Morpho-molecular characterisation and evaluation of TxD, DxT and DxD hybrids of coconut cultivar ayiramkachi (Cocos nucifera L.)

Abstract

Study on “Morpho-molecular characterisation and evaluation of TxD, DxT and DxD hybrids of coconut cultivar Ayiramkachi (Cocos nucifera L.)” was carried out at the Department of Plant Biotechnology, College of Agriculture, Padannakkad during 2018-2020. This investigation aimed at morphological and molecular characterisation of hybrids planted at RARS Pilicode during 1994, in the hybridization programme involving different tall and dwarf genotypes (WCT, Laccadive Ordinary, Philippines, Laccadive Micro, Andaman Ordinary and Malayan Yellow Dwarf) with Ayiramkachi, for important yield attributes and nut quality combined with dwarf stature. The evaluation based on morphological characters recorded during 2018-2020 revealed that the hybrids LMxAYK, MYDxAYK and LOxAYK were promising ones with high yield (155.50, 115.33 and 116.50 nuts/ palm/year respectively) and superior nut characters such as fruit weight, nut weight, shell and meat weight, kernel thickness and copra content. Hybrid PHIxAYK was superior for all the nut characters combined with a shorter stature but the yield was comparatively less (81.67 nuts/ palm/ year). The hybrid CCxAYK was high yielding (150.67 nuts/ palm/ year) but inferior in nut characters. Hybrid AOxAYK recorded good nut characters but was low yielding (61.50 nuts/palm/year). Hybrids of AYK with WCT recorded a moderate yield (95.00 nuts/ palm/ year) with inferior nut characters, and hybrid AYKxMYD was inferior for both yield (21 nuts/ palm/ year) and nut characters. On analysing the TxD, DxT and DxD groups with their tall (T) and dwarf (D) parents, all the hybrids recorded palm height statistically similar to the dwarf cultivars, which may be an indication of inheritance of shorter stature from the common parent AYK. Study on genetic parameters revealed that characters such as palm height, internode length, number of green leaves, rate of leaf production, petiole length, leaf length, number of female flowers per inflorescence, number of female flowers one month after pollination and shell and meat weight had shown high heritability (H2) coupled with high genetic advance as per cent means (GAM%). Hence choice of such characters are best suited for selective breeding. Yield and copra content had shownmedium heritability with high genetic advance. This might be due to the indirect effect of secondary characters contributing to them. Estimation of heterobeltiosis (superiority over better parent) and standard heterosis (superiority over standard check, Kerasree) for the nine hybrids of Ayiramkachi revealed that the hybrids LMxAYK and MYDxAYK were found to be better performers with respect to yield as well as nut characters, and can be exploited for developing commercially important hybrids suitable for culinary as well as processing purposes (copra and other value added products). The hybrid CCxAYK was high yielding but inferior in nut characters. As one of the parent in this cross, Cochin China, is suitable for tender nut purpose due to high nut water content, the hybrid nuts also may be further evaluated at tender nut stage for its suitability for tender nut purpose. Thirty four SSR markers were screened for polymorphism among the eight parental cultivars and the check palm (Kerasree). The markers produced an average of 52.94% polymorphism and 1 to 2 alleles/locus. Out of 34 SSR markers screened for polymorphism, 15 markers viz., CAC02, CAC11, CNZ40, CNZ44, CnCirA9, CnCirB12, CnCirE2, CnCirC7, CnCirH4, CnCirE12, CnCirC3, CnCirF2, CnCirH7, CnCirG11 and CnCirC5 were able to detect the polymorphism between the parental palms and hence can be utilized in future for fingerprinting the hybrid palms.