Major determinants of fruit set and yield fluctuation in coconut (Cocos nucifera L.)

Abstract

Abstract:The final yield of coconut (Cocos nucifera L.) is determined by early fruit set. Thus understanding the factors controlling fruit set including climate change is of importance for assessing the yield and its accurate prediction. This study assessed the survival pattern of female flowers produced in different months of the year, the effects of climate factors during early phase of flowering and the competition for assimilates from previously formed fruits on the fruit set of newly opening inflorescences in a 25 -26 year-old coconut plantation in the Intermediate Zone (IL 1a ) of Sri Lanka over a period of three years. The rate of fruit survival since the onset of flowering to maturity varied with the month of inflorescence opening. Abortion of fruits after three months from inflorescence opening was negligible. The optimum (T opt-in vitro ) and maximum (T max-in vitro ) temperatures for in vitro pollen germination were 28 ºC and 39.7 ºC, respectively. The fruit set of an inflorescence/s opened in a given month (number of set fruits palm -1 month -1 ) was negatively correlated with the total reproductive dry matter requirement of the palm (TDMR) of the month of inflorescence/s opening (first month), and the number of high temperature days (T max ≥ 33 ºC) during the first three months of inflorescence opening, whilst it was positively correlated with the number of female flowers produced in the inflorescence. There was a highly significant correlation between the monthly fruit set (at three month stage) and the corresponding harvested fruit yield palm -1 month -1. The lag period between flowering (opening of the female phase) and fruit maturing was eleven months.

Climate Change and Extreme Events in WL1a Agro-ecological Zone of Sri Lanka: Implications on Coconut Production

“…Percentage of button nut (female flowers after fertilization) fall from the inflorescence is significantly sensitive to total rainfall and minimum air temperature (Peiris et al, 1995;Peiris and Thattil, 1998). The optimum temperature for in vitro pollen germination of coconuts is 28 0 C while maximum can go up to 39.7 0 C (Ranasinghe et al, 2015). Critical temperature for successful reproduction of coconuts is 33 0 C (Ranasinghe, 2012).…”

“…Critical temperature for successful reproduction of coconuts is 33 0 C (Ranasinghe, 2012). Coconut palm experience moisture stress when it is exposed to temperature above 33 0 C and soil water deficit due to rain free period of longer than consecutive two months (Kasturi Bai et al, 2003). The droughts can cause crop failure due to reduced fertilization, button nut fall, immature nut fall, and palm loss due to death of seedlings, immature and mature palms.…”

GENOTYPIC DIFFERENCES IN CARDINAL TEMPERATURES FOR IN VITRO POLLEN GERMINATION AND POLLEN TUBE GROWTH OF COCONUT HYBRIDS

“…The optimum climatic conditions required for coconut production are mean annual temperature of 27–28 °C, abundant sunlight (at least 120 h per month) and a well-distributed annual rainfall between 1300 and 2300 mm (Rajagopal and Ramadasan, 1999). Reduced fruit set and yield due to high temperature stress is one of the major constraints faced by the coconut producing countries in the tropics (Ranasinghe et al , 2014, 2015; Thomas et al , 2012). High temperature stress causes strong yield fluctuations, affecting growers, local consumers and the supply chain of the coconut products to the global market.…”

Weather variability and coconut production in Sri Lanka: state-contingent analysis

“…This research is motivated by the observed trend in the Sri Lankan coconut industry of low production and a decline in export competitiveness over a prolonged period. Ongoing climate change complicates this productivity decline, overshadowing the beneficial influence of Sri Lanka's tropical climate that favoured the establishment of coconut production in Sri Lanka (Ransinghe et al, 2015).…”

“…As coconuts are primarily grown as a rain-fed crop, the proportion of button nuts (female flowers after fertilization) that fall prematurely from the inflorescence is closely related to total rainfall and the minimum air temperature Thattil, 1998, Peiris et al, 1995). The optimum temperature for pollen germination of coconuts is around 28 0 C in laboratory studies, while the maximum can go up to 39.7 0 C (Ransinghe et al, 2015). The relative humidity and temperature also play a key role in nut development (Kumar et al, 2009).…”