Pattern analysis of visible faulty fruits in capitula: A case in cultivated sunflower (Helianthus annuus L.)

The analysis of spatial arrangement of incompletely developed fruits (IDF) in capitula could be used to understand the nature and the relative arrangement of these fruits at maturity, previously unexplained by current models. The objective of this work was to quantify and define the distribution pattern of visible IDF (IDFvis) at physiological maturity in the capitulum of the cultivated sunflower, in two genotypes with different self-compatibility expression grown in three different environments. Spatial characteristics and the possibility of randomness of IDFvis pattern generation were also evaluated. We were able to define four IDFvis patterns: Type I, where the distribution of the IDFvis was located mainly at the capitulum center, Type II, where the distribution remained grouped at its center but spreads towards the periphery, Type III, where the distribution was more homogeneous over the entire capitulum surface and Type IV with a homogeneous but very dispersed distribution over the entire capitulum surface. Second order spatial point pattern analysis techniques for a plane (Ripley’s K) were applied to the distribution of IDFvis in the four predefined IDFvis patterns. Using the ADE-4 software, spatial distribution patterns contained in a circular surface and corrected for edge effects were analyzed. By grouping the different types of IDFvis patterns by environment and genotype, a tendency was observed to generate preferably two types of patterns, Type I and Type IV, directly related to the genotype and not to the environment. The K index obtained for each type of pattern showed that, for the scales analyzed, Types I, II and III can be defined as grouped, since they laid outside the Poisson confidence limits. The Type IV pattern presented results consistent with a completely randomized distribution. It was observed a low- frequency appearance of the IV (random) pattern and only for one genotype in the different environments studied, while in the rest of the genotype x environment combinations there was always a greater degree of grouping (non random; Type; I, II and III patterns). Proved that mostly of the IDFvis patterns presented in the sunflower capitulum were mainly non random, the results shown here suggest that, to the intrinsic characteristics of the plant to express this character, mainly physiological, intra-receptacle physical factors could be added in the post-pollination stage, capable of altering the normal development of the embryos.