BENGALURU: Sex ratio disparity is not just confined to humans. It is also affecting flowering pattern in fruit-bearing plants, say botanists.
Unlike in humans where the disparity is self-caused, in plants, it is largely driven by climatic changes and the most recent victim of this worrying trend affecting flowering and fruiting, is mango. Adding to the woes, the hailstorm and prolonged cloudy conditions in the past few weeks are threatening to wipe out the last standing mango crop around Bengaluru.
Technical officers from the Karnataka State Mango Development and Marketing Corporation Ltd (KSMDMCL), while pointing out that the falling flower sex ratio has affected crop around Bengaluru drastically, attributed it to unseasonal rain and variation in temperature.
KSMDMCL managing director CG Nagaraju, conceding that this year has been an ‘off season’, said there was, however, considerable flowering in all trees which had given hopes of a decent yield. However, according to their latest analysis, there being more male flowers than hermaphrodite flowers, has cast a dark spell on the yield.
“Mango is an andromonoecious plant bearing both staminate (male) flowers and hermaphrodite flowers on the same inflorescence. The ratio between these two is called flower sex ratio. Depending on the species, total number of flowers in a panicle varies from 800 to 5,000. Largely, the hermaphrodite flowers impact setting of fruit and yield. But in the last few years, including this one, there have been more male flowers, affecting fruiting,” Nagaraju said.
A senior technical officer said flower sex ratio is influenced by environmental factors like rainfall, temperature and humidity. Usually, low temperature — 12° Celsius to 20° Celsius — during the flowering season (December to February) results in staminate flowers and high temperature, between 21° Celsius and 30°Celsius, supports hermaphrodite flowers.
Nagaraju, pointing to the unprecedented unseasonal rain during the flowering season, said: “It poured for more than a week making the soil sloppy. This saw mercury levels plunge considerably, resulting in male flowers.”
Although late January and February were better, officials said the temperature was too hot by then. “From intense rain, it immediately switched to hot summer with mercury levels crossing 30° Celsius along with frost during morning hours. In the last few years, variations in temperature and unseasonal rainfall have affected flowering in mangoes regardless of supplements and nutrients farmers feed the plants. This mixed inflorescence with widening disparity in sex ratio is taking toll on the yield,” KSMDMCL chairman KV Nagaraj said.
With more than 1.6-lakh hectares under cultivation, the mango board initially expected this year’s yield to be about 14 to 16 lakh tonnes, which has since been downgraded by 50% to about 7-8 lakh tonnes, as per Nagaraju.
“We are witnessing record fall in temperature making May the coolest month in the last 20 to 25 years. This moist condition will help fruit flies bite fruits and lay eggs inside. Lack of sunlight and increased humidity will result in fungi infection affecting quality of mangoes,” Nagaraju said.