Combining ability and response to CMS in reverse diploid maize lines developed at VIR

Abstract

Abstract. Hybrid maize breeding requires constant renewal of the source material. In this regard, broadening of genetic variation in parental lines is one of the primary tasks in heterotic hybrid breeding programs. The use of reverse diploid inbred lines derived from a tetraploid population is considered as an innovative approach to achieve this goal.Results. The investigated material comprised 106 reverse diploid (rediploid) inbred lines originating from diploid plants selected in segregating selfed progenies of triploid populations and consequently subjected to inbreeding, while triploid populations resulted from a cross between plants of a tetraploid population with a broad genetic basis and a diploid line. The use of a system of crosses with 37 sterile testers belonging to different FAO maize maturity groups allowed the evaluation of the rediploid lines’ combining ability and the response to M and C types of CMS. Field tests were conducted in 2019 in the steppe zone of Kabardino-Balkaria. Forty-six lines (43.3%) with the combining ability ranging from ultra-high to good, and 78 lines (73.6%) maintaining the CMS character were identified. Among them, 59 lines (55.7%) were maintainers for the M type CMS, 15 lines (14.1%)  for C type CMS, and 4 lines maintained sterility for both CMS types. Sixteen lines (15.1%) restored pollen fertility of the forms with M type CMS, 11 lines (10.4%) were restorers for the C-type and one line turned out to be a universal restorer for both CMS types. Ranking by the “sprout - flowering of ears” interstage period duration showed that most of the lines (66.0%) with the ability to maintain sterility or restore male fertility of M and C CMS types, as well as with the combining ability from ultrahigh to good (32.6%) fell into the group with the flowering period duration of 51-55 days. According to the results of the harvested grain moisture assessment, the hybrids ♀(РГС246с × OL213) × ♂92с5986·2·3, ♀714М  ×  ♂1/67-1 and ♀714М  ×  ♂92н136-4, with the values of 13, 6%, 13.9%, 14.0%, respectively, were identified. The hybrids ♀714М × ♂1/67- 1 and ♀(OL563С × KL1392) × ♂92с0653 2 1 2 were characterized by the maximum value of the selection index, i.e. 5.03 and 5.13, respectively.Conclusions. The results of the studies showed the breeding value of rediploid lines as an initial material for hybrid maize breeding.