Analysis of Blackberry Fruit Firmness in Crispy Fruit Segregating Populations

Flesh firmness of blackberry fruits is critical for successful postharvest handling. Therefore, this trait is a priority in the development of new cultivars in breeding programs. The University of Arkansas blackberry breeding program has released several cultivars with excellent postharvest quality for the fresh and shipping industries. Fruits having a crispy texture and exceptional firmness have been identified in the program. Two Arkansas selections carry this trait, A-2453T and A-2454T. They were used in 2011 in crosses with other Arkansas selections with the intention of increasing firmness in progeny. Another objective for these crosses was to evaluate the inheritance of firmness. In 2014, fruit firmness of five populations (1145, 1146, 1147, 1148, and 1151) was measured. All populations were from firm x crispy parents.  Thirty to 37 plants were evaluated per population.  Fruit compression, skin penetration, and drupelet penetration forces were measured. For penetration and compression, 1.0 mm and 7.2 cm cylinder probes were utilized, respectively. Fruit compression values indicated that four of five populations had progeny that exceeded the average firmness value of the firmest parent. Conversely, population 1146 produced no progeny exceeding the firmest parent, and most of the progeny were softer than either of the parents. The average firmness value of the firmest parent of each population was exceeded by 1.9 to 4.1 Newton (N) in the progeny, depending on the population. The number of individuals exceeding the parental force values varied from 2 (1146) to 17 individuals (1147). No progeny were measured to be in the “soft” category due to all parents being firm or crispy. Skin and receptacle penetration firmness measurement values were less consistent and values did not parallel the phenotype of the parents. Compression force values better explained the firmness of a genotype compared to penetration values. Fruit firmness reflected quantitative inheritance. Additional data is needed to quantify and fully explain the inheritance of exceptional firmness in very firm parent crosses, but the preliminary data shows great promise for achieving further firmness in blackberry progeny.