ORIGINAL ARTICLE A mutational approach for the detection of genetic factors affecting seed size in maize Stefano Sangiorgio 1 • Laura Carabelli 1 • Damiano Gabotti 1 • Priscilla Sofia Manzotti 1 • Martina Persico 1 • Gabriella Consonni 1 • Giuseppe Gavazzi 1 Received: 23 August 2016 / Accepted: 7 November 2016 Ó Springer-Verlag Berlin Heidelberg 2016 Key message Genes influencing seed size. Abstract The designation emp (empty pericarp) refers to a group of defective kernel mutants that exhibit a drastic reduction in endosperm tissue production. They allow the isolation of genes controlling seed development and affecting seed size. Nine independently isolated emp mutants have been analyzed in this study and in all cases longitudinal sections of mature seeds revealed the absence of morphogenesis in the embryo proper, an observation that correlates with their failure to germinate. Complementation tests with the nine emp mutants, crossed inter se in all pairwise combinations, identified complementing and non- complementing pairs in the F 1 progenies. Data were then validated in the F 2 /F 3 generations. Mutant chromosomal location was also established. Overall our study has iden- tified two novel emp genes and a novel allele at the pre- viously identified emp4 gene. The introgression of single emp mutants in a different genetic background revealed the existence of a cryptic genetic variation (CGV) recognizable as a variable increase in the endosperm tissue. The unmasking of CGV by introducing single mutants in dif- ferent genetic backgrounds is the result of the interaction of the emp mutants with a suppressor that has no obvious phenotype of its own and is present in the genetic background of the inbred lines into which the emp mutants were transferred. On the basis of these results, emp mutants could be used as tools for the detection of genetic factors that enhance the amount of endosperm tissue in the maize kernel and which could thus become valuable targets to exploit in future breeding programs. Keywords Cryptic genetic variation (CGV) Á Empty pericarp Á Interaction Á Seed development Á Seed size Á Zea mays Introduction The seeds of cereals such as maize, wheat and rice are major sources of food and feed. The increasing demand for more abundant food sources to nourish the growing human population is undoubtedly the main reason for the interest in the study of seed development. In flowering plants, the seed is the result of a double fertilization event leading to the production of two compartments, the embryo and the endosperm. The latter represents the major portion of the seed and, like the placenta in mammals, is the source of nutrients for the developing embryo and its early phases of germination until the resulting seedling acquires autonomy in its growth. Understanding the genetic control underlying seed for- mation is a prerequisite for establishing breeding programs aimed at yield enhancement. To achieve this goal requires a genetic dissection strategy that includes the isolation and analysis of mutants impaired in seed formation. In maize, mutations disrupting seed formation are easily obtained and have long attracted the attention of researchers. They are usually referred to as defective kernel (dek). In general, both embryo and endosperm development are altered in Communicated by Thomas Dresselhaus. Electronic supplementary material The online version of this article (doi:10.1007/s00497-016-0294-6) contains supplementary material, which is available to authorized users. & Gabriella Consonni gabriella.consonni@unimi.it 1 Dipartimento di Scienze Agrarie e Ambientali–Produzione, Territorio, Agroenergia, Universita ` degli Studi di Milano, Via Celoria, 2, 20133 Milan, Italy 123 Plant Reprod DOI 10.1007/s00497-016-0294-6