In Vitro Prevention of Browning in Persian Walnut (Juglans regia L.) cv. Sulaiman

Abstract

The present investigation was undertaken to standardize the media and the anti-browning regime in order to minimize the phenolic browning of an in vitro culture of Persian walnut cv. Sulaiman. The experiments involved two types of explants, forced and unforced shoot tips, two types of media, Driver and Kuniyuki Walnut (DKW) medium andMurashige and Skooģs (MS) medium, and three types of anti-browning agents, namely, Polyvinylpyrrolidone, ascorbic acid and activated charcoal at 150, 350 and 550 mg/L each. The investigation was replicated thrice under a completely randomized design. Forced shoot tips of cv. Sulaiman on DKW medium showed the best performance in terms of least browning (13.6 ± 10.5%) and highest survival percentage of explants (74.5 ± 2.4%) when treated with ascorbic acid at 550 mg/L. However, unforced shoot tips in MS medium did not perform well and manifested maximum browning (52.9 ± 5.2%). Based on the results, we conclude that incorporation of ascorbic acid in the DKW medium significantly reduced the media and explant browning, thus, it could set the basis of successful in vitro-propagation of walnuts.

Seasonal variation in contamination and browning of Acacia nilotica nodal explants in vitro

“…These contaminants may vary from bacteria, fungi, microorganisms, mites, and thrips (TheodosyMsgoya et al, 2012). Of these, the most serious is bacterial infection, which can be systemic and difficult to detect Gioushy et al, 2020;Bhat et al, 2022). They may be present within the pith, sclerenchyma, xylem lumen or parenchyma tissues, causing plant culture losses and affecting the micropropagation efficiency.…”

“…Contamination may be introduced due to insufficient heating or mishandling of instruments during inoculation (Yahia et al, 2019). In some cases, the bacteria become resistant to standard glassware sterilization techniques, but upon reaching the culture medium, these grow faster than the cultured tissue (Varghese and Joy,2015;Bhat et al, 2022). Apart from contamination, another major problem encountered in culturing plant tissues in vitro is the browning of excised plant tissues and nutrient media.…”

“…Apart from contamination, another major problem encountered in culturing plant tissues in vitro is the browning of excised plant tissues and nutrient media. The severity of browning varies in different plants, species, tissues or organs, their developmental phase, age of tissue/organ, nutrient medium and a number of other variables (Huang et al, 2002 ;Tao et al, 2007;Gioushy et al, 2020;Bhat et al, 2022). Browning and necrosis are common problems in cultures in vitro.…”

The role of walnut bZIP genes in explant browning

“…Browning, also known as the browning reaction, is a phenomenon that occurs in all life stages of a plant and results in the creation of a brown polymer through a series of reactions [ 19 ]. Plant tissues produce large amounts of unstable phenolics that are secreted after damage, and the formation of brown quinones from these phenolics is then catalyzed by a variety of oxidative enzymes.…”

“…Some studies have found that overexpression of StSPI128 significantly alleviated potato browning and increased phenolic content [ 22 ]. Browning inhibition in mushrooms can be achieved by using nano-PM to inhibit TYR activity, which in turn delays the conversion of GHB to GDHB and tyrosine to DOPA, ultimately reducing melanogenesis [ 23 ], and the addition of ascorbic acid to DKW medium significantly reduced the browning of the medium and the explants [ 19 ]. Aloe vera gel can be used as an edible coating (dry environment) and as a gel solution (aqueous environment: a new method) to prevent browning during the refrigeration of fresh Persian walnut kernels [ 24 ].…”