INDUCED MALE STERILITY IN JUTE (CORCHORUS CAPSULARIS L.)

Transcription

1 SCIENTIFIC NOTE JAPAN. J. GENETICS Vol. 42, No. 2 : (1967) INDUCED MALE STERILITY IN JUTE (CORCHORUS CAPSULARIS L.) Received October 17, 1966 S. C. RAKSHIT Faculty of Agriculture, University of Kalyani, West-Bengal, India ABSTRACT: A slow growing male sterile mutant, `Ribbon', was first observed in the M2 progenies of 70,000 R treatment of the dry seeds of Corchorus capsularis L. Genetically, normal leaf trait was found to be dominant over `Ribbon' trait and male fertility over sterility. The leaf variation is controlled by one factor pair and similar is the case with male sterility. The trend of fluctuation of pollen sterility in F2 population indicates the probability of the presence of two closely linked genes controlling the two traits. JRC-212 is an improved cultivated strain of Corchorus capsularis L., evolved at the Jute Agricultural Research Laboratories (Kundu 1956). Dry seeds of JRC-212, were irradiated with 50 kv. 2 ma., X-rays for dosages ranging from 10,000 R to 100,000 R. In the M2 generation, mutants with outstanding phenotypic peculiarities were isolated from a line of 70,000 R treatment, in the year 1959 at the Jute Agricultural Research Institute, Barrackpore. These mutants were designated as `Ribbon' because of their leaf character. Of the many variations, `Ribbon' also possesses complete male sterility. Morphological and genetical observations were made in subsequent generations from the segregating lines obtained from the heterozygous normal sib of the mutants as well as from the progenies of crosses between the mutants and the parental strain. The `Ribbon' mutants are dwarf with slow growth rate. Lower leaves are flat, narrow, ribbon like with very irregular margins (Figs. 1 & 2). Narrow lamina is sometimes interrupted by a slender midrib portion only. Upper leaves and leaves of the axillary branches are very narrow with a long slender whip-like apex. In mother strain, however, the leaves are typically ovate-lanceolate with regular serrated margins and acute apex. Distinguishing morphological features of JRC-212 and the `Ribbon' are given in Table 1. Normal setting of pods with viable seeds was observed when `Ribbon' plants were grown in fields along with normal sib. However, `Ribbon' plants when isolated by means of 120 mesh wire net cages, did not set pods (Fig. 6). Segregation pattern of the progenies from seeds of naturally set pods in `Ribbon' as well as that of normal sib, show difference (Tables 2 & 3). In crosses with `Ribbon' mutant as female parent and JRC-212 as male parent, F, population resembled the male parent. F2 population, however, segregated in a 3 : 1

2 140 Plate S. C. RAKSHIT 1. Fig. 1. A plant of `Ribbon' mutant, x '/12; Fig. 2. Leaf of JRC-212 (A) and those of `Ribbon' mutant (B), x )4 ; Fig. 3. Normal anther with pollens, x 50; Figs. 4 & 5. Bi-lobed and unlobed tips of staminodes, x 40; Fig. 6. (a) showing free setting of pods in open pollination and (b) showing non-setting of pods when isolated by wire-net cage, x 1/12; Fig. 7. Longitudinal section of a bud of `Ribbon' mutant showing developing staminodes without microsporogenous tissue, x 240.

3 INDUCED MALE STERILITY IN JUTE 141 Table 1. Distinguishing morphological characters of JRC-212 and `Ribbon' mutant Table 2. Segregating progenies from naturally set pods of normal sib Table 3. Segregating progenies from naturally set pods of `Ribbon' ratio of normal : `Ribbon' traits, as shown in Table 4. In each of the twelve lines, as shown in Table 4, the mutant population is always less than the expected. This can be accounted for their non-survival upto the time of counting due to the feeble and delicate nature of the mutants and probably this has resulted in larger values of x2 in some of the lines. Sterility was observed to be directly associated with `Ribbon' trait. In F1 population pollen sterility ranged from 3.1 to 7.7 with a mean of 5.8 per cent., while in the parent strain, JRC-212, pollen sterility is 5.7 per cent. In the F2 population the sterility range was from 00.0 to 36.3 per cent., in all the apparently normal looking plants. The `Ribbon' segregates were, however, totally male sterile. Frequency distribution shows that about 86 per cent., of the total population possess sterility upto a maximum of 9 per cent., (Table 5).

4 142 S. C. RAKSHIT Table 4. Segregating progenies in the F2 generation Table 5. Frequency distribution of pollen sterility in F2 population Previous studies with X-ray irradiated plant materials have shown that various male sterility types are not of infrequent occurrence (Gustafsson 1947, Prakken 1959). Cause of sterility has mainly been reported to be due to reduced vigour, pre-meiotic or postmeiotic irregularities. Evidences are also there of the spontaneous occurrence of male sterile lines due to developmental irregularities of the androecium (Smith 1939, Jamn 1959). But in induced mutant, the persistant occurrence of teratological male sterility with characteristically altered phenotype, as observed in case of the `Ribbon' mutant, has not so far been reported. The `Ribbon' mutant is structurally male sterile due to rudimentation of anthers and complete absence of microsporogenous tissue. The total male sterility has imparted a high rate of natural crossibility as evidenced by free pod setting in open pollinated conditions, to the basically self-pollinated crop. This also indicates that sterility induced in the mutant genotype, is strictly restricted to the male organ, while the megasporogenesis has in no way been affected. The `Ribbon' mutant is thus a very suitable prerequisite for breeding purpose. However, its stunted growth and drastically altered phenotype are handicaps for utilizing it in breeding programme. To overcome these difficulties, the possibility to transfer male sterility to normal parental genotype was studied by crossing `Ribbon' mutant with the parental strain, JRC-212. F2 progenies

5 INDUCED MALE STERILITY IN JUTE 143 segregate into typically 3 parental : 1 mutant ratio, so far as phenotypic abnormality and sterility are concerned. Similar pattern of segregation was noticed in the progenies from naturally set pods of normal sib, indicating unifactorial heterozygosity of the normal sib of F1, whereas segregation from the naturally set pods in `Ribbon' shows 1 normal : 1 mutant. The evidences presented above indicate that leaf variation `Ribbon' is controlled by one factor pair. Similar is the case with male sterility. Whether these two traits are controlled by different closely linked alleles or whether the traits are controlled by a pleiotropic gene could be ascertained only after studying the sterility percentages from a larger population of hybrid progenies. The trend of fluctuation of pollen sterility in F2 population (Table 5), however, indicates the probability of two closely linked genes and that there is a chance to obtain recombinants with total male sterility and normal leaf trait. The author is thankful to Dr. S. Sen, Reader in Cytogenetics, University of Kalyani, for his valuable help. REFERENCES 0 Gustafsson, A., 1947 Mutations in agricultural plants. Hereditas 33: Jam, S. K., 1959 Male sterility in flowering plants. Bibliog. Genet. 18: Kundu, B. C., 1956 A review of the research works carried out at the Jute Agricultural Research Institute. pp Prakken, R., 1959 Induced mutation. Euphytica 8: Smith, L., 1939 Cytogenetic studies in Triticum monococcum and T, aegilopoides Bal. Missouri Univ. Agr. Expt. Sta. Res. Bull. 248: 1-38.