Applied Botany Section, Indian Institute of Technology, Kharagpur
1. To interpret the results of the genetical study in green gram, genes P-p, C-cb-c affecting the presence and distribution of purple pigments in different parts of plants have been assumed. The plants with P and C genes had purple hypocotyl, epicotyl, stem and leaf rachis; plants with P and cb had purple hypocotyl, purple spotted epicotyl, green stem, many spotted leaf rachis; p and cb plants had purple spotted hypocotyl, green epicotyl, green stem and few spotted leaf rachis; and the plants with cc genes did not have pigment in any part. The primary effect of these colour genes are to produce purple pigment in the hypodermal cells throughout or in alternating patches of variable sizes. The intensity of colour was also effected. In the multiple allelic series C-cb-c, increasing pigmentation was progressively dominant over the lower member.
2. Though partially affected by sap soluble pigment on the back of the standard, flower colour was mainly due to the effect of chromoplastids. Oil yellow flower O was dominant over palm-leaf yellow o. The sulphur yellow flower, however, was found to be the effect of cc anthocyanin factor.
3. Seed colours were found to be due to sap soluble pigments and to the colour and number of chloroplastids in the seed coat. Two gene pairs B-b and Bf-bf have been assumed for the inheritance of sap soluble colours and a gene pair G-g for number of chloroplastids. The blue colour was the effect of B and the buff colour of bf; and no sap soluble pigment was seen in bb or Bf-plants except in bbbf-bf which was buff. More green chloroplastids were seen in G-plants and a few yellowish green ones in gg plants.
4. A few more colour genes had to be assumed to explain the nature of inheritance of pigmentation in other parts, for example lp for light popcorn fruit and a for almond biscuit fruit. Their dominant members Lp and A together gave black fruit. Brown hair was recessive to the colourless ones and two dominant genes were found to be necessary for the production of colourless hairs.
5. Absence of complete dominance of the lobed leaf over the entire one, giving intermediately lobed leaf in the hybrid and 1 lobed (pinnatisect): 2 intermediate lobed (pinnatipartite): 1 entire leaves were seen. Such inhibitory effect on the development of an organ was also seen in simple X compound inflorescence, where the development of the two buds at the base of the inflorescence stalk was seen to be affected by two recessive genes.
6. Tapering fruit tip was monogenically recessive to swollen fruit tip and glossy seed surface to rough. The swollen fruit tips were found to have larger cells at the fruit tip than the tapering one; and the rough seed was due to innumerable small papillate outgrowths on the surface. A few glossy X glossy crosses gave rough seeds segregating into 9 rough: 7 glossy in F2, for which interaction of two dominant genes giving rough seeds have been assumed.
7. A linkage group of hypocotyl colour (P-p), seed colour (B-b) and fruit colour (Lp-lp) has been found and the distance between P-p and B-b has been estimated as 4.3 units and between B-b and Lp-lp as 15.6 units and the distance between P-p and Lp-lp as 19.4 units.
