Guar gum and chitosan-based composite edible coating extends the shelf life and preserves the bioactive compounds in stored Kinnow fruits.

The present investigation aimed to elucidate the effects of chitosan (CH) and guar gum (GG) based composite edible coating on physicochemical quality and storability of Kinnow fruit under ambient conditions. Composite coating materials were prepared by using tamarind (TAM) seed starch and jackfruit (JACK) seed starch with CH and GG separately. The results indicated that GG + TAM coated fruits maintained significantly (P ≤ 0.01) lower physiological losses in weight (PLW) (3.12 %), decay incidence (0.83 %), and respiration rate (13.57 ml CO2 kg-1 h-1) compared to control. The reduced activity of pectin methylesterase (PME) (0.97 µmol min-1 g-1 FW) and lipoxygenase (LOX) (1.97 µmol min-1 g-1 FW) were noted in GG + TAM coated fruits. Also, the GG + TAM coated fruits retained higher fruit firmness (6.77 N), titratable acidity (TA) (0.94 %), ascorbic acid (AA) (27.83 mg 100 g-1), total phenols (213.05 mg GAE 100 g-1 FW), antioxidants activity (23.57 µmol TE g-1) along with higher sensory score over the control. Based on findings, it can be concluded that GG + TAM coating could be gainfully utilized for prolonging the shelf life of Kinnow fruits up to 25 days without losing desirable quality traits at ambient storage.

Distinct morpho-physiological and biochemical features of arid and hyper-arid ecotypes of Ziziphus nummularia under drought suggest its higher tolerance compared with semi-arid ecotype.

Tree species in the arid and semi-arid regions use various strategies to combat drought stress. Ziziphus nummularia (Burm. f.) Wight et Arn., native to the Thar Desert in India, is highly drought-tolerant. To identify the most drought-tolerant ecotype of Z. nummularia, one ecotype each from semi-arid (Godhra, annual rainfall >750 mm), arid (Bikaner, 250-350 mm) and hyper-arid (Jaisalmer, <150 mm) regions was selected along with two other Ziziphus species, Ziziphus mauritiana Lamk. and Ziziphus rotundifolia Lamk., and screened for parameters contributing to drought tolerance. Among these, Z. nummularia (Jaisalmer) (CIAHZN-J) was the most drought - tolerant. The tolerance nature of CIAHZN-J was associated with increased membrane stability, root length and number, length of hairs and thorns, root dry/fresh weight ratio, seed germination (at -0.5 MPa), proline content (31-fold), catalase and sugar content (two- to three-fold). Apart from these characteristics, it also exhibited the longest duration to reach highest cumulative drought stress rating, maintained higher relative water content for a longer period of time with reduced leaf size, leaf rolling and falling of older leaves, and displayed sustained shoot growth during drought stress. To determine drought tolerance in Ziziphus, we developed a morphological symptom-based screening technique in this study. Additionally, transcriptome profiling of CIAHZN-J in response to drought revealed the up-regulation of genes involved in sugar metabolism and transport, abscisic acid biosynthesis, osmoregulation, reactive oxygen species homeostasis and maintaining water potential. Expression profiles and semi-quantitative reverse transcription PCR results further correlated with the physiological and biochemical mechanisms. In conclusion, CIAHZN-J is an excellent genetic stock for the identification of drought-responsive genes and can also be deployed in crop improvement programs for drought tolerance.