Pre-harvest sprouting in pecans

Abstract

The temperature effect on germination response and physiological activities were compared between sprouting resistant northern pecan [Carya illinoensis (Wang) K. Kock] cultivars and sprouting susceptible southern cultivars. The sprouting resistant character of northern cultivars was incorporated into sprouting susceptible southern cultivars to alleviate a pre-harvest sprouting of pecan. The germination of 'Cherokee' and 'Wichita' were more rapid than 'Johnson' when nuts were incubated at 27° and 34°C. When nuts were incubated at 20°C, the southern and northern cultivars germinated at approximately 20% and 1.5% respectively. The delayed germination characteristic of northern cultivars proved to have excellent potential as a screening method for measuring pecan vivipary. Total lipid content of southern cultivars decreased 17.51% in 'Cherokee', 5.2% in 'Wichita', and did not change in 'Johnson' and 'Pawnee' during germination. The lipids gradually decreased with a concomitant increase in total sugar and reducing sugar. The compositional changes were accompanied with an increasing germination percentage in the southern cultivars during 40 days of germination. However neither compositional change nor germination percentage was changed in 'Johnson' at 20°C and 27°C during 40 days of germination. Immature embryos of open-pollinated seeds of 'Wichita' were excised from ovaries 132-139 days after pollination and grown on different levels of ABA and GA at 20°, 27°, and 34°C to evaluate temperature and growth regulator effects on embryo growth and development..