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Pericarp resistance to mechanical puncture using a penetrometer was determined for achenes of 72 sunflower (Helianthus annuusL.) genotypes grown in a greenhouse and sampled at 1, 5, 10, 15, and 20 days after fertilization. This study was undertaken to determine resistance of developing sunflower achenes to mechanical puncture and to relate this to possible genetic resistance to the sunflower moth, Homoeosoma electellum(Hulst). Pericarp resistance to puncture was found to be directly correlated with presence of phytomelanin. Significant genotypic differences in resistance to puncture were found among restorer (RHA) and maintainer (HA) lines. Achenes of the restorer lines RHA 272 and RHA 274 were most resistant to pericarp puncture. Of the maintainer lines, achenes of HA 65, HA 246, and HA 250 showed greatest resistance to pericarp puncture. Prediction equations indicated a positive linear relationship between resistance to puncture of the pericarp and age of the respective achene.

To determine the potential of genetically different lines and cultivars of guar [Cyamposis tetragonoloba(L.) Taub.], breeders must observe many different characteristics in their breeding and selection programs. Factor analysis is a type of multivariate analysis that can be used to reduce a large number of correlated variables to a smaller number of main factors, thus helping to elucidate the number and nature of causative influences and aiding in the selection of better genotypes. The objective of this study was to use factor analysis to determine the dependence relationship between 10 components of yield and morphological characteristics of 12 field‐grown guar genotypes from three locations. Principal factor analysis was used for factor extraction and varimax rotation was used to uniquely define factors. Four factors adequately accounted for most of the intercorrelations. Grams of seed/plant, number of pods/plant, number of seeds/plant, and number of racemes/plant constituted the productivity per plant factor (Factor 1). Factor 2 was considered a branchingproductivity factor consisting of number of primary branches and number of pods/raceme. Factor 3, a growth factor, consisted of plant height and number of nodes/plant. Factor 4 was considered a yield per unit area factor, and consisted of variables concerned with number of seeds/pod and wt/100 seeds. Factor analysis reduced a large number of correlated variables to a small number of main factors and also clarified the relationship between correlated characters in the dependence structure. This study indicated that selection of variables concerned with productivity per plant (Factor 1), and yield per unit of area (Factor 4) should enable breeders to better realize the desired gains in seed yield of guar.