Etiology of cushion gall disease of Cacao (Theobroma cacao L.)

Abstract

The study entitled “Germplasm collection and diversity analysis of Kiriyathu [Andrographis paniculata (Burm. F.) Wall. ex. Nees] ecotypes of Southern districts of Kerala” was carried out in the Department of Plantation, Spices, Medicinal and Aromatic Crops, College of Agriculture, Vellayani, during the period 2023- 2024 with the objective of collecting Kiriyathu ecotypes, estimation of morphological and genetic variation using Simple Sequence Repeat (SSR) markers. Kiriyathu ecotypes, 35 nos. viz., Kalakkode, Chirakkara, Perinad, Karicode, Vellimon, Kundara, Karunagappally, Kayamkulam, Thamarakkulam, Mavelikkara, Chengannur, Alappuzha, Thiruvalla, Kottayam, Chottanikkara, Ernakulam, Mala, Kodungallur, Vellayani, Kattakkada, Neyyattinkara, Parassala, Kachani, Karakulam, Bharanikkavu, Sasthamcotta, Adoor, Vellanad, Kadakkal, Pathanamthitta, Odakkali, Palode, Aryanad, Vithura and Nedumkandam were collected from nine different Agro Ecological Units (AEUs) of Kerala. The indigenous traditional uses of Kiriyathu gathered from the inhabitants/ localities/traditional medicinal practitioners include its utilisation for curing fever, malaria, jaundice, snake/insect bite, wounds, dysmenorrhea, digestive ailments and managing diabetes. Genetic variation of the Kiriyathu ecotypes using SSR primers identified seven polymorphic primers viz., Ando 4-26, Ando 4-27-2, Ando 4-43/1, Ando 5-12-1, Ando 5-14-2, Ando 5-26-2 and Ando 5-29. The polymorphism percentage was 64.08 per cent and the Polymorphism Information Content (PIC) value ranged from 0.11 to 0.64. Among the primers, Ando 4-27-2 recorded high PIC value and hence, considered to be more informative for diversity analysis. The dendrogram developed using molecular data could group Kiriyathu ecotypes into three major clusters - Cluster I containing seven subclusters (I to VII) and 27 ecotypes, Cluster II consist of five ecotypes and Cluster III having three ecotypes. In addition, the scatter plot developed using Principal Coordinate Analysis (PCoA) could identify a genetically diverse ecotype viz., Chirakkara belonging to AEU 1, Southern Coastal Plain. Morphological diversity of nine Kiriyathu ecotypes, one each selected from the subclusters of Cluster I, Cluster II and Cluster III respectively were studied by raising its seeds in pro-trays, transplanting it into polybags containing soil and cow dung powder (2:1) and maintained up to harvest at 50 per cent flowering. Seedling characteristics such as seedling height (15 DAT) and no. of leaves per seedling were maximum for Bharanikkavu (16.33 cm) and Thamarakkulam (14.33) respectively. Plant characteristics viz., days to 50 percent flowering, no. of primary branches, no. of secondary branches, plant duration up to seed set (days) and plant height were maximum in Chirakkara (141.66), Alappuzha (7.33), Thamarakkulam (5.66), Chirakkara (161.66) and Vellanad (75.06 cm) ecotypes respectively. Maximum leaf length and leaf girth were recorded for Chirakkara, 9.23 cm and 3.50 cm respectively. However, maximum stem girth was recorded by Vellanad, 2.53 cm. Yield characteristics such as herbage yield per plant (g) and leaf/stem ratio were maximum in Chirakkara (12.93g) and Vellanad (1.10) respectively. The study concluded that the 35 Kiriyathu ecotypes collected from nine different AEUs in the Southern districts of Kerala varied genetically. Chirakkara ecotype (AEU 1, Southern Coastal Plain) showed higher genetic variation and it showed superior morphological characteristics too - maximum days to 50 per cent flowering (141.66), plant duration up to seed set (161.66 days), leaf length (9.23 cm), leaf girth (3.50 cm) and herbage yield per plant (12.93g).