Abstract
Exploitation of hybrid vigour has been visualized as the most efficient option for increasing productivity in pigeonpea [Cajanus cajan (L.) Millspaugh]. Cytoplasms from various wild relatives of pigeonpea have been transferred to develop CMS lines in the background of cultivated pigeonpea. However, A2 (Cajanus scarabaeoides) and A4 (Cajanus cajanifolius) cytoplasms have been utilized most frequently. In order to study fertility restoration efficiency in F1 hybrids having either A2 or A4 cytoplasms, an experiment was conducted at the Indian Institute of Pulses Research (IIPR), Kanpur during 2008-2012. Four CMS lines namely Hy4A, H28A (each with A2 cytoplasm), ICP 2039A and ICP 2043A (both with A4 cytoplasm) were crossed with ten genotypes/restorers of long duration pigeonpea for two years. The F1 hybrids so-obtained were assessed in the succeeding years for pollen fertility and pod setting. All the pollinators except IPA 203 restored fertility in F1 hybrids derived from ICP 2039A and ICP 2043A (both having A4 cytoplasm). However, none of the restorers were effective in restoring fertility in hybrids derived from Hy4A and H28A (each with A2 cytoplasm). This could be ascribed to undesirable linkage drag still present in these two CMS lines having A2 cytoplasm. The F2 progenies derived from 4 hybrids (ICP 2039A × NA-1, ICP 2039A × Bahar, ICP 2043A × NA-1 and ICP 2043A × Bahar) segregated approximately into 3 fertile: 1 sterile plants. However, 2 F2 progenies having Pusa 9 as the restorer revealed approximately 15 fertile:1 sterile ratio. Thus monogenic and digenic duplicate gene action with complete dominance for fertility restoration was observed in F1 hybrids derived from CMS lines having A4 cytoplasm. F3 progenies from individual F2 plants of these crosses also confirmed the same pattern of fertility restoration. This study indicated that CMS lines based on A4 cytoplasm would be more desirable as these might have more number of restorers compared to those having A2 cytoplasm.
Highlights
Heterosis breeding was resorted to improve productivity of pigeonpea which has been static for the last three decades the world over [1]
Pollens of all F1 hybrids except “ICP 2039A × IPA 203 and ICP 2043A × IPA 203 were observed densely stained with 2% acetocarmine, and showed fertile pollen reaction during the year 2009
It was obvious that a total of 9 pollinators were able to restore fertility in F1 hybrids having A4 cytoplasm; none
Summary
Heterosis breeding was resorted to improve productivity of pigeonpea which has been static for the last three decades the world over [1]. CMS lines derived from Cajanus scarabaeoides [2] (A2 cytoplasm) and C. cajanifolius [3] (A4 cytoplasm) have been widely utilized to develop commercial hybrids. Despite release of a few hybrids from both sources, hybrids did not gain ground on farmers’ fields due to several factors including partial fertility restoration and high genotype-environment interaction [4]. The CMS lines containing A4 cytoplasm have been reported to be highly stable across environments and years without showing any morphological deformity [6]. The present study reports a comparative assessment of fertility restoration in hybrids containing individually either A2 or A4 cytoplasm and their significance in breeding hybrid pigeonpea. In order to take advantage of this CMS hybrid technology, it is essential to breed high-yielding hybrids based on diverse genetic backgrounds. To achieve this, breeding of promising hybrid parents and knowledge of the inheritance of fertility restoration are essential [7]. In addition to the F1, F2 and F3 generations were generated from A4 CMS lines to determine the nature of gene action in the F1 generation, the segregation pattern in F2 generation and its confirmation through F3 generation in pigeonpea
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