Vol. 84 No: 1

Title:
Low light and low leaf calcium and boron concentrations are associated with fruit pitting, a new disorder in mango (Mangifera indica L.) in India

Authors:
R.R. SHARMA and MANISH SRIVASTAV

pp: 83-86

Abstract:
A study was conducted to investigate factors associated with fruit pitting, a new physiological disorder in mango (Mangifera indica L.). The incidence of pitting, along with intercepted light (photosynthetic photon flux density; PPFD) and net CO₂ assimilation (A) were measured over 2 years at the top of the tree, and 1.0 m and 0.5 m above the crotch (i.e., the main branch-point) in the SE, NE, NW, and SW directions of the tree canopy in the mango cultivars ‘Alphonso’, ‘Amrapali’, ‘Bangalora’, ‘Bombay Green’, ‘Chausa’, ‘Dashehari’, ‘Langra’, ‘Neelum’, ‘Sensation’ and ‘Tommy Atkins’. Leaf nutrient concentrations were also determined in branches bearing normal and pitted fruit.The incidence of pitting was lowest (6.3%) in fruit at the top of the tree, followed by fruit 1.0 m (13.6%) or 0.5 m (20.0%) above the crotch. Similarly, the incidence of pitting was lowest (4.9%) in fruit from the SE of the canopy, followed by those from the NE (8.3%), SW(13.6%), and NW (20.0%). The incidence of pitting in different parts of the canopy reflected the PPFD and A values (A = 0.03 × PPFD – 5.736; R² = 0.91; Pitting (%) = 0.002 – 0.05 × PPFD² – 0.56 × PPFD + 37.79; R² = 0.894). ‘Dashehari’ mango had the highest incidence of fruit pitting (21.8%), and ‘Tommy Atkins’ had the lowest incidence (9.1%). The concentrations of leaf calcium (Ca) [1.17% (w/v) vs. 2.08% (w/v)], and boron (B) (28 μg g^-1 vs. 45 μg g^-1) were lower in branches bearing pitted fruit than in those bearing normal fruit, respectively. There were inverse quadratic relationships between the mean incidence of pitting and mean leaf Ca levels (Pitting (%) = 11.40 × Ca² – 48.84 × Ca + 61.95; R² = 0.48), and mean leaf B levels (Pitting (%) = 0.040 × B² – 3.67 × B + 90.26; R² = 0.97), and a linear relationship between leaf B and Ca concentrations (B = 20.93 × Ca + 0.156; R² = 0.76). These results suggest that pitting is related to low light levels, and to low concentrations of Ca and B. Experiments are in progress to resolve this problem using foliar or soil applications of Ca and B, and pruning of trees.

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