Evidence that genes from the male parent may influence the morphology of potato dihaploids

A number of recent studies have provided evidence that potato dihaploids (S. tuberosum) contain and express DNA from the male (dihaploid inducer) parent, S. phureja. The importance of this for breeding programmes that use dihaploid potatoes is to some extent dependent upon whether the S. phureja DNA influences dihaploid morphology. In the present study, 21 characters were used to compare the morphology of six dihaploids with those of their parents: S. tuberosum (cvs `Pentland Dell' and `Pentland Crown') and S. phureja (IVP48). Characteristics of S. phureja were found in all of the dihaploids examined. In principal component analyses, dihaploids formed intermediate groupings positioned between those of the parents, although much closer to S. tuberosum. It is concluded there is evidence that DNA originating from the dihaploid inducer can affect the morphology of potato dihaploids. Implications of the findings are discussed. Received: 26 November 1995 / Accepted: 9 February 1996     

Haploidy from Hordeum interspecific crosses

Summary Interspecific crosses of Hordeum brachyantherum (2n = 28) and H. depressum (2n = 28) with H. bulbosum (2n = 14 or 28) and H. vulgare (2n = 14 or 28) were made. Crosses between brachyantherum and diploid bulbosum resulted in dihaploids (2n = 14) of brachyantherum and hybrids (2n = 21), whilst the crosses of brachyantherum by tetraploid bulbosum or vulgare gave hybrid progeny. Similarly, crosses between H. depressum and diploid bulbosum resulted in dihaploids (2n = 14) of depressum and hybrids (2n = 21), whereas depressum by tetraploid bulbosum or vulgare invariably produced hybrids.Cytological observations on 12 day old embryos obtained from these crosses revealed chromosome variability down to 14 in crosses with diploid bulbosum indicating thereby that chromosome elimination leads to haploid formation. Embryonic cells from the brachyantherum by diploid vulgare cross also exhibited a certain degree of chromosomal instability as micronuclei.The results indicate that the ratio of parental genomes in the zygote determines whether haploids or hybrids will be produced in crosses of brachyantherum or depressum with bulbosum. Furthermore, brachyantherum appears to be more efficient in eliminating bulbosum chromosomes in comparison with depressum.     

High frequency androgenesis in indica × Basmati rice hybrids using liquid culture media

An improved procedure has been developed for high frequency androgenesis in indica × Basmati rice hybrids using a liquid culture medium. Anthers from fourteen genotypes comprising of indica × Basmati rice F₁ hybrids, F₂ plants and the parental rice cultivars, were floated in liquid RZM, N6M, and Heh5M media. Anther culture frequencies (percentage of anthers forming calluses) in most of the genotypes were significantly higher in RZM medium (16–75%) compared to those obtained in N6M (7–29%) and Heh5M (7–41%) media. Agarose (1.0% w/v)-solidified MSR1 medium containing 3.0% (w/v) maltose, 1 mg l⁻¹ kinetin, 1 mg l⁻¹ 6-benzyladenine (BA) and 0.5 mg l⁻¹α-naphthalene acetic acid (NAA) induced green shoot regeneration at high frequencies compared to the medium (MSR2) lacking BA. In all the genotypes, microspore calluses initiated in RZM medium regenerated green shoots with over tenfold higher frequencies compared to the calluses initiated in other two media. High plant regeneration frequencies (up to 270 green plants/1000 anthers) were obtained from microspore-derived calluses of some of the F₁ hybrids (Gobind × Basmati 370, Gobind × Taraori Basmati) and F₂ plants (Gobind × Basmati 370, Gobind × Taraori Basmati, HKR86-3 × Taraori Basmati) as compared to their actual parents. Cytological analysis of the root tips of the progeny seedlings of the microspore-derived plants revealed haploids at a frequency of about 50%; 22% of the microspore- derived plants had > 5% spikelet fertility and were diploid. Use of RZM liquid and MSR1 media, respectively for anther culture and plant regeneration resulted in several fold increase in the recovery of green plants from recalcitrant indica × Basmati rice F₁ hybrids/F₂ plants which were comparable to those reported for japonica rice varieties/hybrids leading to the improved feasibility of using doubled haploids in genetic, breeding and mapping research with indica rice. This revised version was published online in June 2006 with corrections to the Cover Date.