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Genetic diversity analysis for nutrient efficiency and identification of nutrient responsive genes in cassava (Manihot esculenta Crantz)
(Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2023-02-10) Swathy Sivan; KAU; Arya, K
The present study entitled “Genetic diversity analysis for nutrient efficiency and identification of nutrient responsive genes in cassava (Manihot esculenta Crantz)” was carried out in the Department of Plant breeding and Genetics, College of Agriculture, Vellayani and Division of Crop Improvement, ICAR-CTCRI, Sreekariyam, during 2019-2022. The study was undertaken to screen and characterize N and K-efficient genotypes in cassava and identify the traits contributing to nutrient efficiency and study their gene expression. Thirty genotypes of cassava comprising of landraces, released varieties and pre-release accessions from ICAR-CTCRI and KAU were taken for the study. Field evaluation was done to identify low input nutrient efficient lines where analysis of variance revealed significant difference among the genotypes for all the characters studied except the girth of tuber. High GCV, PCV, heritability and genetic advance were observed for traits like tuber yield, N and K efficiency, plant height, number of leaves, number of branches, stem N and K content. Tuber yield was positively correlated to N and K efficiency, plant height, leaf and stem weight, stem girth, mean weight of tubers, number of nodes, girth and length of tubers, while negatively correlated to tuber starch and dry matter content. Path analysis showed that tuber length gave highest positive direct effect on yield followed by number of tubers, number of leaves, tuber starch content, plant height and nitrogen efficiency. Diversity studies grouped the genotypes into eleven clusters and the characters that gave the maximum contribution to divergence were tuber dry matter content, N and K efficiency. Root studies on thirty genotypes revealed that root traits like number of nodal roots, basal roots, adventitious roots, storage roots and root length displayed significant positive correlations with N and K efficiency. Evaluation of five highly nutrient efficient genotypes at the three levels of fertilizers (0%, 25% and 50% of the recommended dose of fertilizers) showed overall significance for traits like plant height, the number of leaves retained, stem weight per plant, girth of the stem, tuber yield, length of tuber, stem K content, tuber K content, total N and K uptake, N and K efficiency. The highest yielder was KBH 18 followed by 8S501-2. Maximum N efficiency was observed for KBH18 followed by 15S409, while maximum K efficiency was recorded for 8S501-2 followed by 15S409. Results showed that from 0 to 25 % there is an escalation in tuber yield as well as N and K efficiency, while the values at 25 and 50% are on par. All the selected four genotypes showed significant superiority over the K efficient check variety – Sree Pavithra – in terms of tuber yield, N efficiency and K efficiency. The study identified nine nutrient responsive genes in cassava which includes NRT1, NRT3, NLP1, GPT2, AMT1, TAR2 for nitrogen and KUP3, KUP4, KUP8 for potassium. Expression studies done using these genes in contrasting genotypes for N and K efficiency raised under field conditions showed significant upregulations and downregulations in their expression for efficient and less efficient genotypes. Allele mining for allelic variations in contrasting genotypes (15S409 and Export kappa) for two genes (AMT2 and NTR3) didn’t show much significant variation. Although SNP differences were observed for NRT3 gene, further functional studies are required to confirm this result. The study identified three main nutrient efficient genotypes viz., KBH18, which was the highest yielder, highest in N efficiency and third highest in K efficiency, 8S501-2, which was second highest in yield, highest in K efficiency, third highest in N efficiency and also exhibited early bulking and 15S409, which was the third highest yielder, second highest in N efficiency & K efficiency. The superior genotypes identified in the present study can be subjected to field trials for confirming their superiority and release as a variety.
Open Access
Genetic variability, path analysis and stability parameters in sesame
(Department of Plant Breeding, College of Agriculture, Vellayani, 1985) Sverup, John; KAU; Gopinathan Nair, V
Biometric analysis in a varietal collection of sesame was undertaken to study the genetic variability, correlations, path analysis and stability parameters. One hundred sesame types were evaluated in replicated trials at Vellayani in uplands during rabi and at Kayamkulam in rice fallows during summer. Genetic variability and correlations were estimated and path analysis worked out independently as both the locations. Location trials for estimating stability parameters were conducted at three places viz. in uplands during rabi at Pattambi and Vellayani and in rice fallows during summer at Kayamkulam. Large values for genotypic coefficients of variation were obtained for characters such as number of capsules on branches, number of capsules perplant, number of capsules on main stem and number of branches during rabi as well as summer. The lowest genotypic coefficient of variation was obtained for number of days to maturity during both rabi and summer. High values of heritability were recorded by seed protein content , seed oil content, height upto first capsule and weight of 1000 seeds under both conditions.
Embargo
Gene action and gene expression analysis in yardlong bean(Vigna unguiculata ssp. sesquipedalis(L.) Verdcourt) for drought tolerance
(Kerala Agricultural University, 2022) Rahana, S N; KAU; Beena, Thomas
Open Access
Diallel analysis in rice bean(Vigna umbellata( Thunb.) ohwi & ohashi)
(Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 1999) Preeti, S V; KAU; Radha Devi, D S
A diallel analysis in ricebean (Vigna umbellata (Thunb.) Ohwi and Ohashi) was carried out in the Department of Plant Breeding and Genetics, during 1997 - '98. The experimental material consisted of six parental lines and 30 F I hybrids, laid out in Randomised Block Design with three replications. The six parents were 3 LG, 5 LG, 6 LG, 8 LG, 9 LG, and 100 LG obtained from the germ plasm collection maintained at NBPGR, Thrissur. The observations were recorded on yield and yield attributing characters. Significant differences were detected among the mean performance of the genotypes, for all the characters studied. The combining ability analysis carried out by Method I, Model I of Griffing's approach (1956), revealed that the parent, 8LG was the best general combiner for most of the yield attributing traits. Among the crosses, 8LG x 3 LG exhibited outstanding sea for seed yield per plant. The crosses involving 8 LG were found to be good specific combiners. The combinations involving 3 LG and 6 LG also gave good specific combining ability effects. The numerical analysis by Hayman's approach indicated overdominance for almost all characters, which was confirmed by graphical analysis. The dominance of decreasing alleles in the parents was indicated by the negative value of F for all characters except, plant height, length of pods and number of seeds per pod. An almost equal distribution of genes with positive and negative effects was indicated by the ratio of H2 to 4H} for all the characters. The regression coefficient of covarince between parents and their offsprings in each array (Wr) on variance of all progenies in each parental array (Vr) did not- differ from unity, for plant height, length of pods, seed yield, 100 seed weight, days to maturity and protein content, indicating that assumption of non-allelic interaction was satisfactory for these characters. The Vr - Wr graph indicated that the parents were genetically divergent for days to first flowering, number of pods per plant, number of seeds per pod, 100 seed weight, days to maturity, root weight and nodule weight. Manifestation of heterosis was seen for all the characters studied. Among the hybrids, 8 LG x 3 LG was the most outstanding for yield and yield related characters. The crosses, 8 LG x 9 LG, 8 LG x 100 LG, 6 LG x 9 LG, 100 LG x 8 LG and 6 LG x 3 LG also performed better in yield and yield attributing characters. In general, hybrids involving 8 LG and 6 LG were found to be heterotic.
Open Access
Combining ability in vegetable cowpea
(Department of Plant Breeding, College of Agriculture, Vellayani, 1992) Rejatha, V; KAU; Ramachandra Nair, N
A 6 x 6 diallel analysis was conducted at the Department of Plant Breeding, College of Agriculture, Vellayani, during 1990, aimed at analysing the combining ability, gene action and heterosis of six vegetable cowpea (Vigna unguiculata var-sesquipedalis) lines collected from the germplasm maintained in this department. The experiment I consisted of crossing the six parental lines in all possible combinations, without reciprocals. The material for experiment II consisted of the six parental lines and fifteen hybrids. They were grown in a Randomised Block Design with three replications.The combining ability analysis was carried out based on method 2 under model I as suggested by Griffing (1956). The treatments showed significant differences in most of characters except number of pods/plant and fruit yield/plant. The variance due to general combining ability was significant and higher in magnitude than specific combining ability for the characters days to flowering, mean weight of pod, mean length of pod, number of seeds/pod, length of internode and seed/pod ratio. It was found that the parent selection 104 and selection 145 were the best general combiners for most of the characters studied. The parent selection 129 was the best general combiner for earliness. The hybrids selection 145 x selection 129 was the best specific combiner for mean weight of pod and number of seeds/pod. The hybrid selection 145 x kurutholapayar was the best specific combiner for earliness. The significance of g.c.a. and s.c.a. variances for most of characters indicate the importance of additive and non-additive gene action in controlling the inheritance of these characters. But additive gene action played a major role suggesting that improvement could be made through selection. Heterosis was calculated over mid and better parental values. Maximum positive heterosis was found for the character fruit yield/plant. Since considerable heterosis was evident in most of the characters, heterosis breeding can be attempted in cowpea
Open Access
Morpho-molecular characterisation of D x D hybrids developed using 'annur', the dwarf ecotype of WCT coconut ( Cocos nucifera L.)
(Department of Plant Breeding and Genetics, College of Agriculture, Padannakkad, 2021) Anuprasad, T E; KAU; Sujatha, R
Coconut is one of the most extensively grown crop in the world, playing a significant role in the economic, cultural, and social life of over 80 tropical countries. Coconut cultivars are classified into tall (variety typica) and dwarf (variety nana) types. Short statured palms are currently receiving more attention due to various socio-economic factors. However, the poor quality of nuts for various processing aspects and high susceptibility of dwarf palms to pest and diseases makes them unsuitable for large scale cultivation. The solution for this problem is development of suitable hybrids by combining the desirable features of tall and dwarf palms. West Coast Tall (WCT) is the most widely cultivated variety in Kerala and several ecotypes of WCT were reported. In a study initiated in 2005 at RARS Pilicode, an ecotype of WCT was detected in Annur, a place in Kannur district which showed dwarfing nature with nut qualities similar to WCT. The Annur ecotype was crossed in 2007-08 with the dwarf cultivars Malayan Yellow Dwarf (MYD) and Gangabondam (GB). The hybrid seed nuts along with interse seed nuts of Annur were planted at RARS Pilicode in 2009. The first flowering was recorded in 2014. The present study aims at evaluation of plant stature, yield, nut quality and other important morphological traits of Annur and the hybrids developed from it. The interse of Annur, Annur x GB and Annur x MYD were compared with corresponding characters of the respective parents as well as WCT, Keraganga (WCT x GB) and Kerasree (WCT x MYD). Significant reduction in height was observed for hybrids viz. Annur x MYD (2.251 m) and Annur x GB (2.065 m) which was on par with Annur (2.725 m) and considerably lower than the corresponding values of dwarf cultivars viz., MYD (5.2 m) and GB (8.885 m). Number of nuts per palm per year was on par in Annur (58.2) and Annur x MYD (55.4) while that was lower in hybrid Annur x GB (34.3). However, since the palms started flowering only in 2014, stabilization of yield is not attained. Nut weight and kernel thickness were significantly higher in Annur x MYD whereas these were on par in Annurand Annur x GB. Copra content in Annur and both hybrids were on par. In general, Annur x MYD showed superior performance for nut characters compared to Annur x GB. Annur palms were significantly similar to WCT for most of the characters except height, rate of leaf production, nuts per bunch, nut water content. When the yield of hybrids of Annur were compared with the standard check varieties viz., Keraganga (WCT x GB) and Kerasree (WCT x MYD), (101.5 and 104.25 nuts per palm per year) yield of Annur x GB and Annur x MYD were low. However, both hybrids showed nut characters similar to the respective released varieties ie, Annur x GB was similar to Keraganga and Annur x MYD showed similar nut characters with Kerasree except copra content (161.432 g and 193 g respectively). Better palms from each cross were analysed and palm numbers 1, 2, 15, 19, 20 and 28 were identified as better palms from interse of Annur. The better performing palms of hybrid, Annur x MYD were palm numbers 43, 44, 47 and 49. Three palms from Annur x GB (palm numbers 53, 55 and 56) were identified as better palms. Correlation analysis revealed significant positive genotypic correlation of nut yield per palm with all reproductive and yield characters and with most of vegetative and nut characters. Path coefficient analysis showed high positive direct effect on number of female flowers per inflorescence, number of bunches per palm per year, number of nuts per bunch, pole to pole circumference of nut, nut weight (with husk), shell and meat weight, quantity of liquid endosperm and copra content. High heritability coupled with high genetic advance was exhibited by the characters height of palm, leaf length, number of green leaves, number of inflorescences at the time of observation and number of female flowers per inflorescence. This indicates that these characters are governed by additive gene action and selection based on these characters will be effective. For both hybrids, height of the palm showed negative heterosis which indicates the dwarf nature of the hybrids. In hybrid Annur x MYD, most of nut charactersshowed heterosis over mid parent (relative heterosis) and better parent (heterobeltiosis). The standard heterosis was significant when compared with Keraganga but was not significant with Kerasree. Molecular characterization of the Annur (interse) and the hybrids from it was also attempted using Simple Sequence Repeat markers (SSR). Good quality genomic DNA is the prerequisite for any molecular work. DNA was isolated from all the parental palms as well as check cultivar Kerasree. The quality and quantity of genomic DNA obtained was verified using agarose gel electrophoresis and spectrophotometer. The quantity of DNA samples ranged from 350 to 1300 ng/μl with good quality. Screening of SSR markers for parents and check palms revealed polymorphism for the primers CAC02, CAC11, CNZ40, CnCirA9, CnCirB12, CnCirC3, CnCirC5, CnCirC7, CnCirE2, CnCirE12, CnCirF2, CnCirG11, CnCirH4 and CnCirH7. Out of 34 SSR markers, 27 were monomorphic between WCT and interse of Annur. Genetic Similarity analysis using the SSR markers revealed the high similarity between of interse palms of Annur and WCT. Dwarf palms viz. MYD and GB also showed high genetic similarity with each other. The present study revealed that the genotype Annur is a dwarf ecotype of WCT with similar nut quality and hence is a very promising genotype for breeding for dwarfness. The hybridization of ecotype Annur with MYD is found to be superior in yield characters compared to the hybridization with Gangabondam. However, both hybrids inherited the short stature from Annur and are promising. Since the yield characters needs to be stabilized, evaluation based on important vegetative and reproductive characters as well as molecular fingerprinting needs to be continued inorder to identify the full potential of these dwarf hybrids.
Open Access
Genetics of shattering resistance in rice (Oryza sativa L.)
(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2020) Akhil, K P; KAU; Biju, S
Rice is the staple food crop of Kerala. Among the plethora of rice varieties available Jyothi is by far the most popular in the state owing to its consumer preference. Easy seed shattering leads to significant loss in Jyothi which can be overcome by transferring shattering resistance to it. Screening of genotypes for shattering resistance identified donors like Athira and Triveni with good combining ability. The present experiment was thus envisaged to transfer shattering resistance to Jyothi from the donors and to study the nature of inheritance of seed shattering trait using six parameter model of generation mean analysis. Observations were recorded in the two crosses viz., Jyothi x Aathira and Jyothi x Triveni for eleven quantitative characters viz. days to 50 per cent flowering, plant height, tillers per plant, panicles per plant, panicle length, spikelets per panicle, seeds per panicle, days to maturity, test weight, grain yield per plant and shattering per cent in six generation (P1, P2, F1, F2, B1 and B2) obtained from the two crosses. Panicle per plant, test weight, grain yield per plant and shattering per cent recorded significant heterosis in the desirable direction in both the crosses. Mean effect (m) was significant and positive for all the characters studied in both the crosses. The additive component (d) was significant and positive for days to 50 per cent flowering, tillers per plant, panicles per plant, days to maturity, grain yield per plant and shattering per cent in the cross Jyothi x Triveni while the other characters recorded significant and negative additive gene effect. The characters tillers per plant, test weight and shattering per cent showed significant positive additive gene effect in the cross Jyothi x Aathira and rest of the characters showed significant and negative additive component. Dominance gene effect was observed to be significant and negative for most of the characters studied in both the crosses. Non-allelic interactions were observed to be significant in most of the characters except days to 50 per cent flowering, tillers per plant, days to maturity and shattering per cent in the cross Jyothi x Aathira. The epistatic interaction model of generation mean analysis was found adequate for obtaining gene actions for all the characters. Among the three type of interactions dominance x dominance interaction was found to be more important for all the characters. Additive x additive and additive x dominance gene interactions were found to be equally important for most of the characters studied in both the crosses. Dominance gene effect was observed controlling the genetic variance in most of the traits studied. Presence of additive and non-additive along with epistatic interaction revealed the complex nature of inheritance of the characters. Predominant dominant gene effect along with duplicate epistasis limits the scope of direct selection. In the F2 populations characters showed high heritability in both the populations studied. Plant height, panicle length and days to maturity were found to have low genetic advance. Plant height recorded moderate genetic advance, whereas, other characters exhibited high genetic advance in F2 population derived from the cross Jyothi x Triveni. Days to maturity showed low genetic advance, days to 50 per cent flowering and panicle length recorded moderate genetic advance and other characters recorded high genetic advance in F2 population derived from the cross Jyothi x Aathira. As shattering resistance is governed predominantly by additive gene effects selection in the early segregating generations will be highly rewarding. The selected lines may be advanced to further generations to identify lines with high yield coupled with shattering resistance and can be forwarded to develop high yielding varieties with low shattering or bi-parental mating among the selected lines may be undertaken to recover superior recombinants with high yield and shattering resistance.
Open Access
Development of doubled haploids for iron toxicity tolerance in rice (Oryza sativa L.)
(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2020) Chakravarthi Mari, Bastian; KAU; Dijee, Bastian
Rice is the staple food crop of the people of Kerala. The production of rice in Kerala is impeded by many biotic and abiotic stresses. Iron toxicity is one of the major abiotic stresses of acidic soils in Kerala. The present study “Development of doubled haploids for iron toxicity tolerance in rice (Oryza sativa L.)” was taken up with the objective of developing doubled haploids with tolerance to iron toxicity through in vitro anther culture. Doubled haploids being homozygous stable lines, can be used both as immortal populations for QTL mapping as well as varieties, if suitable agronomic traits are present in them. Therefore, this study was taken up which comprised of three experiments. In experiment I, two tolerant genotypes (Swetha and Mangala Mahsuri) and two susceptible genotypes (Cul-90-03 and Cul 8709) were crossed with Tulasi. In the second experiment the parents along with their hybrids were evaluated for biometric characters and yield. The hybrids obtained from the crosses were significantly different for all the characters observed. Panicles per plant and grain yield per plant recorded highly significant and positive relative heterosis and heterobeltiosis. The anthers from the F1s produced in the previous experiment were used for anther culture studies in the third experiment. Sterilisation with various sterilants like 70 % ethanol, 0.1 % mercuric chloride, 5.25% sodium hypochlorite and their combinations were done. Explant sterilisation with 5.25% sodium hypochlorite for 5 to 20 minutes was effective in controlling contamination in the in vitro cultures. Study to know the best number of days of cold pre-treatment at 10oC was done (0, 3, 6, 9, 12, 15 days). Cold pre-treatment of anthers at 10oC for 9 days was found to be optimum for most of the genotypes studied. Two different media viz., N6 and B5 were tried with different combinations of 2,4 - D and Kn. N6 media responded better than B5 media for callus induction in all the growth hormone combinations. The effect of carbon source on callusing was studied using maltose and sucrose at various levels (30,40,50 mg/L) and it was found that maltose at 30g/L gave the best callus induction (7.95%). Among the auxins used in the present study,2,4-D was found to be better than NAA for callus induction while among cytokinins, Kinetin responded better than BAP for callus induction. The growth hormone combination 2,4- D (2mg/L) + Kn (0.5mg/L) was adjudged the best for callus induction. Additives like silver nitrate (AgNO3), casein hydrolysate (CH), yeast extract (YE), proline and activated charcoal were added to the basal media to improve callusing. when AgNO3 is applied from 0 to 1ml with 0.1 ml gradation, 0.5-0.6ml of 0.1N AgNO3 was found to be better in callus induction as well as the days to callus induction was reduced at these concentrations. 250 – 500 mg/L of CH and 250mg/L proline were found to induce significant response for callusing while activated charcoal and yeast extract did not have any considerable effect on callus induction. Hybrid H1 recorded good callus response when maltose at three levels was tried in the media (30, 40, 50g/L) whereas hybrid H2 gave uniform response at all the levels of maltose. There was significant variation among the genotypes in their response to all the factors studied. The best responses were as follows: - H1(Swetha x Tulasi) - N6+2,4-D (2mg/L) + Kn (0.5mg/L) + 30g/L maltose +0.5ml (0.1 N AgNO3) + 250mg/L proline + 250mg/L CH +2.5g/L gelrite gellan gum. H2(Mangala Mahsuri x Tulasi) - N6+2,4-D (2mg/L) +Kn (0.5mg/L) + 30g/L maltose +0.5ml (0.1N AgNO3) +250mg/L proline+250mg/L CH +2.5g/L gelrite gellan gum. H3(Cul-90-03 x Tulasi) - N6+2,4-D (2mg/L) +Kn (0.5mg/L) + 30g/L maltose + 0.5ml (AgNO3) + 250mg/L proline + 250mg/L CH + 2.5g/L gelrite gellan gum. H4(Cul 8709 x Tulasi)- B5 + 2,4-D (2mg/L) + Kn (0.5mg/L) + 30g/L maltose + 0.5ml (0.1N AgNO3) + 250mg/L proline + 250mg/L CH + 2.5g/L gelrite gellan gum. The calli obtained from the different genotypes were plated on two different callus regeneration media R1 (MS+ NAA(1mg/L) + Kn (2mg/L) + IAA (0.5mg/L) + CW (5%)) and R2 (MS+NAA (0.25mg/L) + BAP (0.75mg/L) + Kn(0.25mg/L)). There was no response in R1 media. Callus regenerated into plantlets in R2 but all the plantlets obtained were albinos leading to mortality and hence plantlet hardening and field planting could not be undertaken.
Open Access
Preliminary evaluation of double cross hybrids for yield and vascular streak dieback (VSD) disease resistance in cocoa (Theobroma cacao L.)
(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2020) Alfiya, A R.; KAU; Minimol, J S
Cocoa is highly influenced by the climate change and growing environment, necessitating a long term and dynamic breeding programme. Even though the breeding programmes primarily focus on the development of high yielding varieties, outbreak of new pests and pathogens shift the priority to the development of resistant varieties. Vascular Streak Dieback disease (VSD) caused by Ceratobasidium theobromae (Samuels et al., 2012), pose a great threat to cocoa crop, causing complete defoliation and eventual death (Abraham et al., 2002). Even the high volume spray of chemicals was ineffective in disease control (Prior, 2007), and the only way to tackle it is to breed resistant varieties. Resistance breeding may result in yield reduction (Xu et al., 2017) however, breeding for double cross hybrids can overcome this situation (Gallais and Guy, 1971). Average yield superiority of the double cross hybrids over the F1 hybrids has been shown by many scientists (Sriani et al., 2003; Ghanwat et al., 2016). Twenty double cross hybrids, bred for vascular streak dieback disease and planted during 2017, were used for the present study. Morphological characterization of the hybrids was carried out based on the quantitative and qualitative characters. Thirteen pod characters, twelve floral characters, six bean characters and flush colour of the leaves were studied. Except colour of the petal and number of the ridges and furrows, all other characters have expressed high variability among the double cross hybrids. The double cross hybrids have exhibited significant difference for fat and polyphenol content. All the twenty double cross hybrids were screened and scored for the VSD resistance in the field condition, using the score chart (Abraham et al., 2000). Based on the disease intensity, they were classified into eleven resistant and nine partially resistant.

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