagated plants were shorter than seedlings, bore flowers earlier and lower on the trunk compared to thinned seedlings. Fruit were harvested 1-3 months earlier compared to the thinned seedlings resulting in higher overall yields. The savings in resources and labor in addition to earlier harvests and higher overall yields make the clonally propagated plants an economically attractive alternative to seedling transplants for growers.
Technical Abstract: Papaya seedlings segregate for sex expression as females or hermaphrodites. Typically only hermaphrodites are marketed. The agronomic practice of direct multiple seeding for later culling to a single hermaphrodite tree is wasteful of seed, labor, and resources, especially when hybrid seed is costly. We compared growth and yield of plants propagated in two clonal propagation methods, rooted cuttings and micropropagation, with seedling transplants in three field tests. The seedlings were single hermaphrodites, identified by polymerase chain reaction (PCR), and thinned, multiple-planted seedlings in two of the three field tests. In the third test, only thinned, multiple-planted seedlings were compared with clonally propagated plants. The experiments were carried out for 15 months (Mokuleia), 19 months (Helemano), and 26 months (Keaau) in 3 different locations on two islands in Hawaii. The data showed that clonally propagated plants were significantly shorter than seedlings and bore flowers earlier and lower on the trunk, at heights of 54-84 cm vs. 104-137 cm for thinned seedlings. Diameter differences were not significant although, at planting time, plant size varied. Fruit were harvested 1-3 months earlier compared to the thinned seedlings. The earlier maturation of the clonally propagated plants resulted in significantly higher yield differences (p = 0.05) in the first three months of harvest in Keaau, the rain-fed, lava field location, in the second month of harvest in Mokuleia, and in the second to fifth harvests in Helemano. The latter two sites were on irrigated, weathered soil at different elevations. Thereafter, monthly yields at all three sites were not significantly different. When the data were analyzed as cumulative yields, the clonally propagated plants in Keaau showed significant yield differences over 8 harvests. The Mokuleia plants showed significant yield differences over two harvests and Helemano plants, over six harvests. Since the clonally propagated trees were shorter compared to the seedlings, 17 months after transplanting, >93% of all clonally propagated trees and 66% of the thinned seedlings were harvested without picking devices in Keaau. In contrast, taller growth in Mokuleia resulted in the requirement of harvesting devices for thinned seedlings in the 10th month and for all other treatments in the 13th month after planting when average fruit height in all treatments exceeded 183 cm.