Approach to Screen Coconut Varieties for High Temperature Tolerance by in-vitro Pollen Germination

C S Ranasinghe,A P C Pradeep,K P Waidyarathna,M S K Meneripitiya

doi:10.4038/cocos.v19i1.4748

Abstract

Successful fruit set in coconut depends on several reproductive processes including pollen quality, pollen germination percentage (%PG) and pollen tube growth processes. Three preliminary experiments were conducted at the Coconut Research Institute, Lunuwila, Sri Lanka to quantify the response of in vitro pollen germination in coconut to time of incubation, the response of in vitro pollen germination and pollen tube growth to temperature and to determine the cardinal temperatures (Tmin, Topt, Tmax) of coconut varieties for in vitro pollen germination. Pollen was collected from palms of six cultivars / varieties expressing variable tolerance to abiotic stresses. Pollen germination and pollen tube length were recorded after incubation in artificial growth media at the respective treatments. For pollen collected during October / November periods, cultivars differed for in- vitro pollen germination percentage with a mean values of 23%. The mean cardinal temperatures (Tmin, Topt, Tmax) averaged over cultivars were 20.0 ºC, 28.0 ºC, and 38.8 ºC, respectively, for pollen germination. The information generated in this study will be tested in different seasons of the year for consistency and used to develop a heat tolerance index for coconut. This index will be used to identify coconut varieties suitable for high-temperature prone areas. In addition, the identified cardinal temperatures and response functions could be incorporated into process-based coconut models to increase prediction accuracy under current extreme and projected future climates. DOI: http://dx.doi.org/10.4038/cocos.v19i1.4748

Highlights

Sexual reproduction in plants is more sensitive to high temperature than vegetative processes, and plant reproductive organs will be more vulnerable to changes in short episodes of high temperature prior to and during early flower stage
It would be advantageous for plants to exhibit greater reproductive survivability at extreme temperatures normally encountered during plant reproduction and for processes leading to yield such as pollen grain development, pollen germination, pollen tube growth, fertilization and embryo development
The palms were selected from experimental blocks of Genetics and Plant Breeding Division in Bandirippuwa Estate, Lunuwila (TT, SR, DR), Genetic Resource Centre, Ambakelle (DG) and Pottukulam Research Station (DB, Dwarf Yellow (DY)) of Coconut Research institute, Sri Lanka

Summary

Introduction

Sexual reproduction in plants is more sensitive to high temperature than vegetative processes, and plant reproductive organs will be more vulnerable to changes in short episodes of high temperature prior to and during early flower stage. Fruit set in cowpea (Ahmed and Hall, 1993), cotton (Reddy et al, 1997), ground nut (Prasad et al, 2003) and tomato (Sato et al, 2002) is sensitive to high temperatures. Short episodes of extreme events including high temperatures projected to occur more frequently in the future climate will impact fruit set and yield. It would be advantageous for plants to exhibit greater reproductive survivability at extreme temperatures normally encountered during plant reproduction and for processes leading to yield such as pollen grain development, pollen germination, pollen tube growth, fertilization and embryo development. The major cause of low pollen fertility under high temperature was reduced pollen germination (Sato and Peet, 2005)

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