Coconut Varieties Research Articles

SUPPLY‐MAXIMISING AND VARIATION‐MINIMISING REPLACEMENT CYCLES OF PERENNIAL CROPS AND SIMILAR ASSETS: THEORY ILLUSTRATED BY COCONUT CULTIVATION

The paper argues that maximum sustainable yields rather than net present values often need to be considered for policy and identifies the length of the replacement cycle required for maximum sustainable yield or supply in multi‐point or interval output time‐phased production conditions, such as apply to perennial crops and to similar productive processes. It enables point‐input point‐output models which have been well explored (for instance, for forestry) to be treated as special cases. A virtue of the analysis is its use of a simple technical relationship to determine the replacement rate of a perennial crop to maximise sustainable yield. The analysis is illustrated by an empirical example drawn for the cultivation of the Sri Lankan ‘tall’ variety of coconut.

Density Related Yield Functions for Coconut (Cocos nucifera): an Empirical Estimation Procedure

SUMMARYObtaining yield–density relationships for perennials is difficult. Apart from the long time span involved, problems are also posed by the different types of uncertainty associated with field experimentation. Consequently researchers have explored alternative means. This study uses survey data as an alternative. The data show sufficient variability around the density which is regarded as optimal for Typica variety of coconut (158 palms ha−1) to be of value for estimating its yield–density function. A quadratic function gives a good fit to the data. Results suggest that the yield maximizing density of variety Typica form typica is relatively insensitive to the influence of fertilizer practices adopted by farmers and to variations by agroclimatic sub-regions.

Dwarf variety of coconut, Cocos nucifera (Palmae), a hostplant for the African armyworm, Spodoptera exempta (Wlk.) (Lepidoptera, Noctuidae)

The dwarf variety of coconut, Cocos nucifera L. (Palmae), was found to be eaten by the larvae of the African armyworm, Spodoptera exempta (Wlk.). The comparison of the armyworm infestation on the leaves of the coconut seedlings and the adjacent grass species revealed lower larval density and growth rate on Coconut seedlings. This observation suggests that a small population of the African armyworm can survive and develop on the leaves of the dwarf variety of coconut.

Microclimate of coconut varieties and cacao and cinnamon grown as mixed crops with coconut

During the peak period of evaporation (December-May) when evaporation from the open surface (observatory) exceeded 5 mm/day, the corresponding values for the microclimate of cacao and cinnamon, during the early stages of their growth as mixed crops with coconut palms, were 2-4 mm. The diurnal variations in relative humidity and vapour pressure in the microclimate of cacao and cinnamon were relatively much less compared to those of observatory and microclimate of coconut. There were no differences in the microclimate of tall and dwarf varieties of coconut at their full bearing stage.

Past Studies on and Present Status of Lethal Yellowing Disease of Coconuts

Abstract The symptoms and extent of lethal yellowing disease of coconuts are described. In research into the cause of the disease nutrient deficiencies, fungi, bacteria, nematodes and, more recently, viruses have been investigated without implicating any causal agent. Mechanical and insect transmissions were attempted by a number of methods. The incubation period was shown to be 3–9 months for young palms and 7–15 months for bearing palms. Experiments to control the disease have been unsuccessful. Local and introduced coconut varieties and hybrids are being tested for resistance by field exposure. The Malayan Dwarf variety has been shown to have high resistance and is being used to replant the industry. No other variety or hybrid is deemed as yet to be sufficiently resistant for farm planting. Mycoplasms were recently found associated with the disease. Future research must include confirmation of mycoplasm-lethal yellowing association, continuation of the search for the vector, experimental chemotherapy, ...

Cytology of Development of Abnormal Endosperm in Philippine Makapuno Coconuts

SUMMARYThe cytology of development of the buttery kernel (endosperm) in the Philippine makapuno coconuts has been studied. Though the first formed cellular endosperm is predominantly triploid, higher levels and grades of ploidy like 6 n, 9 n, 12 n, 24 n and 48 n (and above) characterise the maturing endosperm. The cytological situation in early stages of the makapuno endosperm is comparable to that in other coconut varieties, particularly the dwarf coconuts with which they share the relatively higher levels of polyploidy, presence of 2 n and 9 n nuclei and the greater frequency of mitotic abnormalities including considerable stickiness of chromosomes.The later stages of development of the makapuno endosperm characterised by unlimited growth and proliferation, accompanied by high polyploidy, increase in frequency of abnormalities, cessation of normal mitosis, onset of amitosis, attainment of high nuclear polymorphism, appearance of characteristic cell inclusions, etc. followed by degeneration of the nuclei...

Cytology and Origin of the Dwarf Coconut Palm

DISTINCT varieties of dwarf coconut (Cocos nucifera L.) occur in Malaya, Philippines, Fiji Islands, Viet Nam, Ceylon and India. These varieties grow to a height of 15–30 ft. compared with more than 50 ft. among normal tall types and need only 3–5 years to commence bearing in contrast to 8–10 years taken by the tall strains. While the tall varieties are largely obligatorily cross-pollinated, the dwarfs usually undergo self-pollination owing to the overlapping of the female and male phases in the same inflorescence. As a result, many dwarf strains yield homogeneous progenies and they can be used with advantage for identifying the most pre-potent males1. The poor vigour and copra quality of the dwarf palms, however, render them unsuitable for cultivation on a plantation scale2. In addition to the typical tall and dwarf palms, various intermediate categories occur in Nature and have also been obtained by crossing the tall and dwarf strains3.