Generation of a berry cracking index for the entire ARC genebank

PROJECT TITLE:    Generation of a berry cracking index for the entire ARC genebank

Project leader:       Justin Lashbrooke (Stellenbosch University)

Contact:                     jglash@sun.ac.za

Duration:                   1 January 2023 – 31 December 2023

Problem identification and project objectives:

Berry cracking is a major problem for grape growers worldwide, and for an export dominated industry, like that of South Africa, the problem is further amplified. Cracking typically occurs due to the physical failure of the waxy skin layer of the grape berries, and is often exasperated by environmental conditions (such as fungal infection or rainfall shortly before harvest) (Considine et al, 1972; Khanal et al, 2013; Lara, 2018; Ramteke, 2017). However, it is also under genetic control, evidenced by the fact some cultivars are more susceptible to cracking than others (Ramteke et al., 2017; Yamamoto and Satoh, 1994). Currently knowledge of which cultivars are prone to cracking remains relatively anecdotal, which hampers grower’s ability to select suitable cultivars for their growing regions and for breeders to select appropriate cultivars for crosses (Zoffoli et al, 2009). Furthermore, with no standardised measurement or index, new cultivars cannot be objectively scored for their resistance to cracking, leading to an ever-increasing reliance on anecdotal and word-of-mouth information. In a currently ongoing SATI project assays have been developed to quantify and score cultivars for their susceptibility to berry cracking, making use of a water submergence assay and a texture analyser machine (Lashbrooke et al., 2015). This project aims to implement this optimised assay across the entire ARC hosted table grape gene bank (consisting of approximately 500 cultivars) and develop an index for cracking resistance/susceptibility that can be used to rank cultivars and score newly developed cultivars. This information can be used directly by growers to select cultivars, by breeders to select the best starting material for future crosses, and to screen (and rank) new cultivars imported into South Africa.