Uniparental inheritance of purple leaf and the associated resistance to leafminer in castor bean

Leafminer (Liriomyza trifolii Burgess), Diptera Agromyzidae, is one of the insect pests that causes economic damage to castor bean (Ricinus communis L.) foliage. Green leaf type is a common phenotype in castor bean and highly susceptible to leafminer. The rare purple leaf type germplasm accessions showed stable resistance to leafminer. Studies were carried out to understand the inheritance of purple leaf and the associated leafminer resistance. Direct and reciprocal crosses were made between a purple leaf parent RG1930 and a green leaf parent RG2788. RG1930 is resistant to leafminer while RG2788 is susceptible. Reciprocal differences were noted in segregation pattern of purple leaf colour as well as resistance to leafminer. Purple leaf phenotype was obtained only in purple x green (RG1930 x RG2788) cross where the female parent was a purple leaf phenotype. The reciprocal cross green x purple (RG2788 x RG1930) produced only the green leaf phenotype. Uniparental inheritance was observed for purple leaf phenotype and resistance to leafminer in F₁, F₂, F₃ and backcross generations. Progenies with a dark purple leaf were resistant to leafminer while those with a green leaf were susceptible. Visual association between a purple leaf and resistance to leafminer and their uniparental inheritance were clearly established. The role of heritable epigenetic effects are discussed in expression of purple pigment in offspring.