Genetics of semi-determinacy and identification of molecular marker linked to Dt1 locus in chickpea (Cicer arietinum L.)

Abstract

Chickpea is predominantly an indeterminate (IDT) plant due to which high fertility and irrigation have adverse effect on seed yield. The semi-determinate (SDT) types are relatively early, lodging resistant and found to be similar in their yield potential to that of IDT genotypes. However, the inheritance of SDT stem type is not well understood in chickpea. The present investigation was aimed at studying the genetics of SDT stem type and identifying molecular marker linked to Dt1 locus through Bulked Segregant Analysis (BSA). The genetics of semi-determinacy was studied in BGD 72 (IDT) x BG 3078-1(SDT) cross in which the genetic constitution of BGD 72 was already known as Dt1Dt1Dt2Dt2 based on the previous study. The F1 was IDT indicating the dominance of indeterminacy over semideterminacy. The segregation in F2 and F3 revealed that SDT stem growth in the new-found genotype BG3078-1 was governed by a single dominant gene Dt2 and its genotype designated as dt1dt1Dt2Dt2. The study of polymorphic survey between BGD-72(IDT) and BG 3078- 1(SDT) using 581 SSR markers found 50 markers polymorphic. The BSA using 50 polymorphic markers has identified TA42 and TR29 as polymorphic between IDT and SDT parents as well as IDT and SDT bulks and hence considered putatively linked to Dt1 locus governing IDT stem growth in chickpea. The two linked markers were validated in 15 IDT and 15 SDT F2 plants individually. These two markers were also validated in 3 IDT, 8SDT and 3 DT genotypes. This is the first report on the identification of a molecular marker associated with stem growth habit in chickpea.

Unraveling Genetics of Semi-Determinancy and Identification of Markers for Indeterminate Stem Growth Habit in Chickpea (Cicer Arietinum L.)

“…The F 1 plants obtained from the cross made between BG 362 (IDT) X BG 3078-1 (SDT) were indeterminate suggesting that gene (s) regulating the IDT stem growth habit was dominant over the SDT stem growth habit. The dominance of the IDT stem has also been reported earlier in chickpea [5,17]. The dominant nature of the IDT stem growth was also noticed in Glycine max [1], Vicia faba [3] and Cajanus cajan [7,20].…”

“…These observed segregation patterns are in good t as per expected proportion of 3 IDT: 1 SDT stem types (χ 2 value= 0.029, P= 0.9 -0.5) and indicates that the IDT and SDT parents which are involved in the cross differed for a single gene. The segregation pattern observed in F 2 of this cross is according to the expected ratio as predicted in the previous study [5].The genotype of IDT parent BG 362 was assumed as Dt1Dt1Dt2Dt2 on the basis of previous study [5]. Hence, the genotype of the SDT genotype BG 3078-1 is assigned as dt1dt1Dt2Dt2.…”

“…The two non-allelic genes regulate stem growth habit in chickpea which is designated as Dt1/dt1, Dt2/dt2 with Dt1 epistatic to Dt2 as well as dt2 [5]. The Dt1 allele develops indeterminate growth habit, whether it is present in homozygous (Dt1Dt1Dt2_ and Dt1Dt1dt2dt2) or in heterozygous state (Dt1dt1Dt2_ and Dt1dt1dt2dt2).…”

“…In the current study, an indeterminate (BG 362) x semideterminate (BG 3078-1) cross was studied to know the genetics of a semi-determinate (SDT) stem growth habit. BG 362 is an indeterminate parent and based on the earlier study [5] it is assumed that it carries Dt1 and Dt2 alleles in homozygous condition at both the loci and its genotype is designated as Dt1Dt1Dt2Dt2. The genetic control and the inheritance of semi-determinacy of BG 3078-1 genotype are dissected in this study.…”

“…Two different stem elongation patterns could be seen in F 2 of IDT x SDT cross. All F 2 plants with elongated owering offshoots that ended with the vegetative elongation phase are categorized as indeterminate, plants like those of indeterminate varieties with continuous owering offshoots but ending with a ower bud or fully opened ower are termed as semi-determinate [5]. The expected values were calculated on the basis of Mendelian ratio, corresponding to the observed values for indeterminate: semi-determinate plants.…”