A study of the progeny of hybridization in lupinus
Authors:   , Schaller Leandra Margaret 
Published: May 2024

Several modes of study were undertaken utilizing hybridization between L. bilineatus and L. campestris. The study of cytology revealed the two species and their progeny to apparently be octaploid, possessing 48 (2n) chromosomes. Because of the high degree of polyploidy genetic determinations were difficult. Several hypotheses were formulated to account for the morphological and chemical variability of the hybrid progeny. The study of the alkaloid contents of L. bilineatus, L. campestris and their progeny revealed several different situations: 1) some compounds were present in both the parents and the segregates, 2) some compounds occurred in common in the F2 and one parent, 3) new compounds appeared which were not present in either of the parents, 4) compounds were also found in both parents but were absent in the F2 segregates. The variety of situations illustrate the genetic complexity of these parental plants and their progeny. Because of polyploidy multiple sets of chromosomes and many possible expressions of the genome exist. The morphological traits of any organism have long been held as the key to species determination. In this study 14 traits, among them both vegetative and reproductive characters, were chosen as a means of numerically scoring the parents and their F2 progeny. From the data it was found that the majority of the F2 segregates fell in the center of an "Andersonian" hybrid spindle. A large range of variation was found with only a few plants approaching the parental scores. Thus, the typical F2 variation of character expression was exhibited. Pollen viability and hybrid fertility have often been used as criteria for the fertility of the individuals. Occasionally pollen viability has been used as the sole criterion of fertility. However, it was found in this study that in the taxa considered pollen viability can not stand alone as an indicator of fertility of the particular plant. Two situations were found: 1) A high F2 pollen viability and low F2 fertility for the same plant more commonly, 2) The reverse situation, a high fertility yet low pollen viability, occasionally. From this data it is obvious that not only pollen viability but also fertility, based on actual seed production, must be used to make a statement on the fecundity of the progeny for an interspecific cross. The genetic analysis of the morphological traits places the hybrid progeny into four categories. In the first, six of the characteristics placed the plants in the intermediate group. Thus, a blending of parental characteristics was observed. The second category listed four characteristics most resembling L. bilineatus, while the third listed two characteristics appearing as the L. campestris condition. In this case one of parents was expressing dominance of a single or several genes. In the fourth category an even distribution among the parents and intermediates was expressed. The polyploid condition made this analysis of the morphological traits difficult. Two kinds of situations occurred in the fertility studies on the F2 and F3 progeny. It was found that those F2 plants which were weak and poor seed producers gave rise to weak individuals in the F3 generation. Occasionally a vigorous F2 plant was found which produced a great amount of seed and healthy progeny in the F3 generation. Because of the vigor of some of the F2 and F3 plants it can be hypothesized that a successful cross between L. bilineatus and L. campestris could occur. It is also hypothesized that L. hartwegii could arise from such a cross, particularly since many of the F2 and F3 progeny produced in this study were indistinguishable from L. hartwegii. Thus, the development of the cultivar L. hartwegii could occur if a hybrid habitat (a garden or roadside embankment) was available.