Pre-fertilization Barrier, Crossability and Meiotic Behavior of Interspecific Hybrids Among Brassica Species

Inter-specific hybridization is an important driving force in plant evolution, speciation and creation of novel genetic variations those are not available with the naturally occurring species. Present investigation includes study of pre-fertilization barriers, phenotypic characterization and the meiotic abnormalities during microsporogenesis in the interspecific hybrids. Mean pollen tube germination percent in interspecific hybrids was recorded to be highest in case of B. carinata x B. nigra (33.67±11.35) and lowest between B. carinata x B. napus (18.68±6.62) whereas in the reciprocal crosses it was highest for B. napus x B. carinata (33.06±13.41). Siliqua set ranged from 33% in B. carinata x B. napus to 72% in selfedB. carinata. Seed set % ranged from 0% in B. rapa x B. carinata and B.nigra x B.carinatato 25.64 % for B. carinata x B.nigra. Mean pollen tube growth was recorded highest in B. carinata x B. nigra (21.23±5.33) while was lowest in B. carinata x B. napus (10.18±3.17) and among reciprocals it was highest for B. nigra x B. carinata (21.39±7.53). Pollen tube abnormalities viz., coiling and bending of pollen tube, hairpin shaped pollen tube, swelling of tube tip, tube bifurcation, more than one tube emerging from pollen, tubes growing in wrong direction were observed. B. carinata as pollen parent showed highest mean pollen tube abnormality percent with B. napus (36.32±8.62) whereas lowest with B. nigra (18.09±6.73). It was observed highest with B. rapa (49.170 ±13.55) when B. carinata was used as pollen parent. Some of the pre fertilization barriers related to stylar and ovule region can also be observed through fluroscent microscopy. As per the observations B. carinata performed better as a seed parent with B. nigra, B. juncea and B. rapa whereas, with B. napus it performed good as a pollen parent. Correlation study gave the association the above traits with each other. The meiotic abnormalities showed improper alignment at M-I, M-II, A-I, A-II and Telophase.

Meiotic behaviour and pollen fertility of F1, F2 and BC1 progenies of Iris dichotoma and I. domestica

Pollen characteristics are very important for Iris interspecific hybridisation. In this study, the pollen viability and male meiosis were studied in yellow-flowered Iris dichotoma (Y2), I. domestica (S3) and their hybrids F1, F2 and BC1 (BC1-Y and BC1-S). The BC1-Y hybrids showed higher pollen viability than that of F1, F2 and BC1-S hybrids, which were between I. dichotoma (26.1%) and I. domestica (35.1%). Two sterile hybrids, F2-1 and BC1-S-1, exhibited more meiotic abnormalities (57.3% and 58.7%) than other individuals. During the first meiotic division, a diffuse diplotene stage was observed for the first time in the genus Iris. The meiotic abnormalities included non-congressed chromosomes, chromosome bridges, lagging chromosomes, unequal division, abnormally oriented spindle fibres, nonsynchronous division and polyad, and resulted in reduced pollen fertility. The relatively high frequency of 2n pollen grains was found in hybrids of BC1-Y-2, BC1-Y-1, BC1-S-2, BC1-S-3 and BC1-S-4. Our research provides a new resource for meiotic behaviour and pollen fertility of the genus Iris.

Meiotic behaviour and morpho-phenological variation in cut stock (Matthiola incana L.) flower

Morpho-phenological and meiotic studies were performed in twelve cultivars of Matthiola incana. All of the cultivars were diploid (2n = 2x = 14) with basic chromosome number x = 7. A number of aneuploid PMCs (n + 1) were observed in plants of two cultivars, named ‘Nobel’ (NB) and ‘Goddess’ (GD), at the diakinesis stage. Trisomic individuals with the frequency of 20% and 5% and (2n + 1 = 15) somatic chromosomes were observed in seeds obtained from single-flowered plants of the cultivars NB and GD, respectively. An additional chromosome was mostly observed in the form of a chain trivalent or a rod univalent. Various meiotic abnormalities were found in all the cultivars to different degrees. In these cultivars, the percentage of cells with meiotic abnormalities was higher in anaphase I. Cytomixis was observed for the first time in Matthiola incana. ANOVA tests revealed significant differences in morpho-phenological characteristics. ‘Nobel’ differs from the others in all of the vegetative features investigated in this study. All the cultivars studied except ‘Nobel’ and ‘Pacific Crimson’ possessed high pollen fertility (> 90%). Five groups of the cultivars based on morpho-phenological features disagree with the clustering of cultivars based on meiotic traits. It is thought that the various morpho-phenological features observed among the cultivars could be due to their different genetic background and not only to meiotic anomalies.

Meiotic chromosome behavior of Haworthia limifolia

Haworthia limifolia is a xerophytic plant belonging to the family Liliaceae and is indigenous to Africa. It is use extensively for its medicinal properties like antibacterial, antifungal properties and used for the treatment of sores, superficial burns, as a blood purifier and to promote pregnancy in women and cattles. In present investigation chromosomal behaviour of H. limifolia in meiosis was studied. In diplotene stage chiasmata was observed showing the possibilities of genetic recombination. Chromosome clumps were observed in diakinesis indicating sticky nature of chromosomes. Meiotic abnormalities like stickiness, precocious movement, formation of bridges and laggards were also reported in both meiosis I and II. A fairly high percentage of pollen sterility that is 73.41% was recorded resulting in failure of fruit formation. This plant could be designated as facultative apomict (Swanson, 1957) as the only means of reproduction found was asexual or vegetative.