MOKARA HYBRIDS

Performance and Ethylene Tolerance in Cut Mokara Hybrids



Abstract

Ethylene-sensitive cut flowers despite having nice shape and color, display short vase life and normally after shipment, their ethylene injury would be very high and this character is a negative point for them. The objectives of the research was first, evaluation of level of ethylene sensitivity and second categorizing of six cut Mokara hybrids based on the ethylene sensitivity containing: Mokara 'Chak Kuan Blue' (MCKB), M. 'Chao Praya Classic'(MCPC), M. 'Calypso Jumbo' (MCJ), M. 'Boy Blue'(MBB), M. 'Red' (MR)and M. 'Chitty Gold'(MCG).

The inflorescences were harvested from a commercial orchid farm and transported to the postharvest laboratory as soon as possible. They were treated with 10 µl/l ethylene gas for 24 hours before placing them in bottles containing the standard solution. Water loss, vase life, anthocyanin contents and ethylene production were determined after the treatments. Expressions of 1-aminocyclopropane-1-carboxylic acid synthase and oxidase genes before and after exposure to ethylene in the lips of third florets were also determined. Ethylene caused reduction of vase life tremendously. This was displayed by florets and buds wilted and dropped in all tested hybrids. Weight loss and anthocyanin degradation increased when the flowers were exposed to ethylene. Both genes were expressed in fully open florets but after exposure to ethylene, the levels of expressions were higher in all hybrids. However, different hybrids showed distinct variances in ethylene sensitivities and degrees of deterioration. M. 'Calypso Jumbo' (MCJ) and M. 'Red' (MR) exhibited the utmost anthocyanin degradation in sepals and petals and declining in length of vase life. Thus, these two hybrids were categorized as the very sensitive group. M. 'Chak Kuan Blue' (MCKB), M. 'Chao Praya Classic' (MCPC), M. 'Boy Blue' (MBB) and M. 'Chitty Gold' (MCG) categorized as the less sensitive group.

Table of Contents

Introduction4

Material and Methods9

Ethylene Treatment10

Fresh Weight Changes and Weight Loss10

Vase Life11

The Production of Ethylene11

Anthocyanin Content11

RNA Extraction12

Reverse Transcription Polymerase Chain Reaction (RT-PCR)12

Results and Discussion13

Statistical Analysis13

Effect of Ethylene on Anthocyanin Content13

Effect of Ethylene on Weight Loss and Vase Life14

The Effect of Exposure to 10 L/L Ethylene on Ethylene Production14

Expression of Acc Syntheses and Acc Oxidase Genes in Before and After Treatment15

Discussion of the Findings15

Conclusion16

References18

Performance and Ethylene Tolerance in Cut Mokara Hybrids

Introduction

One of the largest families in the plant kingdom is Orchidaceae with about 750 different genera and at least 25,000 native species and more than 30,000 cultivated hybrids (Hew and Yong, 1997). Mokara is the generic name of one hybrid that has been produced in Singapore in 1969. It has generated from the hybridization of three genera including: Arachnis, Ascocentrum and Vanda. Mokara hybrids normally seem very similar to Aranda. They are very popular cut flowers now (Fadelah, et al, 2010). Until 1996, about one hundred Mokara hybrids have been registered. The majority of Mokara hybrids are diploid or triploid. Diploid Mokaras are generally produced from crossing diploid Arachnis with diploid Ascocendas. Plants of diploid Mokaras are generally small and not very strong, and the diameter of their flowers is only ...