The Genetics and Characterization of an Open Flower Mutant in Chickpea

THE GENETICS AND CHARACTERIZATION OF AN OPEN FLOWER MUTANT IN CHICKPEA

Cicer arietinum, also known as the chickpea, is a self-pollinated grain legume from the family Fabaceae, making it a type of seed or pod. When the chickpea plant is in its flowering stage, normally the petals completely enclose the reproductive organs (stamen and gynecium). And the stamens are in a diadelphous condition where 9 out of its 10 stamens are fused and 1 remains free. Recently, however, an open-flower mutant (called OFM-3) was identified that did not have its organs enclosed by petals and all 10 of its stamens were free instead of the normal 9 free 1 fused ratio.

In years past many mutations have occurred in the hybridization of chickpeas, some spontaneous and others induced. Two other open-flower mutants, like OFM-3, have occurred over the years and have been studied. These two mutants are designated as ICC 16341 and ICC 16129. In this study of the mutant chickpea a team of researchers in International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), OFM-3 was crossed with the ICC 16341 and ICC 16129 open-flower mutants in order to determine OFM-3’s patterns of inheritance. Aside from the open flower trait and free stamens other traits were studied such as pod yield, growth habits, and pollen fertility.

When the growth habits of OFM-3 were studied it was found to have light pink flowers, normal green leaves, and a weak main stem that grew horizontally over the soil. Its flower structure was considered unique in comparison to a normal closed flower plant, but it was also different from the ICC 16341 and ICC 16129 types. Like a standard flower OFM-3 had 5 petals but they were all free (open instead of closed) like the other two mutant varieties, but its petal size was larger than that of the two. However, OFM-3 was similar to ICC 16341 in that all 10 stamens were free instead of 9 fused and 1 free.

One of the oddest traits of OFM-3 was that in 73% of the pods seeds did not develop, meaning there was only 27% seed development. This was very low in comparison to ICC 16341 and ICC 16129 which both had seed development rates over 50%. In all three years of the crop growth period OMF-3 consistently had a low seed rate, so it could not have been due to factors in the environment. It was possible that pollen sterility could have contributed to the lack of seeds, but after running multiple tests on the pollen researchers found that over 90% of the pollen grains in OFM-3 were fertile.

When crossed between OFM-3 x JG-11 (normal) and OFM-3 x ICCV 96030 (another mutant variety) were performed it was found in the F1 generation of all the crosses that the allele for closed flower was dominant. In the F2 generation the progeny was segregated into a 3:1 ratio, meaning that open flower trait is controlled by 1 allele. This was similar to the open flower trait in ICC 16129. When open flower trait and double flower trait (2 flowers per node/ normal has one) were combined in a dihybrid there was found to be weak linkage between the two traits. But in a dihybrid between open flower and plant type (semi-spreading and spreading of the plant structure) there was a strong connection because none of the progeny in either the F2 or F3 generations were normal plant type with open flower trait.

In crosses between OFM-3, ICC 16129 and ICC 16341 the F1 plants were all normal closed flowers, showing that the open flower trait in all the mutants are controlled by different genes. From this the F2 generations fell into a 9:3:3:1 ratio. When combined with either ICCV 96030 or JG-11, OFM-3 had a higher seed production rate. The highest was at 82.1% when crossed with JG-11. This showed the possibilities of being able to have and open flower trait with a higher percentage of filled pods and it also suggested that the lack of filled pods in an OFM-3 x OFM-3 cross could be due to independently inherited genes that would affect embryo development.

By studying the trait relationships and patterns of inheritance among the different open flower mutant varieties it was found that each mutant variety had a unique gene for the open flower trait. Also, the study of the open flower trait saw opportunities for the hybridization of the chickpea and the creation of breeding lines from the progeny between OFM-3 and normal flowered chickpea.

Hannah Quick